Dr. Susanna Søberg: How to Use Cold & Heat Exposure to Improve Your Health

00:00:00.000 | - Welcome to the Huberman Lab Podcast,

00:00:02.280 | where we discuss science and science-based tools

00:00:04.880 | for everyday life.

00:00:05.900 | I'm Andrew Huberman,

00:00:10.280 | and I'm a professor of neurobiology and ophthalmology

00:00:13.200 | at Stanford School of Medicine.

00:00:15.220 | Today, my guest is Dr. Susanna Soberg.

00:00:17.980 | Dr. Susanna Soberg completed her doctoral thesis work

00:00:21.180 | at the Center of Inflammation and Metabolism

00:00:23.120 | and the Center for Physical Activity Research

00:00:25.200 | at the University of Copenhagen in Denmark.

00:00:27.880 | Her research has focused on how deliberate cold exposure

00:00:30.880 | and deliberate heat exposure

00:00:32.700 | can be used to enhance human metabolism.

00:00:35.160 | She is the first author of a seminal study

00:00:37.640 | which discovered the minimum thresholds

00:00:39.640 | for deliberate heat and deliberate cold exposure

00:00:42.220 | for increasing brown fat thermogenesis,

00:00:44.920 | which is essentially a mode of increasing heat production

00:00:48.220 | and metabolism in the body,

00:00:50.120 | and for establishing actionable protocols

00:00:52.960 | that can be used outside of the laboratory

00:00:55.240 | to improve metabolism and human health.

00:00:57.560 | Dr. Soberg's research was published in the journal

00:00:59.760 | Cell Reports Metabolism in 2021,

00:01:02.700 | adding to a long and important history of research

00:01:05.600 | focusing on the role of cold and the role of heat

00:01:08.560 | in altering various aspects of the body's physiology,

00:01:11.640 | including hormone health, metabolism,

00:01:14.000 | and changes in neurotransmitters

00:01:15.880 | such as dopamine and epinephrine.

00:01:18.000 | In fact, today's discussion with Dr. Soberg

00:01:20.200 | focuses on the role of deliberate heat

00:01:21.840 | and deliberate cold exposure on metabolism,

00:01:24.160 | but it also includes discussion of the effects of cold

00:01:26.720 | and heat on things like neurotransmitter production,

00:01:29.940 | namely dopamine and epinephrine and norepinephrine,

00:01:32.920 | the so-called catecholamines,

00:01:34.560 | which strongly impact mood and metabolism.

00:01:38.280 | In addition, Dr. Soberg answers many common questions

00:01:41.180 | about deliberate cold and deliberate heat exposure,

00:01:43.460 | including, for instance, the difference between cold showers

00:01:46.880 | versus cold immersion up to the neck

00:01:48.460 | versus total body cold immersion,

00:01:50.820 | including whether or not going back and forth

00:01:53.100 | between heat and cold changes fundamentally

00:01:56.040 | the way that heat and cold impact the metabolism,

00:01:58.480 | hormones, and neurotransmitter production.

00:02:00.640 | And we talk about almost every single nuance and variation

00:02:04.120 | on deliberate cold and deliberate heat exposure protocols

00:02:07.160 | as it relates to the underlying science,

00:02:09.600 | in particular, how cold receptors

00:02:11.880 | at the level of the skin are impacted

00:02:13.660 | versus cold reception and perception

00:02:16.320 | at the level of the brain

00:02:18.200 | and how all of that impacts systems of the brain and body

00:02:20.940 | relating to mental health, physical health, and performance.

00:02:24.260 | Based on her scientific research

00:02:25.720 | and academic training,

00:02:27.320 | as well as her understanding and use of deliberate heat

00:02:30.160 | and deliberate cold exposure protocols,

00:02:32.380 | Dr. Soberg is considered one of the world's leading experts

00:02:35.160 | on these topics.

00:02:36.360 | In fact, she is the author of a recent book

00:02:38.260 | entitled "Winter Swimming,"

00:02:40.200 | which is, I have to say, a terrific book

00:02:42.520 | because it breaks down chapter by chapter

00:02:44.560 | the different aspects of deliberate heat and deliberate cold

00:02:47.400 | into its various constituent parts,

00:02:49.760 | including cold acclimatization, the cold shock response,

00:02:54.220 | dangers and safeties of cold water,

00:02:56.140 | the impact of cold and the impact of heat

00:02:59.000 | on various aspects of human health,

00:03:01.620 | as well as specifics relating to sauna

00:03:04.180 | versus ice versus cold swimming, showers, et cetera.

00:03:07.360 | It's a very thorough read

00:03:08.680 | and a very easy and accessible read

00:03:10.920 | that if you are interested in deliberate cold

00:03:12.740 | or deliberate heat exposure or both,

00:03:14.580 | will allow you to embrace those protocols

00:03:17.160 | with the greatest degree of confidence

00:03:18.860 | that you're going to obtain the specific endpoints

00:03:21.240 | that you're interested in and to do so safely.

00:03:24.080 | Before we begin, I'd like to emphasize that this podcast

00:03:26.720 | is separate from my teaching and research roles at Stanford.

00:03:29.300 | It is, however, part of my desire and effort

00:03:31.360 | to bring zero cost to consumer information

00:03:33.220 | about science and science-related tools

00:03:35.140 | to the general public.

00:03:36.400 | In keeping with that theme,

00:03:37.460 | I'd like to thank the sponsors of today's podcast.

00:03:40.300 | Our first sponsor is Plunge.

00:03:42.480 | Plunge makes what I believe is the most versatile

00:03:44.940 | at-home self-cooling cold plunge

00:03:46.720 | for deliberate cold exposure.

00:03:48.600 | I've talked numerous times on this podcast

00:03:50.960 | about the many benefits of deliberate cold exposure,

00:03:53.500 | and indeed, today's episode is focused entirely

00:03:56.020 | on the benefits and the science of deliberate cold exposure.

00:03:59.520 | Plunge uses a powerful cooling filtration

00:04:01.540 | and sanitation unit to give you access

00:04:03.700 | to deliberate cold exposure in clean water

00:04:06.120 | whenever you want.

00:04:07.360 | As we will discuss during today's episode

00:04:08.800 | with Dr. Susanna Soberg, deliberate cold exposure,

00:04:11.560 | especially deliberate cold exposure

00:04:13.000 | done up to the neck in water,

00:04:15.360 | can be used to achieve a number of important endpoints

00:04:17.660 | related to mental health, physical health, and performance.

00:04:20.120 | I've been using a plunge for more than two years now.

00:04:22.620 | I can tell you that it makes it very easy

00:04:24.760 | to get your deliberate cold exposure at home.

00:04:27.160 | It doesn't require much cleaning.

00:04:28.560 | In fact, it's very easy to keep clean, which is essential.

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00:04:33.580 | Basically, everything about the plunge is made easy

00:04:36.180 | so that anyone, including myself,

00:04:38.160 | can get their deliberate cold exposure

00:04:39.760 | on a regular basis at home.

00:04:41.440 | If you're interested in getting a plunge,

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00:07:02.480 | Both live events will include a lecture

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00:07:13.240 | And I should mention that a lot of that content

00:07:15.720 | will have absolutely no overlap

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00:07:35.260 | I hope to see you there.

00:07:36.800 | And now for my discussion with Dr. Susanna Soberg.

00:07:40.120 | Dr. Susanna Soberg, welcome.

00:07:42.420 | - Thank you.

00:07:43.260 | - So great to have you here.

00:07:44.500 | I feel like I should give a little bit of the backstory

00:07:46.640 | of how we got connected,

00:07:48.320 | which was that for many years,

00:07:50.780 | I've been interested in cold thermogenesis.

00:07:53.460 | It was the topic of my senior thesis in college.

00:07:56.560 | And I've, of course, followed the popularity of Wim Hof.

00:08:01.320 | And we've had Dr. Craig Heller,

00:08:03.540 | my colleague from biology department at Stanford

00:08:07.120 | who works on cold and its impact on physiology

00:08:10.280 | and sports performance.

00:08:11.120 | So for a long time, I've been interested in this area,

00:08:14.160 | but there's been a real lack of new,

00:08:19.160 | let's say high profile quality scientific information

00:08:23.160 | in terms of how, for instance, cold plunges and sauna,

00:08:27.760 | how that impacts human physiology.

00:08:29.800 | I know there's been some information out there,

00:08:31.440 | but it's been sort of scattered.

00:08:33.200 | And then a little over a year ago, I see this paper

00:08:37.200 | in Cell Reports Medicine and was immediately struck the,

00:08:41.840 | first of all, the fact that it was in Cell Reports Medicine,

00:08:44.140 | I've been on the Cell Press editorial board

00:08:46.120 | for a long time now.

00:08:47.000 | So press journals are, of course, phenomenal journals.

00:08:50.240 | And the title and the content of the paper

00:08:53.240 | was directly in line with the sorts of practices

00:08:56.560 | that people are very curious about

00:08:58.340 | and then are starting to emerge,

00:08:59.400 | things like sauna, cold plunges.

00:09:01.640 | And there was your name first on the author list.

00:09:05.000 | And I reached out to you through social media

00:09:07.480 | and we've done a little bit of live content there together.

00:09:10.220 | And I've been tracking what you've been doing in the world

00:09:12.660 | in terms of your book and talking about the results

00:09:15.640 | in your manuscript and talking about the science

00:09:18.440 | and impact of deliberate cold exposure and sauna.

00:09:21.600 | And I have to say that it's been a wonderful

00:09:24.260 | and remarkable thing to see.

00:09:25.600 | And you're bringing so much quality information

00:09:28.140 | about this area that for a long time,

00:09:29.500 | I think was kind of niche and is now becoming

00:09:32.560 | more and more mainstream.

00:09:33.740 | So I'm going to start off with a thank you for being here

00:09:36.000 | and a thank you for the work that you've done.

00:09:38.640 | And I'm looking forward to talking to you about it today.

00:09:41.740 | So my first question to get things started

00:09:45.300 | is what is happening when we get into

00:09:50.100 | an uncomfortably cold environment?

00:09:52.700 | So for instance, if I'm really hot on a hot day,

00:09:56.060 | jumping into a cold pool feels really good.

00:09:58.920 | But if I'm already kind of at room temperature,

00:10:02.700 | I'm a little bit chilly,

00:10:03.800 | getting into that same temperature of water

00:10:05.740 | doesn't feel so good, right?

00:10:07.160 | There's a shock there.

00:10:08.400 | So if you could just walk us through what happens

00:10:10.340 | when we get into uncomfortably cold water,

00:10:12.940 | whether or not it's by way of shower or cold plunge

00:10:15.540 | at the level of our physiology

00:10:17.280 | and if you'd like our psychology,

00:10:18.700 | I think that's a good place for us to start

00:10:20.300 | because I think it will orient people

00:10:22.100 | to their own experience if they do that.

00:10:24.360 | And for those that haven't done it

00:10:26.300 | might start to peel back some of the layers

00:10:28.820 | as to what the underlying mechanisms of cold are.

00:10:32.120 | - Yeah, thank you for that question.

00:10:33.980 | It's really good to just address what actually happens

00:10:36.560 | in our physiology when we get cold.

00:10:39.260 | And you can get cold in many ways.

00:10:40.920 | So you can just head out for the one that gives you

00:10:44.540 | the most potent stressor,

00:10:46.060 | which is submerging into cold water.

00:10:48.400 | And, but you could also go in outside in the cold wind.

00:10:51.760 | That's also gonna activate your sympathetic nervous system.

00:10:55.720 | So get all these neurotransmitter going in your body

00:10:58.660 | and so your catecholamines.

00:11:01.940 | Let's just address that we are taking

00:11:03.780 | a cold plunge, for example.

00:11:05.380 | So if you are very hot, for example,

00:11:09.140 | before you go into the cold water,

00:11:10.660 | it's gonna feel less stressful,

00:11:13.380 | but the temperature difference from your skin to the cold

00:11:17.620 | is definitely gonna give you a shock,

00:11:20.200 | but your core temperature is warmer

00:11:22.300 | and that's gonna feel a little bit better.

00:11:24.220 | So that's why when people go into a sauna, for example,

00:11:26.660 | and go out then into the cold water,

00:11:29.480 | they can do it easier than if they were cold beforehand.

00:11:34.480 | - Could I just ask you a few questions?

00:11:37.620 | So you mentioned the sympathetic nervous system,

00:11:39.620 | which for people listening who aren't familiar with that

00:11:42.300 | is that the branch of our nervous system

00:11:44.420 | that's responsible for creating accelerations

00:11:47.060 | in heart rates, feelings of alertness,

00:11:49.900 | it's accompanied with stress and the stress response,

00:11:52.800 | but it's accompanied with waking up in the morning

00:11:55.580 | for that matter.

00:11:56.420 | So it's not always about stress.

00:11:57.580 | And then you mentioned the catecholamines,

00:11:59.080 | which are dopamine, epinephrine, and norepinephrine.

00:12:02.420 | So maybe a little bit later,

00:12:03.260 | we'll talk about those individual neurotransmitters,

00:12:05.500 | but you raise a really important point,

00:12:07.420 | which is something I get asked about a lot

00:12:10.260 | for people that are curious

00:12:11.200 | about using deliberate cold exposure,

00:12:13.060 | which is how cold should the water be?

00:12:15.540 | And I know it's very hard

00:12:16.540 | to give a straight prescription for that

00:12:19.300 | because I think it boils down to what you just said,

00:12:21.460 | which is it's really the difference

00:12:23.240 | between your current temperature

00:12:25.660 | and really the temperature of the surface of your skin

00:12:27.500 | and the temperature of the water.

00:12:28.560 | So if you're very warm, getting into cold feels good.

00:12:31.440 | If you're already cold,

00:12:32.540 | getting into more cold feels stressful.

00:12:35.920 | Is there any way that we can start to gauge

00:12:39.800 | what is the best way to approach

00:12:42.220 | a deliberate cold exposure protocol?

00:12:44.660 | I mean, should it feel uncomfortable?

00:12:47.200 | And that leads into the question

00:12:48.820 | of how do we balance the discomfort

00:12:51.100 | with the amount of time that we spend in?

00:12:53.060 | So for instance, if it's just a little bit uncomfortable,

00:12:55.220 | will spending more time in the cold

00:12:57.020 | get us the same benefit

00:12:58.100 | as getting into very uncomfortably cold water

00:13:00.520 | for a very short period of time?

00:13:02.500 | - Yeah, it's really good question.

00:13:04.140 | And I definitely think that this could be future studies

00:13:08.160 | on this as well to really unravel

00:13:09.980 | what kind of protocols are the best way

00:13:14.460 | or also for which outcomes, of course.

00:13:17.200 | So if the temperature is very cold

00:13:21.160 | and you also feel very cold,

00:13:23.880 | then you should stay in the water a little bit longer.

00:13:26.140 | So I think it's just, you should get uncomfortable cold.

00:13:29.020 | So as long as you get uncomfortable cold,

00:13:30.780 | it's cold enough and you get this,

00:13:32.500 | what we call the cold shock.

00:13:33.900 | So the cold shock is activation

00:13:35.700 | of your sympathetic nervous system

00:13:37.720 | and these activation of the catechola mines,

00:13:40.520 | which you just mentioned before.

00:13:42.400 | - Does the shock mean

00:13:43.240 | that I'm having trouble controlling my breathing?

00:13:45.500 | Is that a good gauge?

00:13:46.800 | - Yeah, you can say so

00:13:48.620 | because that's kind of like how we define it.

00:13:51.660 | So you hyperventilate, so you have a faster breathing rate.

00:13:56.660 | So that increases also

00:13:59.060 | because you activate your gasping reflex

00:14:01.500 | if you are new to this, but if you are adapted,

00:14:04.900 | it kind of subsides with time with adaptation.

00:14:08.460 | So what you can do is that you can train this cold exposure

00:14:13.140 | and you can kind of like get adapted to it.

00:14:15.240 | So you don't have this hyperventilating response

00:14:18.540 | every time you go out in the cold water.

00:14:20.280 | So this is like building up your resilience,

00:14:23.060 | building up your adaptation.

00:14:25.120 | It's gonna make the shock like subside a bit.

00:14:28.100 | So it's always harder in the beginning,

00:14:31.300 | but you should do hard things, right?

00:14:33.100 | It's not something that we,

00:14:34.580 | you shouldn't think about cold water

00:14:36.020 | and cold water immersion as something that is comfortable.

00:14:39.220 | It should be hard because that's the point of it, right?

00:14:41.720 | If you enjoy it, then yeah,

00:14:43.500 | then I'm thinking something is wrong.

00:14:45.260 | It's not right.

00:14:46.220 | You should not enjoy it.

00:14:47.280 | - Well, this is an important point that you're making

00:14:48.860 | because I think that many people shy away

00:14:51.720 | from deliberate cold exposure because it's uncomfortable

00:14:55.900 | in a way that at least from my experience

00:14:57.780 | is very different than the discomfort of exercise.

00:15:00.380 | Because with exercise, for instance,

00:15:02.720 | if running fast and breathing hard is uncomfortable,

00:15:06.860 | you can slow down or walk.

00:15:08.700 | If lifting weights is uncomfortable,

00:15:11.120 | you can remove some weight

00:15:12.920 | or reduce the number of repetitions or stop.

00:15:16.740 | With deliberate cold exposure,

00:15:18.660 | I suppose you can be sort of halfway in,

00:15:21.060 | halfway out of the water

00:15:22.660 | or partially underneath the cold shower,

00:15:24.620 | but it's very hard to titrate and adjust the level.

00:15:29.060 | It's kind of all or none.

00:15:30.820 | And I've seen, I should just, I can tell this by anecdote.

00:15:34.060 | I've done some work with military special operations.

00:15:37.220 | I won't say which country.

00:15:38.180 | This was outside the US.

00:15:39.380 | And these are very tough individuals.

00:15:43.860 | They're used to going without sleep and doing hard,

00:15:46.360 | high consequence, high risk kind of work.

00:15:49.080 | And they were asked to do some cold water exposure training.

00:15:53.180 | And I was there that day and it was remarkable.

00:15:55.080 | About a third of them just went straight in

00:15:58.880 | and just kind of grinded through it.

00:16:01.320 | They looked stoic anyway, to me.

00:16:03.600 | There were a few whimpers, no cries.

00:16:05.480 | About a third talked a lot and got really,

00:16:09.760 | you could tell that they were agitated and anxious,

00:16:11.600 | but they made it through.

00:16:12.440 | And then about a third of them just simply would not get in

00:16:15.600 | past their knees or thighs.

00:16:18.220 | Were just, it seemed like they were just dreading

00:16:20.680 | the whole experience.

00:16:21.520 | Some actually didn't actually go in completely,

00:16:24.640 | which was really surprising to me.

00:16:25.880 | And you couldn't tell based on their physical appearance

00:16:28.840 | or anything else about them.

00:16:30.160 | They're all high performers

00:16:31.120 | as to who would have this response.

00:16:32.360 | So it seems like people vary tremendously

00:16:35.280 | in terms of their ability to embrace

00:16:37.600 | the discomfort of the cold.

00:16:38.940 | Is that, from your studies,

00:16:40.520 | is that your experience as well?

00:16:42.040 | Or are there these weird mutants

00:16:43.840 | who seem to just love going into the cold

00:16:45.680 | for the first time?

00:16:47.240 | - So some people just feel better in the cold

00:16:50.160 | and some people dread the cold even more.

00:16:53.640 | And you can say the more people are pushing the cold away,

00:16:57.420 | they might feel the cold pain even more.

00:16:59.780 | So they would definitely,

00:17:02.360 | people who are maybe the soldiers you just talked about,

00:17:05.400 | some of them might be already adapted to the cold.

00:17:09.800 | So if they are not scared of the cold,

00:17:12.040 | they go out and they embrace the cold in a better way.

00:17:15.600 | It could also be that some people

00:17:17.080 | have a more sensitive nervous system.

00:17:18.800 | And when you are a bit sensitive to the cold,

00:17:21.560 | you will, of course, try to get away from it, right?

00:17:24.640 | And you will also have the cold pain more,

00:17:27.720 | feel the cold pain more if you avoid it.

00:17:30.920 | So the more you avoid the cold,

00:17:32.960 | the more painful it will feel when you go into it, so yeah.

00:17:37.960 | - You mentioned being outside in a t-shirt

00:17:40.560 | versus cold immersion up to the neck versus shower.

00:17:43.740 | I think this is something a lot of people wonder about.

00:17:46.500 | What are the differences in terms of impact,

00:17:48.600 | short-term and perhaps even long-term,

00:17:51.440 | between cold showers, cold plunge to the neck,

00:17:55.180 | so that could be an ice water or just very cold water,

00:17:57.880 | immersion with dunking one's head and then coming up,

00:18:02.560 | because obviously people have to come up for air

00:18:04.360 | at some point, and then simply being outside on a cold day

00:18:09.100 | in shorts and a t-shirt or something of that sort.

00:18:11.540 | - So there are different outcomes

00:18:14.340 | because they are very different exposures of the cold

00:18:18.680 | to your cold receptors in your skin.

00:18:20.700 | So the more you can say you cover your body in the cold,

00:18:24.840 | which you would do in cold water,

00:18:26.640 | because they're, of course, covered totally

00:18:29.440 | and the molecules are closer to your skin,

00:18:32.760 | you will have a more potent activation

00:18:35.600 | of all your cold receptors in the skin.

00:18:38.600 | So that one will definitely activate

00:18:41.400 | your autonomous nervous system more and rapid

00:18:45.780 | compared to going out in a t-shirt in the cold wind,

00:18:48.340 | just go for a walk, but that is also something

00:18:51.740 | that's gonna activate your sympathetic nervous system,

00:18:55.460 | meaning that you will have an increase in norepinephrine

00:18:59.340 | and you will activate something called the brown fat.

00:19:03.320 | So this is a healthy kind of fat tissue

00:19:05.940 | that we have in our body, and when you activate that,

00:19:08.980 | that's gonna increase your metabolism.

00:19:11.600 | - Before we talk about brown fat,

00:19:12.820 | and I'm so glad you brought it up

00:19:14.960 | because there's so much to talk about there,

00:19:16.940 | what about cold shower?

00:19:18.340 | I mean, obviously cold shower is somewhere in between

00:19:21.600 | being outside in the air, cold air,

00:19:24.940 | versus being immersed up to the neck.

00:19:27.800 | - If we had more studies on cold showers,

00:19:30.220 | we would learn more about how does that activate

00:19:32.820 | our metabolism, how does that increase our neurotransmitters

00:19:36.420 | in the brain, which could also have an impact

00:19:39.180 | on our mental balance.

00:19:40.660 | So I think that would be interesting for the future.

00:19:43.260 | But what we do know is from activating brown fat

00:19:49.080 | and both from rodent studies, but also in humans,

00:19:53.380 | is that as soon as we get cold on our skin,

00:19:56.100 | we will activate our brown fat.

00:19:58.280 | So it is kind of like our first responder in the body

00:20:01.540 | to keep our temperature up.

00:20:04.740 | So our muscles is like the second tissue in our body.

00:20:08.100 | We have two tissues which can increase our thermogenesis.

00:20:11.380 | So the brown fat, which is like always like temperature

00:20:14.820 | regulating our body, and then we have the muscles,

00:20:18.660 | which will secondarily start to shiver,

00:20:21.560 | and that's gonna increase our temperature in the body.

00:20:25.240 | But as soon as you go into a cold shower,

00:20:27.460 | you will activate your brown fat also immediately.

00:20:30.760 | So it could be good also for increasing metabolism,

00:20:33.860 | in theory, because we haven't really any studies

00:20:36.620 | showing how much does it actually activate the brown fat.

00:20:40.200 | So if someone out there wants to do a study on that,

00:20:43.040 | that would be great.

00:20:43.880 | - I've thought about why there are fewer studies

00:20:45.620 | of cold showers than cold immersion.

00:20:47.360 | And I think the answer to my mind

00:20:49.460 | is that from a methodological standpoint,

00:20:51.640 | it's just harder to do because if people are getting

00:20:54.740 | into cold water up to the neck,

00:20:57.340 | they're getting into cold water up to the neck.

00:20:58.960 | Whereas if people are getting into a cold shower,

00:21:01.140 | some people are larger or smaller.

00:21:02.820 | Some people are gonna stand under the shower

00:21:05.160 | with it hitting their head.

00:21:06.040 | Some people, the back of the neck.

00:21:06.980 | You could direct people to do it,

00:21:08.860 | but it's a little bit more difficult.

00:21:10.780 | Also, I think for, you and I are both research scientists,

00:21:14.720 | there's a little bit of a methodological challenge

00:21:17.980 | that might seem silly to people, but it's a real one,

00:21:19.900 | which is if people are in a cold shower,

00:21:21.500 | also the water is going to be,

00:21:23.340 | I'm kind of pushing their clothing against their skin.

00:21:25.180 | There's a certain vulnerability for most people

00:21:28.560 | coming to a laboratory in the first place,

00:21:30.580 | let alone being absorbed while they shower.

00:21:32.860 | Whereas when you get into cold immersion,

00:21:35.240 | you're getting under the water.

00:21:36.860 | And some people might roll their eyes and say,

00:21:38.740 | "Okay, really, is that the barrier?"

00:21:40.040 | But science exists in these real world contexts.

00:21:43.200 | And this will vary by culture and things of that sort,

00:21:45.540 | but we run human subjects in my lab.

00:21:47.500 | And I'll tell you just the process of getting people

00:21:49.660 | to the laboratory and having them park and find the lab.

00:21:51.980 | And it's a whole new environment with people in lab coats

00:21:55.800 | and people moving around and where's the restroom?

00:21:57.820 | I mean, there's a certain amount of stress

00:21:59.620 | just associated with taking part in a study

00:22:01.640 | for most human subjects.

00:22:02.740 | So I totally agree, however,

00:22:05.660 | we need more studies of cold showers.

00:22:07.880 | It's just a harder environment to control in my mind.

00:22:11.540 | So it sounds like any form of cold to the skin

00:22:16.540 | that people register as what you call the cold shock

00:22:20.820 | or uncomfortable, like, oh, like this is kind of jarring,

00:22:24.440 | activates the brown fat.

00:22:26.060 | Do we know what the pathway is from cold receptors

00:22:28.740 | on the skin to the brown fat?

00:22:29.940 | I mean, how does the brown fat know that we're cold?

00:22:32.700 | - Yeah, really good question.

00:22:34.020 | And it seems that I think that, of course,

00:22:36.660 | in the future, we will know much more about these pathways.

00:22:39.260 | But what we do know is that the co-receptors

00:22:41.980 | will send a signal to our temperature regulating center

00:22:44.620 | in the brain, so hypothalamus,

00:22:47.420 | and that's going to be taking in this message.

00:22:51.580 | And we have so many co-receptors in the skin.

00:22:53.560 | So it's going to be very fast, as you can say,

00:22:56.240 | if you immerse the body into cold water,

00:22:58.600 | this is going to be so rapid.

00:23:00.820 | So it will have a rapid increase in neurotransmitters

00:23:05.280 | in the brain to no adrenaline, adrenaline and cortisol,

00:23:08.760 | which is not that much, but it's still there.

00:23:11.200 | So you have this increase in no adrenaline,

00:23:15.000 | which will then immediately activate the brown fat

00:23:18.000 | because you can say the activator is the most potent one,

00:23:22.420 | cold and no adrenaline,

00:23:24.040 | that's going to activate the brown fat.

00:23:25.220 | But there's also a direct pathway from the co-receptors

00:23:28.620 | in the skin to the brown fat,

00:23:30.660 | which really shows that if,

00:23:32.680 | because of these different pathways,

00:23:34.280 | it shows that it could be that this tissue to keep us warm

00:23:39.280 | was developed in our evolvement as humans to keep us warm

00:23:44.740 | and to save us whenever the temperature on our skin varies

00:23:50.500 | just a little bit to keep us in that right

00:23:53.040 | homeostatic balance so we don't get hypothermic,

00:23:57.640 | but also so we don't get hyperthermic,

00:23:59.920 | but because it seems that the brown fat is also activated

00:24:02.920 | when we get warmer in our skin.

00:24:05.180 | So it's also maybe a temperature regulator in our body,

00:24:09.560 | but the pathways is different.

00:24:11.520 | I think it's also a third pathway

00:24:13.800 | from directly from the muscles.

00:24:15.280 | So the brown fat is also activated

00:24:18.840 | even though the muscles are starting to shiver.

00:24:21.160 | So there's an extra pathway that way

00:24:23.920 | to keep our temperature up.

00:24:26.680 | So muscles and brown fat are working together

00:24:28.940 | to keep us warm so we don't suffer too much

00:24:32.080 | in the cold water.

00:24:33.920 | - That's super interesting.

00:24:34.800 | And what I hear you pointing to is the existence

00:24:37.600 | of three parallel pathways.

00:24:39.320 | And this notion of parallel pathways comes up

00:24:41.240 | over and over again in biology, as you and I know.

00:24:43.720 | And I think it's important for people to know about

00:24:46.360 | because as you said so eloquently,

00:24:50.960 | when something is very important to our survival

00:24:53.160 | and/or evolution, the brain and body

00:24:57.080 | install multiple mechanisms for it, not just one.

00:25:00.960 | And so it sounds like it's cold skin,

00:25:04.840 | cold on the skin triggers a response in the hypothalamus,

00:25:08.260 | which then activates brown fat,

00:25:10.080 | cold receptors in the skin directly to the brown fat,

00:25:13.040 | and then shivering in the muscle to the brown fat.

00:25:16.640 | I want to talk about brown fat in depth

00:25:19.400 | and learn from you more about brown fat.

00:25:22.800 | Before that, however, I want to ask about shiver.

00:25:26.080 | I've heard that shiver causes the release of succinate,

00:25:32.040 | which then activates the brown fat.

00:25:36.260 | Is it known whether or not inducing shiver is important?

00:25:39.440 | And when should people shiver?

00:25:42.000 | I mean, I've gotten into cold plunges

00:25:43.560 | and shivered while I was in there.

00:25:44.960 | And then I've also had the experience

00:25:47.520 | of getting into a cold plunge or a cold shower,

00:25:49.880 | then getting out, or even standing outside on a warm day

00:25:53.340 | after swimming in a pool and then starting to shiver.

00:25:55.640 | So the shiver comes later.

00:25:57.060 | So how important is shiver

00:25:58.460 | and does it matter when shiver happens?

00:26:00.840 | - Yeah, well, shivering is good

00:26:03.760 | because that increases your metabolism

00:26:05.640 | and that's going to burn some calories in your body.

00:26:08.240 | You shouldn't be so afraid of shivering, I think,

00:26:10.560 | because the shivering, as long as you don't get

00:26:12.880 | too hypothermic, so if you don't sit in the cold water

00:26:15.960 | for too long, and what you just said by shivering

00:26:20.080 | after you get up, that is because of the after drop.

00:26:23.440 | Something called the after drop is when your core temperature

00:26:26.960 | decreases even after you get out of the cold water.

00:26:29.520 | And it always does that, your body,

00:26:31.980 | because as soon as you get into the cold water,

00:26:35.320 | all your blood vessels is going to constrict

00:26:38.360 | because you need to keep your blood in your core

00:26:41.720 | and keep your vital organs warm.

00:26:44.700 | So as soon as you get up,

00:26:46.160 | those blood vessels will open again

00:26:47.900 | and the warm blood will flow out and get colder

00:26:51.200 | and then flow back again into the core.

00:26:53.640 | And that's going to decrease the temperature

00:26:55.280 | in your core, of course.

00:26:56.480 | - So that's the drop.

00:26:57.680 | - So that's the drop, yeah, after drop.

00:26:58.520 | - Got it, oh, I'm so glad you explained that.

00:27:00.600 | I've heard, years ago, Wim Hof,

00:27:03.000 | I heard him talk about the drop

00:27:04.220 | and I've heard colleagues of mine talk about the drop,

00:27:06.240 | but that's the first time I've ever heard it

00:27:07.880 | explained clearly.

00:27:09.000 | Let me make sure I understand this.

00:27:10.180 | So I get into cold water, obviously, I'm cold.

00:27:14.580 | Vessels constrict to keep blood near the center of my body,

00:27:17.600 | keep me alive.

00:27:19.080 | I get out, the warming up of my body

00:27:24.080 | allows those vessels and capillaries to dilate again.

00:27:26.520 | The blood goes out to the surface,

00:27:27.900 | but the surface is still cold.

00:27:29.840 | And so that blood is cooled

00:27:32.580 | and then my core body temperature drops.

00:27:34.760 | And that's what you're referring to as the drop.

00:27:36.600 | And that's what induces shiver.

00:27:37.960 | - Exactly.

00:27:38.800 | - Great, and then, am I right in thinking

00:27:40.440 | that then the shiver activates brown fat,

00:27:42.720 | which then warms me up again?

00:27:44.280 | - Yes.

00:27:45.120 | - Got it.

00:27:45.940 | - That's why you should end on the cold.

00:27:47.380 | We can get back to that.

00:27:48.220 | - Yeah, let's talk about, yes.

00:27:49.060 | Ending on cold is, you know, it's what I refer to as,

00:27:52.520 | and what has now become known as the Soberg principle,

00:27:55.560 | which is a really important principle

00:27:57.600 | about the importance of ending on cold

00:28:00.520 | and not doing what I do,

00:28:01.480 | which is to get into a hot shower or back in the sauna.

00:28:04.000 | But we'll get back to that in a few minutes.

00:28:06.380 | So that's wonderful that you can explain that so clearly,

00:28:11.380 | because I think that shiver is something

00:28:13.480 | that a lot of people do avoid.

00:28:15.160 | People think, oh, I don't want the chattering of the teeth.

00:28:19.200 | And it feels like a loss of bodily control,

00:28:21.440 | which really it is.

00:28:22.340 | It's an autonomic response.

00:28:24.460 | - Yeah, but I don't think that people

00:28:25.640 | should avoid it that much.

00:28:27.320 | It's just like seeing shivering as a way of your body in,

00:28:31.960 | like it's training.

00:28:33.020 | It's training for all your cells.

00:28:34.840 | It's training for your muscles.

00:28:36.280 | It's training of your metabolism.

00:28:38.060 | And that's gonna increase your,

00:28:39.600 | what's called the insulin sensitivity.

00:28:41.580 | So if you can like, in your mind,

00:28:45.160 | get used to the thought of shivering

00:28:47.660 | is just like when you go exercising in the training center

00:28:51.160 | and get that feeling of like, oh, this is tough.

00:28:53.420 | Now it hurts a little bit.

00:28:54.700 | Yeah, it's gonna hurt

00:28:55.620 | because that's what shivering also does,

00:28:57.880 | but it's just a different way

00:28:59.300 | of training your cells and your body.

00:29:01.160 | It's gonna create what is healthy stress.

00:29:02.860 | It's called homeosis in the cells.

00:29:04.780 | And the more you expose your muscle cells

00:29:07.700 | or your brown fat cells

00:29:09.040 | to these kind of like healthy stresses,

00:29:11.040 | exercise, cold, and heat exposure,

00:29:13.760 | it's gonna make them better at like activating

00:29:17.140 | and also at keeping you healthy.

00:29:19.760 | So as long as the cells get exposed to this,

00:29:23.580 | it's gonna keep them on its toes, you can say,

00:29:25.900 | because it becomes more robust,

00:29:28.300 | increasing these heat shock proteins

00:29:30.860 | and cold shock proteins in the cells

00:29:33.040 | to make you more robust for the next time.

00:29:37.240 | And that is also what happens

00:29:38.420 | when you go to the training center.

00:29:40.360 | And I keep like drawing that parallel

00:29:42.620 | because people today know more about,

00:29:45.020 | we know more about exercise

00:29:46.660 | and what that is gonna do to your muscle cells.

00:29:50.060 | But the same kind of like training

00:29:53.920 | is also what you do when you go out into the cold water

00:29:57.380 | and submerge into cold water,

00:29:59.040 | because that is just your cold training center,

00:30:01.820 | you can say that.

00:30:02.660 | And also your heat training center going into the sauna

00:30:05.440 | because the cells are getting stronger with hermetic stress.

00:30:08.600 | So it's the same process, just different practices.

00:30:11.220 | - I'm so glad that you brought up the fact

00:30:14.160 | that the discomfort or the embarrassment or both of shiver

00:30:18.180 | is still crucial to actually to reach for

00:30:21.940 | and try and experience the same way that with exercise,

00:30:25.560 | I think a lot of people don't realize this,

00:30:26.860 | but when we did our series with Dr. Andy Galpin,

00:30:29.980 | it became clear to me

00:30:31.080 | what should have already been clear to me.

00:30:32.500 | And I think that most people don't realize,

00:30:34.100 | which is that if we were to measure heart rate,

00:30:37.540 | blood pressure, stress hormones, and inflammation

00:30:41.740 | in a human being during exercise,

00:30:44.740 | it would look as if they were ready to die.

00:30:46.700 | Blood pressure would be high,

00:30:47.660 | inflammation is through the roof,

00:30:48.940 | but all of that is setting in motion and adaptation

00:30:52.120 | or set of adaptations

00:30:53.500 | that allow blood pressure to be lower at rest,

00:30:56.140 | that allow inflammation markers to be lower at rest,

00:30:59.820 | all the things that everybody is seeking with exercise.

00:31:02.040 | In addition to, of course, the aesthetic changes

00:31:03.900 | that people are seeking with exercise.

00:31:05.680 | It sounds like the exact same things

00:31:06.820 | are happening with the cold.

00:31:07.820 | So the redundant message here seems to be

00:31:10.620 | that the more discomfort, provided it's done safely,

00:31:15.080 | just like with exercise,

00:31:16.500 | the more shivering, the more cold shock,

00:31:20.740 | provided it's not to the extreme

00:31:22.620 | and stop somebody's heart, right?

00:31:24.180 | We can talk about thresholds for that a little bit later.

00:31:27.420 | It sounds like all of that is going to set in motion

00:31:29.700 | some long-term changes that will make people feel better

00:31:32.700 | and will improve health.

00:31:34.360 | Could you just touch on a few of the longer-term changes

00:31:37.780 | that are known to occur?

00:31:39.900 | I mean, I'm well aware of the study showing that,

00:31:43.000 | I think it was European Journal of Physiology,

00:31:45.180 | it was the European Journal of Physiology,

00:31:47.200 | showing long-lasting increases in catecholamines,

00:31:50.080 | dopamine, norepinephrine, and epinephrine

00:31:52.760 | for many hours after deliberate cold exposure.

00:31:55.440 | What are some of the other things that happen

00:31:57.320 | at the level of metabolism and brown fat

00:32:00.080 | in, let's say, the hours and day

00:32:02.400 | after a deliberate cold exposure?

00:32:04.520 | - As soon as you go in, of course, there's an activation,

00:32:08.000 | but it seems like, no, you're asking for the later outcomes

00:32:11.280 | like blood pressure and stuff like that.

00:32:12.860 | Is that what you mean?

00:32:13.700 | - Yeah, blood pressure, but also in terms of metabolism.

00:32:16.040 | I know that in your study,

00:32:17.880 | and we'll talk about brown fat in depth here in a moment,

00:32:20.020 | but that there were changes to the brown fat

00:32:22.680 | that equate to changes in, for instance,

00:32:26.720 | people's ability to be comfortable in colder environments

00:32:29.800 | when they're not doing deliberate cold exposure,

00:32:32.320 | or in the same way that I can exercise on an exercise bike

00:32:35.680 | or go out for a hard run,

00:32:36.800 | but then if I go hiking with the family on Sunday

00:32:39.920 | and it's a steep climb,

00:32:41.180 | I could do that steep climb more easily

00:32:42.660 | because I'm quote unquote fit

00:32:44.240 | as a consequence of the exercise.

00:32:46.480 | What are some of the fitness adaptations

00:32:49.640 | of deliberate cold exposure?

00:32:51.800 | - Yeah, so what happens is that you get adapted

00:32:55.520 | a little bit every time you go.

00:32:57.240 | So you will, like exercise, get a little bit stronger.

00:32:59.960 | So every time you go into the cold water for every time,

00:33:02.680 | you will be more exposed to it.

00:33:04.800 | You will feel more comfortable in the cold.

00:33:07.280 | So you're gonna build your adaptation,

00:33:09.940 | which happens on a metabolic level,

00:33:11.920 | which is gonna be the brown fat.

00:33:13.560 | So we have more activation of your brown fat.

00:33:15.760 | The mitochondria in the brown fat cells are gonna be,

00:33:19.700 | you have more of those,

00:33:20.920 | and they will be more efficient at heating you up

00:33:23.260 | because the body expects you to do this again.

00:33:26.640 | So you are prepared in a way.

00:33:28.680 | The capillaries in your skin

00:33:30.360 | will also become better at like constricting.

00:33:34.580 | So you will have a better shield of your body

00:33:37.660 | to prepare you for the next time.

00:33:40.380 | So you will become better at going into the cold water

00:33:44.020 | in that way.

00:33:44.860 | So the body makes these mechanism

00:33:46.960 | and changes your body in a way

00:33:48.800 | so you can expose yourself to the next time, right?

00:33:51.720 | And also you will have also your stress response

00:33:56.720 | will also be subside a bit.

00:33:59.280 | So you will have a less increase

00:34:01.260 | of your catecholamines with time.

00:34:05.520 | With time also you have,

00:34:06.960 | because of this activation of your brown fat or your muscles

00:34:10.920 | you will have an increase in your metabolism,

00:34:14.900 | which will then make your insulin sensitivity better.

00:34:18.680 | And this is shown in studies, for example,

00:34:21.500 | there was this interesting study I found

00:34:23.460 | just before I started my PhD,

00:34:25.640 | which was from Gieber Stomer et al from 2016,

00:34:30.560 | where they measured metabolism not on brown fat,

00:34:35.560 | but they measured insulin sensitivity

00:34:38.120 | in middle-aged men and women

00:34:40.900 | during one winter swimming season.

00:34:43.040 | So they were not very young like they were in my study,

00:34:46.520 | but they were middle-aged.

00:34:48.640 | And I think this is very interesting.

00:34:50.200 | So during these four or five months,

00:34:52.720 | they were winter swimming,

00:34:53.660 | they saw that they had a lower blood pressure

00:34:55.940 | after the season and they had a lower heart rate.

00:34:59.380 | And they also saw that they have

00:35:01.860 | better insulin sensitivity.

00:35:03.440 | And I think that is very interesting

00:35:05.460 | because if you can have a better insulin sensitivity,

00:35:08.880 | you can prevent lifestyle diseases.

00:35:11.440 | So, and with lower blood pressure,

00:35:13.640 | which is a very strong outcome also

00:35:16.040 | for telling how much inflammation you have in the body.

00:35:19.320 | And because it didn't measure brown fat,

00:35:22.600 | I figured that it could be, that was the missing link.

00:35:25.920 | That was one of the explanations

00:35:27.640 | to why we see this less inflammation in the body.

00:35:31.920 | So the longer outcomes, the long-term outcomes

00:35:35.720 | could be that you lower your blood pressure

00:35:37.760 | and have a lower heart rate.

00:35:39.880 | You also have a better insulin sensitivity

00:35:44.000 | and a better glucose balance,

00:35:45.940 | but that is shown in my study.

00:35:48.640 | I'd like to take a quick break

00:35:50.160 | and acknowledge one of our sponsors, Athletic Greens.

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00:36:07.280 | and the reason I still take Athletic Greens

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00:36:14.960 | Our gut is very important.

00:36:16.040 | It's populated by gut microbiota.

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00:37:00.080 | and the year's supply of vitamin D3K2.

00:37:03.300 | - And we'll get back to the insulin sensitivity

00:37:05.840 | and glucose balance.

00:37:07.240 | That's an impressive list of benefits.

00:37:09.920 | Blood pressure, of course,

00:37:12.820 | most people are aware of blood pressure and what it is.

00:37:15.420 | It's what they measure when we go to the doctor.

00:37:17.500 | And it's not very sexy nowadays, you know, blood pressure,

00:37:20.280 | people go, oh, you know, blood pressure.

00:37:21.640 | It's not, you know, people want to hear

00:37:22.980 | about the inflammatome and the microbiome

00:37:25.520 | and all of that stuff is really interesting.

00:37:27.000 | But I think that blood pressure

00:37:28.880 | doesn't get enough attention.

00:37:31.480 | And we have spoken to, on this podcast, to Dr. Peter Attia,

00:37:37.500 | who is an expert in longevity and healthspan

00:37:40.480 | and things of that sort.

00:37:41.700 | And I was surprised to learn,

00:37:43.480 | again, I shouldn't have been surprised,

00:37:45.100 | that the number one reason people die,

00:37:47.300 | worldwide, is cerebral vascular disease

00:37:50.000 | and cardiovascular disease.

00:37:51.600 | And there are basically three things

00:37:52.980 | on the list of things to address.

00:37:55.620 | One is not smoking, or vaping, by the way, not smoking.

00:37:59.960 | There are a few other things related to blood markers,

00:38:02.020 | ApoB and things of that sort.

00:38:03.500 | But then the big one is blood pressure.

00:38:06.020 | And so it's interesting because we don't think

00:38:08.240 | about blood pressure that much anymore

00:38:10.380 | as the kind of people interested

00:38:12.280 | in health optimization and health,

00:38:14.120 | but blood pressure is so vital to control.

00:38:16.960 | So it's wonderful to hear that deliberate cold exposure

00:38:20.140 | is one way to control blood pressure,

00:38:22.620 | I'm guessing in concert with other forms of exercise.

00:38:25.700 | Let's talk about brown fat.

00:38:29.260 | And if you're willing, I'd love to drill

00:38:32.180 | into brown fat at a deep level.

00:38:35.540 | Again, my understanding of this

00:38:37.700 | is far more elementary than yours, obviously.

00:38:41.280 | You're the expert.

00:38:42.380 | My understanding about brown fat

00:38:44.860 | is that it's located in specific areas of our body,

00:38:48.080 | maybe more widespread than when I learned in school.

00:38:51.660 | I thought it was, I was taught it was just at the clavicles

00:38:54.040 | in the back of the neck and upper back, but who knows?

00:38:56.580 | I learned that there's more of it when we're children,

00:38:59.160 | maybe more distributed throughout our body,

00:39:01.560 | and that it's rich in mitochondria.

00:39:03.740 | But what is so special about the brown fat?

00:39:06.560 | Like if we could just go into the biology

00:39:08.660 | of brown fat a little bit, what does it look like?

00:39:11.560 | You've measured it in human subjects.

00:39:14.000 | Where is it distributed really?

00:39:16.000 | Can it expand its distribution?

00:39:18.120 | Can we activate and expand the amount

00:39:20.500 | of brown fat as adults?

00:39:23.140 | And for those of you that are cringing already

00:39:25.600 | thinking we're talking about getting fatter,

00:39:27.340 | it's quite the opposite.

00:39:28.220 | We're talking about not subcutaneous fat,

00:39:30.520 | but fat located around the organs.

00:39:32.580 | But please educate me, tell me where I'm wrong,

00:39:35.660 | and expand my knowledge on brown fat.

00:39:39.040 | - Okay, yeah, you are not wrong,

00:39:40.700 | but it's true that there are more locations

00:39:45.020 | of the brown fat than we previously thought.

00:39:48.920 | There's this very nice study from 2017 by Leitner et al.

00:39:53.840 | where they had made these pettities overlays

00:39:57.620 | of their subjects, where they could see

00:40:00.420 | where in the body do we have brown fat,

00:40:03.020 | and where can we grow more brown fat, so to say.

00:40:06.760 | So the brown fat is very plastic,

00:40:10.640 | so it means that it can grow and it can decrease.

00:40:13.020 | And this is proven in studies where we have seen

00:40:16.140 | people with a failed cryocytoma,

00:40:19.940 | it's like a very specific cancer type,

00:40:23.100 | where from the '70s, where we can see

00:40:26.340 | that if they have this specific kind of cancer type,

00:40:30.700 | they have this tumor on the adrenal gland,

00:40:34.460 | so they have like a huge increase in noradrenaline.

00:40:37.820 | And because of that, they have this continuous activation

00:40:41.160 | of the brown fat, and they have grown a lot of brown fat

00:40:44.420 | in the whole body, I don't know where it's located

00:40:48.000 | in these six different places,

00:40:49.740 | but it is like very much compared to like normal people.

00:40:54.340 | And what they then see, what we learned from this study

00:40:57.800 | is that brown fat can apparently grow

00:41:00.840 | if you have an increase in noradrenaline in the body.

00:41:04.700 | It's not like you want that because when that happens,

00:41:07.020 | you have a high blood pressure,

00:41:08.220 | you don't want it chronically, right?

00:41:09.500 | You just want it on like a short amount of time,

00:41:12.280 | and then it can grow for a bit,

00:41:13.940 | but you don't want it chronically, of course not,

00:41:16.180 | but because it activates also your sympathetic nervous system

00:41:19.640 | so they have also showed they have high blood pressure,

00:41:22.580 | they had, they lost a lot of weight, of course,

00:41:25.520 | because this is activating your metabolism.

00:41:28.060 | So they found luckily that when they removed

00:41:31.940 | this benign tumor, that the brown fat

00:41:37.660 | decreases again to normal size and they gained weight again,

00:41:40.780 | and they had normal blood pressure.

00:41:42.820 | So the story ends well, but it's kind of like proof

00:41:45.960 | of concept of the brown fat can actually grow.

00:41:48.560 | So it's plastic in its way of like it can grow

00:41:52.020 | and it could decrease again.

00:41:53.180 | So that's very good, good studies to see

00:41:56.340 | what the body is capable of.

00:41:58.920 | But we don't, of course, want all that brown fat.

00:42:01.220 | We just want it to be, we just want to keep it actually

00:42:04.740 | and keep it activated because what we see in studies

00:42:07.660 | is also that after the age of 40, people,

00:42:11.460 | studies have shown that there is an association

00:42:14.880 | with having less brown fat, but increased obesity.

00:42:18.020 | So of course we don't know yet whether brown fat decreases

00:42:22.860 | with AIDS and therefore we get obese or we get obese

00:42:25.820 | and therefore we have less brown fat,

00:42:28.320 | but as brown fat is an insulin sensitive organ in our body

00:42:34.180 | and we get obese, just like the muscles get less sensitive,

00:42:39.180 | insulin sensitive, the brown fat does as well,

00:42:42.540 | and therefore it maybe decreases.

00:42:44.660 | It could be a theory that I think could be one of the reasons

00:42:49.100 | why we don't see that much brown fat in elderly people.

00:42:53.320 | Some have a lot, especially people working outside.

00:42:56.500 | There are studies showing this.

00:42:57.980 | - People who- - Who work outside.

00:42:59.900 | - Do physical work outside, farmers and, interesting.

00:43:04.060 | - Yeah, they expose themselves to it,

00:43:05.980 | so they'll just keep it in that way.

00:43:08.440 | - And I suppose we should clarify for people

00:43:13.260 | in case they don't know that insulin sensitivity

00:43:16.540 | is a very good thing, you want that.

00:43:18.300 | You want your cells to be sensitive to insulin.

00:43:20.440 | Insulin insensitivity is type two diabetes

00:43:23.620 | and is associated with obesity.

00:43:26.300 | So just a point of clarification there.

00:43:28.300 | Yeah, it's interesting to me, I usually work out at home,

00:43:33.220 | but I go to a gym once or twice a week if I can,

00:43:35.740 | because it's good if I see the outside world.

00:43:38.820 | And there are a few individuals at the gym who,

00:43:44.360 | they're not particularly large or muscular,

00:43:47.200 | but they are incredibly lean and their posture is great,

00:43:52.200 | presumably from the musculoskeletal work,

00:43:55.580 | and they're in their 70s and 80s.

00:43:59.860 | I mean, it's remarkable, right?

00:44:01.180 | And I know all the telltale signs of hormone augmentation.

00:44:04.540 | I'm very good at spotting that.

00:44:05.380 | There are a few telltale signs.

00:44:06.700 | I've talked about this on other podcasts,

00:44:08.060 | and that's not why they're fit.

00:44:12.420 | They're clearly of that look,

00:44:14.880 | and you see this outside the gym too, of course,

00:44:17.300 | for people that look like they've done

00:44:18.580 | a lot of physical labor their whole life.

00:44:21.540 | They're just moving a lot.

00:44:22.980 | They have strong hands and features,

00:44:25.700 | and they're not necessarily excessively lean,

00:44:30.060 | but you can tell that they've been using

00:44:32.020 | their musculoskeletal system.

00:44:33.980 | And I like to talk to these people and ask them like,

00:44:36.420 | not what are you doing now for your workout,

00:44:38.060 | but what did you grow up doing?

00:44:40.820 | And I would say,

00:44:42.140 | and obviously I haven't run statistics on this,

00:44:44.020 | but more than 75% of them respond

00:44:47.540 | that they grew up on a farm

00:44:49.900 | or that they did some sort of manual labor

00:44:53.520 | or were a postman or a postwoman

00:44:55.340 | or doing something where they moved a lot

00:44:57.740 | for their early years and throughout middle age.

00:45:00.720 | And most of them are now in retirement,

00:45:02.260 | but some of them are still working

00:45:03.940 | and they all still moving a lot.

00:45:06.540 | So the relationship between shiver and brown fat

00:45:10.280 | makes sense to me.

00:45:11.980 | But is it the case that as we're just moving around,

00:45:14.940 | I've heard of NEAT, non-exercise induced thermogenesis.

00:45:18.100 | So if we're just moving around

00:45:20.420 | that we are activating brown fat,

00:45:22.100 | or does there need to be this stressor?

00:45:24.100 | Does there need to be shiver

00:45:25.380 | and a cold stimulus or a heat stimulus

00:45:27.840 | to activate the brown fat?

00:45:29.160 | In other words, is just staying active enough

00:45:33.020 | or do we need to do some sort of temperature shock

00:45:36.680 | type thing like deliberate cold exposure?

00:45:39.680 | - Yeah, I think that is really good question

00:45:41.220 | because how, also why do we have this tissue?

00:45:44.940 | Then if it has to be extreme,

00:45:47.140 | then you can question what do we need this tissue for?

00:45:50.200 | But it seems that you can activate the brown fat

00:45:52.660 | with just a little bit of exposure to cold.

00:45:55.060 | So cold is the most potent stressor activator

00:45:58.260 | of our brown fat

00:45:59.700 | because it's our temperature regulating organ in our body.

00:46:03.140 | So first responder to that.

00:46:04.500 | So the muscles will be a little bit too late

00:46:07.100 | and therefore we have maybe these two kinds of tissues.

00:46:10.080 | So actually just exposing yourself or hand actually

00:46:14.380 | just to cold water.

00:46:15.240 | So studies have shown

00:46:16.860 | that if you just put your hand in cold water,

00:46:19.100 | not that you're gonna do that all day

00:46:21.680 | or every day or anything,

00:46:23.300 | it's not something you have to do,

00:46:26.220 | but it just shows that you can activate your brown fat

00:46:29.820 | just by getting a temperature change on your skin.

00:46:32.860 | So you can go outside and t-shirt.

00:46:34.340 | That's why also we were just talking about,

00:46:36.280 | well, people who works outside or move a lot

00:46:39.140 | or get out in and out of it,

00:46:41.180 | like changing the temperature of their body all the time,

00:46:44.240 | they will have more brown fat

00:46:46.060 | and activating that is gonna keep your metabolism higher

00:46:50.260 | and your insulin sensitivity.

00:46:51.860 | The study has also shown this.

00:46:53.300 | So the brown fat can be activated

00:46:56.020 | as soon as you just change your temperature in the skin.

00:46:57.900 | So going outside in a t-shirt, wearing cooling vests,

00:47:00.780 | also studies have shown this for 10 days,

00:47:02.980 | it's gonna also grow your brown fat.

00:47:06.300 | So you can get more brown fat

00:47:08.500 | if you expose yourself to the cold.

00:47:10.580 | You don't have to start in a cold shower.

00:47:13.460 | You don't have to start in a cold plunge

00:47:16.180 | if you're not really ready for that yet,

00:47:18.140 | but just exposing yourself to the cold wind

00:47:21.300 | has also shown to activate your brown fat.

00:47:23.980 | Or if you don't wanna be like in this awake state,

00:47:28.580 | then you can also just sleep in the cold

00:47:30.260 | and you won't notice it that much maybe,

00:47:32.060 | but studies have shown that

00:47:33.220 | if you sleep in 19 degrees Celsius,

00:47:35.760 | then you will activate your brown fat

00:47:39.500 | and you will grow your brown fat.

00:47:41.580 | So you have more of it.

00:47:42.820 | So this very nice studies from Hansen et al. from 2017

00:47:49.640 | showed that a group of subjects

00:47:52.400 | who slept in a room at 24 degrees,

00:47:55.280 | and then they made this PET/CT scanning

00:47:57.020 | to see how much brown fat do they have from the beginning,

00:48:00.040 | so what we call baseline.

00:48:01.900 | Then they measured again

00:48:03.580 | after a month of sleeping in 19 degrees,

00:48:06.460 | and they saw, I think it's remarkable,

00:48:08.340 | just one month at 19 degrees sleeping there.

00:48:10.780 | They had a duvet on,

00:48:12.560 | and they were still had clothes on when they were sleeping.

00:48:16.060 | - So they're under a cover, under a duvet?

00:48:17.380 | - Yeah, under a duvet, yeah, yeah.

00:48:19.460 | The subjects were sleeping at 19 degrees

00:48:21.080 | for one month, had increased insulin sensitivity.

00:48:24.020 | The next month, they slept at 24 degrees,

00:48:26.420 | they measured this again,

00:48:27.480 | and they had decreased actually a little bit,

00:48:30.080 | and then they slept at 27 degrees.

00:48:32.380 | So quite warm room actually for the fourth month,

00:48:36.820 | and they saw even less activation of the brown fat

00:48:40.200 | and also insulin sensitivity.

00:48:41.900 | So it seems that you can expose yourself

00:48:44.780 | and pretty rapidly the brown fat will respond to this

00:48:48.860 | because it's so sensitive to noradrenaline, right?

00:48:51.980 | So if you keep exposing yourself to a little bit of cold,

00:48:55.840 | you will also get a little bit adapted to it,

00:48:57.720 | but that's because the brown fat

00:48:59.860 | has grown these more mitochondria in the cells.

00:49:02.900 | So these small energy fabrics

00:49:04.660 | that's gonna activate the cells,

00:49:06.240 | and that's gonna take up glucose and fat from the,

00:49:09.140 | fatty acids from the bloodstream

00:49:11.260 | to keep the thermogenesis up.

00:49:14.540 | And that's gonna clear up some sugar,

00:49:16.780 | and it's gonna clear up so in the bloodstream

00:49:19.500 | and some fat as well.

00:49:20.700 | So the brown fat can in that way,

00:49:22.940 | decrease our unhealthy fat, which is the white fat.

00:49:27.100 | And the white fat is what we don't want too much of,

00:49:30.140 | but we still need some, of course.

00:49:32.020 | And it's our energy storage.

00:49:34.620 | So it's very important that it's there.

00:49:36.320 | We just don't need a lot of it.

00:49:38.220 | So on our thighs and also around our inner organs,

00:49:41.460 | that's where it's located.

00:49:43.380 | So if we can have activation of the brown fat

00:49:46.300 | just by going out in the cold

00:49:47.820 | and just by sleeping in a cold room,

00:49:49.700 | or if you have courage for it,

00:49:51.460 | you can go out and expose yourself in a cold plunge.

00:49:54.800 | Cold showers is also gonna do the trick.

00:49:57.220 | So you can do different variations of this.

00:50:00.300 | Just exposing yourself to various temperatures

00:50:02.820 | is gonna activate the brown fat

00:50:04.340 | because it was involved to keep us

00:50:06.960 | in a perfect homeostatic balance regarding temperature.

00:50:10.620 | So to keep us alive.

00:50:12.540 | - Incredible.

00:50:14.020 | I wanna just get a clarification around this 19 degrees

00:50:16.860 | Celsius room that they're sleeping in.

00:50:19.420 | So they're under a comforter, a duvet,

00:50:21.920 | and you mentioned they had clothes on.

00:50:24.780 | The room is 19 degrees Celsius,

00:50:26.980 | but the temperature underneath their blanket

00:50:28.900 | might not be 19 degrees Celsius.

00:50:30.380 | So presumably it's the cold on their face

00:50:32.620 | that's activating the increase in brown fat

00:50:37.480 | that was observed.

00:50:38.560 | Is that a reasonable expectation?

00:50:40.780 | - I think so, yeah.

00:50:41.980 | Because you have so many co-receptors in your face.

00:50:45.700 | So actually it's enough.

00:50:47.540 | And I think it corresponds very well

00:50:49.380 | with the studies showing that you can activate

00:50:51.420 | the brown fat just by putting a hand

00:50:52.960 | into a bucket of cold water.

00:50:55.060 | And I did this experiment myself in my studies

00:50:58.340 | just to see how well did they respond to cold water.

00:51:02.340 | So it was four degrees Celsius cold water for four minutes.

00:51:06.820 | And then I just measured blood pressure and heart rate

00:51:09.180 | to see do they have like an activation of this.

00:51:12.100 | I actually also measured the brown fat

00:51:13.860 | during this cold exposure for four minutes

00:51:17.100 | with an infrared thermography camera

00:51:19.380 | to see can I see that the brown fat is activated.

00:51:22.660 | And just to go back to the location of the brown fat.

00:51:26.860 | So usually you cannot really see activation

00:51:29.540 | of your brown fat because it's located centrally

00:51:32.780 | in your, around your central nervous system.

00:51:36.620 | And the biggest depot, as you mentioned before,

00:51:39.780 | is up here under the clavicular bones.

00:51:43.320 | So, and very close to the skin surface.

00:51:47.260 | And because it's so close to the skin surface,

00:51:49.460 | I could measure it with this very expensive camera.

00:51:52.020 | And it's not very feasible for people to go home

00:51:54.100 | and do this.

00:51:55.420 | Don't because it takes a lot of practice, I can tell.

00:51:58.940 | But we measured the brown fat with this.

00:52:01.580 | And I could see that after a few minutes

00:52:04.100 | that the activation was there an increase in temperature

00:52:07.460 | arose from that activation, just four minutes.

00:52:10.660 | So it's very rapid.

00:52:12.040 | And I'm also measured in my study,

00:52:14.420 | how deep was the brown fat under your skin?

00:52:17.380 | So it's very close to the surface,

00:52:19.300 | which also shows that it needs to be there

00:52:22.300 | to heat you up and heat your inner organs.

00:52:25.780 | - Well, I'm delighted to hear all of this

00:52:27.840 | and I'll tell you why.

00:52:29.060 | One is by way of anecdote.

00:52:30.660 | I mentioned a little bit earlier that as an undergraduate

00:52:33.060 | I worked in a lab that studied thermogenesis

00:52:35.160 | and we were doing that in animals,

00:52:36.420 | but we had this room that was very cold.

00:52:38.740 | The whole room was cold.

00:52:40.220 | The guy who I worked for at the time,

00:52:42.220 | and I'm Harry Carlisle is a very accomplished physiologist.

00:52:44.640 | He came from this lineage.

00:52:46.080 | I don't know if this literature is still discussed much,

00:52:48.700 | but it's a beautiful literature from Rothwell and Stock.

00:52:52.380 | They were the ones who discovered

00:52:54.360 | non-exercise induced thermogenesis.

00:52:56.320 | The fact that people bounce,

00:52:57.500 | who bounce their legs a lot and move around a lot

00:52:59.540 | and have a lot of kind of stochastic movement burn

00:53:03.300 | up to 1,800 calories more per day

00:53:07.700 | than people who sit more still.

00:53:09.500 | - Fascinating. - Incredible.

00:53:10.900 | Just incredible.

00:53:12.420 | I don't think that work gets as much attention

00:53:15.040 | as it deserves.

00:53:15.880 | Published in journals like Nature, so very fine journals.

00:53:19.560 | But in any event, one of the things that I noticed

00:53:24.160 | when I started working in that laboratory

00:53:25.720 | was that I was cold because the room was cold.

00:53:28.120 | And Dr. Carlisle, Harry, said,

00:53:31.560 | "Well, the key is to wear a t-shirt in here

00:53:33.540 | "for about two or three days and then you will cold adapt."

00:53:37.460 | I thought, well, wouldn't I want to put on a hoodie

00:53:39.580 | and get warm in there so I was comfortable?

00:53:41.180 | And he said, "No, actually what you want to do

00:53:43.140 | "is get yourself uncomfortably cold,

00:53:44.580 | "activate your brown fat."

00:53:45.900 | And indeed, when I did that,

00:53:47.940 | I think it was just two days

00:53:49.260 | of being in that cold environment.

00:53:50.520 | Then I could come back on the third day

00:53:51.740 | and be perfectly comfortable

00:53:53.280 | because the brown fat had expanded

00:53:56.900 | or added mitochondria or both.

00:53:59.440 | And I was perfectly comfortable in that environment.

00:54:01.400 | I also got very, very lean in those days and weeks.

00:54:05.760 | Now, I've never been somebody who's very lean,

00:54:08.000 | nor am I somebody who carries a lot of excess adipose tissue.

00:54:10.680 | I'm kind of somewhere in the middle.

00:54:11.980 | I'm sure I could adjust that with feeding if I want to.

00:54:14.600 | But it was striking what a powerful effect it had

00:54:18.360 | on my entire system of thermal regulation.

00:54:21.120 | And one of the things that I also delighted in

00:54:24.160 | when Cell Reports Medicine published your study

00:54:27.660 | is they had an accompanying press release

00:54:30.640 | that went out to those of us that receive press releases.

00:54:33.460 | And it described a saying in Scandinavia,

00:54:37.780 | which is essentially,

00:54:39.280 | I'm not going to attempt to speak Danish,

00:54:41.940 | even though I have much of my family is in Denmark,

00:54:44.500 | believe it or not, from Denmark.

00:54:46.220 | We have a lot of Danes in my family.

00:54:48.400 | I won't embarrass myself by trying to speak Danish

00:54:50.260 | as I did before the microphones were rolling.

00:54:53.300 | But that there's a saying that I think essentially

00:54:58.300 | translates to in the fall, when you're approaching winter,

00:55:03.380 | you want to actually wear fewer layers,

00:55:06.040 | not bundle up when you go outside

00:55:07.700 | so that you can prepare yourself for the cold of winter

00:55:10.900 | and be able to heat yourself up using your brown fat.

00:55:13.000 | And that in the spring, as the temperatures are warming,

00:55:16.840 | rather than removing layers, you want to wear more layers

00:55:20.100 | in order to be a little bit uncomfortably warm

00:55:23.140 | so that in the heat of the summer,

00:55:25.340 | you're better at cooling your body.

00:55:27.260 | Do I have that right?

00:55:28.100 | And maybe, do you know the saying,

00:55:29.300 | and would you be willing to share it?

00:55:30.540 | Only the Swedes and Danes will be able to understand.

00:55:34.260 | Maybe the Norwegians too.

00:55:36.680 | If you don't know it, that's okay.

00:55:38.560 | - Yeah, so I know the concept of it because we say it,

00:55:42.820 | you should wear less before winter and more before summer.

00:55:47.820 | - Oh, well, there it is in English,

00:55:49.040 | so it doesn't have to be esoteric, but okay.

00:55:51.900 | - Yeah, and you're completely right.

00:55:53.500 | And I think this is just something that we know

00:55:56.520 | in the Scandinavian countries.

00:55:58.000 | I think that we intuitively know this,

00:56:01.080 | but if we just go back a little bit in history,

00:56:04.040 | I think that around the 1950s,

00:56:07.780 | the Russian government went out and said,

00:56:11.280 | well, we should do something about the tuberculosis

00:56:14.040 | and pandemic or epidemic, the worst at this time.

00:56:18.140 | So they wanted to have the people be more resilient

00:56:23.140 | to the cold and also increase our immune system.

00:56:27.820 | So in Scandinavia, and actually also in Russia,

00:56:31.340 | we put our babies outside to sleep in the prom.

00:56:35.300 | And that is like to also to get more resistant to the cold,

00:56:39.860 | but also to increase our immune system.

00:56:42.260 | And we still do that in Denmark.

00:56:43.660 | So we- - Do you really?

00:56:45.080 | - Yeah, we do.

00:56:45.920 | - Babies are taken out in the cold?

00:56:47.060 | - In the snow, in frosty rain, everything.

00:56:50.580 | My two boys have been sleeping out in winter

00:56:54.420 | of at least their first many three, four, five years,

00:56:58.400 | because it's like very good for them.

00:57:00.380 | And they get a better immune system

00:57:03.320 | and get resilient to the cold so they will have less colds.

00:57:07.220 | And also they run around in a t-shirt when it's super cold

00:57:10.860 | because they have activated all the brown fat.

00:57:12.800 | I didn't understand at that time, I must say,

00:57:15.140 | but I kind of like intuitively also knew

00:57:17.500 | because we have inherited this way of doing things

00:57:21.300 | with our culture.

00:57:22.620 | So, and I have heard people coming from the US saying,

00:57:25.900 | Danes are crazy.

00:57:26.820 | They put the babies outside in proms and leave them there.

00:57:29.280 | And then they go inside and drink coffee on the cafe.

00:57:31.980 | [both laughing]

00:57:33.300 | - Well, I don't think Danes are crazy.

00:57:34.580 | I adore the Danes, they're amazing culture and people.

00:57:39.580 | I'm so fortunate to have family members from Denmark,

00:57:43.500 | but I did notice.

00:57:44.380 | So when we were in Copenhagen,

00:57:46.180 | and I know we saw you there not long ago, that was June,

00:57:51.180 | the water in the harbor was cold,

00:57:55.620 | even though the Pacific is close to here,

00:57:57.580 | which is very cold, it felt pretty cold,

00:58:00.460 | but it was summertime-ish.

00:58:02.600 | So people were in summertime mode, right?

00:58:06.620 | T-shirts and shorts and things of that sort.

00:58:08.900 | But it did strike me that people in Copenhagen

00:58:13.720 | are dramatically fitter than they are in the United States.

00:58:18.720 | I mean, first of all, everyone's bicycling everywhere.

00:58:21.980 | - Yeah.

00:58:23.340 | - Not many people wearing sunglasses.

00:58:25.420 | So trying to extract as much photon energy

00:58:27.940 | from the sun as possible, which I support.

00:58:30.420 | As everyone knows, I'm a big fan of getting sun.

00:58:33.380 | But also when we did see swimmers,

00:58:36.200 | they were swimming in this cold water and like it was nothing

00:58:41.260 | and the range and age of the swimmers was remarkable.

00:58:46.220 | You saw the kind of fit triathlete looking types,

00:58:48.900 | but also young kids, like really young kids.

00:58:51.260 | And then people probably in their,

00:58:52.400 | again, their 70s, 80s, maybe even 90s, really remarkable.

00:58:57.400 | Vastly different than what you see

00:58:59.020 | if you go to the ocean here in Los Angeles or elsewhere.

00:59:03.120 | So yeah, you Scandinavians are onto something with this.

00:59:07.200 | I'd like to take a quick break

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01:00:16.920 | I'd like to talk about your study.

01:00:19.100 | If you could give us a little bit of the backdrop

01:00:22.020 | about what motivated that study,

01:00:24.060 | and then walk us through what you did,

01:00:28.500 | who the subjects were, what you had them do,

01:00:31.940 | what you measured, in as much detail

01:00:34.660 | as you would like to share,

01:00:35.480 | because I think it's such an important,

01:00:37.940 | even fair to say landmark study,

01:00:40.900 | because it also explored not just cold, but sauna,

01:00:45.100 | and the co-use of cold and sauna

01:00:48.700 | as a way to probe metabolism and brown fat

01:00:51.740 | and other markers as well.

01:00:53.380 | And as you do this, I'm hoping at some point

01:00:55.940 | that you might tell us some of the observations

01:00:58.220 | that you might've made that interested you

01:01:00.540 | that perhaps were not in the paper,

01:01:02.660 | 'cause that's one of the great benefits

01:01:03.900 | of sitting across from somebody who did the work in detail.

01:01:06.500 | So yeah, if you could tell us about your study

01:01:08.980 | and what you did and what you discovered.

01:01:12.380 | - Thank you for that question, Andrew.

01:01:13.860 | I love to also explain a little bit what did we do,

01:01:17.940 | because when people read this kind of paper,

01:01:20.380 | they just see the numbers.

01:01:21.620 | They don't see what happened before that.

01:01:23.980 | And human studies are very different from my study.

01:01:27.320 | My study, you can do a knockout of something,

01:01:29.320 | and then everything is perfectly matched and controlled.

01:01:32.660 | Doing human studies is very far different from that,

01:01:35.840 | because people are different even in the groups.

01:01:38.800 | So yeah, but when I started this research in 2016,

01:01:43.800 | I did not really know what the brown fat was.

01:01:48.140 | So I started reading up on all this,

01:01:49.940 | and I was very interested in preventive medicine.

01:01:53.600 | Also the studies that I did before brown fat

01:01:56.740 | was also like very much in the preventive side,

01:02:00.180 | like how can we, that was about something else,

01:02:02.220 | but the sweet tooth and how can we lower our sweet tooth

01:02:06.080 | and stuff like that.

01:02:06.920 | So, but after that, I wanted to do something new.

01:02:09.480 | So I looked into the brown fat,

01:02:11.360 | got hired in this fantastic research group

01:02:13.960 | where they, it's a cell group.

01:02:15.840 | So they mostly did cell studies

01:02:17.840 | and they didn't have anyone to do a human study yet.

01:02:20.880 | But they really wanted me to do that.

01:02:24.620 | So I read upon a lot of research

01:02:27.340 | about how does the brown fat get activated,

01:02:30.320 | what have been done already.

01:02:31.680 | And I mentioned the paper before with sleeping in the cold.

01:02:34.640 | I found that particular paper very fascinating.

01:02:37.720 | And that was also where at that time I was like,

01:02:40.880 | okay, so cold exposure as an intervention

01:02:43.820 | of sleeping in the cold could be a good thing

01:02:46.060 | to go out and say, well, people do this.

01:02:48.440 | But on the other hand is, first of all, it was already done.

01:02:52.200 | That was one thing.

01:02:53.840 | But the other thing was like,

01:02:55.000 | well, I wanted to see if we can do some kind of activity

01:02:58.840 | so we can have people move also, go and do something,

01:03:03.040 | do something together or whatever.

01:03:05.040 | And the cold made us think about,

01:03:08.240 | well, what about winter swimming?

01:03:10.080 | And it was kind of like a bit of a joke in the beginning.

01:03:12.280 | It's like winter swimming,

01:03:13.360 | yeah, it's gonna activate the brown fat, right?

01:03:15.960 | But when we read the literature,

01:03:18.000 | we couldn't really find anything about activation

01:03:21.160 | of the brown fat with cold water

01:03:23.280 | besides hand in a bucket of cold water.

01:03:25.840 | That really, that was already there.

01:03:28.120 | So we were just thinking, okay,

01:03:29.400 | so it should be very potent activation of the brown fat

01:03:33.400 | if it's cold water, but very different from cold air.

01:03:37.680 | So it was kind of also a new thing we were going into

01:03:41.160 | and we knew that we were gonna do

01:03:43.320 | like a more of a proof of concept study

01:03:47.200 | at the beginning of it because it was like winter swimmers

01:03:50.680 | must in theory activate the brown fat, right?

01:03:54.880 | But we kind of didn't really know

01:03:56.760 | was this kind of stressor too much, too little,

01:03:59.880 | or what will happen actually.

01:04:01.800 | But we had this idea about,

01:04:03.160 | well, we always say that cold water and winter swimming

01:04:06.080 | will activate your metabolism,

01:04:07.560 | but do we know if it does that?

01:04:10.340 | No, we don't.

01:04:11.220 | And while this idea was a little bit fun at the beginning,

01:04:18.000 | we kind of accepted it.

01:04:18.840 | It was like, okay, let's just try this out.

01:04:21.040 | But because we didn't have the funding for it,

01:04:22.760 | we was like, okay, let's do a proof of concept study.

01:04:26.200 | Let's go with a small number,

01:04:28.000 | but enough to see a difference between the groups.

01:04:32.000 | So the power calculation of that study is done

01:04:35.320 | on what we know from PET CT scannings of the brown fat.

01:04:40.320 | So that's the main outcome of that, of course.

01:04:43.020 | So, and we wanted to go a little bit small

01:04:46.640 | on the numbers of participants

01:04:48.520 | because we wanted to dig a little bit deeper

01:04:50.780 | into the different mechanisms

01:04:52.400 | and also redo some of the days.

01:04:55.920 | So I really wanted to do that

01:04:57.320 | to see if I can replicate also the findings.

01:05:00.040 | And that's gonna take a lot of funding,

01:05:02.860 | but it's also gonna take a lot of time to do it.

01:05:05.840 | So the proof of concept was just going small,

01:05:08.420 | but looking at different mechanisms.

01:05:10.420 | We also took fat biopsies, for example,

01:05:14.440 | and looked at the white fat

01:05:15.520 | to see if there was any differences between the groups

01:05:17.960 | before and after and stuff like that.

01:05:20.120 | So that's kind of like how it started.

01:05:22.000 | And the first year was like a field study for me.

01:05:25.280 | So I was not a winter swimmer when I started this.

01:05:27.640 | It was just- - Oh, really?

01:05:28.720 | - No, I wasn't at all.

01:05:30.940 | I would say I was a bit afraid of the cold myself,

01:05:34.400 | bit of a cold sissy,

01:05:35.800 | always cold having big socks on

01:05:38.200 | and sweaters and stuff like that.

01:05:39.480 | So I was like, I am so comfortable.

01:05:41.720 | I'm just like everybody else, very comfortable.

01:05:43.920 | I like being completely temperature neutral,

01:05:47.180 | but I started like playing with the storage,

01:05:48.800 | like, well, if this is so healthy in theory,

01:05:52.040 | I should not pack myself up.

01:05:54.320 | I should start not doing that.

01:05:56.500 | Yeah, but the first year observation

01:05:59.700 | of winter swimmers on the jetty,

01:06:01.800 | they kind of joked about it and say,

01:06:03.240 | "Come on, Zainu, you need to try this.

01:06:04.960 | You cannot study this unless you have tried it."

01:06:08.320 | And I was like, "Ha ha, very funny.

01:06:10.020 | Of course I can do that." (laughs)

01:06:12.280 | But I couldn't.

01:06:13.600 | I read the literature.

01:06:14.840 | I understood in theory what happens

01:06:17.280 | when you go into cold water,

01:06:18.640 | but I completely understood it when I first tried it.

01:06:22.700 | The first few times, not so funny, it felt painful.

01:06:26.340 | It was just like running too long after a long break

01:06:30.980 | and your muscles hurt the day after, right?

01:06:33.160 | You completely regret that you took that extra mile.

01:06:36.400 | - What about, when you say uncomfortable,

01:06:37.880 | you mean uncomfortable when you got in

01:06:40.000 | and when you were in or uncomfortable afterwards?

01:06:42.400 | Because I find that on rare occasions,

01:06:47.240 | well, I should just, full disclosure,

01:06:48.920 | I do deliberate cold exposure every morning

01:06:52.240 | for about a minute to two minutes in a cold plunge.

01:06:54.900 | There are days that I miss,

01:06:56.900 | but when I'm at home, I do that.

01:06:58.460 | And when I travel, I do a cold shower.

01:07:00.580 | I do finish with a warm shower. (laughs)

01:07:03.100 | So, and we'll talk about

01:07:04.540 | why that's probably not the best idea.

01:07:06.400 | But, and I've been doing it for some years now, on and off.

01:07:11.400 | But, so just full disclosure, I'm a devotee

01:07:14.460 | and I have family members that hate the cold,

01:07:19.260 | but have gotten into it and are starting to like it.

01:07:22.060 | But they don't, and I don't necessarily like the experience

01:07:25.780 | in the cold water, but I love the way I feel when I get out.

01:07:29.900 | And I'm 100% on that statement

01:07:33.320 | about loving it when I get out.

01:07:34.940 | Occasionally, it feels good to be in there.

01:07:36.460 | It feels invigorating.

01:07:37.780 | And I think I've learned to control the gas reflex

01:07:39.860 | and the hyperventilation.

01:07:41.000 | And I just have told myself what we know,

01:07:43.040 | which is that the forebrain struggles to engage

01:07:45.860 | for the first 20 or 30 seconds.

01:07:47.360 | But if you can get past that wall,

01:07:49.200 | it's far easier to push through.

01:07:52.440 | But when you say that it was really uncomfortable,

01:07:55.320 | do you mean the experience of getting in

01:07:57.040 | or you also felt lousy afterward?

01:08:00.240 | - Yeah, and very important to clear that out.

01:08:03.380 | I only felt very uncomfortable doing it at the moment.

01:08:06.680 | But afterwards, the first time I went with a group

01:08:10.880 | and actually my husband was there as well,

01:08:13.160 | because I really wanted someone I knew coming along

01:08:17.200 | because it's very normal if you haven't done this

01:08:19.080 | before you feel a little bit anxious about it.

01:08:21.680 | This is shown in studies as well,

01:08:23.000 | because blood pressure and heart rate goes up

01:08:24.840 | in those who are new to this kind of activity.

01:08:28.120 | So I was a little bit anxious about it.

01:08:30.500 | So it was really uncomfortable just doing it.

01:08:32.960 | But afterwards, as soon as I got up, I felt fantastic.

01:08:37.080 | And we went into the sauna and I did three rounds

01:08:40.160 | because I just loved it.

01:08:42.040 | I loved the feeling afterwards,

01:08:43.680 | because you have all these neurotransmitters

01:08:45.640 | going in your brain and you feel more positive.

01:08:47.840 | You feel, I feel invigorated, I had so much energy.

01:08:51.160 | And I could totally see why people would do this

01:08:55.360 | to get energy throughout the day,

01:08:57.040 | because I definitely had that.

01:08:58.580 | I didn't have to do three dips to get that.

01:09:02.040 | I think one would be enough.

01:09:03.440 | And I often do that also now today.

01:09:05.780 | I do one dip, sometimes I do two or three dips in one round,

01:09:10.780 | you can say in one day.

01:09:12.080 | But often it's like just one or two times a week.

01:09:15.260 | For me, that is enough to get that energy

01:09:18.620 | and to get that positive feeling.

01:09:20.860 | And I think that that is also why

01:09:23.740 | I put up my study in that way.

01:09:26.460 | I wanted to study the lowest dose, you can say,

01:09:30.540 | the lowest amount that we can get away with,

01:09:32.820 | but still see health benefits.

01:09:36.280 | So what I observed there on the jetty

01:09:38.700 | was that some did it a long time.

01:09:40.460 | They were in the water for a very long time.

01:09:42.260 | And to me, it seemed maybe a little bit extreme.

01:09:44.660 | - Could you give me an example of a long time?

01:09:46.380 | - Well, so maybe they were like really swimming

01:09:48.780 | and they could be 20 minutes or half an hour.

01:09:51.020 | - That's a long time.

01:09:51.860 | - That's a long time.

01:09:52.680 | And there was like ice and people who came up.

01:09:55.460 | I mean, I just didn't really feel that this is something

01:09:59.820 | that I wanted to go out and recommend to people

01:10:02.420 | after my PhD. - You don't want

01:10:03.260 | any research subject dying either,

01:10:05.340 | because if you're not adapted, I mean,

01:10:06.900 | people can do that.

01:10:08.540 | Also a 20 minute cold shower or 20 minute cold plunge.

01:10:12.100 | I know people do it, but it's probably not a good idea.

01:10:14.900 | - No, probably not.

01:10:15.820 | It's gonna exhaust your cells and make them age too fast.

01:10:19.780 | So exactly, that's when you pass that hermetic stress,

01:10:23.780 | the healthy stress level, that's what is happening.

01:10:26.420 | The quite opposite is almost chronic stress

01:10:29.580 | actually in the cells.

01:10:30.640 | Well, what happened then was that I found out

01:10:34.280 | if I want to have this protocol get through ethical comity,

01:10:38.420 | I really needed to go like very like sleek

01:10:41.740 | with the not too long and make sure

01:10:44.460 | that they were also very healthy

01:10:46.060 | and to get approval, of course, of this study.

01:10:49.860 | But what I did was to recruit winter swimmers

01:10:53.900 | who already have been swimming for two or three seasons.

01:10:56.580 | And I just observed them.

01:10:58.100 | I said, I'm not gonna do an intervention study yet.

01:11:01.160 | I did that after, but I wanted to do like a proof of concept

01:11:05.140 | where they were already adapted to the cold

01:11:07.740 | and then compare them to a match control group

01:11:10.460 | who were matched on, you can say diet.

01:11:14.260 | So were they vegetarian or not?

01:11:17.620 | And one of them was in each group.

01:11:20.420 | Also- - They weren't

01:11:21.260 | all vegetarians. - No, no, no.

01:11:22.660 | Just one in each group, yeah.

01:11:23.900 | - I was gonna say with all the amazing fish and meat

01:11:25.820 | in Denmark, I'd have a hard time being a vegetarian.

01:11:29.380 | The breads are amazing, the fruits and vegetables too.

01:11:31.220 | But okay, so there were a couple of vegetarians

01:11:32.900 | in each group. - Yeah, one in each, yeah.

01:11:35.460 | And they were matched- - token vegetarian.

01:11:37.620 | I have family members who are vegetarian,

01:11:39.120 | so I'm just poking fun. - Yeah, but they were matched

01:11:43.440 | on different things.

01:11:44.380 | So what we usually match them on is also BMI.

01:11:47.740 | We chose one gender in this study

01:11:51.980 | and we would always choose both men and women normally,

01:11:55.620 | but we do see that there are different brown fat levels

01:12:00.440 | depending on gender.

01:12:01.460 | So women have more brown fat than men.

01:12:03.500 | - Really? - Yeah.

01:12:05.180 | - Interesting. - Yeah.

01:12:06.420 | I think it's interesting.

01:12:08.220 | - That deserves study.

01:12:09.800 | - Yeah. - Yeah.

01:12:10.700 | - Why actually?

01:12:11.760 | I think it's interesting because women are also smaller.

01:12:15.060 | So in size, mass, right?

01:12:17.140 | But they also have a lower peripheral temperature,

01:12:21.040 | especially on hands and ears and-

01:12:22.860 | - Is that right?

01:12:23.700 | That's documented? - Yeah.

01:12:24.780 | - Women do run colder than men?

01:12:26.680 | - Yeah, and there's also- - Physiologically,

01:12:28.640 | I didn't say psychologically.

01:12:30.180 | - No, no, no.

01:12:31.120 | - We won't go to the psychological cold heat.

01:12:33.600 | - Yeah, that's different, something else.

01:12:35.960 | That's a different podcast. - Yeah, another time.

01:12:39.360 | So women are just colder physically.

01:12:42.100 | So on hands and ears, it's measured on that

01:12:44.840 | and feet as well, so compared to men.

01:12:48.840 | And men have bigger hearts than women

01:12:51.660 | and they can pump out more blood,

01:12:54.320 | peripheral than in a woman's body.

01:12:57.200 | So that could be an explanation

01:12:59.160 | for the colder hands, for example.

01:13:01.280 | Thermocompatible state is also different between genders.

01:13:05.080 | So men are more comfortable at 22 degrees Celsius

01:13:09.760 | and women are thermo-comfortable at 24 degrees Celsius.

01:13:14.080 | And this is- - Okay, so the thermostat

01:13:15.300 | wars of home have been now validated.

01:13:18.000 | - Yes, yes, there's a study- - Two degrees Celsius.

01:13:20.280 | By the way, prior to starting recording,

01:13:24.240 | I made the executive decision

01:13:25.720 | that we were going to go with Celsius

01:13:27.360 | throughout the podcast,

01:13:29.200 | because the majority of the world uses Celsius.

01:13:32.640 | So for those of you that think in Fahrenheit,

01:13:35.440 | the internet is your friend in making those conversions.

01:13:38.640 | So we're sticking with Celsius.

01:13:39.940 | So men tend to be thermo-comfortable at 22 degrees Celsius,

01:13:43.620 | women at 24.

01:13:46.260 | Okay, interesting.

01:13:47.640 | - It explains a lot about also some arguments in the homes

01:13:51.360 | where men are turning down the heater

01:13:53.020 | and women are turning up the heater and they cannot really.

01:13:56.080 | So it's really, I'm on both sides here.

01:13:58.720 | I understand the men, we understand the women,

01:14:00.680 | but there is a difference there.

01:14:02.760 | Which was also one of the reasons

01:14:04.760 | why we in this proof of concept study chose one gender.

01:14:08.420 | So it is not like only because we wanted to study men.

01:14:11.320 | It was just to see,

01:14:12.440 | to eliminate all the confounding factors

01:14:16.080 | which could have an impact on our results.

01:14:19.680 | So that was one of the reasons.

01:14:22.460 | But also because we, yeah,

01:14:25.940 | so women have more brown fat than men,

01:14:28.720 | and otherwise we would have to do four groups

01:14:31.040 | or something like that.

01:14:32.040 | And not having funding yet,

01:14:33.360 | we were like, okay, we need to do just one group,

01:14:36.760 | just a control group,

01:14:38.100 | and then a group who were already winter swimmers.

01:14:42.200 | So I recruited winter swimmers

01:14:43.740 | who have been swimming for two to three seasons

01:14:46.040 | because I wanted them to be already adapted,

01:14:49.320 | but not going too long in the water.

01:14:52.260 | So they told me, I did a lot of screening here, of course,

01:14:56.280 | beforehand and interviews to see, to ask them,

01:14:59.080 | how much do you do and how long do you stay in the water?

01:15:03.460 | And I monitored how long did they stay in the water

01:15:06.760 | and recruited based on that they only did

01:15:10.440 | like two to three times per week.

01:15:11.960 | It seems reasonable for Denmark, at least, to do that.

01:15:16.960 | And they stayed only in the water for one to two minutes.

01:15:20.880 | So the coast subsides very quickly

01:15:23.260 | and you will get this activation of your rest and digest

01:15:26.820 | system, which is your parasympathetic nervous system.

01:15:29.420 | So the other branch of your autonomous nervous system.

01:15:34.040 | And you get that activation

01:15:35.720 | because you submerge into cold water.

01:15:37.860 | And when you do that,

01:15:39.020 | you have an activation of your diving response,

01:15:42.140 | and that's gonna slow down the, you can say,

01:15:45.620 | the consumption of oxygen also in your body,

01:15:48.900 | and that's gonna slow down your heart rate.

01:15:50.960 | - Could I pause you on this?

01:15:51.900 | 'Cause I've heard this before,

01:15:53.180 | that when we get into cold water, shower or immersion,

01:15:56.800 | we get this sympathetic autonomic response.

01:15:59.040 | So increased blood pressure, increased heart rate,

01:16:00.980 | release of norepinephrine from the locus coeruleus

01:16:03.640 | in the brain, release of adrenaline, dopamine,

01:16:07.540 | adrenaline from the adrenals,

01:16:10.280 | dopamine presumably within the brain,

01:16:12.120 | but that the parasympathetic response is activated

01:16:17.380 | when we put our face into cold water or go underwater.

01:16:21.260 | And that's a calming relaxation response.

01:16:24.960 | So this brings us back to,

01:16:27.060 | I don't want to take us off track

01:16:28.160 | from you describing the study,

01:16:29.220 | but this brings us back to the first question,

01:16:31.340 | which is if I go completely underwater for a moment

01:16:34.260 | when I start my cold plunge,

01:16:36.060 | does that change the physiological outcome

01:16:38.580 | as compared to if I just submerge myself up to the neck?

01:16:41.540 | And actually nowadays there seems to be

01:16:43.340 | a little bit of a movement online

01:16:45.420 | of people putting a bowl of ice water on their countertop

01:16:48.640 | and submerging their face into it.

01:16:50.320 | Did you see this?

01:16:51.160 | I've seen more and more posts about this.

01:16:53.360 | So can you just touch on what the dive reflex is

01:16:56.320 | and why it perhaps activates the parasympathetic response,

01:17:00.780 | this calming response?

01:17:02.840 | - Well, so the diving reflex is activated

01:17:05.320 | when you submerge into cold water.

01:17:07.620 | - Even just to the neck?

01:17:09.020 | - Yeah.

01:17:09.860 | - Or I thought you had to get your face under.

01:17:11.620 | I'm not arguing different.

01:17:12.940 | You're the expert.

01:17:13.780 | I just want to, yeah.

01:17:14.700 | - I haven't really, I haven't read that.

01:17:17.200 | I've just seen that you can activate your diving response

01:17:21.980 | as soon as you go underwater with your body.

01:17:24.800 | So you don't have to do it with your face

01:17:27.180 | as far as I understand.

01:17:28.540 | I could be wrong though.

01:17:30.120 | Yeah.

01:17:31.900 | So when you activate your diving response,

01:17:35.500 | you will slow down your oxygen consumption in your body.

01:17:40.020 | And that is because the body tries to preserve oxygen.

01:17:44.500 | So you will not get hypothermic too fast.

01:17:47.640 | So it's kind of like a survival system in your body.

01:17:50.840 | So this survival system is very important for us, of course.

01:17:55.480 | So that will be activated.

01:17:56.960 | And because of that, you will after maybe one minute or so,

01:18:01.400 | I can't be precise on that

01:18:02.900 | because maybe it also varies a bit in humans.

01:18:06.080 | So one to two minutes,

01:18:07.580 | you will have full activation

01:18:09.340 | of the sympathetic nervous system,

01:18:10.700 | but also the parasympathetic nervous system.

01:18:13.600 | And that's gonna activate, for example,

01:18:15.640 | something like serotonin in your brain,

01:18:17.620 | which is also good for mental balance

01:18:20.120 | and people feeling in mental balance afterwards

01:18:23.140 | after they go up.

01:18:24.360 | So that is measured on questionnaires

01:18:28.840 | and also measured on anecdotes.

01:18:31.680 | Of course, people tell all the time

01:18:33.260 | that they feel good afterwards.

01:18:34.880 | We need studies on this.

01:18:35.960 | So if anyone's sitting out there thinking

01:18:37.620 | that's interesting, then please do some studies on that

01:18:41.020 | to get more out on that.

01:18:43.120 | - Yeah.

01:18:44.320 | - So you observed these winter swimmers

01:18:47.000 | who have done this for a few seasons.

01:18:49.540 | They're coming around for a new season of winter swimming

01:18:52.380 | and you've decided to recruit them as subjects.

01:18:55.560 | They are getting into cold water,

01:18:58.240 | climbing down a ladder or jumping into the water

01:19:00.520 | up to their neck.

01:19:01.360 | - Yeah, climbing, yeah.

01:19:02.200 | - Okay, climbing down a ladder

01:19:03.400 | 'cause this is done outdoors.

01:19:04.440 | What a fun study to do.

01:19:05.560 | My graduate thesis was done under fluorescent lights

01:19:08.760 | with no windows in a building that,

01:19:11.480 | I mean, I had a ton of fun as a PhD student.

01:19:13.360 | I actually lived in the laboratory as a PhD student.

01:19:15.560 | I loved it so much,

01:19:16.780 | but not something required to do a PhD, by the way.

01:19:20.700 | But they're climbing down the ladder,

01:19:23.480 | getting in up to their neck,

01:19:25.540 | staying in for one to two minutes and then getting out.

01:19:28.720 | And how many times a week are they doing this?

01:19:30.640 | - So they do this two to three times per week.

01:19:32.680 | And for each time they go, each day they go,

01:19:36.280 | they take three rounds of,

01:19:38.640 | so three dips and two sauna sessions.

01:19:41.280 | So they start in the cold and they end in the cold water.

01:19:44.040 | - Okay, so it's get in for one to two minutes,

01:19:47.380 | then get out and get into the sauna.

01:19:49.160 | - Yeah.

01:19:50.300 | - What is the temperature of the sauna?

01:19:52.220 | - About 80 degrees Celsius.

01:19:54.360 | - Okay, then how long are they in the sauna?

01:19:57.480 | - So they stayed there for 10 to 15 minutes.

01:20:00.480 | So depending on if they went two times per week

01:20:03.280 | or three times per week.

01:20:04.440 | - Okay, and then they get back into the cold

01:20:06.260 | for a few minutes, two minutes?

01:20:08.200 | - Up to two minutes, yeah.

01:20:09.120 | - Okay, then back into the sauna, 15 minutes or so,

01:20:13.520 | then back into the cold for a third round,

01:20:15.880 | back into the sauna, and then they're-

01:20:20.000 | - Ending on the cold.

01:20:20.840 | - And then back into the cold again,

01:20:22.120 | and then ending on cold.

01:20:23.680 | And we will talk about why it's important to end on cold,

01:20:26.920 | the so-called sober principle.

01:20:28.640 | How cold was the water in this particular,

01:20:33.600 | given average, 'cause I realized

01:20:35.080 | it's outdoor winter swimming.

01:20:36.320 | So it's gonna vary depending on windchill and things as well.

01:20:39.140 | - Of course, so it's a very uncontrolled environment

01:20:42.280 | to do this kind of study in,

01:20:43.720 | but I wanted to do something that was also very close

01:20:47.100 | to something people could do for free,

01:20:48.960 | going out in nature and use that,

01:20:50.620 | and also have the nature-like.

01:20:52.200 | It's a very healthy impact on us.

01:20:53.920 | It lowers our stress level as well.

01:20:57.120 | So by doing so, I also measured the temperature

01:21:01.080 | every time they went.

01:21:02.600 | So I have this graph,

01:21:04.000 | and it's actually in the "Winter Swimming" book.

01:21:05.920 | It shows the temperature in Denmark

01:21:07.680 | going from October to April.

01:21:10.560 | And it starts at 12 degrees.

01:21:13.040 | I think it's around 12 degrees Celsius in the water.

01:21:16.800 | And then it goes down to two degrees

01:21:19.560 | on average in January, and then up again.

01:21:22.640 | So it's within the spectrum of very cold water,

01:21:25.160 | I would say from around 15 degrees Celsius and down.

01:21:30.120 | But it was actually not colder than two to four degrees

01:21:34.440 | on average when it was the coldest.

01:21:37.720 | So it doesn't have to be that cold to be good enough

01:21:40.240 | and enough to activate our metabolism.

01:21:43.460 | - And what time of day are the participants

01:21:47.380 | doing this cold sauna alternation?

01:21:50.240 | - So I think they did this throughout the day.

01:21:53.560 | So I didn't control whether they wanted to go

01:21:56.240 | in the morning, in the afternoon, or in the evening.

01:21:59.320 | At the time where I set up the study,

01:22:01.640 | I was not controlling it in that way.

01:22:05.000 | I wanted them to go whenever they had time.

01:22:07.280 | And I also think that is the most important message

01:22:09.600 | to give to people is do it when you have time.

01:22:12.960 | It's not, if doing it when you get home from work

01:22:17.760 | and it's six o'clock in the evening,

01:22:19.720 | and this is the time where you can do it,

01:22:22.960 | then try out if it's gonna impact your sleep or not.

01:22:26.720 | If it doesn't impact your sleep, then fine.

01:22:29.380 | But you have to try for yourself and find out

01:22:31.680 | what works for you.

01:22:32.520 | It's the same for coffee, for example, right?

01:22:34.560 | Some people can drink coffee in the evening

01:22:36.280 | and go to bed and they can sleep.

01:22:38.280 | I can't.

01:22:39.120 | - Or exercise.

01:22:39.960 | - Or exercise, exactly.

01:22:41.560 | So I can't do that.

01:22:43.020 | And that's because the coffee exercise,

01:22:45.040 | cold water immersion, it's gonna activate

01:22:47.960 | your sympathetic nervous system.

01:22:49.780 | You have an increase in stress response in your body

01:22:51.960 | and that's gonna make it really hard to fall asleep

01:22:54.640 | for some people at least.

01:22:56.320 | Maybe you are super exhausted anyways,

01:22:58.240 | and then you will just crash anyways, but yeah.

01:23:01.500 | But that's the only thing.

01:23:03.720 | So I just told them to do this if they can

01:23:06.140 | during the daytime.

01:23:07.540 | And that's primarily what they also did.

01:23:10.780 | - And then all along you're measuring brown fat

01:23:14.040 | by way of this infrared camera, right?

01:23:18.540 | So what did you observe in terms of changes in brown fat?

01:23:21.160 | How quickly did that occur?

01:23:23.000 | And then I'd like to ask also about sauna a bit more

01:23:27.700 | because earlier you mentioned

01:23:28.740 | that you can activate brown fat with sauna as well,

01:23:31.800 | with heat on the surface of the skin.

01:23:34.860 | How long did it take

01:23:37.620 | before you observed significant increases in brown fat?

01:23:41.460 | And was it increased density of brown fat or distribution?

01:23:45.780 | Was it showing expansion to different regions

01:23:48.580 | throughout the body?

01:23:49.920 | And maybe you could also touch on some of the changes

01:23:52.280 | in insulin sensitivity and metabolism.

01:23:54.820 | - Yeah, a very good question.

01:23:57.060 | And I didn't mention this before,

01:23:59.420 | but besides measuring temperature

01:24:03.660 | as an outcome for brown fat activity,

01:24:05.780 | we also did PET-MRR scanning of the brown fat.

01:24:10.140 | So this is like the golden standard for measuring brown fat.

01:24:14.160 | And it's not very feasible for normal people

01:24:15.920 | to get a PET-CT or PET-MRR scanning of the brown fat.

01:24:20.920 | It's super expensive.

01:24:23.180 | So we had both to see if we could have like a continuous

01:24:28.180 | measure of brown fat in humans

01:24:31.060 | because that was already not out there.

01:24:34.060 | So I wanted to see during both the experimental days,

01:24:37.460 | but also during day and night,

01:24:39.840 | what kind of like circadian rhythm do we have

01:24:43.860 | in our brown fat activity?

01:24:45.180 | So that's why I wanted to have that as well.

01:24:47.820 | So the PET-CT scanning or the PET-MRR scanning

01:24:51.180 | was to see upon cold activation stimulation for some hours,

01:24:56.180 | do we have activation?

01:24:58.080 | Can we see the brown fat in this subject?

01:25:00.580 | And also during thermal neutrality

01:25:02.900 | or thermal comfortable state,

01:25:04.780 | how is that activated in each of the group, of course?

01:25:08.180 | - Ah, so you want to see how comfortable people were

01:25:11.000 | away from the cold water and sauna

01:25:13.900 | just at different temperature environments.

01:25:16.620 | Is that right?

01:25:17.460 | - Yeah, so also measured that.

01:25:18.440 | How comfortable are you?

01:25:19.980 | I made this scale like visual analog scale

01:25:23.420 | and asked them how comfortable do you feel

01:25:25.500 | with this temperature and throughout the study days

01:25:28.900 | during cold exposure and thermal comfortable day.

01:25:31.780 | I had a whole day where I just kept them

01:25:33.980 | thermal comfortable to see, do they activate the brown fat

01:25:37.860 | if they're just completely thermal comfortable?

01:25:40.240 | As good as we could get with that

01:25:42.100 | because you were asking people on a scale from one to 10

01:25:46.980 | and five being thermal comfortable,

01:25:48.860 | where are you on this scale?

01:25:50.300 | So one would be very cold

01:25:52.220 | and 10 would be super burning hot.

01:25:54.860 | Yeah, and so that was the way to try to figure out

01:25:59.500 | how do they actually feel also during the studies.

01:26:02.340 | I also measured electromyography of muscles

01:26:07.340 | to see, do they shiver during the cooling day?

01:26:10.440 | Sometimes people shiver

01:26:11.420 | before they know they're really shivering.

01:26:13.500 | So I had this. - Oh, interesting.

01:26:15.160 | - Yeah.

01:26:16.000 | - So our conscious perception of shivering

01:26:17.880 | might not be the best readout of shiver.

01:26:20.560 | - Yeah, well, if you also get adapted to the cold water,

01:26:23.560 | you will have less shivering.

01:26:26.820 | They will be less vigorous.

01:26:28.440 | They will be very small.

01:26:30.160 | So you wouldn't probably know that you are shivering

01:26:32.880 | because the shivering is so small

01:26:34.500 | and the mitochondria in the muscle cells will be so dense

01:26:39.020 | that it doesn't need to shiver maybe that much

01:26:41.440 | to get that thermogenesis going

01:26:44.900 | compared to when you're completely new

01:26:47.440 | to cold water exposure, you're not adapted,

01:26:50.540 | then the body needs to create these mitochondria,

01:26:53.140 | these energy fabrics to keep you warm.

01:26:55.760 | And that's also what the exercise is in the beginning.

01:27:00.060 | But when we measured this,

01:27:02.560 | we did see that the winter swimmers were shivering less

01:27:06.340 | or having less vigorous shivering when they said I'm cold.

01:27:10.960 | So even though their perception of the cold

01:27:15.180 | was pretty similar in the groups,

01:27:19.260 | we could see that the activation of the muscles

01:27:23.940 | that we measured on were different

01:27:26.780 | and more vigorous in the control group.

01:27:29.120 | - Were the subjects incentivized to be in the study?

01:27:31.520 | Were they paid or anything of that sort?

01:27:33.060 | Or they just happened to like doing cold and sauna.

01:27:36.100 | And so that's why they did the study.

01:27:38.380 | - Well, they got paid a little bit for it, but not much.

01:27:41.440 | And that's how we do this study.

01:27:44.340 | - Sure, I was just curious.

01:27:45.940 | Yeah, I was just curious.

01:27:46.780 | There might be some folks that wonder.

01:27:48.220 | So what did you discover in terms of changes

01:27:50.960 | in brown fat, insulin resistance,

01:27:53.460 | or insulin sensitivity rather, and metabolism?

01:27:57.340 | - So what we saw was we had this kind of different measures

01:28:02.260 | to see what's actually going on

01:28:06.020 | when they are already adapted to the cold water

01:28:08.460 | compared to a control group

01:28:10.020 | who was matched on various parameters.

01:28:14.880 | We did see that the winter swimmers

01:28:16.820 | had an increased insulin sensitivity.

01:28:19.600 | They produced less insulin on all the experimental days.

01:28:24.600 | So besides from just cooling them

01:28:27.620 | and measuring the brown fat on each of these cooling days,

01:28:31.020 | there were two cooling days

01:28:31.980 | and one thermo comfortable day, right?

01:28:34.460 | So I wanted to measure insulin when they were fasting,

01:28:39.300 | meaning that they hadn't eaten in eight hours

01:28:42.340 | before the study day.

01:28:43.560 | And they were completely laying still,

01:28:47.140 | not moving just in a bed.

01:28:48.920 | And we measured insulin during the experimental day

01:28:52.100 | just to see what level are they on.

01:28:55.760 | And we could see that the winter swim

01:28:58.420 | had had lower production of insulin.

01:29:00.980 | And they also, when they had a glucose drink,

01:29:04.380 | so we give them that to see if they,

01:29:06.260 | to test before we enroll them in studies

01:29:08.380 | to see if they have diabetes, for example,

01:29:10.060 | and not knowing, for example,

01:29:11.860 | that that would ruin maybe the study.

01:29:14.980 | So we test for that and see if they have a normal curve.

01:29:19.300 | So what we did see in that was that the winter swimmers

01:29:22.580 | had a faster glucose clearance in the bloodstream.

01:29:25.700 | So after two hours, we could see that they had a lower level

01:29:29.980 | and the curve went down faster than in the control group.

01:29:33.240 | - So despite having lower insulin release,

01:29:35.840 | they have better blood glucose clearance,

01:29:37.860 | which is really what we all seek, right?

01:29:41.100 | Excessive insulin is bad.

01:29:42.700 | Insulin being more or less a chaperone for blood glucose.

01:29:47.420 | We can do all sorts of other things as well, of course.

01:29:51.940 | And having high blood glucose, obviously terrible for cells,

01:29:55.500 | especially brain cells.

01:29:56.500 | I don't think people realize how toxic high blood glucose is,

01:30:00.300 | having high glucose is sort of great.

01:30:02.140 | If you want to kill neurons, you make their,

01:30:06.740 | put them in an environment where there's too much sugar.

01:30:09.180 | Oh yeah, very neurotoxic.

01:30:12.380 | I mean, and there are mechanisms like insulin

01:30:15.080 | that buffer that, keeping blood glucose in a reasonable range

01:30:18.740 | so that that doesn't happen.

01:30:20.340 | I mean, I think that's why people will go

01:30:21.560 | into insulinemic shock.

01:30:23.320 | Hypoglycemic shock is also possible.

01:30:25.800 | So that range in which neurons are happy

01:30:27.940 | is not a tremendously large range.

01:30:30.540 | Incidentally, the range in which neurons are happy

01:30:34.140 | in surviving is much greater as one gets colder

01:30:38.640 | than when you heat up.

01:30:39.640 | I mean, you can basically destroy brain cells

01:30:42.600 | by getting too hot for too long.

01:30:44.060 | - Oh yeah, yeah.

01:30:45.100 | - You can definitely destroy brain cells permanently

01:30:47.620 | by getting too cold for too long,

01:30:48.860 | but you have to get really, really cold

01:30:50.420 | for a really long time.

01:30:51.660 | - Yeah, yeah, very interesting.

01:30:53.720 | - Yeah, we were thinking about doing an episode

01:30:55.940 | on sort of survival of the brain after death kind of things,

01:31:00.940 | which actually happens.

01:31:02.380 | We hear about these people who are declared dead

01:31:04.220 | and then come back.

01:31:05.380 | And there is actually now a lot

01:31:06.540 | of cryopreservation type approaches for that.

01:31:09.240 | This is, anyway, we risk going into the esoteric now,

01:31:13.700 | so I'll steer us back to our discussion about your study.

01:31:16.060 | But so if I do the math,

01:31:19.220 | these subjects are in the cold.

01:31:22.780 | Let's say they're doing three rounds of cold

01:31:25.380 | for one to two minutes, two or three times a week.

01:31:29.740 | What were the thresholds that you discovered

01:31:32.540 | were important for getting these positive changes

01:31:35.820 | such as reduced blood sugar

01:31:39.180 | or clearance of blood sugar being more efficient,

01:31:42.400 | reduced insulin, improved brown fat distribution and density?

01:31:47.400 | How much cold exposure do people need?

01:31:50.540 | How much heat exposure do people need

01:31:52.240 | in order to extract these benefits?

01:31:54.820 | - Yeah, so when we then calculated the numbers together,

01:31:57.860 | we could see that this ended up being 11 minutes

01:32:00.980 | in total per week.

01:32:03.140 | So not in one session, of course,

01:32:04.740 | but they had two to three visits

01:32:07.440 | to the water and the sauna per week.

01:32:09.860 | So when we divide that out,

01:32:12.020 | it corresponds to being in cold water

01:32:14.120 | one to two minutes at a time,

01:32:15.980 | but also in the sauna 10 to 15 minutes at a time.

01:32:18.940 | And I think this is very like also similar

01:32:21.980 | to what we see in other studies

01:32:23.900 | when we look, for example, to the observational studies

01:32:26.940 | from the Finnish cohort study from Lauken et al.

01:32:31.260 | For example, they published this very amazing paper in 2015.

01:32:36.180 | Some results from this long course study

01:32:38.520 | where they show that up to 30 minutes in the sauna

01:32:43.520 | was healthy and you lower your risk of cardiovascular disease

01:32:48.900 | and that's like the threshold.

01:32:50.260 | And if you go further than that,

01:32:52.180 | then there is not more healthy benefits to gain from that.

01:32:57.180 | So, and before that, it's like 19 minutes,

01:33:00.980 | then you will have this dose response relationship

01:33:03.740 | up to 19 minutes.

01:33:04.900 | That's really in decreasing your risk

01:33:07.380 | of cardiovascular diseases.

01:33:09.400 | And I think we really-

01:33:10.240 | - That's per week, 90 minutes per week.

01:33:12.580 | - 90 minutes per session now.

01:33:14.220 | - Per session, okay. - Yeah, per session.

01:33:15.940 | If we then compare that with my study,

01:33:20.980 | which was 10 to 15 minutes per session,

01:33:24.300 | then I think it fits very well

01:33:25.760 | with what we call the hermetic stress or healthy stress

01:33:29.100 | that you expose the cells to this kind of like potent,

01:33:32.060 | very stressful situation

01:33:34.500 | where they increase heat shock proteins in the cells

01:33:37.500 | and that will repair the cells.

01:33:39.180 | But if you then overdo it and you go beyond

01:33:42.180 | the maybe 30 minutes in the sauna,

01:33:44.700 | this observational study from Finland

01:33:47.540 | with more than up to 2,000 sauna bathers

01:33:51.260 | where they have followed these for 20 years,

01:33:53.340 | they see that 30 minutes per session is like enough.

01:33:57.100 | And then if you go above that,

01:33:58.580 | you don't get more health benefits out of it.

01:34:00.880 | So I think there's a window where we can say

01:34:03.060 | the healthy stress corresponds to like 10 minutes

01:34:06.540 | and I think it's like- - Per session.

01:34:08.060 | - Per session and it's not much actually.

01:34:10.960 | So you don't need to,

01:34:13.080 | it shows that you don't have to expose yourself

01:34:15.080 | very much to the heat

01:34:16.420 | or very much actually to the cold

01:34:18.480 | to get this healthy benefits from going into cold,

01:34:22.460 | going to heat and have healthy benefits

01:34:24.220 | on your cardiovascular system.

01:34:25.660 | So I think this is very important also message to get out

01:34:29.620 | that you don't have to go extreme,

01:34:31.980 | you don't have to swim for a half an hour in the cold water.

01:34:35.880 | You can go in the water for one to two minutes per session,

01:34:40.480 | but go up to 11 minutes per week in total.

01:34:44.080 | And for the sauna, my study showed 57 minutes

01:34:48.500 | in total per week.

01:34:49.820 | And if we also then divide it out

01:34:51.840 | on these two to three days and two sessions each day

01:34:55.020 | correspond to 10 to 15 minutes.

01:34:57.180 | So it's a low threshold,

01:34:59.100 | but I think it's good to have that too.

01:35:02.400 | Maybe we can aim for that

01:35:04.400 | if people need to have something to aim for.

01:35:06.880 | And I think it's really good to have that

01:35:09.180 | because then you don't overdo it.

01:35:13.000 | And if you overdo it, you exhaust the cells

01:35:14.980 | and that will increase your risk

01:35:16.980 | of cardiovascular disease also.

01:35:19.860 | - Well, I get a lot of questions about this

01:35:21.460 | and I did solicit for questions

01:35:23.020 | for this podcast on Twitter.

01:35:24.580 | And one of the questions that I got was

01:35:26.360 | as one becomes more cold adapted,

01:35:28.500 | do the benefits start to wear off

01:35:30.180 | or can people do too much cold exposure?

01:35:32.580 | Of course, the answer to that is yes,

01:35:33.940 | you can become hypothermic,

01:35:35.000 | but I'm sensing a different answer now,

01:35:38.100 | which is if I understand correctly,

01:35:40.660 | the threshold is 11 minutes total per week

01:35:43.120 | of deliberate cold exposure

01:35:44.480 | divided into two or three sessions

01:35:46.900 | of maybe one to three minutes,

01:35:48.240 | depending on how long somebody stays in.

01:35:50.360 | And then 57 minutes,

01:35:53.000 | I want to be careful not to round up to an hour,

01:35:56.400 | but divided into maybe three 20 minute sessions or so.

01:36:00.100 | So one doesn't have to be perfect

01:36:03.440 | as long as you get beyond that threshold.

01:36:05.800 | But I wonder something which is,

01:36:09.680 | is it the case that if somebody said,

01:36:11.180 | oh, I'm just going to do one 11 minute session per week,

01:36:14.940 | that might actually not be as beneficial as dividing it up

01:36:19.640 | because what you told us earlier is that

01:36:22.480 | the hormetic response depends on having that cold shock.

01:36:26.100 | You actually don't want to become too cold adapted.

01:36:28.260 | I mean, once the blood pressure response drops down,

01:36:31.400 | so in minute four, five, and six,

01:36:34.040 | you're getting very cold and you're shivering,

01:36:35.740 | but one is not getting the autonomic stimulus

01:36:39.380 | that they want.

01:36:40.220 | I guess I could liken this to if exercise worked in a way

01:36:43.560 | where it was only the first few minutes of exercise

01:36:46.300 | that really triggered the adaptation.

01:36:47.660 | Of course, this is not how it works,

01:36:49.180 | but in fact, probably quite the opposite.

01:36:51.500 | But if that were the case,

01:36:53.760 | then it's not simply the total amount of exercise,

01:36:56.500 | but dividing up the sessions into little bouts

01:37:00.820 | where every single time it acts as a stimulus,

01:37:03.960 | that seems to be the key here.

01:37:07.080 | This is very important because having watched

01:37:09.900 | the landscape of this on social media,

01:37:11.800 | but also in books and generally,

01:37:14.720 | I think you're the first person to really touch on this,

01:37:17.280 | that the goal is not to get so cold adapted

01:37:20.240 | that you can sit in for the full 11 minutes in one session,

01:37:23.240 | where the goal isn't to be able to do an hour

01:37:25.240 | of very hot sauna.

01:37:27.160 | If you want to, I suppose people could do it

01:37:28.680 | for other reasons, but if the goal is to improve

01:37:30.980 | these health metrics, then the idea is

01:37:33.480 | to keep the stimulus a stimulus.

01:37:36.640 | Short, exactly, yeah.

01:37:38.920 | - Great, well, this also,

01:37:40.920 | I think there's practical feasibility, as you pointed out,

01:37:43.200 | 'cause getting into a cold shower or cold immersion

01:37:45.920 | or natural body water for a couple of minutes

01:37:48.440 | is far less challenging to most people

01:37:52.820 | than finding a full morning to go spend there.

01:37:55.840 | But I've never really heard it articulated

01:37:59.880 | that the longer sessions might not be beneficial

01:38:03.600 | and might actually be detrimental.

01:38:06.340 | That's very important.

01:38:09.760 | Were there any other observations that you made

01:38:13.740 | that did not make it into the paper

01:38:15.760 | or that were kind of in the margin notes,

01:38:18.480 | in terms of psychological benefits or anything of that sort?

01:38:23.080 | There was this recent study on soldiers

01:38:25.080 | that talked about weight loss.

01:38:26.600 | It's sort of a controversial study for a lot of reasons.

01:38:29.980 | But one of the things they remarked in the paper

01:38:32.400 | was that there were a lot of psychological changes,

01:38:34.280 | improved buffering against anxiety.

01:38:36.800 | They even, the men and women in that study reported,

01:38:40.240 | one of the significant effects

01:38:41.480 | was significantly improved sexual satisfaction.

01:38:44.360 | Of course, they didn't tell us what that meant

01:38:45.780 | for these subjects, so we won't go there.

01:38:48.280 | But a number of subjective improvements.

01:38:51.360 | Was there anything that you observed or took note of

01:38:53.320 | in your study that perhaps didn't make the main abstract

01:38:56.240 | but that we should be aware of?

01:38:58.520 | - Yeah, there were some.

01:39:01.120 | And today, I regret that I didn't measure on sleep,

01:39:06.120 | for example.

01:39:07.400 | I frankly didn't really think about that

01:39:11.400 | when I designed the study.

01:39:14.880 | So we were very much occupied with the metabolism

01:39:19.880 | and kind of had the thought,

01:39:22.260 | maybe this could impact sleep quality.

01:39:26.040 | And I wish I had the thought

01:39:29.000 | that why don't you just ask them in a questionnaire?

01:39:31.840 | But I asked them every morning,

01:39:33.800 | or every morning, it was not many mornings,

01:39:35.320 | just two mornings, actually, we measured on.

01:39:38.760 | But the winter swimmers told us before I wrote them

01:39:43.760 | that they had a really good sleep quality.

01:39:46.420 | The control group also had that.

01:39:48.400 | But they told me on the day

01:39:50.740 | where we measured the brown fat on a day and a night,

01:39:54.120 | so actually two days and two nights,

01:39:57.720 | they told me that they had a good night's sleep,

01:40:01.200 | but they also woke up.

01:40:02.740 | So it's just telling me that they also had a quick wake up

01:40:06.300 | and then they fell asleep again.

01:40:08.440 | And the winter swimmers told they have a really good sleep.

01:40:13.120 | So it's like, in general, they also say we sleep very well,

01:40:17.360 | I sleep very well.

01:40:18.300 | So it's anecdotally, in general,

01:40:21.000 | it corresponds to what I heard in my study,

01:40:24.200 | but nothing that I measured on,

01:40:27.200 | which could be fun to do in the future,

01:40:29.400 | but we didn't measure on sleep quality.

01:40:32.400 | That would have been a really good idea to do.

01:40:35.240 | They also told me that they were very comfortable

01:40:37.740 | when they were cold.

01:40:38.580 | They don't mind, winter swimmers,

01:40:40.840 | they don't mind going out, for example,

01:40:43.840 | in the cold with a T-shirt.

01:40:45.760 | They were also less scared of showing their skin.

01:40:49.480 | That was also one observation.

01:40:51.440 | - Interesting. - Yeah.

01:40:52.440 | - So kind of a reduced social anxiety.

01:40:54.680 | - Yeah, they were just so comfortable in the lab.

01:40:58.760 | As you just mentioned before,

01:41:00.320 | coats on and everybody's joining around.

01:41:02.200 | It was very busy and all the other scientists

01:41:05.840 | out in the hallway.

01:41:06.840 | And also my supervisor had her office down the hallway

01:41:10.840 | and one of the winter swimmers one day

01:41:13.160 | just got out of bed after,

01:41:15.240 | had been in the study for eight hours.

01:41:18.120 | It was a long day, right?

01:41:19.560 | He jumped out of the bed and had his clothes in the bathroom

01:41:24.280 | and he went out completely naked.

01:41:26.440 | He didn't care.

01:41:27.480 | He just went out.

01:41:28.360 | It was like, oh.

01:41:29.840 | - So that's a side effect perhaps

01:41:31.520 | of getting too comfortable with the cold.

01:41:33.660 | We're not recommending that.

01:41:36.360 | Although in your book, you dedicated some,

01:41:41.360 | let me start that again.

01:41:42.580 | Although in your book, you dedicated some pages

01:41:45.580 | to naked winter swimming,

01:41:48.780 | or I should say naked cold water exposure

01:41:51.640 | as opposed to with bathing suit.

01:41:56.000 | Are there any data on this?

01:41:57.240 | I'm sorry, chuckling.

01:41:58.080 | But I think in most places in the United States,

01:42:01.440 | skinny dipping is not legal, most public beaches.

01:42:06.560 | There are a few.

01:42:07.520 | In fact, my laboratory before moving to Stanford

01:42:10.320 | was in San Diego and I,

01:42:11.880 | at the Salk Institute for Biological Studies,

01:42:13.800 | beautiful building, incredible science is done there.

01:42:16.580 | The beach right below that is called Black's Beach.

01:42:21.480 | And it's a no-nude beach.

01:42:24.040 | And so whenever tourists were heading down the stairway

01:42:27.040 | there, I would sort of let them know,

01:42:29.560 | especially if they had kids, I'd let them know.

01:42:31.800 | And it's a nude beach of a particular genre.

01:42:36.240 | So I'd give them a little warning

01:42:37.600 | about what they could expect down below.

01:42:40.160 | In any event, those beaches are quite rare

01:42:43.000 | in the United States, maybe compared to Europe.

01:42:44.920 | I don't know, but-

01:42:46.600 | - Yeah, maybe.

01:42:47.440 | - Yeah, so is there anything special

01:42:49.040 | about clothesless versus closed exposure?

01:42:53.400 | - Yeah, I think in that sense,

01:42:55.320 | we are a bit more free with this kind of like,

01:42:58.280 | but remember we also had this winter swimming culture

01:43:00.580 | for hundreds of years in Denmark.

01:43:02.600 | And the oldest winter swimming clubs that we have,

01:43:05.700 | especially the one we have in Copenhagen,

01:43:07.700 | where I did my next study, which we haven't talked about,

01:43:10.840 | and it's also not published yet,

01:43:12.520 | but in that winter swimming club,

01:43:15.240 | it's the oldest one we have and it's huge.

01:43:17.640 | And they swim naked at this facility.

01:43:22.040 | - Men and women.

01:43:22.880 | - Men and women, and they have sauna

01:43:24.720 | where they can go in together.

01:43:26.160 | And they also have separate saunas,

01:43:28.140 | but it's very much a Danish thing.

01:43:31.160 | And I think it's good if people want that.

01:43:36.160 | And I had it in my book because people want to know

01:43:39.320 | if they have to swim with their bathing suit on,

01:43:41.480 | or if they can take it off, or what's the difference?

01:43:44.800 | Is there any difference in this?

01:43:46.200 | And if you ask me, there is no difference.

01:43:48.800 | If you have your little skinny bikini on,

01:43:51.520 | it's not gonna do any difference to your cold exposure

01:43:54.920 | or your adaptation, it's not gonna do any difference

01:43:57.280 | for your benefits, of course.

01:43:59.040 | But I think that it has something else.

01:44:01.240 | It has something to do with how you also observe yourself,

01:44:05.280 | how you observe your surroundings.

01:44:07.360 | And it's some sense of freedom in skinny dipping.

01:44:11.240 | So I think people in Denmark who does this,

01:44:15.240 | they do the winter swimming

01:44:16.480 | because they feel free when they do it.

01:44:18.600 | They come home from work, they go to this club,

01:44:21.840 | and they skinny dip, and they feel in touch with nature.

01:44:25.080 | And they have maybe done this their whole life.

01:44:27.440 | So this is an old tradition in Denmark in some of the clubs.

01:44:31.880 | But the newer clubs that are coming,

01:44:34.200 | they don't do a skinny dip.

01:44:36.120 | So everyone has bathing suit.

01:44:38.060 | I never skinny dip because there are people around,

01:44:41.160 | people with phones and taking pictures all the time.

01:44:43.580 | So this- - It's different nowadays.

01:44:45.800 | Everything's recorded. - Yeah.

01:44:47.460 | And also this old tradition is also fading away

01:44:51.820 | because of that.

01:44:53.060 | - Yeah, I use sauna and cold at home,

01:44:56.480 | but when I travel, there's a banya.

01:44:59.260 | So Russian banya has hot sauna and cold plunge.

01:45:03.360 | There's one in San Francisco called Archimedes banya.

01:45:05.920 | And that one is clothing optional.

01:45:08.100 | So some people are clothed, such as myself,

01:45:10.000 | and then other people are not.

01:45:11.060 | And it's co-ed most of the time.

01:45:13.200 | I think they have male, female separated evenings

01:45:16.160 | or something like that.

01:45:17.160 | And then the other banya is Spa 88,

01:45:20.500 | which is on Wall Street in New York,

01:45:22.160 | is an amazing banya as well.

01:45:24.680 | And these are starting to crop up in different cities,

01:45:26.680 | or maybe they've been there for a long time.

01:45:27.980 | And as deliberate cold exposure and sauna gets more popular,

01:45:30.440 | more people are using them.

01:45:32.040 | The one in New York that Spa 88 is always clothed.

01:45:37.040 | And it's interesting because people here are naked

01:45:40.720 | or skinny dipping and they might get certain ideas in mind.

01:45:43.840 | All these places are very well lit

01:45:47.560 | and they all have a tone of kind of health

01:45:50.200 | that is about the kind of health and wellness.

01:45:53.360 | I guess the point being that there's no requirement

01:45:57.200 | to do one thing or the other.

01:45:59.080 | Although in the studies that you did,

01:46:01.080 | obviously people were clothed.

01:46:02.580 | But I did pay attention to those pages in your book.

01:46:06.060 | I thought it was interesting that you put

01:46:08.120 | some dedicated passages in your book that related to this.

01:46:11.360 | - My publisher wanted that.

01:46:12.680 | - Oh, your publisher wanted that, interesting.

01:46:14.020 | - It was not me.

01:46:14.860 | It was like my publisher really wanted

01:46:16.540 | to have a little discussion about that.

01:46:18.360 | So I was like, okay.

01:46:19.320 | - Well, I think it points to a larger theme,

01:46:21.680 | which is I think for a lot of people

01:46:23.320 | who already do these practices, there's no shock there.

01:46:27.740 | For people that do not do deliberate cold exposure or sauna,

01:46:32.400 | I think that there is this idea perhaps that,

01:46:35.940 | oh, these are traditions that are kind of fringe

01:46:39.780 | or that they're cut.

01:46:40.620 | And I just, I want to cue that point

01:46:43.680 | because there's so many things that are happening right now

01:46:46.180 | in biomedical research and medicine.

01:46:48.660 | Serious quality peer-reviewed studies

01:46:51.620 | published in excellent journals like your paper

01:46:54.220 | on things like deliberate cold exposure, sauna,

01:46:56.900 | the use of particular supplements,

01:47:00.760 | natural herbs and supplements.

01:47:03.100 | I mean, there's an entire branch

01:47:04.340 | of the National Institutes of Health in the United States

01:47:07.160 | dedicated just to the study of supplements

01:47:09.480 | and behavioral interventions for health,

01:47:11.220 | like meditation and breath work.

01:47:12.900 | Really incredible. - Fantastic.

01:47:14.120 | - It's really incredible.

01:47:14.960 | And psychedelics, of course, being something

01:47:16.540 | that for a long time was part of a certain community

01:47:18.620 | and feel, and now is being frankly adopted

01:47:22.580 | by mainstream medicine, even pharma.

01:47:25.300 | So the times are changing.

01:47:27.640 | And so, yes, I think it's important to know

01:47:31.100 | that it's perfectly acceptable and encouraged

01:47:33.980 | to wear clothing.

01:47:34.900 | - Absolutely, absolutely.

01:47:36.460 | Yeah, yeah, yeah.

01:47:37.620 | And one other thing that I wanted to mention,

01:47:40.700 | going back to your questions around

01:47:43.140 | with there were any observations in the studies,

01:47:45.860 | which we really maybe haven't discussed yet,

01:47:48.340 | and maybe it's in the back of the paper

01:47:51.380 | and not mentioned that much was one of the winter swimmers

01:47:54.260 | didn't have any brown fat when we measured him.

01:47:57.220 | - Zero. - Zero.

01:47:58.980 | And we do see this in previous studies as well,

01:48:03.980 | that some humans don't have any brown fat.

01:48:07.780 | - Did he carry a lot of white fat adipose tissue?

01:48:09.780 | Was he obese?

01:48:11.020 | - No, he wasn't.

01:48:12.280 | No, he was not obese because he would not have been

01:48:15.020 | in the study then.

01:48:16.260 | - Oh, right, yes, you mentioned this earlier.

01:48:17.760 | Forgive me.

01:48:18.600 | - No, no, it's fine.

01:48:19.760 | But what I did observe before I knew

01:48:23.780 | that he didn't have any brown fat was that

01:48:26.060 | during the cooling experiment where I cooled him

01:48:28.580 | for two hours before they go into the PET CT scanner,

01:48:32.980 | he was not able to control his shivering

01:48:39.100 | like the winter swimmers could.

01:48:42.580 | So he got very cold very easily compared to the others.

01:48:47.580 | So, and without, I didn't know what was different about him,

01:48:52.640 | but we could, all of me and the three others

01:48:55.860 | were working on the experiment.

01:48:57.420 | We were like, okay, what's going on?

01:48:59.100 | Because we turned down the temperature,

01:49:01.620 | but he started shivering and then we had to turn it up again

01:49:05.220 | and it was just all over the place, the temperature.

01:49:08.580 | It wasn't that controlled like the others.

01:49:10.820 | It was pretty similar protocol.

01:49:12.180 | I could just do pretty much the same

01:49:14.040 | because they were same size and also same gender.

01:49:18.060 | So it was easier to foresee what was gonna happen

01:49:22.700 | and when will they start shivering.

01:49:24.340 | I quickly learned that.

01:49:25.660 | But with this subject, it was just,

01:49:27.300 | with this volunteer was just very much different.

01:49:30.980 | And then when we scanned him

01:49:32.300 | and didn't find any brown fat,

01:49:33.580 | I didn't even think about it.

01:49:36.440 | So when we scanned him, we didn't see anything.

01:49:39.080 | I told the PET CT people to like,

01:49:41.220 | oh, you put up the wrong scanning.

01:49:43.620 | - Right, blame the technology.

01:49:44.820 | - Yeah, the technology was like,

01:49:46.580 | this scanning looked like the thermo-neutral day,

01:49:49.140 | the thermo-comfortable day where we also scanned them

01:49:51.280 | to see if they have any brown fat.

01:49:52.780 | So you have made a mistake, I was pretty sure.

01:49:55.300 | And they reanalyzed this scanning

01:49:59.500 | and they just concluded, well, the scanning was fine.

01:50:03.180 | The experiment went well.

01:50:04.700 | It was just that he didn't have any brown fat.

01:50:08.540 | So he was like what we just in the paper

01:50:10.980 | called a brown fat negative.

01:50:13.060 | So he didn't have any.

01:50:14.480 | And in my studies, it would be called a knockout.

01:50:17.500 | So he didn't have any brown fat.

01:50:19.540 | So what the observation with him,

01:50:21.900 | and I think that's interesting,

01:50:23.900 | is that he both shivered very early on

01:50:27.020 | and didn't regulate his temperature as well.

01:50:29.140 | He also told me that then he was like a five

01:50:33.400 | on the scale of how comfortable he felt with the cold.

01:50:37.460 | So it was from one to 10 and five being thermo-comfortable

01:50:44.320 | and 10 being very cold and one very hot.

01:50:49.320 | So on this like scale up and down.

01:50:52.860 | And he was like more up and down on this scale

01:50:55.700 | than any of the others.

01:50:56.620 | It was an observation that I did.

01:50:58.460 | But we did see in his blood samples also

01:51:02.100 | that his blood samples looked a bit more

01:51:04.000 | like the control group.

01:51:05.240 | Also his insulin levels were like the control group.

01:51:10.660 | So a little bit higher than the other winter swimmers.

01:51:12.700 | And he also had his blood glucose clearance

01:51:19.100 | was not as fast as the other winter swimmers.

01:51:23.740 | So he was like an outlier, what we call it.

01:51:25.980 | And in the analysis, we also had to take him out

01:51:28.940 | of the analysis because he was an outlier.

01:51:32.500 | So the results showing that the brown fat

01:51:36.020 | is more efficiently activated in the winter swimmers

01:51:40.760 | is without him having him in that group.

01:51:43.820 | - Got it. - But it didn't ruin

01:51:44.940 | the study if I tried to put him in as well.

01:51:47.340 | And it didn't ruin the results or anything.

01:51:50.060 | But just to keep it more clear,

01:51:52.100 | we took him out of the analysis.

01:51:54.540 | - Yeah, so he was a mutant, a knockout.

01:51:56.960 | Yeah, and I'm sure they're out there.

01:51:58.820 | Very interesting, so if you shiver early,

01:52:01.060 | then perhaps you have less brown fat to begin with.

01:52:04.500 | Although it's hard to conclude from one person,

01:52:06.060 | that's sort of the implication there.

01:52:08.740 | - Oh, you haven't adapted to the code.

01:52:10.500 | So you should build that up, yeah.

01:52:12.980 | - So in addition to looking at regulation of blood sugar,

01:52:16.900 | brown fat, metabolism, and so on,

01:52:20.680 | were there any markers that you examined

01:52:23.140 | in the deliberate cold exposure group

01:52:25.580 | as compared to controls that revealed to you

01:52:28.180 | that deliberate cold exposure

01:52:29.420 | could have additional benefits,

01:52:31.820 | say for immune system function

01:52:35.940 | or for any function for that matter?

01:52:37.820 | - Yeah, so we looked at inflammation.

01:52:41.700 | Of course, we measure the outcome of blood pressure

01:52:44.000 | and so on, but we also measured the IL-6 in the study

01:52:46.900 | just to see also an inflammatory, anti-inflammatory marker.

01:52:50.500 | So IL-6 went up and it also follows with the IL-10.

01:52:55.340 | So that is like also very known in the literature.

01:52:58.340 | So we measured that and I think it's very important

01:53:01.060 | to think about the cold exposure and the heat exposure

01:53:05.020 | as something that then lowers the inflammation in the body.

01:53:07.900 | And if we can do that, we will have an open door

01:53:11.360 | for preventing lifestyle diseases, right?

01:53:14.980 | So for type 2 diabetes,

01:53:17.660 | but actually also for some mental diseases as well.

01:53:20.860 | So as known as depression and anxiety

01:53:23.380 | and also Alzheimer's disease,

01:53:25.460 | which are all associated in research,

01:53:29.100 | also newer research showing that inflammation

01:53:32.660 | increases the risk of depression, anxiety,

01:53:34.940 | and Alzheimer's, if it's neurological diseases.

01:53:37.100 | So if we can decrease inflammation in the body,

01:53:40.220 | we will decrease our modern lifestyle diseases,

01:53:42.780 | but also these increasing mental diseases

01:53:47.340 | that we see in these modern lifestyle times.

01:53:50.400 | So I think that it's, I think it's very interesting

01:53:54.700 | that we can go out in nature

01:53:56.460 | and we can use these natural stressors.

01:53:59.020 | And I don't want to have it sound very romantic or anything.

01:54:02.940 | It's just, it's just exposure to temperature actually,

01:54:06.340 | just a cold or to heat that is gonna twerk our body

01:54:09.720 | into a natural state again,

01:54:11.740 | and reset it where the homeostasis,

01:54:14.580 | the balance is lost a bit.

01:54:17.140 | So the body is gonna repair itself in that way.

01:54:20.500 | And I think it's beautiful that we can do that

01:54:22.620 | just by changing the temperature of our body.

01:54:24.860 | And although people are very scared of doing this,

01:54:27.940 | because in our times we have been away from cold,

01:54:31.740 | away from heat, temperature for some, for decades now,

01:54:37.460 | since we isolated our houses better

01:54:40.480 | and we are more sedentary, we also sit more indoor,

01:54:44.560 | we don't move as much.

01:54:45.980 | So this very modern sedentary lifestyle

01:54:49.920 | has made us more temperature comfortable, just neutral.

01:54:53.320 | So no wonder, I mean, that obesity is increasing.

01:54:58.140 | We don't expose ourselves to the natural stresses

01:55:01.140 | that we did earlier on in our involvement,

01:55:04.940 | but up until maybe the '70s, the '60s,

01:55:08.580 | where we started having more comfortable lifestyles, right?

01:55:12.740 | And obesity increases in the '80s,

01:55:15.540 | we can see that from statistics.

01:55:17.100 | So I think that if we can take in cold and heat,

01:55:21.860 | and you mentioned other things also before,

01:55:24.340 | but of course, exercise is very important here.

01:55:26.940 | And also a bit of fasting actually,

01:55:28.640 | because it all increases the hermetic stress in the body.

01:55:32.180 | So it doesn't have to be other than natural stresses

01:55:36.380 | to the body, which then could keep us

01:55:38.180 | in that natural balance again.

01:55:39.980 | - Could we talk about what I refer to

01:55:41.920 | as the Soberg principle, which is to end on cold.

01:55:44.860 | And the reason I called it the Soberg principle

01:55:47.220 | is because in reviewing, oh, by the way,

01:55:49.900 | I wasn't a official reviewer of your paper,

01:55:52.660 | but I mean, in reading and reviewing your paper

01:55:55.580 | for its after published contents,

01:55:58.660 | I noticed that you had people end on cold.

01:56:01.100 | And this has been a longstanding debate

01:56:03.060 | in the deliberate cold exposure community.

01:56:05.980 | Should you warm up with a warm shower afterwards

01:56:08.500 | or get back in the sauna?

01:56:09.540 | What should you end on, end on cold or end on heat?

01:56:12.100 | And the Soberg principle says, end on cold,

01:56:14.340 | as I understand it, in order to force your body

01:56:18.340 | to heat itself back up and thereby increase metabolism

01:56:23.260 | further still, is that right?

01:56:25.020 | - Yes, so when you end on the cold,

01:56:28.640 | you force your body to heat up by itself.

01:56:31.620 | And that will require that you activate,

01:56:34.500 | you keep your brown fat activated and also your muscles,

01:56:37.680 | which is a good thing.

01:56:38.520 | It's a good collaboration to keep your thermogenesis up.

01:56:41.220 | And that's like an exercise, even when you go home.

01:56:45.080 | So in that way, you don't have to think

01:56:46.840 | about your cold exposure dipping in your plunge,

01:56:50.660 | open sea or what it is,

01:56:53.160 | as just an exercise that you do for one to two minutes

01:56:57.160 | and then it's over.

01:56:58.320 | If you end on the cold, you have an exercise

01:57:01.500 | for your body going on for hours afterwards.

01:57:03.580 | And that's not only on your metabolism,

01:57:05.300 | but it's also gonna keep your neurotransmitters

01:57:08.460 | activated as well and increase that

01:57:10.620 | because your body is still cold.

01:57:12.620 | So you need those neurotransmitters

01:57:15.220 | to activate the brown fat as well.

01:57:17.100 | So that's gonna make your brown fat cells more efficient

01:57:19.820 | and also your muscle cells more efficient,

01:57:21.700 | so increasing mitochondria in the cells,

01:57:24.180 | which will then generate heat very fast.

01:57:26.260 | So if you have done this for a few times,

01:57:28.980 | so maybe three, four, five times, being new to this,

01:57:33.360 | but have tried it a few times,

01:57:35.260 | you will notice a switch where you feel

01:57:38.300 | that you get easily warmer and you can keep yourself warmer.

01:57:42.660 | And that is also what was shown in my study

01:57:45.180 | is that the winter swimmers were physically warmer

01:57:49.000 | on the skin compared to the control group.

01:57:51.740 | - When they are out of the cold.

01:57:53.980 | - When they're out of the cold, just relaxing.

01:57:56.260 | And we tested this on the days

01:57:59.120 | where they were sleeping in the lab.

01:58:00.820 | So we could see that they had more activation

01:58:04.260 | of the brown fat, higher temperature.

01:58:06.440 | So probably because they also lose heat,

01:58:09.100 | they have a higher heat loss to the body

01:58:11.740 | compared to the control group

01:58:13.140 | because they have a more vascular skin

01:58:17.660 | because of the contrast of cold and heat.

01:58:20.160 | So they lose heat faster from the body during that day

01:58:23.940 | but is that a bad thing?

01:58:25.920 | No, probably not because that's going to keep your brown fat

01:58:29.460 | and your muscles a little bit activated.

01:58:31.140 | So you will have to, it has to work to keep you warm.

01:58:36.140 | - And I would hypothesize that it also might lead

01:58:38.980 | to some of the subjectively reported improvements in sleep

01:58:43.040 | because in order to fall asleep,

01:58:44.280 | you need your core body temperature

01:58:45.880 | to drop by about one to three degrees.

01:58:48.300 | So it's not just sufficient to be sleeping in a cold room

01:58:51.840 | and under the blanket,

01:58:52.680 | you also need your body temperature to drop.

01:58:55.380 | And so what you're saying, if I understand correctly,

01:58:57.980 | is that by ending on cold and forcing oneself

01:59:01.700 | to heat up naturally, that increases the brown fat stores,

01:59:06.160 | which I sort of see as kind of like the oil in the candle

01:59:11.160 | of the furnace that is thermogenesis.

01:59:14.240 | And that in turn leads to increased heat loss,

01:59:18.780 | which people might think,

01:59:19.620 | "Oh, I don't want to lose heat from the body."

01:59:20.940 | But there are times when we want to lose heat from the body.

01:59:23.760 | Basically, it sounds like what we want

01:59:25.060 | is to be a very efficient heating and cooling system.

01:59:28.800 | That it's not about being cold or being hot.

01:59:31.260 | It's really about keeping the system tuned well,

01:59:34.800 | keeping the oil in the candle, this brown fat functioning.

01:59:38.260 | Could I ask one question about fed or fasted?

01:59:42.880 | Is there any, or rather, are there any known benefits

01:59:46.740 | of doing deliberate cold exposure and or sauna fasted

01:59:50.820 | versus after a meal, say within the last hour

01:59:55.340 | or something of that sort?

01:59:56.340 | I do my deliberate cold exposure first thing in the morning.

01:59:59.900 | So in general, I'm fasted 'cause I don't eat

02:00:02.140 | until a little bit later in the day.

02:00:04.220 | But what's known about that?

02:00:06.540 | And was that looked at in your study?

02:00:07.940 | I know you measured glucose,

02:00:09.180 | but that was as a separate test away from the cold.

02:00:13.140 | - Away from the cold, yeah.

02:00:14.520 | But I also tested glucose on the days on the cold.

02:00:17.860 | So we measured that as well on the cooling days.

02:00:20.700 | And specifically on fasting and fed, I don't know.

02:00:25.700 | I don't think that I have seen studies specifically on this.

02:00:29.100 | - Okay, more science needed.

02:00:31.800 | A number of people asked about the use

02:00:35.660 | of deliberate cold exposure to offset some of the symptoms

02:00:39.260 | of various diseases.

02:00:40.660 | Now, here, we're not talking about curing disease.

02:00:42.380 | We're talking about offsetting symptoms.

02:00:45.000 | One question I've seen quite often is whether or not

02:00:47.100 | people with Raynaud's syndrome.

02:00:48.860 | - This is a syndrome, and my high school girlfriend

02:00:50.780 | had this syndrome, and I'll never forget.

02:00:52.580 | We were at a school dance together,

02:00:55.180 | and this was when we first started dating,

02:00:57.360 | and she had Raynaud's,

02:00:58.700 | which leads to very poor blood flow to the extremities.

02:01:03.700 | And she was very cold, so she left to go to the bathroom

02:01:08.340 | and warm up her hands in the warm water.

02:01:10.500 | And I was left standing there at the dance,

02:01:12.220 | and people came up to me and asked why I was there

02:01:15.260 | and who I was there with.

02:01:16.100 | And I kept telling them who I was with,

02:01:17.360 | and they didn't believe me

02:01:18.500 | 'cause they couldn't believe that she would be with me.

02:01:20.400 | Made total sense if you knew me at the time.

02:01:22.540 | I was way out of my league with her at the time.

02:01:27.340 | I like to think eventually I caught up.

02:01:28.820 | But in any case, she was in the bathroom for about an hour.

02:01:32.980 | So at one point I did consider the possibility

02:01:35.220 | that she had just left, but indeed she hadn't.

02:01:37.480 | She warmed her hands back up.

02:01:38.520 | But people with Raynaud's suffer from this thing

02:01:42.540 | of very, very cold extremities.

02:01:45.740 | Their fingertips will even turn blue.

02:01:48.580 | You know, as if they were starting to get frostbitten.

02:01:50.580 | It's quite dramatic.

02:01:52.340 | And that question gets asked whether or not

02:01:54.980 | there's any use of cold to try and increase the elasticity,

02:01:59.700 | the plasticity of the small capillaries and vessels.

02:02:03.900 | By everything you've described up until now,

02:02:06.100 | it seems like that would be a logical thing to do.

02:02:08.700 | And in addition to that,

02:02:11.000 | whether or not people with autoimmune conditions,

02:02:13.520 | people with any other types of conditions

02:02:16.360 | are known to benefit from deliberate cold exposure.

02:02:18.960 | I'm not aware of any studies,

02:02:20.380 | but I get asked about this a lot.

02:02:21.860 | And there were a lot of questions about this for you

02:02:23.580 | in the Twitter feed.

02:02:24.620 | - Yeah, thank you for those questions.

02:02:26.340 | And I get them as well on social media.

02:02:28.660 | And I have to say that I haven't seen any studies directed

02:02:33.660 | on this outcome on measuring Raynaud's syndrome.

02:02:37.700 | I do know that it's not that rare actually a problem.

02:02:42.340 | And I know that many women or more women than men

02:02:46.220 | suffer from this.

02:02:47.260 | But logically it would help them

02:02:51.080 | if they expose their hands to cold and also heat

02:02:55.100 | to make it more vascular.

02:02:57.420 | And I have heard from people saying that it had helped them,

02:03:01.180 | but also heard from some others saying it didn't help them.

02:03:04.580 | So studies are needed on this specific topic, I think.

02:03:08.680 | I hurt my hands when I go into the cold one.

02:03:11.420 | I don't have this syndrome at all,

02:03:13.760 | but I keep my hands above the water.

02:03:16.080 | - You do?

02:03:16.920 | - Yeah.

02:03:17.740 | I do that, often I take a little bit of a swim

02:03:21.100 | and then of course I have to have my hands in the water,

02:03:24.480 | but it helps me when I then get back to the daddy

02:03:28.640 | and then take my hands up because then I can stand there

02:03:31.420 | for a little bit and get my one to two minutes exposure.

02:03:35.300 | And then I can go up because then otherwise

02:03:38.500 | that would stop me from being in the water enough time

02:03:42.460 | that I, as long as I would like to.

02:03:44.860 | So if people suffer from having this pain in the fingers

02:03:47.880 | and it can be very intense.

02:03:49.920 | So just take the hands up a bit from the water

02:03:52.880 | and that's going to help you.

02:03:54.760 | Also boots, neoprene boots, it's going to help on the feet.

02:03:57.560 | Some people have the hurt and feel the pain in the feet

02:04:00.500 | and on the ankles and that's going to help them

02:04:03.000 | also a little bit.

02:04:04.240 | - Okay, so there is no problem with keeping hands out

02:04:08.360 | or feet in neoprene booties if people feel the need

02:04:13.360 | to do that.

02:04:14.720 | If pain of the hands or feet is a barrier

02:04:17.740 | for people doing deliberate cold exposure,

02:04:20.420 | then it seems it would be okay to keep hands out

02:04:23.280 | or to keep your feet in the booties.

02:04:24.720 | - Yes, because then you do get the exposure,

02:04:27.820 | but of course hands and feet are very potent places

02:04:32.040 | in your body to get a fast activation

02:04:35.880 | of your nervous system, of course.

02:04:37.700 | But you can also just dip them and then take them up.

02:04:40.900 | It's still going to activate that,

02:04:42.960 | but you have your full body is covered in a coke receptors.

02:04:47.400 | You'll have a full activation anyways, so yeah.

02:04:50.520 | - You are providing very reassuring information to people

02:04:53.580 | 'cause I know a number of people

02:04:54.440 | that do not like to put their hands in.

02:04:56.500 | I find that the more of my body I get in,

02:04:58.980 | the more comfortable I am.

02:05:01.360 | I don't know if it's psychologically and or physiologically.

02:05:04.020 | I find that where there's an interface

02:05:06.880 | between the water and the cold, it's most uncomfortable.

02:05:10.560 | So I prefer to just get everything under.

02:05:12.000 | I keep my head out.

02:05:12.840 | Although these days I've been dunking all the way in

02:05:14.840 | and then coming out and then dunking once more

02:05:17.040 | with my head under before I get out after the plunge.

02:05:20.360 | That raises a different question.

02:05:22.220 | Now we're getting into kind of the practicalities

02:05:23.960 | of deliberate cold exposure, which I think are important.

02:05:27.480 | Sometimes I'll experience, and I hear from a lot of people

02:05:30.920 | that they'll get a kind of back of the head headache

02:05:33.960 | at the interface of the water

02:05:36.200 | when they're doing cold immersion to the neck.

02:05:40.080 | I assume this has to do with blood flow,

02:05:42.340 | that there's vasoconstriction right up until the neck

02:05:44.920 | and in the region surrounding it,

02:05:46.520 | but that maybe there's still blood flow to the head.

02:05:48.460 | But do we know what the origin of these headaches is?

02:05:52.260 | And again, this doesn't happen for everybody,

02:05:53.920 | but some people do experience them.

02:05:55.720 | - Okay, yeah.

02:05:56.560 | I haven't really heard about that one specifically.

02:05:59.400 | But I would say that there are different reasons

02:06:04.140 | for maybe keeping your head out of the water.

02:06:06.440 | But it seems like maybe for some,

02:06:08.160 | that could be a reason for just getting a quick head dunk.

02:06:11.920 | - Going all the way in.

02:06:13.200 | That's what I've started doing to eliminate.

02:06:15.160 | I wasn't getting headaches, but I noticed that interface.

02:06:19.200 | And I wasn't in the rest of the experience of it so much.

02:06:23.200 | So I started dunking all the way in.

02:06:24.680 | I noticed in some of the photos that you've put out

02:06:27.120 | and in your book that you'll sometimes wear a cap

02:06:29.840 | while you go in.

02:06:30.680 | - Yeah. - Okay.

02:06:31.780 | - And well, it comes from different reasons.

02:06:35.900 | So let's talk about some of the physiological reasons.

02:06:38.940 | So when you submerge in cold water up to the neck,

02:06:43.200 | studies have shown, and this is from Denmark,

02:06:45.340 | studies from BSPBI hospital,

02:06:47.980 | that when you submerge into cold water up to the neck

02:06:51.080 | at zero degrees, so zero degrees Celsius, very cold,

02:06:55.700 | you will have a decreased blood flow to the brain

02:06:58.180 | by around 30 to 40%.

02:07:01.300 | And it makes sense because you activate

02:07:02.800 | the sympathetic nervous system.

02:07:04.300 | And therefore you will have less blood flow to the brain.

02:07:07.380 | It makes you maybe a little bit dizzier.

02:07:09.160 | - Proof again that you need a heart more than a brain

02:07:11.960 | because when the sympathetic nervous system gets activated,

02:07:15.180 | blood flow is maintained to the heart to keep you alive,

02:07:17.620 | but obviously taken away from the brain

02:07:19.120 | to keep you from thinking.

02:07:20.340 | That's why it's hard to think when you're stressed.

02:07:22.280 | - Yeah, well, the muscles and your vital organs need to,

02:07:25.080 | you have to be able to run away from that tiger, right?

02:07:28.360 | - The rationale makes total sense.

02:07:30.040 | And who am I to disagree with mother nature?

02:07:33.640 | - Well, but yeah, so one of the reasons being

02:07:36.340 | that you should keep your head out of the water

02:07:38.380 | is that you could increase that decrease

02:07:42.780 | in blood flow to the brain further if you dunk the head.

02:07:46.420 | So there's just a very nice paper

02:07:48.460 | from a research group in Canada

02:07:51.940 | where they have collectively looked at different papers

02:07:55.400 | where they compared heat loss in a group,

02:07:59.100 | in the papers where they dunk the head

02:08:01.160 | and compared to heat loss, submerging up to the neck

02:08:05.500 | to see how much extra heat do we lose from our core

02:08:09.640 | when we dunk the head.

02:08:11.080 | So, and I think it's very interesting

02:08:13.080 | that if you submerge up to the neck,

02:08:15.000 | you have a heat loss of 11% from the body core.

02:08:19.640 | And when you then also dunk the head,

02:08:22.320 | you will increase that heat loss rate by 36%.

02:08:28.360 | So that means, I'm not saying that, I'm not here to say

02:08:31.400 | what is right and what is wrong.

02:08:32.880 | I just think that people should know the information

02:08:35.740 | so they can for themselves evaluate what is best for them.

02:08:38.960 | But if you increase your heat loss rate by 36%

02:08:43.340 | from your core, that's gonna increase your after drop,

02:08:47.040 | which we touched upon a little bit earlier, even further.

02:08:49.920 | So that's meaning that you are closer to hypothermia

02:08:53.680 | than you are if you just submerge up to the neck.

02:08:56.440 | So you should really think about whether this is like

02:08:59.080 | something that you want to do,

02:09:00.760 | or if it's just better for you

02:09:02.520 | not to get that cold in your core.

02:09:05.200 | The beanie is also because I have a little bit

02:09:08.520 | of sensitive ears, so meaning that if there's wind,

02:09:11.580 | and because we swim in the open sea in Denmark,

02:09:14.160 | we have a lot of wind.

02:09:15.720 | Our conditions are just very rainy, very windy,

02:09:20.720 | and when the temperature is also freezing,

02:09:24.000 | you could get this, what is that called?

02:09:27.240 | So very cold and lightheaded just from wind.

02:09:30.840 | So if you also submerge into cold water and you then get up,

02:09:33.960 | you will get a brain freeze immediately.

02:09:36.680 | So it is enough to just go up to the neck,

02:09:39.780 | wear a beanie to just not get dizzy also

02:09:42.440 | because the heat loss is increased, of course,

02:09:46.920 | but also the blood flow to the brain has decreased.

02:09:50.080 | So the beanie will keep you a little bit warmer

02:09:52.120 | so you can stay for one to two minutes.

02:09:53.520 | So it's just a way of getting around

02:09:55.960 | some of the conditions also.

02:09:57.900 | So people can choose that if they feel that,

02:10:00.260 | but it's quite normal to do in Scandinavia wear a beanie.

02:10:04.880 | - Love it.

02:10:06.280 | So for those of you afraid of doing a two-minute cold shower

02:10:09.120 | what Dr. Silberg just described,

02:10:11.880 | you see how she and others are capable

02:10:15.760 | of doing things far harder than that.

02:10:18.200 | When the way you describe it with the cold wind

02:10:19.860 | in Scandinavia is quite striking.

02:10:24.360 | Along the lines of covering the head,

02:10:26.260 | there's this seemingly paradoxical thing

02:10:30.740 | of people going into hot saunas and wearing wool caps.

02:10:35.480 | You know, if you go to a banya or you go to a sauna

02:10:38.820 | and there are people who are, well, from Eastern Europe

02:10:43.080 | or typically are Finland or Russia or Ukraine or elsewhere,

02:10:48.080 | what you'll see is that many of them are wearing wool caps

02:10:50.080 | in the sauna, which many people think is to make it hotter.

02:10:53.220 | That's actually not the case.

02:10:54.260 | It actually insulates you from the heat environment.

02:10:57.080 | The sense of urgency to get out of the hot sauna

02:11:00.960 | is a brain-driven mechanism.

02:11:03.220 | And so the reason that people wear wool hats in the sauna

02:11:06.880 | is it actually lets you stay in the sauna longer

02:11:09.680 | because it takes a lot of heat to the skin

02:11:12.220 | before you feel that you have to get out.

02:11:15.880 | Whereas so when you insulate the brain,

02:11:18.800 | you don't get that signal.

02:11:20.720 | It's pretty interesting.

02:11:21.560 | I've tried this before just by putting a towel over my head

02:11:23.800 | in the sauna and you can stay in there much more easily

02:11:26.820 | and for much longer.

02:11:28.140 | You know, as we talk about these different stimuli

02:11:31.480 | for the hormetic response, the adaptation distress,

02:11:35.040 | you know, it occurs to me that the big ones

02:11:37.880 | in our evolutionary history have been light, right?

02:11:41.960 | I mean, you were talking about seasonal changes.

02:11:45.120 | We know there, especially as you go up to Nordic countries,

02:11:48.120 | there are seasonal changes in the amount of light

02:11:49.760 | by time of year, dramatic ones, in fact,

02:11:52.740 | less so at the equator, of course.

02:11:55.520 | Light, temperature, food, movement.

02:12:00.520 | And it's sort of interesting.

02:12:02.160 | And at the same time,

02:12:03.560 | perhaps it should have been obvious to us

02:12:05.220 | that there are stimuli that our bodies have evolved

02:12:10.220 | to adapt to in very powerful ways.

02:12:13.200 | And so the idea that temperature, heat, and cold

02:12:17.000 | could evoke these tremendous physiological changes

02:12:19.920 | that are beneficial for us

02:12:21.720 | probably shouldn't surprise us at all.

02:12:23.440 | I mean, this is why,

02:12:24.640 | I mean, these are not esoteric mechanisms.

02:12:28.680 | They're actually the foundational mechanisms

02:12:31.120 | by which our body and the bodies of other animals adapt.

02:12:34.560 | So I do have a question about the different ways

02:12:39.040 | that people could approach deliberate cold exposure.

02:12:41.700 | So for instance, children.

02:12:45.640 | I've been to banyas where there are kids

02:12:48.460 | six or seven years old with their parents at the banya.

02:12:51.460 | And so they're in hot sauna.

02:12:53.360 | I'm not suggesting people do this

02:12:54.640 | if they're not adapted to it.

02:12:56.560 | And talk to your parents' kids

02:12:58.220 | and talk to your kids' parents, talk to your doctors.

02:13:01.660 | But it is remarkable.

02:13:02.880 | I mean, children doing sauna from a young age

02:13:05.940 | or deliberate cold exposure.

02:13:07.740 | Are there any data on this and is it safe,

02:13:09.660 | assuming that, you know, obviously that they can swim

02:13:12.100 | and or they're doing this in a tub or shower?

02:13:14.400 | And then I'd also like to ask you about,

02:13:17.460 | are there any additional male, female differences?

02:13:20.440 | I know your study focused on men,

02:13:23.120 | but other studies have focused on both.

02:13:26.040 | And you of course are a woman

02:13:28.240 | and can attest to your own experience with this.

02:13:31.040 | So children, men, women,

02:13:33.880 | differences there in terms of protocols.

02:13:36.040 | Is there anything that people should build

02:13:37.440 | into the structure of their deliberate cold exposure

02:13:39.940 | that's unique to that?

02:13:41.280 | - So yeah, so this was on cold exposure.

02:13:44.920 | So yeah, I think that,

02:13:47.620 | starting with the question about children,

02:13:51.380 | I think that it's important to think about,

02:13:54.880 | as children are smaller than adults,

02:13:57.360 | so we cannot really completely transfer all the information

02:14:01.600 | and the benefits and also protocols for how long

02:14:04.580 | and stuff like that to children.

02:14:06.680 | We cannot do that because they are just smaller in mass.

02:14:09.640 | And one study that actually improves this

02:14:13.760 | is a study where they have compared heat loss

02:14:18.200 | in children, boys who were 12 years old

02:14:22.420 | compared to adults, men,

02:14:25.960 | and looked at heat loss of the core temperature

02:14:29.560 | and exposed them to one or two minutes cold exposure,

02:14:35.320 | so immersion up to the neck.

02:14:38.080 | And what they saw was that the boys in this study

02:14:42.040 | could actually defend the core temperature

02:14:44.480 | in the same way as the adults could,

02:14:47.960 | but they had to use their muscles way faster.

02:14:51.840 | So it means that they couldn't stay for as long

02:14:55.840 | and they use more energy to defend their core temperature

02:14:58.840 | compared to the adults.

02:15:00.280 | But for one minute, it seems that they could actually,

02:15:04.920 | but they will be colder when they then come out

02:15:07.120 | because they are smaller in their mass to their ratio.

02:15:11.520 | So it means that if the surface is so large on children

02:15:16.200 | and their mass and muscles being smaller to that ratio,

02:15:20.000 | it means that they can be in the water less time

02:15:24.120 | before they get hypothermic.

02:15:26.280 | So just think about that.

02:15:28.240 | They are just smaller.

02:15:29.100 | They can't defend their temperature for a very long time.

02:15:32.880 | But in this study, they saw that for up to,

02:15:35.160 | I think it was a minute or so they could-

02:15:37.000 | - One minute. - One minute, yeah.

02:15:38.200 | - I'm glad you mentioned hypothermia

02:15:39.600 | in smaller bodied people, children.

02:15:42.680 | I used to do some Pacific ocean swims in the morning

02:15:47.000 | without wetsuits and I adapted to it pretty quickly.

02:15:49.480 | And these are fairly long swims

02:15:51.080 | and we brought an excellent swimmer with us

02:15:53.800 | that was interning with me for a while.

02:15:58.160 | He's 16 years old at the time and very lean.

02:16:01.960 | And he wasn't small for his age,

02:16:04.120 | but he was smaller than us,

02:16:05.600 | than it was all guys on the swim that day.

02:16:08.220 | Sometimes women join us.

02:16:10.240 | And he got hypothermic and he's an excellent swimmer.

02:16:15.080 | And he didn't report feeling overly cold,

02:16:17.580 | but fortunately we got him to shore and heated him up again.

02:16:21.960 | So he lived.

02:16:23.040 | I don't think his mother is going to ever let him

02:16:24.580 | go swimming with us again.

02:16:25.640 | He's thriving in the world.

02:16:26.840 | He's a university student now and he recalls that swim.

02:16:30.680 | I mean, this is why you always want to ocean swim

02:16:32.560 | with a buddy, with people.

02:16:34.300 | Yeah, he became hypothermic.

02:16:37.520 | His teeth turned yellow.

02:16:39.080 | He was kind of slurring his words.

02:16:40.640 | He wasn't making sense.

02:16:42.360 | We got him onto shore and he was kind of drooling

02:16:45.020 | and a little semi euphoric and then kind of,

02:16:47.840 | hypothermia is no joke.

02:16:50.160 | So I think, yeah, so I'm really glad that this is coming up

02:16:53.520 | because the cold is a powerful stimulus

02:16:55.560 | and kids are at a, and smaller bodied people

02:16:59.640 | are at a greater risk of hypothermia.

02:17:01.520 | So a good reason to approach it with caution,

02:17:03.740 | maybe start with cold showers, get then cold immersion

02:17:07.120 | and still water, natural water and open bodies of water.

02:17:09.840 | Of course, they're always going to be more dangerous

02:17:12.320 | for other reasons, currents and things of that sort.

02:17:14.840 | Okay. - And drowning, yeah.

02:17:16.500 | - So important note there.

02:17:18.200 | What about any additional male, female differences

02:17:21.760 | or similarities that we should be aware of?

02:17:24.080 | And this comes up all the time on social media.

02:17:26.400 | Anytime I post anything about a study,

02:17:28.640 | it's what about women?

02:17:29.600 | Because oftentimes there are differences.

02:17:31.560 | - Yeah, yeah.

02:17:32.400 | And we also just talked about the difference

02:17:36.240 | in temperature in men and women.

02:17:39.600 | So it means that if we replicated my study in women,

02:17:44.600 | it could be that they would have enough,

02:17:48.360 | you can say cold exposure with just nine minutes per week.

02:17:51.480 | It could be because they apparently are also just colder

02:17:56.440 | and they have increased metabolism in their brown fat.

02:17:59.980 | It's just they have more brown fat.

02:18:01.760 | It could be, but this is just something

02:18:03.760 | that I frankly don't know.

02:18:06.080 | But women also do cold exposure winter swimming

02:18:10.000 | with the 11 minutes protocol.

02:18:11.560 | I do it myself and feel good about it.

02:18:15.080 | So I would say that women also regarding activation

02:18:19.720 | of the brown fat, it should be the same in theory,

02:18:24.040 | but I don't know if women actually do need

02:18:27.600 | to have another protocol when it comes

02:18:29.320 | to this rapid cold exposure.

02:18:31.960 | I think that it's another question

02:18:33.600 | if we are talking about ice swimming,

02:18:35.920 | when it comes to how far can you be in the cold water

02:18:38.920 | without getting hypothermic,

02:18:40.520 | then there will be differences in men and female.

02:18:44.720 | But if you do this cold exposure

02:18:47.040 | for a very brief amount of time,

02:18:48.800 | which is what I try to talk about,

02:18:52.560 | what we call also microstressing the body

02:18:54.720 | to increase the hematics stress, the healthy stress,

02:18:58.040 | then this is such a short amount of exposure

02:19:02.480 | that it's fairly the same.

02:19:04.280 | I think women can look at this

02:19:07.120 | as a fairly good protocol for them as well.

02:19:11.040 | - I always say that if you really dread the cold

02:19:13.920 | and don't like the cold, then you are a perfect candidate

02:19:17.680 | for using deliberate cold exposure

02:19:19.280 | because the sympathetic, aka the stress response,

02:19:22.240 | will be greater and thereby the adaptation

02:19:25.720 | to that shorter one or two minutes

02:19:28.720 | is going to be much greater, right?

02:19:31.480 | For people that are perfectly comfortable in the cold,

02:19:33.740 | it's harder to get an adaptation response,

02:19:36.120 | the same way that if somebody is very strong

02:19:37.740 | and they can lift a very heavy weight,

02:19:39.920 | that very heavy weight is unlikely to evoke

02:19:41.880 | the same kind of, or same degree of adaptive responses

02:19:46.440 | if somebody is not quite as strong.

02:19:47.880 | So another reason to keep these exposures relatively short

02:19:51.920 | and more frequent

02:19:53.400 | than to do longer duration exposures frequently.

02:19:57.380 | However, let's say somebody only had two days a week

02:20:00.640 | to do deliberate cold exposure.

02:20:03.860 | Maybe they don't have access to a sauna, maybe they do.

02:20:06.600 | Would you suggest that they get in for one or two minutes,

02:20:09.520 | then get out, then get back in for another couple of minutes,

02:20:13.200 | then get out and call that for four or five minutes

02:20:17.520 | to try and get to that 11 minutes total per week,

02:20:20.720 | as opposed to getting in for a full five minutes

02:20:23.760 | and then getting out and coming back a second time that week.

02:20:26.340 | I know this is getting down into the weeds,

02:20:28.040 | but these are the sorts of things

02:20:29.180 | that I think people really want to know

02:20:30.620 | because a lot of people either don't live close

02:20:33.200 | to a body of water or don't have a cold plunge

02:20:37.360 | that they can do this with,

02:20:38.780 | although cold shower apparently works too.

02:20:41.040 | So most people live close to a shower.

02:20:43.600 | - Yeah, so definitely, I think the changes in temperature

02:20:46.920 | is what is strengthening your cells in the body.

02:20:51.920 | So if you can do the short amount of exposure

02:20:55.320 | and then get out and get back in,

02:20:57.360 | that is gonna, you can say, strengthen your cells

02:21:01.960 | because you are challenging them

02:21:04.120 | to adapt to changing temperatures.

02:21:08.240 | So doing one session, you can change this, right?

02:21:11.720 | You can do it if you are able to go to cold water,

02:21:14.780 | but also a sauna, then you just do it that automatically

02:21:17.360 | and you will have a change in temperature.

02:21:19.120 | But you could also do it by variating the temperature

02:21:21.680 | in your cold plunge if you have a plunge

02:21:24.680 | or if you have the open sea or you have seasons even,

02:21:28.360 | we have that in Denmark, so we have four seasons

02:21:31.080 | and the temperature is gonna vary with that.

02:21:33.360 | So we have nature who can just change this for us

02:21:36.560 | and we don't have to think about it.

02:21:37.840 | But if you have a cold plunge, well, then I would say

02:21:40.400 | that changing the temperature is what is gonna create

02:21:43.200 | this hermetic stress and also keep your cells on its toes,

02:21:47.600 | you can say, because the body will still be stressed

02:21:52.600 | to try to adapt to the new temperature

02:21:55.980 | as it's seen as something actually toxic to the body, right?

02:21:59.100 | It's a small piece of toxicity

02:22:02.400 | that you are exposing yourself to.

02:22:05.020 | You don't have to swallow it,

02:22:06.040 | but it's enough that you touch it actually.

02:22:08.460 | - Yeah, great way to frame it.

02:22:12.120 | That brings me back to this idea of circadian time.

02:22:15.360 | In your study, you didn't control for a specific time of day

02:22:19.480 | and now I'm realizing that may be a great asset

02:22:22.000 | to the whole thing.

02:22:23.020 | So we know, for instance, that our bodies go through

02:22:25.320 | pretty dramatic shifts in temperature

02:22:27.240 | from the time we wake up, our body starts heating up

02:22:29.960 | as we wake up and continues to heat until the afternoon

02:22:33.240 | and then starts to drop in the later afternoon

02:22:35.020 | and then assuming all things are working correctly,

02:22:38.560 | that body temperature drops and we sleep.

02:22:41.140 | So I could imagine that doing deliberate cold exposure

02:22:43.540 | at different times just by way of convenience

02:22:47.300 | or by way of intention could be very beneficial

02:22:49.740 | because my body temperature is going to be

02:22:51.160 | quite a bit warmer at one time of day versus another

02:22:54.000 | and in that way, keeping the system tuned.

02:22:56.320 | And that's really what I keep hearing coming through

02:22:59.100 | as you explain these data and all these beautiful studies,

02:23:02.100 | yours and others, is that it's not really

02:23:04.880 | about getting cold.

02:23:06.120 | It's about going from warm to cold and from cold to warm.

02:23:10.720 | And I love this idea because,

02:23:14.060 | I probably said this a hundred times on my podcast

02:23:16.800 | and a million times in my life and I'll continue to,

02:23:18.940 | which is that biology is not an event, it's a process.

02:23:21.820 | Like these metabolic and thermoregulatory processes

02:23:26.080 | are indeed like the turning of a knob.

02:23:28.240 | It's a verb as opposed to a noun.

02:23:31.060 | And so I think if people can internalize that idea,

02:23:35.260 | that they're going to have a lot more flexibility,

02:23:38.020 | a lot more fun and get a lot more benefit

02:23:40.500 | as opposed to thinking,

02:23:41.340 | okay, I need to get into X degrees of water

02:23:44.100 | for X amount of time on X number of days

02:23:47.920 | in a very rigid way. - And I get this question

02:23:49.320 | all the time, how much and how cold.

02:23:51.980 | And I mean, it's just like, well,

02:23:54.820 | because we also don't have studies showing exactly

02:23:57.180 | if you just keep five degrees in your water

02:23:59.920 | and you do that for a month, then what happens?

02:24:02.860 | Maybe in the future, we will know much more about this

02:24:05.000 | and I'm sure it's going to come and I really hope so.

02:24:08.060 | But I just think by logically changing that temperature

02:24:12.180 | up and down, up and down,

02:24:13.340 | and you also do that in your water,

02:24:14.820 | it doesn't really, it's not that important

02:24:17.420 | what temperature you will have your water then,

02:24:19.620 | then just keep changing it, going up and down.

02:24:21.700 | It could be all up to 12 degrees Celsius.

02:24:24.340 | You're going to activate your brown fat anyways.

02:24:26.200 | I mean, 12, 19 degrees cold air

02:24:30.340 | is enough to activate your brown fats.

02:24:32.100 | So maybe we don't have to go as cold

02:24:34.740 | as I think many people think

02:24:37.100 | and putting ice even all the time, you don't have to.

02:24:41.820 | I don't think it's necessary to expose yourself

02:24:44.760 | to that cold temperature all the time, but vary it a bit.

02:24:49.760 | - So keep the system off balance.

02:24:51.460 | - Yes, off balance. - It's the way

02:24:52.300 | to keep it tuned.

02:24:53.260 | - Yeah.

02:24:54.100 | - You mentioned a study that is more recent

02:24:57.340 | or an ongoing that's not published.

02:24:59.700 | If you're willing, could you share maybe some of the data

02:25:02.900 | from that findings from that study with of course the cue

02:25:07.660 | to everybody that these are not yet published data

02:25:10.300 | so that the conclusions could change,

02:25:11.880 | the data could change for that matter.

02:25:13.820 | - Yeah, so we haven't analyzed all the data yet.

02:25:16.820 | And I know from the study that we did publish

02:25:20.620 | that we would need to look more at the data.

02:25:24.380 | So I don't really have any results yet that I can share

02:25:27.340 | because we are still in very preliminary analysis of this.

02:25:30.500 | So I wouldn't know yet what to exactly say about it.

02:25:34.300 | But what we looked at was both men and women method.

02:25:36.980 | So that's coming.

02:25:38.780 | - Oh, that's fantastic.

02:25:40.340 | That answer is going to please a great number of people

02:25:43.260 | and intrigue everybody.

02:25:44.980 | Well, listen, I want to really thank you

02:25:50.620 | for coming here today to talk about your work

02:25:54.980 | and the incredible direction that it points to.

02:25:58.700 | Because I think that no one study is definitive,

02:26:03.260 | but your study really, again, stands as a landmark

02:26:07.180 | in the landscape of exploring deliberate cold exposure

02:26:10.940 | and heat, how it can impact

02:26:13.420 | and potentially impact our health.

02:26:15.460 | Because frankly, there just haven't been

02:26:17.780 | that many high resolution, detailed modern studies of this.

02:26:22.780 | There have been studies of sauna.

02:26:24.200 | There've been some studies of cold.

02:26:25.480 | There are a lot of groups in physiology

02:26:26.820 | that work on hypothermia and very cold exposure.

02:26:30.840 | But most of the temperatures used in those days

02:26:33.160 | just aren't practical.

02:26:34.160 | So first of all, I just want to thank you

02:26:35.900 | for doing the work that you've done

02:26:37.460 | and for the work that you continue to do.

02:26:38.940 | I'm waiting with bated breath, as they say,

02:26:43.420 | to hear the results of this study

02:26:46.460 | that's ongoing on both men and women.

02:26:48.100 | So we'll have to have you back to inform us about that soon.

02:26:51.620 | And I want to thank you

02:26:52.480 | for the incredible public education efforts

02:26:55.500 | that you've been doing on social media

02:26:57.780 | and with respect to your book.

02:27:01.240 | And we, of course, we'll put links to all of those things

02:27:04.280 | in the show note caption so people can learn from you

02:27:06.640 | and can continue to learn from you.

02:27:08.220 | We certainly need more scientists

02:27:11.020 | who are both experienced with doing hardcore research,

02:27:14.660 | as it's called, and who also do the practices.

02:27:18.840 | I think that's a wonderful additional asset.

02:27:21.460 | You're not just behind a lab coat

02:27:22.780 | or bundled up in a down feather jacket

02:27:26.760 | as everyone else is getting into the cold.

02:27:28.020 | You do these things.

02:27:29.380 | And that you are so open and generous

02:27:32.120 | in the way that you share knowledge,

02:27:34.380 | which includes coming here today

02:27:35.660 | to share knowledge with me and our audience.

02:27:38.620 | So thank you ever so much.

02:27:40.900 | - You're very welcome.

02:27:41.900 | I am so pleased to be here

02:27:43.260 | and thank you so much for inviting me.

02:27:44.800 | And I could explain my study

02:27:46.740 | and I can share some of my insights from doing that.

02:27:50.060 | So I'm very grateful for being here.

02:27:52.540 | Delighted, and we'll have to have you back again.

02:27:54.520 | Thank you for joining me for today's discussion,

02:27:56.420 | all about deliberate cold and deliberate heat exposure

02:27:58.980 | science and protocols with Dr. Susanna Soberg.

02:28:01.780 | If you'd like to learn more about Dr. Soberg's research,

02:28:04.340 | or you would like to learn about the research

02:28:05.840 | of her institute, the Soberg Institute,

02:28:08.220 | please see the links in the show note caption.

02:28:10.640 | Also in the show note caption,

02:28:11.860 | you can find a link to Dr. Soberg's excellent book,

02:28:14.500 | Winter Swimming.

02:28:15.740 | If you're learning from and/or enjoying this podcast,

02:28:18.100 | please subscribe to our YouTube channel.

02:28:19.880 | That's a terrific zero cost way to support us.

02:28:22.500 | In addition, please subscribe to the podcast

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02:28:30.820 | If you have questions for me

02:28:32.060 | or topics you'd like me to cover on the Huberman Lab Podcast

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02:28:40.460 | I do read all the comments.

02:28:42.500 | In addition, please check out the sponsors mentioned

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02:28:46.660 | That's the best way to support this podcast.

02:28:48.900 | Not so much on today's episode,

02:28:50.380 | but on various previous episodes of the Huberman Lab Podcast,

02:28:52.920 | we discuss supplements.

02:28:54.460 | While supplements aren't necessary for everybody,

02:28:56.360 | many people derive tremendous benefit from them

02:28:58.420 | for things like enhancing sleep, focus, and hormone support.

02:29:01.440 | The Huberman Lab Podcast is proud to have partnered

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02:29:14.900 | If you're not already following the Huberman Lab Podcast

02:29:17.120 | on social media, we are Huberman Lab on Instagram,

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02:29:22.360 | And on all those places, I focus on material

02:29:25.180 | that somewhat overlaps with content

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02:29:34.440 | For those of you that haven't already subscribed

02:29:36.240 | to our so-called neural network newsletter,

02:29:38.280 | this is a completely zero cost monthly newsletter

02:29:41.380 | that has summaries of podcast episodes

02:29:43.600 | and so-called toolkits.

02:29:44.920 | Toolkits are lists of about a page to two pages long

02:29:48.840 | that give the critical tools,

02:29:50.420 | for instance, for optimizing sleep

02:29:52.400 | or for neuroplasticity or deliberate cold exposure

02:29:54.480 | or deliberate heat exposure, optimizing dopamine.

02:29:56.700 | Again, all available to you at zero cost.

02:29:59.080 | You simply go to HubermanLab.com,

02:30:01.080 | go to the Menu tab in the corner,

02:30:03.080 | scroll down to Newsletter.

02:30:04.320 | You provide us your email.

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02:30:07.480 | And in addition to that, there are samples of toolkits

02:30:10.760 | on the HubermanLab.com website, again, under Newsletter.

02:30:14.080 | And you don't even have to sign up to access those.

02:30:16.240 | But I think most people do end up signing up

02:30:17.640 | for the newsletter

02:30:18.480 | because it's rich with useful information

02:30:20.240 | and again, completely zero cost.

02:30:21.880 | Thank you once again for joining me

02:30:23.160 | for today's discussion with Dr. Susanna Soberg.

02:30:25.840 | And last, but certainly not least,

02:30:27.940 | thank you for your interest in science.

02:30:29.780 | [upbeat music]

02:30:32.360 | (upbeat music)

Dr. Susanna Søberg: How to Use Cold & Heat Exposure to Improve Your Health | Huberman Lab Podcast

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