The Science & Health Benefits of Deliberate Heat Exposure

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.

00:00:05.880 | I'm Andrew Huberman,

00:00:10.360 | and I'm a professor of neurobiology and ophthalmology

00:00:13.280 | at Stanford School of Medicine.

00:00:15.160 | Today, we are talking about the science of heat,

00:00:18.120 | and more specifically, the science of heating, the verb,

00:00:22.040 | meaning how our body heats up

00:00:24.440 | from both the outside and the inside.

00:00:27.200 | Heat is a remarkable stimulus,

00:00:29.960 | meaning when we are in a hot environment,

00:00:32.240 | it has a profound effect on our biology.

00:00:35.520 | And heating up from the outside,

00:00:38.280 | or as you'll soon learn, from the inside,

00:00:41.320 | has a profound effect on many different aspects

00:00:44.720 | of our health, including our metabolism,

00:00:47.760 | both in the immediate and long-term, our cognition,

00:00:51.320 | meaning our ability to think more or less clearly.

00:00:54.600 | And if you're immediately thinking

00:00:56.380 | that heating up makes you less capable of thinking,

00:00:59.920 | you're wrong.

00:01:01.360 | Heat applied properly as a stimulus

00:01:03.760 | can engage certain neurochemical systems

00:01:06.120 | in your brain and body

00:01:07.300 | that can allow your brain to function far better.

00:01:10.180 | We will talk about those data today.

00:01:12.080 | So we're going to talk about the science of heat and heating,

00:01:15.000 | both in terms of their mechanisms,

00:01:17.080 | and as I know many of you are interested in,

00:01:19.760 | the tools related to the use of heat,

00:01:22.220 | things like sauna, how often to do sauna,

00:01:25.440 | how long to be in the sauna,

00:01:26.860 | how hot to be in the sauna for particular goals and outcomes.

00:01:31.160 | We're also going to talk about

00:01:32.440 | the very exciting new science around local heating,

00:01:36.120 | that is the use of heat applied to specific areas

00:01:39.840 | of the body in order to heal or improve tissues

00:01:42.860 | at that location that you are heating,

00:01:44.740 | as well as your biology and health overall.

00:01:47.840 | In fact, we are going to talk about

00:01:49.260 | one very recently published paper

00:01:51.640 | that came out in the journal Cell.

00:01:53.600 | Cell is one of the three apex journals,

00:01:55.680 | meaning three of the most competitive,

00:01:57.920 | most rigorous scientific journals.

00:02:00.080 | Those are Nature, Science, and Cell.

00:02:02.040 | This particular paper was published in Cell,

00:02:04.080 | and I will go into it in more detail later.

00:02:06.340 | But basically what this paper shows

00:02:09.100 | is that by locally heating up skin and fat,

00:02:13.760 | you can change the identity of certain fat cells

00:02:18.280 | at that location and elsewhere.

00:02:20.540 | We have three kinds of fat,

00:02:21.980 | white fat, beige fat, and brown fat.

00:02:23.800 | And as you will learn more about soon,

00:02:26.360 | white fat is not very metabolically active.

00:02:28.560 | It's more of a fuel reserve.

00:02:30.520 | It's what we typically think of as blubbery fat.

00:02:33.440 | Beige fat and brown fat are rich in mitochondria,

00:02:36.840 | and those mitochondria provide a sort of furnace

00:02:39.320 | or heating mechanism for your entire body

00:02:41.320 | and increase your metabolism and the burning of white fat.

00:02:45.360 | So in other words,

00:02:46.200 | having more beige fat and brown fat is a good thing.

00:02:49.000 | And it turns out that the proper application of heat

00:02:52.420 | to specific areas of your body

00:02:54.300 | can increase the conversion of white fat to beige fat.

00:02:57.860 | In other words, turn an innocuous fuel source

00:03:01.320 | into a metabolically active tissue

00:03:03.600 | that can help you burn off more white fat.

00:03:06.640 | I think many people are going to be interested in this paper

00:03:09.400 | and the tools that emerge from this paper.

00:03:11.840 | It's a fascinating set of findings

00:03:13.640 | that actually emerged from my understanding

00:03:15.880 | of the biology of burn and people who receive intense burns.

00:03:20.240 | And that is not what I'm going to recommend to you

00:03:21.820 | as a tool, of course,

00:03:23.280 | but understanding a little bit about how burns impact

00:03:26.920 | our biology and health

00:03:28.320 | has allowed these pioneering researchers

00:03:30.800 | to develop new tools to combat obesity

00:03:33.400 | and metabolic disorders,

00:03:34.560 | and that you can apply for basic things like fat loss.

00:03:37.700 | I'm pleased to announce that the Huberman Lab Podcast

00:03:40.200 | is now partnered with Momentous Supplements.

00:03:42.840 | Our motivation for partnering with Momentous

00:03:45.040 | is to provide people one location where they can go

00:03:47.920 | to access the highest quality supplements

00:03:50.680 | in the specific dosages that are best supported

00:03:53.700 | by the scientific research

00:03:55.240 | and that are discussed during various episodes

00:03:57.420 | of the Huberman Lab Podcast.

00:03:59.040 | If you go to livemomentous.com/huberman,

00:04:02.440 | you will see those formulations.

00:04:04.000 | I should mention that we are going to add more formulations

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00:04:08.220 | And you will see specific suggestions

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00:04:12.640 | meaning what dosages and times of day,

00:04:14.720 | and in fact, how to combine those supplements

00:04:17.540 | with specific behavioral protocols

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00:04:21.460 | and are science supported

00:04:22.760 | in order to derive the maximum benefit

00:04:25.280 | from those supplements.

00:04:26.760 | And many of you will probably also be pleased to learn

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00:04:34.080 | So once again, if you go to livemomentous.com/huberman,

00:04:37.800 | you will find what we firmly believe

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00:04:44.360 | and the best protocols for taking those supplements

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00:04:52.900 | I'm pleased to announce

00:04:53.740 | that I am hosting two live events in May, 2022.

00:04:57.120 | The first live event will take place

00:04:58.660 | in Seattle, Washington on May 17th.

00:05:01.400 | The second live event will take place

00:05:02.940 | in Portland, Oregon on May 18th.

00:05:05.480 | Both are part of a lecture series entitled

00:05:07.320 | The Brain-Body Contract,

00:05:08.840 | during which I will talk about science

00:05:10.280 | and science-based tools,

00:05:11.660 | many of which overlap with the topics covered

00:05:13.820 | on the Huberman Lab Podcast,

00:05:15.420 | but most of which will not

00:05:17.360 | and will be completely new topics and tools

00:05:19.600 | never discussed publicly before.

00:05:21.380 | Both live events will also include

00:05:23.080 | a question and answer period

00:05:24.820 | during which you, the audience,

00:05:26.220 | can ask me questions directly

00:05:27.980 | about any aspect of science or science-based tools

00:05:30.800 | and I will attempt to answer them.

00:05:32.820 | Tickets for the two events,

00:05:34.120 | again, Seattle on May 17th and Portland on May 18th,

00:05:38.280 | are both available at hubermanlab.com/tour.

00:05:42.360 | Before we begin, I'd like to emphasize that this podcast

00:05:45.020 | is separate from my teaching and research roles at Stanford.

00:05:47.860 | It is, however, part of my desire and effort

00:05:49.740 | to bring zero cost to consumer information

00:05:51.540 | about science and science-related tools

00:05:53.800 | to the general public.

00:05:55.200 | In keeping with that theme,

00:05:56.240 | I'd like to thank the sponsors of today's podcast.

00:05:58.920 | Our first sponsor is Element.

00:06:00.740 | Element is an electrolyte drink

00:06:02.180 | that has everything you need

00:06:03.620 | and none of what you don't need, meaning sugar.

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00:06:23.020 | People out there with pre-hypertension and hypertension,

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00:06:43.960 | I consume Element when I first wake up in the morning,

00:06:46.500 | during exercise, and after exercise,

00:06:49.020 | and sometimes, again, if I've been sweating profusely,

00:06:51.740 | for instance, after doing a sauna

00:06:53.520 | or taking a run on a hot day, things of that sort.

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00:09:32.500 | Okay, let's talk about heat.

00:09:34.220 | More specifically, let's talk about the biology of heat

00:09:36.940 | and heating and the health benefits and tools

00:09:39.880 | related to heat and heating.

00:09:41.580 | The first question that we have to answer is,

00:09:44.440 | how do we heat up?

00:09:46.600 | And the answer to that question is we heat up two ways.

00:09:50.840 | We heat up from the outside,

00:09:53.120 | meaning the things that we come into contact with,

00:09:55.500 | the clothing that we put on our body,

00:09:57.940 | whether or not there's heat in the room

00:09:59.940 | or whether or not it's cold outside or cold in a room,

00:10:02.940 | and we heat up from the inside.

00:10:05.700 | Our body has the capacity to generate more heat

00:10:09.020 | or to cool down, meaning to turn off the heating process,

00:10:12.860 | and it can do that in ways

00:10:15.500 | that match the external environment.

00:10:18.460 | The simplest way to think about this

00:10:20.040 | is that we actually have two body temperatures.

00:10:22.980 | People will say, oh, what's body temperature, 98.6.

00:10:25.620 | That's actually not true.

00:10:27.260 | Body temperature varies between individuals,

00:10:29.500 | it varies across time of day within individuals,

00:10:32.220 | and at every point across your entire lifespan,

00:10:36.060 | you have two distinct temperatures.

00:10:37.780 | One is the temperature on your skin,

00:10:39.900 | what scientists call your shell,

00:10:42.760 | and the temperature of your core, your viscera,

00:10:46.020 | meaning your organs, your nervous system,

00:10:48.100 | and your spinal cord.

00:10:49.500 | And as you can imagine, the temperature of your core

00:10:51.980 | is always higher than the temperature at your surface.

00:10:56.040 | So the important thing to know

00:10:57.100 | is that you have a temperature at your shell

00:10:59.540 | and a temperature at your core.

00:11:01.000 | Now, you don't need to know

00:11:01.900 | exactly what those temperatures are in most cases,

00:11:04.300 | but it is vitally important to understand

00:11:07.180 | that you have those two temperatures

00:11:08.900 | and that your brain is constantly sending out signals

00:11:11.820 | to your body as to whether or not it should heat up

00:11:15.060 | or cool down depending on the temperature of the shell,

00:11:19.740 | which makes total sense.

00:11:20.980 | This is a lot like a thermostat in a room,

00:11:23.720 | which is essentially paying attention

00:11:25.600 | to how cold or hot it is,

00:11:27.040 | and then sending signals to the heating or cooling system

00:11:29.640 | to either heat up the environment

00:11:31.020 | or cool down the environment

00:11:32.400 | depending on the temperature in that environment.

00:11:35.560 | Your brain has neurons that send signals

00:11:38.840 | to other cells in your body

00:11:40.540 | and deploy the release of chemicals in your brain and body

00:11:43.140 | to heat you up when you are too cold

00:11:45.360 | and to cool you down when you are too hot.

00:11:48.140 | So if you can understand that you have two body temperatures,

00:11:51.740 | one at your shell, the surface,

00:11:53.120 | and one at your core inside,

00:11:55.180 | and that your body and brain are always trying

00:11:57.440 | to balance those two temperatures in the appropriate way,

00:12:00.640 | well, then you're halfway there

00:12:01.920 | to understanding the biology of thermal regulation

00:12:04.660 | and heating, and you'll be a lot further along

00:12:07.800 | in understanding how specific tools can be used

00:12:10.800 | to improve metabolism or improve cognition, for instance.

00:12:14.840 | In fact, later you will learn that one way

00:12:18.360 | that you can heat up

00:12:19.520 | is by cooling down the surface of your body.

00:12:21.800 | That's right.

00:12:22.700 | If I were to throw a cold towel, ice cold towel

00:12:25.240 | onto your torso right now and ask you,

00:12:28.080 | well, how do you feel?

00:12:28.920 | You'd say, oh, that's cold, that's chilly.

00:12:30.760 | However, because your brain is acting

00:12:33.020 | like a bit of a thermostat as the surface,

00:12:35.200 | the shell of your body felt cool,

00:12:38.080 | it would make sense that that thermostat

00:12:39.920 | would activate biological mechanisms

00:12:41.760 | that would heat up your core.

00:12:43.380 | Similarly, if I were to put you into a very hot environment,

00:12:47.440 | you'd say, oh, wow, it's really, really warm in here,

00:12:50.060 | but your brain and your body would go through a lot of effort

00:12:52.920 | to activate mechanisms to cool you down.

00:12:55.760 | So anytime we're talking about heat,

00:12:57.240 | meaning deliberate heat exposure, things like sauna,

00:13:00.160 | it's very important to understand not just the stimulus,

00:13:03.800 | how hot something is, how long you're in a sauna, et cetera,

00:13:06.820 | but the effect that has on your shell and on your core.

00:13:10.560 | If you can understand that, you can design protocols

00:13:13.160 | that are literally perfect for your goals.

00:13:15.920 | And as a final point about this,

00:13:17.600 | if you want to develop the best tools,

00:13:20.340 | leveraging heat for your biology and health and performance,

00:13:23.480 | you want to understand heat as a process, as a verb,

00:13:27.220 | as heating, not just heat,

00:13:30.020 | because there's the temperature that you are at

00:13:33.000 | before you encounter the heat stimulus,

00:13:35.600 | before you get in the sauna, for instance,

00:13:37.620 | during the heat stimulus, so while you're in the sauna,

00:13:40.660 | and then afterward.

00:13:42.420 | Everything in biology is a process.

00:13:44.420 | So as you'll soon learn,

00:13:45.420 | there is a specific sauna protocol that can allow you,

00:13:49.140 | can allow anybody in fact,

00:13:50.460 | to increase the amount of growth hormone released

00:13:52.880 | into their brain and body 16 fold.

00:13:55.020 | That's right, 16 fold.

00:13:57.340 | However, it involves shifting from a hot environment

00:14:02.220 | to a cool environment, to a hot environment,

00:14:04.300 | to a cool environment over and over and over again,

00:14:06.680 | over a very short period of time,

00:14:08.640 | because it engages a switch, a process that compounds,

00:14:12.160 | it builds on itself to increase growth hormone

00:14:14.560 | further and further.

00:14:15.760 | In fact, if you were to just get into a sauna

00:14:17.860 | for a very long period of time and crank up the temperature

00:14:21.000 | to match the exact temperature that was used in that study,

00:14:24.420 | you would not experience those increases in growth hormone.

00:14:27.820 | It really is the transition between hot

00:14:29.860 | and cool temperatures that engage the process of heating

00:14:33.680 | and reheating over and over again.

00:14:35.740 | So today you're going to learn about the use of sauna.

00:14:37.580 | You're going to learn about the use

00:14:38.940 | of other heat related tools for health and optimization,

00:14:42.540 | not just for growth hormone, but also metabolic health,

00:14:44.840 | for controlling cortisol,

00:14:45.860 | even to impact mental health in positive ways.

00:14:50.080 | And in order to do that,

00:14:51.340 | you need to understand a little bit about the mechanisms

00:14:53.980 | of how you heat up and how you cool down,

00:14:57.020 | where the cells and circuits are in the brain and body,

00:14:59.540 | how those cells and circuits work.

00:15:01.280 | I promise to make the description of that,

00:15:02.900 | which follows very clear,

00:15:04.460 | even if you don't have a background in biology.

00:15:07.060 | And once you have that in hand,

00:15:08.720 | along with the understanding you now have

00:15:11.220 | about the fact that you got a shell and a core,

00:15:13.180 | and you need to think about both the shell and the core,

00:15:15.660 | well, then you will be in the best possible position

00:15:18.260 | to use sauna or hot tub or other tools,

00:15:21.160 | even just a hot shower as a powerful stimulus

00:15:24.260 | to optimize your biology.

00:15:25.920 | Now, the science of heat and heating,

00:15:27.420 | and cold and cooling for that matter,

00:15:30.140 | goes back well over a hundred years.

00:15:32.380 | In fact, it's kind of amusing to me

00:15:33.860 | that nowadays there's a kind of renewed interest

00:15:36.260 | in the use of heat and cold and the science of heat and cold

00:15:39.420 | because this was the first topic that I studied

00:15:41.780 | as an undergraduate.

00:15:43.020 | And in fact, I did my graduate thesis on thermal regulation.

00:15:46.740 | And at the time, thermal regulation

00:15:48.680 | wasn't really considered one of the hot topics

00:15:51.060 | in neuroscience.

00:15:52.180 | People were more focused on things like memory

00:15:54.220 | and consciousness.

00:15:55.140 | And of course those topics are still of vital interest

00:15:57.880 | to many people in many laboratories.

00:15:59.520 | But thermal regulation was considered more,

00:16:02.380 | I think for the physiologists.

00:16:04.140 | Nowadays, not just on social media,

00:16:06.900 | not just in the landscape of biohackers and athletes,

00:16:09.880 | but in the landscape of mental health,

00:16:11.760 | and frankly in the general ethos around health optimization,

00:16:16.760 | people are really interested in heat and cold.

00:16:19.900 | And the reason they're so interested in heat and cold

00:16:22.100 | is that a lot of the science has been done

00:16:23.980 | both in animal models in mice and in humans,

00:16:26.660 | and translates immediately to protocols that anyone can use.

00:16:30.760 | Now, a brief warning now and another brief warning later,

00:16:35.300 | anytime you're talking about heating up your body,

00:16:38.060 | you need to be very cautious because unlike cooling down

00:16:41.540 | where you have a fairly broad range of cold temperatures

00:16:44.380 | that you can go into before it's damaging to tissue,

00:16:47.220 | well, you don't get to heat up the brain and body very much

00:16:50.460 | before you start getting into the realm of neuron damage.

00:16:53.780 | And neurons in the central nervous system,

00:16:55.820 | the brain and spinal cord,

00:16:56.740 | once they're damaged, they don't come back.

00:16:59.100 | So hyperthermia is a serious thing to avoid.

00:17:01.320 | Later, I'll talk about ways to rapidly protect

00:17:03.960 | against hyperthermia.

00:17:05.980 | But I do want to give everybody a cautionary note upfront.

00:17:09.180 | Obviously, if you're pregnant, nursing,

00:17:11.120 | if you're very sensitive to hot environments,

00:17:13.360 | you want to stay out of saunas and things of that sort.

00:17:15.920 | I'm sure there are exceptions to that.

00:17:17.340 | You definitely have to talk to your doctor

00:17:20.040 | if you're going to violate that rule.

00:17:22.680 | And for everybody, you want to approach any kind of tool

00:17:26.240 | related to heating very cautiously.

00:17:28.840 | You always have the opportunity

00:17:30.440 | to increase the temperature later.

00:17:31.640 | So proceed with caution, be smart about it.

00:17:33.500 | I don't just say that to protect me.

00:17:34.900 | I say that also to protect you.

00:17:37.060 | So now let's talk about what are the circuits for heating up?

00:17:40.860 | How does that happen?

00:17:42.240 | Many of you have probably experienced a fever.

00:17:44.160 | How does that happen?

00:17:45.340 | What happens when you go into a cold environment

00:17:48.140 | and you're shivering, but you put on a coat

00:17:50.940 | and then you feel warmer?

00:17:51.820 | What's really going on there?

00:17:53.380 | Well, there's a very basic circuit,

00:17:56.100 | meaning neurons that exist in the skin,

00:17:59.740 | in the brain and in the body

00:18:01.100 | that communicate with one another that allow you

00:18:04.040 | to heat up if you need to and cool down if you need to.

00:18:06.900 | I'm going to throw a little bit of nomenclature,

00:18:08.820 | a few new words at you.

00:18:10.180 | You don't need to memorize these words except for one.

00:18:13.420 | Actually, you need to memorize one acronym,

00:18:15.180 | but it's very easy.

00:18:16.940 | It's called the POA.

00:18:18.060 | If you remember POA,

00:18:19.380 | you'll be home free for the rest of the episode.

00:18:21.380 | But I know that there are some aficionados out there

00:18:23.320 | and people interested in getting

00:18:24.980 | a little bit deeper mechanism.

00:18:26.380 | And I do think it's important to understand this circuit

00:18:28.300 | because once you understand this circuit

00:18:29.900 | and the way it's structured,

00:18:31.660 | then you are going to be in a great position

00:18:33.440 | to use the tools related to heating.

00:18:35.260 | So here's how this circuit is structured.

00:18:37.540 | You have this shell, which is basically skin.

00:18:40.300 | And within the skin, you have neurons, nerve cells.

00:18:43.380 | Those nerve cells have channels or receptors on them.

00:18:47.420 | They're called trip channels.

00:18:48.620 | There are some other ones as well,

00:18:49.980 | which basically sense changes in heat.

00:18:53.260 | So if I were to put a hot object on your hand or your arm,

00:18:57.100 | or for instance, if I were to put a hot object

00:18:59.960 | on your hand or arm, and then remove that hot object,

00:19:03.480 | those neurons would respond to that.

00:19:05.220 | They would send electrical signals into your spinal cord.

00:19:07.780 | And that's where the next station of this circuit resides.

00:19:10.740 | In your spinal cord, you've got a little cluster of neurons

00:19:13.860 | that exists at the top part of your spinal cord

00:19:16.420 | called the dorsal horn.

00:19:18.080 | The name again doesn't matter.

00:19:19.340 | And those neurons specifically relay heat information

00:19:22.580 | up to another area of your brain.

00:19:24.080 | Now here's where we get into some fancy names.

00:19:25.980 | It's the lateral parabrachial area.

00:19:29.320 | You don't need to know lateral parabrachial area,

00:19:31.360 | but it's a relay station.

00:19:32.780 | The lateral parabrachial area sends electrical signals

00:19:36.200 | to the POA.

00:19:37.460 | And I would like you to know POA.

00:19:38.940 | The POA stands for preoptic area.

00:19:41.800 | Neurons in the preoptic area basically reside

00:19:44.940 | over the roof of your mouth.

00:19:45.920 | These are neurons within the hypothalamus.

00:19:48.620 | And neurons in the preoptic area have the ability

00:19:53.140 | to send signals out to the rest of your brain and body

00:19:56.340 | to get you to heat up and actually to change your behavior

00:20:00.500 | so that you heat up.

00:20:02.180 | That's right.

00:20:03.540 | If neurons in the preoptic area receive an electrical signal

00:20:07.500 | through the circuit I just described

00:20:08.900 | that goes from skin to dorsal horn of the spinal cord

00:20:11.780 | to lateral parabrachial,

00:20:13.620 | they will start sending signals out to the organs

00:20:17.340 | of your body and the tissues of your body

00:20:19.400 | to get those organs and tissues to do things.

00:20:21.580 | And believe it or not, your POA, your preoptic area

00:20:24.540 | will actually change the way that you think

00:20:26.740 | and feel immediately.

00:20:28.920 | For instance, if something warm contacts your skin

00:20:33.860 | or something very hot contacts your skin,

00:20:36.000 | the preoptic area will send signals out

00:20:39.660 | to the endothelial cells, the blood vessels,

00:20:43.300 | both of the brain and body that get them to dilate,

00:20:47.820 | to essentially increase their volume and their surface area

00:20:51.260 | in order to cast off heat.

00:20:53.240 | You will also start sweating.

00:20:56.340 | That sweating response is initiated not by the hot day

00:21:00.340 | or the hot sun, but by the preoptic area neurons

00:21:03.460 | that send signals out to what's called the periphery

00:21:06.060 | of your body and other chemicals are released,

00:21:08.580 | things like acetylcholine that get you to sweat.

00:21:11.540 | And if you happen to be shivering,

00:21:15.740 | neurons in the preoptic area will make sure

00:21:18.300 | that you stop shivering.

00:21:21.120 | You're probably familiar with the feeling

00:21:23.060 | of being somewhat lethargic or spreading out your limbs

00:21:26.000 | on a hot day.

00:21:27.100 | Well, that is the result of neurons in your preoptic area

00:21:31.340 | impacting your musculature to get you

00:21:34.180 | to increase your surface area so you can sweat off

00:21:37.260 | or release more heat.

00:21:39.260 | So there are all these different mechanisms

00:21:40.860 | by which we dump heat.

00:21:43.020 | Some of those are purely physiological,

00:21:46.120 | below our conscious control, things like sweating,

00:21:49.920 | which you can't just make yourself sweat on demand.

00:21:53.240 | Maybe you can through a set of stressful thoughts,

00:21:55.300 | but you can't just make yourself sweat.

00:21:57.660 | That is autonomic, it's below your conscious control.

00:22:00.980 | Things like vasodilation, the dilation of your veins

00:22:05.980 | in particular and capillaries in particular,

00:22:08.400 | these sorts of things.

00:22:09.340 | And of course there are these behavioral,

00:22:11.720 | somewhat voluntary aspects of dumping heat.

00:22:14.960 | And the lethargy, the kind of tiredness that we feel

00:22:17.820 | on a really hot day, that's also controlled by this circuit

00:22:21.000 | that I just described.

00:22:22.240 | In fact, I just got back from a visit to a very warm place

00:22:26.700 | and it was remarkable to me how lethargic I felt

00:22:29.940 | in the afternoons.

00:22:30.780 | I just felt like a total slug.

00:22:32.680 | I just could not move or rally to do anything,

00:22:36.740 | except if I waited until the evening,

00:22:39.500 | even though it was later in the day,

00:22:41.220 | even though I hadn't napped,

00:22:42.980 | as the temperature in my environment cooled off,

00:22:45.080 | as my body temperature cooled off,

00:22:46.700 | I felt like I had more energy.

00:22:47.780 | I was actually waking up,

00:22:48.860 | even though I had been awake for longer.

00:22:50.900 | So the relationship between temperature and lethargy

00:22:53.380 | is a very intimate one.

00:22:55.560 | If we're warm enough, we feel active

00:22:58.020 | and like we want to move around.

00:22:59.700 | If we're too warm, we feel like we need to stay put

00:23:02.660 | and spread out our limbs and dump heat.

00:23:05.180 | And that brings me to a quick and kind of fun point

00:23:07.580 | about how we dump heat versus how other animals dump heat.

00:23:10.660 | Many of you know, of course, that we dump heat by sweating.

00:23:14.460 | Other mechanisms as well, some of which I described,

00:23:16.940 | but that's our main way of dumping heat.

00:23:19.380 | Other animals like dogs don't have the capacity to sweat,

00:23:22.340 | at least not very much.

00:23:23.520 | So they pant, right, in order to dump heat.

00:23:26.740 | And still other animals like rodents,

00:23:29.020 | when they get too hot, they spit on their paws

00:23:32.120 | and they rub that spit on the surface of their body,

00:23:35.000 | which might sound kind of gross

00:23:36.120 | and probably will get you to think twice

00:23:37.420 | before petting any of those animals

00:23:38.860 | or holding any of those animals again,

00:23:40.740 | unless that's your thing.

00:23:42.620 | Now, one other key thing to understand about this circuit

00:23:45.140 | related to heat is that the preoptic area

00:23:47.860 | also can send electrical signals to the amygdala,

00:23:51.100 | a brain area that is often talked about

00:23:53.900 | in the context of fear, but is really just a brain area

00:23:57.380 | that can activate your sympathetic nervous system.

00:24:00.020 | The sympathetic nervous system

00:24:01.820 | is part of your autonomic nervous system

00:24:04.060 | and is the one associated with fight or flight

00:24:06.300 | or with the stress response,

00:24:08.100 | or even just the excited response, right?

00:24:10.280 | The sympathetic nervous system is also what gets activated

00:24:12.380 | when you're really excited about something.

00:24:14.140 | The preoptic area has the opportunity

00:24:16.980 | to trigger the activation of the amygdala.

00:24:19.740 | Now, it doesn't do it every time, but it can.

00:24:22.100 | And it tends to do that when you are suddenly

00:24:24.140 | in an environment that feels too hot,

00:24:26.900 | that you feel is risky levels of hot.

00:24:30.040 | If you ever have gotten into a sauna that was very, very hot,

00:24:33.260 | maybe 210 degrees Fahrenheit, you sit there for a minute,

00:24:37.480 | you'll notice that your heart rate increases

00:24:39.520 | and there are reasons for that.

00:24:40.360 | And we'll talk about some of the health benefits of that.

00:24:42.220 | in a few minutes, but it's pretty uncomfortable.

00:24:46.280 | You may not feel like your skin is going to burn up,

00:24:48.620 | but you often will feel the impulse to get out,

00:24:51.600 | especially if you stay in there for a little while.

00:24:53.860 | That impulse is the consequence of this preoptic area

00:24:57.840 | communicating with your amygdala saying,

00:24:59.380 | "Hey, this environment is really hot

00:25:01.120 | and I'm trying to cool down and it's not really working.

00:25:03.460 | I'm dumping heat, but I'm not able to adjust the core

00:25:06.980 | of my body temperature in ways

00:25:08.240 | that are going to protect my neurons."

00:25:09.740 | And so it's a signal that you probably shouldn't stay

00:25:12.300 | in that environment too long.

00:25:13.820 | Now, later, we'll talk about the advantage

00:25:15.300 | of pushing yourself a little bit

00:25:16.660 | through some of these very hot environments,

00:25:18.540 | provided you can do it safely.

00:25:20.160 | But the impulse to get yourself

00:25:22.380 | out of a very hot environment is the consequence

00:25:25.820 | of the POA communicating with your amygdala.

00:25:28.660 | And the amygdala then in turn activating your adrenal glands,

00:25:31.660 | which sit right above your kidneys,

00:25:33.580 | the release of adrenaline and this feeling of agitation

00:25:36.460 | like you want to move.

00:25:37.560 | Usually you want to move out of whatever hot environment

00:25:40.320 | you happen to be in.

00:25:41.440 | So now you know the circuit.

00:25:42.840 | Again, it's simple.

00:25:43.680 | It goes from skin to spinal cord,

00:25:45.600 | one brain area to another brain area.

00:25:47.580 | That's the key one in this discussion,

00:25:49.320 | which is the POA, the preoptic area.

00:25:51.360 | And the preoptic area can kick off

00:25:53.240 | a bunch of autonomic subconscious responses to heat,

00:25:57.580 | which make us attempt to get cooler,

00:26:00.020 | things like sweating, vasodilation, et cetera.

00:26:02.340 | And it can kick off behavioral responses,

00:26:05.140 | spreading out our limbs in an attempt to dump even more heat,

00:26:07.640 | feeling lethargic, so a lack of desire to run and move.

00:26:11.980 | And it also has the opportunity to kick off a mild

00:26:15.540 | or maybe not so mild panic response

00:26:17.480 | to get us out of that hot environment.

00:26:19.500 | If you can conceptualize that circuit,

00:26:21.300 | or if you can even just understand what I just said,

00:26:23.680 | even at a top contour level,

00:26:25.700 | you're going to be in a great position to understand

00:26:27.880 | the rest of the information and the tools that follow.

00:26:30.460 | Next, I'd like to talk about the use

00:26:32.300 | of deliberate heat exposure, including sauna,

00:26:35.000 | but other tools as well as a way to understand

00:26:39.140 | how heat and heating changes our biology.

00:26:42.720 | So you're going to learn some mechanism

00:26:44.380 | and you're going to learn some tools.

00:26:46.080 | But first I'd like to just emphasize

00:26:48.140 | that the use of deliberate heat exposure

00:26:50.660 | can be a very powerful way to improve health and longevity.

00:26:55.100 | There's a wonderful study on this that was published in 2018

00:26:59.120 | that includes a lot of data from a lot of participants

00:27:02.300 | in a lot of different conditions.

00:27:04.000 | For instance, people that only did sauna once

00:27:05.960 | versus two to three times a week

00:27:07.420 | versus four to seven times a week

00:27:08.900 | and so on and compares all those.

00:27:11.140 | The title of the study is sauna bathing is associated

00:27:14.360 | with reduced cardiovascular mortality

00:27:16.520 | and improves risk prediction in men and women,

00:27:19.620 | a prospective cohort study.

00:27:22.060 | This is one of several papers that clearly demonstrate

00:27:26.140 | that regular use of sauna

00:27:28.140 | or other forms of deliberate heat exposure

00:27:31.060 | can reduce mortality to cardiovascular events,

00:27:34.000 | but also to other events,

00:27:35.880 | things like stroke and other things

00:27:38.260 | that basically can kill us.

00:27:40.800 | What I like so much about this and the related studies,

00:27:43.220 | and yes, I will provide a link to these in the show notes,

00:27:46.340 | is that they involve a lot of participants.

00:27:48.600 | So for instance, in this particular paper,

00:27:50.200 | which was published in BMC medicine,

00:27:52.120 | they looked at a sample of 1,688 participants

00:27:58.280 | who had a mean age of 63,

00:28:00.240 | but there was a range of ages around 63

00:28:03.360 | and of whom 51.4% were women, the rest were men.

00:28:07.220 | So it's a pretty nicely varied study

00:28:09.220 | in terms of the populations that they looked at.

00:28:12.160 | And basically what they found was the more often

00:28:15.260 | that people do sauna, the better their health is

00:28:18.960 | and the lower the likelihood they will die

00:28:22.060 | from some sort of cardiovascular event.

00:28:24.320 | Now, what do we mean by sauna?

00:28:25.760 | We need to define some of the parameters around sauna

00:28:28.660 | and I promise to provide you some alternative ways

00:28:32.140 | to access some of the health benefits

00:28:34.100 | that were observed in this and related studies

00:28:36.580 | without the need to have a sauna,

00:28:38.220 | 'cause I do realize that a lot of people

00:28:39.960 | don't have access to sauna.

00:28:42.180 | First off, the temperature ranges that were used

00:28:44.460 | in this study and pretty much all the studies

00:28:46.760 | that I'm going to talk about, unless I say otherwise,

00:28:49.860 | are between 80 degrees Celsius,

00:28:51.940 | meaning 176 degrees Fahrenheit and 100 degrees Celsius,

00:28:57.260 | meaning 212 degrees Fahrenheit.

00:29:00.260 | So somewhere in that range,

00:29:02.260 | how hot should you make the sauna

00:29:04.200 | or the environment that you get into

00:29:05.780 | should you decide to use these tools?

00:29:07.860 | Well, that will depend on your tolerance for heat,

00:29:11.420 | how heat adapted you are.

00:29:13.100 | Yes, some people are better at sweating than others

00:29:15.500 | and over time, we all get better at sweating.

00:29:17.580 | Meaning if you go into the sauna more frequently,

00:29:19.440 | you become a better sweater.

00:29:21.740 | Not a sweater you wear, but the verb, sweater.

00:29:24.260 | You get better at sweating,

00:29:25.500 | at dumping heat through the loss of water.

00:29:27.720 | So it's going to depend.

00:29:29.900 | I recommend starting on the lower end

00:29:31.980 | of the temperature scale.

00:29:33.280 | And if that's too hot for you,

00:29:34.640 | that you even lower the temperature further.

00:29:36.620 | Now, how long were people exposing themselves

00:29:39.340 | to these hot environments?

00:29:40.640 | Anywhere from five to 20 minutes per session.

00:29:45.300 | And as you'll soon learn,

00:29:46.700 | very brief periods of just five minutes of heat exposure

00:29:49.740 | can be a powerful stimulus

00:29:51.580 | if the heat exposure is significantly great enough for you.

00:29:56.580 | 20 minutes can also be beneficial,

00:30:00.220 | but 80 to 100 degrees Celsius,

00:30:03.500 | meaning 176 degrees Fahrenheit to 212 degrees Fahrenheit

00:30:07.260 | is the general range that this and most studies use.

00:30:10.580 | In this particular study,

00:30:12.540 | they compared the effects of people that did sauna

00:30:15.300 | once a week, two or three times per week,

00:30:18.220 | or four to seven times per week.

00:30:19.980 | And what they saw was really remarkable.

00:30:22.380 | What they observed was that people who went into the sauna

00:30:25.100 | two or three times per week,

00:30:27.020 | were 27% less likely to die of a cardiovascular event

00:30:31.540 | than people that went into the sauna just once a week.

00:30:33.900 | Again, at the temperature levels

00:30:36.180 | and the duration that I talked about earlier.

00:30:38.540 | And as you can imagine,

00:30:39.500 | the duration and the temperature levels were related.

00:30:42.780 | So if people went into very hot environments

00:30:44.980 | that were really uncomfortable for them,

00:30:46.180 | maybe they only went in for five minutes.

00:30:47.840 | Whereas if they were more comfortable and heat adapted

00:30:50.940 | in a given environment or their tolerance for heat

00:30:53.260 | was just simply higher for whatever reason,

00:30:55.580 | well, then they tended to stay in longer.

00:30:57.720 | We can take a sort of average of this five

00:30:59.540 | to 20 minute range.

00:31:00.600 | And today we're mainly going to talk about exposures

00:31:03.360 | between 10 and 20 minutes at temperatures between,

00:31:07.460 | again, 80 degrees and 100 degrees Celsius,

00:31:09.520 | 176 degrees Fahrenheit or 212 degrees Fahrenheit.

00:31:13.120 | So these data point to the fact that going in the sauna

00:31:15.420 | two or three times per week is really beneficial

00:31:17.240 | and can lower mortality to cardiovascular events.

00:31:20.620 | And in fact, the benefits were even greater

00:31:22.220 | for people that were going into the sauna

00:31:23.660 | four to seven times per week.

00:31:25.660 | Those people were 50% less likely to die

00:31:28.700 | of a cardiovascular event compared to people

00:31:30.900 | that went into the sauna just once a week.

00:31:33.400 | So these are really impressive

00:31:34.820 | and frankly encouraging studies.

00:31:37.220 | Certainly they caught my eye and encouraged me

00:31:39.260 | to start using deliberate heat exposure on a regular basis.

00:31:43.660 | What's particularly nice about this study

00:31:45.500 | and the related study that again is linked in the show notes

00:31:49.660 | is that they looked at a number

00:31:51.480 | of potentially confounding variables,

00:31:53.620 | things like whether or not people smoked,

00:31:55.480 | things like whether or not people were overweight,

00:31:57.180 | whether or not they tended to exercise or not exercise,

00:32:00.400 | and they were able to separate out those variables.

00:32:03.060 | So the percentages that I described earlier,

00:32:05.100 | 27% less likely to die of a cardiovascular event

00:32:09.260 | for those that went in the sauna two to three times a week

00:32:11.560 | and 50% less likely to die of a cardiovascular event

00:32:13.820 | for those that went into the sauna four times per week

00:32:16.060 | as compared to just once a week.

00:32:17.940 | Those effects really do seem to be the consequence

00:32:21.020 | of the sauna exposure and not some other effect

00:32:24.020 | that's correlated with sauna exposure,

00:32:25.740 | like going to the gym where people are working out

00:32:28.780 | seven times a week and then also happen to get into the sauna

00:32:31.240 | or quitting smoking right about the same time

00:32:33.180 | they adopt a sauna protocol, these sorts of things.

00:32:36.320 | And now there have been additional analysis

00:32:38.480 | of the use of sauna for improving health,

00:32:40.700 | or I should say for offsetting mortality

00:32:43.980 | that have found that it's not just reductions

00:32:46.660 | in cardiovascular events,

00:32:47.820 | but so-called all-cause mortality.

00:32:50.220 | This is kind of medical geek speak.

00:32:52.420 | We're saying, how likely are you or somebody

00:32:55.580 | to die from a cardiovascular event,

00:32:57.980 | but maybe also from some other event,

00:33:00.880 | some other health-related event,

00:33:02.260 | like cancer or something of that sort.

00:33:04.340 | And in every case, regular exposure to sauna,

00:33:07.380 | starting at about two or three times per week,

00:33:09.760 | all the way up to seven times per week greatly improves,

00:33:13.500 | meaning statistically significant improvements in longevity

00:33:18.020 | in the sense that people are less likely to die

00:33:21.460 | of cardiovascular events and other things that kill us.

00:33:25.320 | So I and many other people who are interested,

00:33:27.280 | not just in our own health,

00:33:28.380 | but in educating about health-related tools

00:33:31.340 | to the general public find this really exciting.

00:33:34.460 | But knowing what we know about how heat impacts our biology,

00:33:39.400 | it probably shouldn't surprise us

00:33:41.860 | that this sauna type exposure or deliberate heat exposure

00:33:44.980 | has these incredible effects.

00:33:46.620 | So before we get into the biological mechanisms

00:33:49.020 | of how heat can have all these impressive health effects,

00:33:52.660 | I want to just talk about the use of sauna as a tool

00:33:56.900 | and emphasize that you don't have to use a sauna

00:34:00.220 | in order to get these benefits.

00:34:02.060 | It is simply a matter of making sure

00:34:04.620 | that your shell and your core heat up properly a bit,

00:34:09.620 | not too much, not too little, but that you heat those up.

00:34:13.660 | And no, you do not need to carry a thermometer around

00:34:16.560 | or place a thermometer into your core.

00:34:19.360 | You know, in laboratory studies and in humans,

00:34:22.040 | if you really want to know someone's core temperature,

00:34:24.080 | basically you try and put the thermal probe

00:34:25.720 | as close to the core as you can.

00:34:26.880 | So typically that's done rectally or a mouth thermometer,

00:34:30.000 | or even up the nose.

00:34:31.440 | You don't need to do any of that, all right?

00:34:33.180 | This isn't a laboratory study.

00:34:34.280 | There are ways to create a hot environment

00:34:37.660 | such that you heat up your shell and your core safely

00:34:41.020 | without having to measure your core temperature all along.

00:34:44.160 | If you want to do that, be my guest,

00:34:46.820 | but I'm not going to provide a protocol.

00:34:49.160 | So the question is, how are you heating up your environment?

00:34:51.600 | And I realized that there are dry saunas,

00:34:54.340 | there are steam saunas, there are infrared saunas,

00:34:57.660 | there are hot tubs, and there are simply rooms

00:35:01.200 | that you crank up the heat, okay?

00:35:03.980 | There are also ways in which you can increase your shell

00:35:06.720 | and your core temperature by moving around a lot

00:35:09.360 | and doing that wearing a lot of clothing.

00:35:11.480 | There's nothing special about any one of these approaches

00:35:16.060 | or protocols.

00:35:17.060 | It's just so happens that sauna

00:35:19.420 | is one of the more convenient ways to do this.

00:35:21.620 | And certainly for the studies that I've talked about,

00:35:24.300 | not just the ones I referenced before,

00:35:25.740 | but all the studies that I researched

00:35:27.540 | looking at this episode,

00:35:29.080 | it makes sense why they would use sauna

00:35:30.740 | because it's very hard, for instance,

00:35:32.820 | to create conditions where you have five people go out

00:35:37.060 | jogging, wearing heavy sweaters and hats, wool hats

00:35:39.860 | on the middle of summer.

00:35:41.020 | It's very hard to set up those conditions

00:35:42.800 | in a way that's controlled for everybody.

00:35:44.440 | Whereas it's pretty straightforward to have a sauna

00:35:46.500 | where you have one or several people

00:35:48.060 | just get into that one uniformly hot environment.

00:35:51.200 | That's a much easier study to run.

00:35:53.860 | So just to be clear, the temperature range is important.

00:35:58.260 | You want to get between 80 and 100 degrees Celsius.

00:36:00.620 | Now you know the conversion to Fahrenheit.

00:36:02.880 | You could however, immerse yourself in a hot tub

00:36:06.900 | or hot water bath up to your neck.

00:36:08.860 | That's another way to approach it.

00:36:10.620 | If you didn't have access to either of those,

00:36:12.900 | you could also put on a hoodie or a wool hat and a hoodie,

00:36:17.900 | or you could do like the wrestlers do.

00:36:21.400 | And you could actually buy one of these plastic suits.

00:36:24.140 | They're literally called plastics that wrestlers

00:36:27.060 | or other athletes that wish to drop water weight will wear

00:36:29.420 | and then go jogging that.

00:36:30.540 | All of those will increase your shell

00:36:32.080 | and your core body temperature, right?

00:36:33.500 | Especially if you do it on a hot day,

00:36:34.600 | but of course be careful, hydrate and don't overheat,

00:36:36.580 | don't become excessively hyperthermic

00:36:38.500 | 'cause you can get heat stroke and you can potentially die.

00:36:42.220 | But if you're going to use sauna,

00:36:44.820 | often I get the question, how hot should the sauna be?

00:36:47.220 | Well, now you know.

00:36:48.060 | How long should you be in there?

00:36:48.920 | Five to 20 minutes per session.

00:36:51.240 | Although I will talk in a minute

00:36:52.780 | about ways to optimize hormone output,

00:36:54.860 | in particular growth hormone output

00:36:56.180 | by doing four very brief sessions.

00:36:59.660 | So maybe not a continuous session.

00:37:01.040 | We'll get into that in a few minutes.

00:37:02.260 | And of course you have to ask yourself wet sauna, dry sauna.

00:37:05.020 | You know what?

00:37:05.860 | Doesn't matter, use what you prefer.

00:37:08.140 | Many people ask me, well, what about infrared sauna?

00:37:11.220 | We have an entire episode all about the use of light

00:37:13.460 | and low level light therapy, including infrared light.

00:37:17.660 | It does have certain benefits for skin

00:37:19.860 | and other organs and tissues of the body if used properly.

00:37:23.780 | My understanding, or at least my assessment

00:37:26.300 | of most infrared saunas out there

00:37:28.500 | is that they don't get hot enough.

00:37:30.660 | They don't get up to that 80 to 100 degrees Celsius range.

00:37:34.500 | Some do, most don't.

00:37:36.700 | So what you end up with is a situation

00:37:38.580 | where you've got a red light,

00:37:39.860 | low level light therapy stimulus,

00:37:42.100 | and you've got a sauna that's not quite hot enough.

00:37:44.900 | And there are a lot of ideas and claims

00:37:46.560 | about how they work together

00:37:48.440 | in order to get you improved benefits.

00:37:50.440 | I personally am of the stance based on the literature

00:37:54.100 | that I've read that you want to get into those ranges

00:37:57.440 | of an 80 to 100 degrees Celsius before you start,

00:38:01.260 | considering whether or not you're also going to include

00:38:03.020 | red light therapies, et cetera.

00:38:04.680 | So there's nothing special about red light sauna.

00:38:07.620 | It's really the temperature of the sauna

00:38:10.120 | that you happen to get into.

00:38:11.220 | So which tool, right?

00:38:12.800 | Which sauna, which stimulus do you run in wearing plastics

00:38:16.040 | and a hoodie and a wool hat?

00:38:17.340 | When you get into a sauna,

00:38:18.180 | that's going to depend a lot on your circumstances,

00:38:20.160 | your budget, and what you have access to on a regular basis.

00:38:22.860 | This is a lot like our discussion about the use of cold.

00:38:26.300 | Most of the studies have looked at immersion in cold water

00:38:29.880 | up to the neck because that's a very controlled situation

00:38:32.040 | that you can do in a laboratory.

00:38:33.620 | They have not explored cold showers as much.

00:38:36.740 | So there's just less data

00:38:37.740 | or walking around in a cold environment.

00:38:39.620 | But we'll talk a little bit about those data

00:38:42.240 | because as you'll soon learn, when you talk about cold,

00:38:44.320 | you're actually talking about heating as well.

00:38:46.600 | So what kind of mechanisms are activated in your brain

00:38:49.220 | and body that allow for the various health benefits of sauna

00:38:54.040 | or other forms of deliberate heating?

00:38:57.320 | Well, we talked about reduced risk

00:39:00.280 | of cardiovascular event-related mortality

00:39:02.400 | and all-cause mortality.

00:39:04.340 | As you'll soon learn, there are also tremendous benefits

00:39:08.240 | in terms of increases in growth hormone,

00:39:10.440 | reductions in cortisol, et cetera.

00:39:12.360 | I will detail those.

00:39:13.640 | So what happens when you get into a hot environment?

00:39:16.360 | What are the mechanisms that allow

00:39:17.720 | for the various health effects of that?

00:39:20.080 | Well, your shell, your skin senses that,

00:39:25.000 | and through the circuit that I described earlier,

00:39:27.200 | activates neurons in the POA, the pre-optic area,

00:39:30.260 | which in turn activates mechanisms

00:39:32.400 | in your autonomic nervous system like vasodilation.

00:39:35.100 | So blood flow increases,

00:39:36.600 | plasma volume of your blood increases, and stroke volume.

00:39:41.240 | The volume of blood that is mobilized

00:39:44.560 | with each beat of your heart also increases

00:39:47.120 | and your heart rate increases to anywhere between 100

00:39:51.080 | to 150 beats per minute.

00:39:52.980 | That general constellation of effects looks a lot

00:39:56.460 | like cardiovascular exercise.

00:39:58.680 | And in fact, for all intents and purposes,

00:40:01.520 | it really is cardiovascular exercise,

00:40:03.940 | except that there isn't the mobilization

00:40:06.560 | and the loading of joints and limbs and things of that sort.

00:40:09.560 | And of course, there are additional benefits

00:40:11.200 | of cardiovascular exercise that relate to impact

00:40:15.200 | on the ground, improvements in bone density,

00:40:17.440 | et cetera, et cetera.

00:40:18.800 | But basically your heart starts beating,

00:40:20.640 | more blood starts circulating,

00:40:22.960 | your vasculature changes shape literally

00:40:24.980 | to accommodate those increases

00:40:26.760 | in heart rate and blood volume.

00:40:29.420 | And you're basically getting a cardiovascular workout

00:40:31.980 | in that hot environment, even if you're just sitting down.

00:40:35.540 | Another set of positive effects related

00:40:37.400 | to being in these hot environments are hormone effects.

00:40:42.020 | Shifts in the output of hormones,

00:40:43.980 | both from your adrenals and possibly from the testes

00:40:47.520 | and ovaries, and even within the brain.

00:40:49.880 | One of the more striking examples of that comes

00:40:52.880 | from a study that was published in 2021.

00:40:56.640 | The title of the study is endocrine effects

00:40:59.120 | of repeated hot thermal stress

00:41:00.640 | and cold water immersion in young adult men.

00:41:03.640 | And indeed the study was in this case, just done on men.

00:41:06.280 | I'll just briefly describe the protocol they use.

00:41:09.160 | They had these men attend four sauna sessions

00:41:11.760 | of 12 minutes each.

00:41:13.400 | So again, well within that range of five to 12 minutes.

00:41:17.320 | The temperature of those saunas was 90

00:41:20.040 | to 91 degrees Celsius.

00:41:21.460 | So I'll just quickly do the calculation,

00:41:24.120 | admittedly not in my head.

00:41:25.260 | That's 194 degrees Fahrenheit.

00:41:28.000 | And they did that four times.

00:41:31.140 | Afterwards, they had a six minute cool down break

00:41:33.820 | during which they did get into some cool water

00:41:36.600 | or cold water of about 10 degrees,

00:41:39.160 | which is 10 degrees Celsius is 50 degrees Fahrenheit.

00:41:43.880 | And then they measured hormones at various times

00:41:46.040 | throughout this study, before, during, and after.

00:41:48.800 | They looked at testosterone.

00:41:50.080 | They looked at DHEA, which is in the androgen pathway.

00:41:53.980 | They looked at prolactin and they looked at cortisol.

00:41:57.120 | The significant effects of the protocol

00:41:59.160 | that I just described were on cortisol,

00:42:02.000 | a so-called stress hormone, so-called,

00:42:04.840 | because when we are very stressed for long periods of time,

00:42:07.240 | cortisol levels tend to increase dramatically.

00:42:09.740 | But I should point out that a increase in cortisol each day,

00:42:14.440 | right about the time of waking,

00:42:15.800 | and specifically right about the time of waking

00:42:17.600 | is actually beneficial for our alertness and our energy.

00:42:19.920 | So having some increase in cortisol every 24 hours

00:42:23.280 | is a good thing provided it happens early in the day.

00:42:26.460 | Late day increases in cortisol

00:42:28.480 | are associated with depression.

00:42:30.280 | That's been shown by studies at Stanford and elsewhere.

00:42:33.480 | The major effect of this study

00:42:34.720 | is a significant decrease in cortisol output

00:42:37.960 | in these subjects.

00:42:38.980 | I think this is really interesting and important

00:42:41.780 | because many people suffer from acute,

00:42:44.260 | meaning immediate and long-term stress,

00:42:46.320 | and are looking for ways to control their stress.

00:42:49.160 | Controlling your cortisol is tricky.

00:42:51.540 | In the episode on stress,

00:42:52.760 | I talked about supplements such as ashwagandha

00:42:54.800 | that can be used to limit cortisol,

00:42:56.880 | but you have to be careful not to use ashwagandha

00:42:59.120 | for extended periods of time,

00:43:00.880 | meaning for longer than two weeks,

00:43:02.320 | because you can get into other issues.

00:43:04.360 | I talk about breathwork protocols

00:43:06.000 | that can allow you to clamp or reduce the stress response

00:43:08.880 | in real time.

00:43:09.960 | Again, see that episode for those,

00:43:11.580 | but many people are overworked, they're overstressed.

00:43:14.560 | They're, for one reason or another,

00:43:16.640 | they're subjected to many, too many stressors

00:43:19.280 | or their level of stress resilience isn't high enough

00:43:22.400 | to keep their cortisol levels clamped at a healthy level.

00:43:25.440 | So the protocol I described of 12 minute exposures

00:43:29.000 | to 90 degree environment, that's again, 90 degrees Celsius,

00:43:33.160 | followed by a six minute cool down break in cool water,

00:43:37.320 | 50 degrees or so, that's pretty cold.

00:43:40.280 | I can imagine that you could also just take a cool shower

00:43:42.560 | or a cold shower afterwards.

00:43:43.980 | That had a very significant effect on lowering cortisol.

00:43:47.080 | So there you have a tool,

00:43:48.580 | it's not a completely zero cost tool

00:43:50.160 | 'cause you need to heat the water,

00:43:51.200 | you need to have access to hot and cold water,

00:43:53.000 | at least hot and cold contrast of some sort,

00:43:55.800 | but it's fairly minimal cost for most people,

00:43:59.080 | especially if you start getting creative

00:44:00.680 | about maybe taking a 12 minute jog,

00:44:03.140 | wearing a lot of clothing,

00:44:04.360 | if it's hot out, then getting into a cool shower,

00:44:06.640 | you might not get the same extreme

00:44:09.200 | or significant reduction in cortisol

00:44:10.960 | that was observed here with these very specific protocols,

00:44:13.440 | but it's likely that you would get

00:44:14.720 | a similar result overall.

00:44:17.000 | Now, I mentioned they did look at these other hormones

00:44:19.300 | and I'll just tell you that they did not see

00:44:21.180 | significant shifts in testosterone, prolactin,

00:44:23.400 | DHEA, et cetera, using this protocol.

00:44:26.200 | As you'll soon see, there are other sauna protocols

00:44:28.240 | that can impact those other hormones.

00:44:30.220 | So if you're seeking to use sauna to reduce stress,

00:44:32.600 | I think this is a very interesting

00:44:34.720 | and potentially useful research-backed protocol.

00:44:37.280 | And again, we will provide a link to the paper

00:44:39.940 | if you'd like to read more about the data.

00:44:42.420 | So that is one set of biological effects on cortisol

00:44:45.940 | and the related protocol.

00:44:48.540 | What about some of the other benefits of sauna?

00:44:50.640 | Well, we'll talk about those,

00:44:51.700 | but I want to talk about those

00:44:53.200 | in the context of the underlying mechanisms,

00:44:56.120 | because if you understand those underlying mechanisms,

00:44:58.120 | you can really tailor your sauna protocols

00:45:00.800 | for your particular needs.

00:45:02.600 | One of the more dramatic and important effects

00:45:04.860 | of going into a hot environment for some period of time

00:45:09.160 | is the activation of so-called heat shock proteins, or HSPs.

00:45:13.280 | Heat shock proteins are a protective mechanism

00:45:15.800 | in your brain and body to rescue proteins

00:45:19.800 | that would otherwise misfold.

00:45:21.780 | Now, what do I mean by this?

00:45:22.620 | Well, most of you are familiar with the fact

00:45:25.560 | that if you have protein in the kitchen, like a steak

00:45:28.140 | or a piece of chicken or a piece of fish,

00:45:29.920 | and you heat it up, it changes its texture, right?

00:45:33.680 | Raw meat is different than cooked meat,

00:45:36.040 | to be quite blunt about it.

00:45:37.660 | Heat changes the quality of proteins,

00:45:42.600 | not just in terms of how they taste,

00:45:43.880 | but the way in which they are configured.

00:45:46.600 | It changes it right down at the molecular level.

00:45:49.000 | When your body goes through changes in temperature each day,

00:45:53.500 | and we'll talk about those changes,

00:45:54.700 | but in response to hot environments or cold environments,

00:45:57.920 | heat shock proteins are deployed to go and rescue

00:46:01.740 | and prevent the changes in proteins

00:46:04.080 | that would be detrimental to your health.

00:46:06.260 | So at least in the short term,

00:46:08.120 | activating heat shock proteins is a good thing.

00:46:11.200 | You don't want heat shock proteins to be activated

00:46:13.220 | for long periods of time,

00:46:14.460 | because that gets to be problematic for other reasons.

00:46:17.240 | But these heat shock proteins,

00:46:18.640 | of which there are many varieties,

00:46:20.220 | basically have the job of traveling in your brain and body

00:46:23.460 | and making sure that cells that contain proteins

00:46:27.060 | that are misfolding because they got heated up too much,

00:46:30.860 | don't misfold.

00:46:32.320 | And they also serve a protective mechanism,

00:46:35.020 | making sure that proteins within the cells

00:46:37.360 | of your brain and body don't fold in the wrong ways.

00:46:41.280 | Again, I'm describing this in very general terms,

00:46:43.480 | but it's well-established in animal models and in humans

00:46:47.440 | that sauna exposure of the sort that I described earlier

00:46:50.700 | activates these heat shock proteins.

00:46:52.740 | There are some interesting studies that were carried out

00:46:54.700 | in animal models that really nicely mechanistically support

00:46:59.340 | the role of heat shock proteins in some of the benefits

00:47:02.420 | of deliberate heat exposure.

00:47:04.320 | Some of these studies were done in flies,

00:47:06.940 | meaning drosophila, fruit flies,

00:47:08.320 | 'cause they're a great model organism

00:47:10.100 | because you can delete genes or add genes easily.

00:47:13.340 | Other studies have been done in mice.

00:47:14.620 | And now there are also studies being carried out in humans.

00:47:17.380 | And I will talk about those.

00:47:18.640 | One of the more dramatic examples that's always touted

00:47:21.900 | in this field of deliberate heat exposure

00:47:24.220 | as it relates to longevity is that if they expose

00:47:27.660 | these flies, these fruit flies to 70 minutes

00:47:31.200 | of a heat stimulus that obviously didn't kill them,

00:47:35.400 | but activated heat shock proteins,

00:47:37.240 | it could extend their life by 15%

00:47:39.980 | in a heat shock dependent way.

00:47:42.940 | Meaning if they made flies that didn't have

00:47:45.700 | these heat shock proteins,

00:47:47.300 | well then they didn't see this extension in life.

00:47:50.340 | And this is one of the reasons to use model organisms.

00:47:52.260 | This is not an experiment that you could do in people.

00:47:54.940 | However, there have been interesting studies done in humans

00:47:57.740 | examining some of the downstream molecular pathways

00:48:00.460 | of deliberate heat exposure that point to the mechanisms

00:48:03.660 | by which deliberate heat exposure can help protect

00:48:06.460 | against different forms of mortality,

00:48:08.300 | improve health overall, and possibly,

00:48:10.960 | and I want to highlight possibly, possibly extend life.

00:48:14.720 | One such mechanism involves a genetic program involving

00:48:19.300 | a molecule called FOXO3.

00:48:22.020 | FOXO3 is a very interesting molecule

00:48:24.100 | because it's involved in DNA repair pathways.

00:48:27.720 | DNA repair is part of the process of remaining healthy.

00:48:32.620 | We'd all like to think that we're born

00:48:34.660 | and based on the genes we have,

00:48:36.780 | we are healthy, healthy, healthy,

00:48:38.400 | then eventually we age and then we die.

00:48:40.860 | But from the time we're born until the time we die,

00:48:44.100 | there's a constant repair of our proteins and our cells

00:48:46.960 | and a modification of the genes that are being expressed.

00:48:49.960 | Puberty being the most dramatic example, right?

00:48:52.160 | You see a kid before puberty and after puberty,

00:48:54.520 | looks like a different kid, sounds like a different kid,

00:48:56.000 | thinks like a different kid, in fact,

00:48:57.440 | basically is a different human being, right?

00:48:59.480 | It's not just the hormones,

00:49:00.520 | it's that hormones themselves have the capacity to turn on

00:49:03.780 | and turn off certain genes,

00:49:05.120 | literally converting certain tissues and cells

00:49:08.440 | in the brain and body to do entirely different things.

00:49:10.920 | So it's not just the sprouting of new aspects

00:49:13.820 | of our biology, it's literally the conversion

00:49:16.640 | of different brain centers from one function to another.

00:49:20.100 | That's puberty, and we'll do a whole episode about puberty.

00:49:24.080 | We actually did an episode on sexual development

00:49:26.000 | that talks a little bit about those mechanisms,

00:49:28.040 | but the point is that throughout our entire lifespan,

00:49:31.280 | genes are being turned on, genes are being turned off,

00:49:33.900 | genes are being turned on, genes are being turned off,

00:49:35.600 | and DNA, the stuff of genes, gets damaged in that process.

00:49:40.600 | FOXO3 sits upstream in a pathway

00:49:44.600 | related to DNA repair,

00:49:47.080 | and again, clearing of these senescent cells.

00:49:49.500 | Sauna exposure, in particular,

00:49:53.120 | sauna exposure two to three times,

00:49:55.280 | or ideally four to seven times per week,

00:49:57.700 | in that 80 to 100 degree Celsius range

00:50:01.360 | has been shown to upregulate levels of FOXO3.

00:50:04.960 | FOXO3, in turn, upregulates pathways related to DNA repair

00:50:10.360 | and clearing out of these senescent or dead cells,

00:50:12.780 | which is known to be important for various aspects

00:50:16.380 | of maintaining cognition

00:50:17.500 | and other aspects of maintaining health.

00:50:20.400 | So these are the likely biological mechanisms

00:50:23.460 | for the improvements in lifespan,

00:50:27.420 | or rather, I should say,

00:50:29.180 | these are the biological mechanisms

00:50:30.920 | that apparently offset some of the cardiovascular risk

00:50:35.160 | and other forms of mortality that were described earlier.

00:50:38.680 | One especially interesting thing about FOXO3,

00:50:42.180 | there are individuals out there

00:50:44.380 | that have either additional copies of FOXO3

00:50:47.680 | or who have versions of FOXO3 that are hyperactive,

00:50:52.360 | so to speak.

00:50:53.920 | Those people tend to be 2.7 times more likely

00:50:58.640 | to live to 100 years of age or longer.

00:51:01.800 | So these are people that were just naturally,

00:51:03.600 | and fortunately for them,

00:51:05.040 | endowed with more FOXO3, more clearance of senescent cells,

00:51:08.520 | more DNA repair, et cetera.

00:51:10.420 | For the rest of us, at least to my knowledge,

00:51:13.120 | I don't have one of these

00:51:15.200 | health-promoting FOXO3 mutations.

00:51:17.920 | Remember, mutations can be beneficial

00:51:19.680 | or they can be detrimental.

00:51:20.660 | This, if your goal is to live longer,

00:51:23.180 | is a beneficial mutation.

00:51:25.000 | Well, if you don't have these FOXO3 mutations

00:51:27.480 | that allow you to be a centenarian

00:51:29.580 | at 2.7 times higher likelihood than other people,

00:51:34.040 | deliberate heat exposure is one way

00:51:35.840 | that you can increase FOXO3 activity.

00:51:38.520 | At this point in time,

00:51:39.940 | meaning when looking at the research out there,

00:51:42.960 | it isn't clear what the optimal Sauna protocol

00:51:45.800 | is going to be specifically to increase FOXO3,

00:51:48.360 | and that's probably because there isn't one.

00:51:51.320 | There is no Sauna protocol designed specifically

00:51:54.600 | to reduce cortisol or specifically to increase FOXO3

00:51:58.840 | or specifically to activate heat shock proteins.

00:52:01.760 | Any deliberate heat exposure

00:52:03.080 | is likely to impact all of those mechanisms.

00:52:06.040 | Again, I encourage you to use this guide

00:52:07.960 | of 80 to 100 degrees Celsius as your kind of bookends

00:52:12.940 | for what you can tolerate and where you want to start

00:52:16.240 | and eventually transition to

00:52:18.140 | in terms of deliberate heat exposure.

00:52:19.840 | And I would encourage you to use that five to 20 minutes

00:52:23.460 | per session for the Sauna as your rough guide

00:52:27.900 | of how long to remain in the Sauna.

00:52:29.700 | Now, there was a study published just this last year

00:52:32.160 | that was mainly focused on deliberate cold exposure.

00:52:34.860 | I detailed this quite extensively in the episode on cold.

00:52:38.980 | This is the beautiful work of Susanna Soberg.

00:52:42.040 | And that study looked at deliberate cold exposure,

00:52:43.940 | but also Sauna exposure.

00:52:45.840 | And that study found that 57, yes,

00:52:49.860 | 57 minutes per week of Sauna exposure

00:52:53.740 | in conjunction with 11 minutes per week,

00:52:57.080 | total of deliberate cold exposure was the threshold

00:53:01.760 | for getting improvements in metabolism

00:53:04.720 | and increases in brown fat.

00:53:06.840 | This very active fat tissue

00:53:08.760 | that improves mitochondrial function and thermogenesis,

00:53:12.160 | meaning heating of the body.

00:53:13.000 | We'll talk more about the brown fat later.

00:53:14.860 | Why do I mention this?

00:53:15.740 | Well, for those of you that are interested

00:53:17.580 | in increasing metabolism,

00:53:19.500 | it does seem to be most beneficial

00:53:21.120 | to do that 11 minutes per week of cold exposure.

00:53:24.840 | Again, divided up across two or more sessions.

00:53:27.220 | So it's not 11 minutes all at once, but shorter sessions.

00:53:29.860 | And to get 57 minutes minimum per week of Sauna exposure,

00:53:34.700 | again, in the temperature ranges that I've talked about here.

00:53:37.460 | And again, it's not 57 minutes in the Sauna all at once.

00:53:42.240 | That's 57 minutes total per week as the minimum threshold.

00:53:46.420 | So you might divide that into three sessions of 20 minutes.

00:53:49.720 | And again, I don't think 57 is the magic number.

00:53:53.340 | It could be 60, it could be 64, it probably could be 55.

00:53:57.240 | Remember your biological systems are not counting things off

00:54:00.380 | minute by minute, second by second,

00:54:01.580 | at least not in most cases.

00:54:02.900 | So for those of you that are interested

00:54:04.180 | in improving metabolism, check out the episode on cold,

00:54:07.080 | or just take the SOBERG protocol, as I call it,

00:54:10.980 | which is 11 minutes total per week of uncomfortably cold,

00:54:15.140 | but safe cold exposure.

00:54:16.820 | So uncomfortably cold means you really,

00:54:18.420 | really want to get out of the shower or the ice bath

00:54:21.340 | or whatever environment, but you can stay in.

00:54:23.140 | 11 minutes total per week divided across a couple of sessions

00:54:25.740 | and then 57 minutes per week or so

00:54:29.660 | of deliberate heat exposure.

00:54:31.980 | Again, uncomfortably hot, excuse me, but safe to stay in,

00:54:36.980 | probably divided up across three or more sessions.

00:54:39.780 | Okay, so we've talked about the use of sauna

00:54:41.700 | to decrease cortisol.

00:54:43.580 | We've talked about the use of sauna

00:54:44.620 | to increase heat shock proteins.

00:54:47.120 | We've talked about the use of sauna to increase FOXO3.

00:54:51.340 | Now I'd like to talk about the use of sauna

00:54:53.180 | to increase growth hormone.

00:54:55.460 | Growth hormone is a hormone that we all naturally secrete

00:54:58.520 | from our pituitary,

00:54:59.780 | which also resides near the roof of our mouth.

00:55:02.780 | The signal for the pituitary to release growth hormone

00:55:06.540 | arrives from neurons that exist in the hypothalamus.

00:55:10.440 | So growth hormone releasing hormones, believe it or not,

00:55:13.940 | that's what they're called,

00:55:14.820 | stimulate the release of growth hormone

00:55:17.220 | from the anterior pituitary gland

00:55:19.680 | into the general circulation.

00:55:21.180 | And then growth hormone impacts metabolism

00:55:24.740 | and growth of cells and tissues of the body.

00:55:27.540 | It is responsible for tissue repair as well.

00:55:30.520 | And the growth spurt that everyone experiences

00:55:33.180 | during puberty is the consequence of growth hormone.

00:55:36.520 | What I'm about to describe is a study that found dramatic,

00:55:41.520 | really dramatic, I should say, increases in growth hormone.

00:55:45.180 | But I also want to emphasize

00:55:46.620 | that these increases in growth hormone

00:55:48.360 | were not of the sort that are observed in puberty

00:55:50.800 | or in infants becoming adolescents or adolescents

00:55:53.700 | growing into teenagers.

00:55:55.000 | Those levels of growth hormone

00:55:56.420 | that are associated with those massive transformations,

00:55:59.400 | excuse me, of body morphology, of shape,

00:56:02.760 | are far greater than the sorts that I'm talking about here.

00:56:06.260 | And yet, as all of us age,

00:56:10.100 | when we go from adolescence to our teenage years

00:56:13.060 | and then into young adulthood,

00:56:14.500 | but then starting in our early thirties or so,

00:56:17.360 | the amount of growth hormone that we secrete

00:56:19.320 | is greatly diminished.

00:56:20.640 | Normally, we would release growth hormone every night

00:56:24.760 | after we go to sleep,

00:56:25.620 | in particular in the early part of the night

00:56:27.620 | when our sleep is comprised mostly of slow wave sleep.

00:56:31.560 | As we age, less growth hormone is released

00:56:34.420 | during that slow wave sleep.

00:56:36.460 | There are various things

00:56:37.580 | that can promote the release of growth hormone.

00:56:39.860 | And we will talk about some of those other things

00:56:42.080 | in a moment.

00:56:42.920 | Things like low blood sugar, turns out,

00:56:46.520 | is a stimulus for growth hormone release.

00:56:50.440 | And I don't mean hypoglycemia of the sort

00:56:52.680 | that makes you dizzy and want to pass out, that's bad.

00:56:54.700 | I mean, not having high levels of glucose and insulin

00:56:57.480 | in your bloodstream.

00:56:58.320 | This is one of the reasons why many people

00:57:00.300 | are drawn to intermittent fasting or even prolonged fasting.

00:57:04.400 | It's because of the reported increases in growth hormone.

00:57:07.420 | I'll touch on those briefly,

00:57:08.660 | but if you want to learn more about those

00:57:10.060 | and what their real impact is

00:57:13.220 | and the extent of growth hormone,

00:57:14.920 | check out the episode I did on fasting.

00:57:17.140 | You can find that at hubermanlab.com.

00:57:19.280 | Certain forms of exercise have also been shown

00:57:21.400 | to stimulate growth hormone release.

00:57:23.440 | And in a few moments, I'll talk about

00:57:24.700 | how exercise and fasting can be combined

00:57:26.780 | or how heat can be combined with exercise

00:57:29.960 | or certain patterns of food intake

00:57:31.260 | to further increase growth hormone.

00:57:32.580 | But before I do that, I want to review some of the data

00:57:35.040 | and one study in particular that discovered

00:57:38.600 | certain forms of deliberate heat exposure using sauna

00:57:41.440 | can stimulate very large increases in growth hormone output,

00:57:45.400 | which for people in their 30s, 40s and beyond

00:57:48.380 | could be very useful and may also be useful

00:57:50.340 | for people who are just trying to stimulate

00:57:52.100 | the release of more growth hormone

00:57:53.680 | in order to, for instance, recover from exercise

00:57:55.860 | or stimulate fat loss or muscle growth

00:57:57.840 | or repair of a particular injury.

00:57:59.500 | The title of this paper is endocrine effects

00:58:02.860 | of repeated sauna bathing.

00:58:04.600 | And this is a paper that was published in 1986,

00:58:07.340 | which is some years ago, but nonetheless serves as a basis

00:58:10.960 | for a lot of other studies that followed.

00:58:13.560 | So let me describe what they did in this study.

00:58:16.340 | They used an 80 degree Celsius environment.

00:58:18.420 | So that's 176 degrees Fahrenheit.

00:58:21.820 | And they had subjects do this sauna for 30 minutes,

00:58:25.860 | four times per day.

00:58:27.560 | So that's two hours total in one day,

00:58:30.820 | 30 minutes in the sauna, a period of cool down rest,

00:58:33.460 | 30 minutes in the sauna again, cool down rest,

00:58:35.500 | a third and a fourth time, okay?

00:58:36.940 | So two hours total in this 80 degree Celsius environment.

00:58:41.020 | So that's a lot,

00:58:42.180 | but what they observed was really quite significant.

00:58:45.500 | So they had subjects do this protocol.

00:58:47.460 | And I should mention they had both male and female subjects

00:58:50.200 | in the study and the entire study lasted a week.

00:58:53.580 | They did this two hours of sauna exposure on day one,

00:58:56.420 | day three and day seven of that week.

00:58:59.600 | And they measured a lot of different hormones, cortisol,

00:59:03.300 | thyroid stimulating hormone, thyroid hormone itself,

00:59:07.200 | luteinizing hormone and follicle stimulating hormone,

00:59:10.320 | which are hormones that essentially drive the production

00:59:14.120 | of other hormones.

00:59:15.040 | We won't get into that too deeply,

00:59:16.540 | but if you'd like to learn about FSH,

00:59:18.280 | follicle stimulating hormone and luteinizing hormone,

00:59:20.180 | please see the episode on optimizing testosterone

00:59:23.280 | and estrogen at hubermanlab.com.

00:59:25.440 | They looked at prolactin and they looked at growth hormone.

00:59:29.020 | I'll just cut to the chase and tell you the effects

00:59:31.460 | on growth hormone.

00:59:32.300 | In subjects that did this two hour a day,

00:59:35.960 | 80 degree Celsius protocol,

00:59:38.820 | experienced 16 fold increases in growth hormone.

00:59:43.540 | So they measured growth hormone before the sauna

00:59:45.700 | and after the sauna and growth hormone levels

00:59:48.260 | went up 16 fold, which is obviously an enormous

00:59:52.600 | and it turns out statistically significant effect.

00:59:55.940 | Now, one important caveat here.

00:59:59.780 | Remember earlier when I talked about people who did sauna

01:00:03.360 | once a week versus two to three times a week

01:00:05.640 | versus four to seven times a week.

01:00:07.160 | And the more often people did sauna,

01:00:09.360 | the less likely they were to die of cardiovascular events

01:00:12.160 | or other things of that sort.

01:00:13.840 | Well, in this case,

01:00:15.280 | the effects of sauna exposure on growth hormone

01:00:18.180 | actually went down the more often

01:00:21.400 | that people did this deliberate heat exposure.

01:00:24.320 | So as I mentioned, they did this two hour a day,

01:00:26.680 | divided into 30 minute sessions protocol on day one,

01:00:29.360 | day three and day seven of a week.

01:00:33.040 | And what they found was on day one,

01:00:35.120 | there was a 16 fold increase in growth hormone.

01:00:38.320 | On day three however,

01:00:39.640 | there was still a significant effect on growth hormone

01:00:42.780 | as compared to before sauna,

01:00:44.720 | but that effect was basically cut by two thirds, okay?

01:00:49.380 | So now instead of getting a 16 fold increase,

01:00:51.980 | it was more like a three or four fold increase,

01:00:54.940 | which is still a huge increase,

01:00:56.740 | but not as great as the increase observed on day one.

01:00:59.660 | And then on day seven, there tended to be a two,

01:01:02.680 | maybe a three fold increase,

01:01:05.140 | but not as great as the one observed on day one.

01:01:08.000 | What does this mean and why does this happen?

01:01:11.060 | Well, the reason this happens is because heat,

01:01:15.420 | just like cold is a shock or a stressor to the system.

01:01:20.420 | In the context of cold,

01:01:22.580 | if you get into a very cold ice bath, for instance,

01:01:25.860 | a five degree ice bath, even for 20 seconds,

01:01:29.540 | it's known to increase norepinephrine 200%.

01:01:33.580 | It can double the amount of norepinephrine

01:01:35.500 | that you suddenly release into your brain and body,

01:01:37.660 | which actually can have some positive effects.

01:01:39.260 | I'll talk about those in a little bit,

01:01:41.380 | but if you were to do that every day,

01:01:43.820 | you become cold adapted.

01:01:45.800 | This circuit that compares the shell and core of your body

01:01:50.240 | would adjust in ways that it could either predict

01:01:54.180 | that cold stimulus or more likely

01:01:56.460 | to create some thermogenic mechanisms

01:01:58.620 | in preparation for that cold exposure.

01:02:02.420 | This is why, for instance,

01:02:03.800 | people that use deliberate cold exposure

01:02:05.500 | to try and increase lipolysis, the burning of fat,

01:02:08.100 | oftentimes will get results for a while,

01:02:09.720 | but then if they're doing it a lot, a lot,

01:02:11.300 | they stop getting those effects.

01:02:13.120 | I talk a lot about avoiding cold adaptation

01:02:15.340 | if that's your goal in the episode on cold,

01:02:18.400 | but similar mechanisms are at play here.

01:02:20.820 | So we have to imagine that when these subjects

01:02:22.860 | got into the sauna on day one,

01:02:24.180 | whatever pathways went from measurement of temperature

01:02:27.400 | at the shell to changes in temperature at the core

01:02:30.620 | led to these big increases in growth hormone,

01:02:32.700 | which is basically a way of just describing the result

01:02:34.580 | I already told you before.

01:02:36.220 | But the fact that that result diminished over time

01:02:38.860 | either means that the circuit was not as efficient

01:02:41.140 | in communicating that shift in temperature

01:02:43.700 | or that that shift in temperature was of less impact

01:02:46.620 | because the downstream effectors

01:02:49.220 | were not engaged to the same extent

01:02:51.140 | because it wasn't as much of a shock.

01:02:52.860 | And I think the latter explanation is far more likely.

01:02:55.060 | This is very much akin to weight training

01:02:57.740 | or cardiovascular exercise,

01:02:59.180 | where if you run up a hill very fast, for instance,

01:03:01.700 | and your lungs are burning

01:03:03.080 | and you're heaving and breathing hard,

01:03:05.300 | on the first day, that's a very painful thing.

01:03:07.820 | But if you do it every day or every other day,

01:03:09.940 | provided you allow yourself to recover,

01:03:11.540 | pretty soon you're running up that hill

01:03:12.720 | and you're not breathing as hard.

01:03:14.420 | There isn't much burning in your muscles,

01:03:16.620 | et cetera, et cetera, your body adapts.

01:03:19.340 | So one of the key things to understand

01:03:21.580 | about the use of deliberate heat exposure

01:03:23.700 | is if you're going to use it in order to try

01:03:25.900 | and trigger massive increases in growth hormone,

01:03:28.340 | you're going to need to be careful about not doing it more

01:03:30.740 | than let's say once a week.

01:03:32.400 | Now I'm extrapolating from this study,

01:03:34.420 | maybe once every 10 days would be even better.

01:03:36.900 | But if you start getting heat adapted,

01:03:39.640 | it's very unlikely that you're going to get

01:03:42.060 | these massive increases in growth hormone.

01:03:44.460 | So I don't mean to be discouraging

01:03:45.880 | of using deliberate heat exposure

01:03:47.380 | to access growth hormone increases,

01:03:49.640 | but if that's your specific goal or your main goal,

01:03:52.920 | then I think it's reasonable to say

01:03:55.240 | that you don't want to do deliberate heat exposure,

01:03:57.380 | at least not of the sort that I described here,

01:03:59.480 | more than once a week, or maybe even once every 10 days.

01:04:02.140 | And that you would want to time that to other events

01:04:04.400 | in your life, maybe hard workouts,

01:04:06.340 | or if you're trying to push through a fat loss barrier,

01:04:10.380 | or simply in order to access growth hormone at peak levels,

01:04:14.020 | maybe three times per month or four times per month.

01:04:17.160 | If you start doing deliberate heat exposure more often,

01:04:19.540 | you'll still get increases in growth hormone,

01:04:21.660 | but they are not going to be nearly as large

01:04:24.140 | as the increases in growth hormone

01:04:25.940 | that you're going to experience if you shock your system

01:04:29.420 | with deliberate heat exposure every once in a while.

01:04:32.620 | An important way to frame this

01:04:34.520 | is actually in the context of cold.

01:04:36.140 | And while you might say,

01:04:36.980 | "Wait, this is an episode on heat and heating, not cold."

01:04:39.820 | You really can't have a conversation about heat and heating

01:04:41.980 | without talking about cold, because as I mentioned earlier,

01:04:45.780 | if you cool the outside of your body, the shell,

01:04:48.400 | you're actually heating up your body.

01:04:50.020 | In fact, the circuits that control heating of the body

01:04:52.620 | and that control cooling of the body,

01:04:55.100 | for instance, the activation of things like shiver

01:04:57.340 | or fat loss in response to cold and shiver,

01:04:59.880 | those are also controlled by the preoptic area

01:05:02.260 | of the hypothalamus.

01:05:03.980 | So we can take a step back and start to think about

01:05:06.920 | what it would take to design the optimal protocol

01:05:10.220 | for deliberate heat exposure by looking at cold.

01:05:13.300 | And here's what I mean.

01:05:14.460 | There have been beautiful studies showing

01:05:16.740 | that if people get into a very cold body of water,

01:05:20.500 | four degrees Celsius for 20 seconds, as I mentioned earlier,

01:05:23.120 | that will cause a 200 to 300% increase in norepinephrine.

01:05:28.080 | Norepinephrine is also called noradrenaline,

01:05:30.400 | and norepinephrine and other so-called catecholamines

01:05:33.080 | like dopamine increase dramatically

01:05:35.560 | in this very brief cold water exposure.

01:05:37.920 | And those increases in norepinephrine and dopamine

01:05:40.280 | are known to have long lasting effects

01:05:43.280 | that generally to improvements in mood, focus,

01:05:45.720 | and alertness.

01:05:46.600 | They're pretty significant.

01:05:48.020 | However, they aren't significant enough

01:05:50.240 | to increase metabolism to a very high degree.

01:05:53.120 | Whereas other studies have shown that if people go outside

01:05:57.000 | in 16 degrees Celsius weather with a proper amount,

01:06:01.240 | but a fairly minimum amount of clothing,

01:06:03.920 | you can experience even greater increases in norepinephrine.

01:06:07.560 | But the time that's required in order to experience

01:06:10.720 | those increases is six hours at, for instance,

01:06:13.840 | 16 degrees Celsius.

01:06:15.360 | So if you have six hours a day to be out there in the cold,

01:06:17.540 | or if you're going to turn the air conditioning on

01:06:19.060 | in an environment, make it very, very cold, fine.

01:06:21.380 | But basically what I'm describing is that you can sort of

01:06:23.420 | bookend the parameters that you can use.

01:06:25.880 | You can use a very brief exposure to cold or to heat

01:06:29.440 | in order to stimulate heat shock proteins,

01:06:31.180 | growth hormone, et cetera.

01:06:32.560 | Or you can use longer exposure in less intense versions

01:06:36.780 | of heat and cold.

01:06:38.240 | You really have to find what's going to work for you

01:06:39.780 | and what you can do safely.

01:06:41.420 | And if you're confused about where to start,

01:06:44.200 | please use the parameters that I described earlier.

01:06:46.560 | First of all, check with your doctor as always,

01:06:48.720 | make sure that you're somebody who can do deliberate cold

01:06:51.600 | or heat exposure safely, but that 80 to 100 degrees Celsius,

01:06:55.720 | meaning 176 degrees Fahrenheit to 212 degrees Fahrenheit,

01:06:58.660 | that I keep repeating over and over,

01:06:59.920 | 'cause I know somebody is going to ask,

01:07:01.160 | even though I repeat it over and over, which is fine.

01:07:03.420 | I'm delighted to keep saying it and to respond

01:07:06.440 | if someone asks again.

01:07:07.540 | Well, those parameters are going to kind of bookend

01:07:09.960 | what you should do in terms of the intensity

01:07:12.160 | of the heat stimulus.

01:07:13.720 | How long?

01:07:14.540 | Well, we heard earlier, five to 20 minutes.

01:07:16.180 | Why not start with five and then ramp it up to 10 or 15?

01:07:19.780 | And then if you're feeling really bold

01:07:21.820 | and you really want to crank out growth hormone,

01:07:23.500 | well, then you could do that 30 minute,

01:07:25.060 | four times in one day stimulus every once in a while.

01:07:28.000 | So you have to really figure out

01:07:28.980 | what you're using heat exposure for.

01:07:31.900 | This is one of the reasons why when people say,

01:07:34.020 | is it better to get in a wet sauna or dry sauna?

01:07:36.220 | What's the optimal temperature?

01:07:38.160 | Is it better to take a hot shower or a hot bath

01:07:40.100 | or a hot tub?

01:07:40.940 | To be completely honest,

01:07:42.020 | it depends on what you're going to be able to do regularly,

01:07:44.640 | whether or not you want to do it regularly,

01:07:46.100 | and what your specific goals are.

01:07:47.560 | So the purpose of this episode is really to arm you

01:07:49.660 | with the underlying mechanisms

01:07:50.980 | and to arm you with the general parameters

01:07:52.920 | that are going to allow you to access the results

01:07:54.920 | that you're seeking.

01:07:55.760 | For what it's worth, I personally use a protocol

01:07:58.200 | and I've been using a protocol for a long time

01:08:00.120 | that involves trying, meaning I accomplish this most weeks,

01:08:03.500 | not all, trying to get into a sauna

01:08:06.360 | for three 20 minute sessions every week.

01:08:10.100 | I use a dry sauna, so it's not a steam room.

01:08:13.220 | If I don't have access to it,

01:08:14.380 | I might take a hot bath or something of that sort.

01:08:16.180 | But in general,

01:08:17.020 | I just stick to doing the sauna three times a week.

01:08:19.740 | And I generally will do that either after a workout,

01:08:23.380 | either a cardiovascular workout or a weight workout,

01:08:26.080 | or I'll do it later in the evening.

01:08:28.240 | Why later in the evening?

01:08:29.860 | Well, it has to do with the circadian shifts in temperature

01:08:33.100 | that we all experience.

01:08:34.780 | Talked a lot about this in the circadian episodes

01:08:37.580 | and the episodes related to sleep,

01:08:38.800 | but in a nutshell, here's how it works.

01:08:42.280 | Every early morning, about two hours

01:08:44.680 | before your typical wake-up time,

01:08:47.560 | your body temperature is at its all time lowest.

01:08:51.160 | We call that your temperature minimum.

01:08:53.200 | Right about waking, your body temperature increases.

01:08:55.400 | In fact, an increase in body temperature

01:08:56.860 | is part of the reason you wake up at all,

01:08:59.300 | unless of course you're setting an alarm.

01:09:01.400 | Increases in body temperature are going to be

01:09:04.420 | one of the major things that wakes up your brain and body.

01:09:08.320 | Body temperature will tend to continue

01:09:10.160 | to increase through the morning.

01:09:11.580 | You'll get that increase in cortisol

01:09:12.980 | that's a healthy increase in cortisol.

01:09:14.900 | Body temperature will increase into the afternoon,

01:09:17.000 | and then will start to drop in the later afternoon.

01:09:20.220 | This general contour can be shifted

01:09:22.160 | by whether or not you exercise, how often you eat,

01:09:24.540 | because of the so-called thermogenic effects of food.

01:09:27.040 | That is, every time you eat,

01:09:28.120 | there's a slight increase in body temperature and metabolism,

01:09:30.600 | but it's not really that significant

01:09:32.960 | to throw off this general contour and rhythm.

01:09:35.560 | But toward the afternoon, around four or five o'clock,

01:09:38.000 | most days, depending on time of year,

01:09:39.740 | your body temperature will peak,

01:09:41.140 | and then it will start to drop.

01:09:42.640 | And as your body temperature drops by one to three degrees,

01:09:45.240 | and here I'm referring to your core body temperature,

01:09:47.040 | not your shell body temperature,

01:09:49.280 | you will start to get sleepy and to transition into sleep

01:09:52.560 | and to maintain sleep throughout the night,

01:09:55.300 | your body temperature will remain low

01:09:57.040 | until you hit that temperature minimum,

01:09:58.240 | and then it'll start to come up again, okay?

01:10:00.560 | What that means is that when you decide to do sauna,

01:10:04.520 | or cold exposure for that matter, is going to be important.

01:10:07.640 | Why?

01:10:08.460 | Well, as I mentioned earlier,

01:10:09.800 | if you were to make the surface of your body cold,

01:10:11.860 | at least in the immediate period after that,

01:10:14.580 | your body temperature will increase.

01:10:16.880 | So for those of you that are challenged in getting to sleep

01:10:20.300 | and are still working on your sleep,

01:10:21.860 | remember, sleep is the foundation

01:10:23.160 | of all mental and physical health and optimal performance.

01:10:25.660 | You should try to get really quality sleep

01:10:28.000 | of sufficient duration at least 80% of nights.

01:10:30.420 | That should be an ongoing goal throughout your lifespan

01:10:32.860 | for a huge number of reasons.

01:10:34.540 | Watch the master sleep episode

01:10:36.960 | if you'd like to hear more of those reasons

01:10:38.280 | and the mechanisms to make sure that you do that.

01:10:40.340 | But in any event, cold exposure late in the evening

01:10:44.520 | will start to increase your body temperature again,

01:10:48.280 | and that can make it hard for some people to fall asleep.

01:10:50.440 | Now, if you're very, very tired,

01:10:52.360 | because you've been working hard or training hard

01:10:54.000 | or both throughout the day,

01:10:55.320 | might not throw off your sleep so much.

01:10:57.500 | I've gone through bouts where I'm just so, so busy

01:10:59.640 | from morning till night that the only time I can get

01:11:01.560 | into the ice bath or the cold shower is late in the evening,

01:11:03.840 | and I have no trouble sleeping after that.

01:11:05.800 | However, if you have trouble sleeping,

01:11:07.240 | I would recommend doing the cold exposure early in the day

01:11:10.080 | to match that natural heating,

01:11:12.340 | that natural increase in body temperature

01:11:15.280 | that occurs across the 24 hour so-called circadian rhythm.

01:11:18.700 | Similarly, if you're going to use deliberate heat exposure,

01:11:23.100 | you'd be wise to do that later in the day.

01:11:27.160 | You'd be wise to do it later in the day

01:11:28.800 | because when you get into a warm environment,

01:11:31.560 | sure, the surface of your body, the shell heats up,

01:11:34.280 | the core of your body heats up,

01:11:36.560 | but then it also activates cooling mechanisms

01:11:39.520 | through the preoptic area.

01:11:41.280 | And when you get out of that hot environment,

01:11:43.800 | sauna or otherwise, your body will continue to cool down.

01:11:47.660 | And so many people find that if they do sauna

01:11:49.640 | in the later half of the day, or even just before sleep,

01:11:53.040 | and then take a warmish shower afterwards,

01:11:56.140 | then they find it easier to fall asleep.

01:11:57.860 | And that makes sense

01:11:58.700 | because their body temperature is dropping.

01:12:01.200 | And in fact, if your goal is to really promote

01:12:03.800 | the maximum amount of growth hormone release,

01:12:05.720 | that's also going to be the best time of day to do it,

01:12:07.640 | especially if you haven't eaten

01:12:08.920 | in the two hours before sleep, okay?

01:12:11.800 | So if you're really going for growth hormone release,

01:12:13.920 | you're really trying to optimize sleep,

01:12:15.360 | and the two things are actually linked

01:12:16.920 | because of the release of growth hormone

01:12:18.240 | that happens from the pituitary in the early night's sleep,

01:12:21.120 | well, then you would be wise to do your sauna

01:12:23.600 | maybe once or maybe twice a week in the evening

01:12:27.160 | or at nighttime, then taking a warm or cool shower,

01:12:29.880 | just briefly, just enough to kind of rinse off

01:12:31.880 | all the sweat from the sauna, and then get ready for sleep

01:12:35.600 | and to do that, not necessarily fasted,

01:12:38.080 | but to try and keep your levels of glucose and insulin

01:12:41.000 | somewhat low in your bloodstream.

01:12:42.580 | The reason I say that is that

01:12:44.280 | having elevated blood glucose and/or insulin

01:12:48.420 | tends to blunt or reduce growth hormone release,

01:12:51.480 | and that's true for any number of different stimuli,

01:12:54.520 | including exercise and including sauna.

01:12:57.920 | So there's a really nice study on this

01:12:59.240 | that I can point you to.

01:13:00.800 | There's a study that was published in the journal "Stress,"

01:13:03.120 | literally, that's the name of the journal.

01:13:04.600 | I love it when journals have these names like pain or stress.

01:13:08.360 | I find that somewhat amusing for reasons that escape me,

01:13:11.160 | but nonetheless, amuse me.

01:13:13.080 | The title of this study is "Growth Hormone Response

01:13:15.040 | "to Different Consecutive Stress Stimuli in Healthy Men.

01:13:18.300 | "Is There Any Difference?"

01:13:19.280 | And I don't want to go into all the details of the study

01:13:21.320 | because it's pretty extensive and complicated,

01:13:23.440 | but basically what they did is that they had people do sauna

01:13:26.080 | and then gave them a drug or a condition of having low,

01:13:30.600 | not dangerously low, but low blood sugar,

01:13:33.260 | or they had them in a condition

01:13:34.600 | where they had low blood sugar and then did sauna,

01:13:37.320 | or they had them do an exercise protocol

01:13:39.260 | that led them to increase growth hormone

01:13:42.860 | and then had them do low blood sugar,

01:13:44.260 | basically mixing and matching the various stimuli

01:13:47.160 | that could increase growth hormone.

01:13:48.980 | And what they found was very straightforward.

01:13:51.660 | What they found was that doing sauna once

01:13:54.340 | and then waiting some period of time

01:13:56.360 | and then later that day doing sauna again,

01:13:58.820 | they didn't see the same increase in growth hormone

01:14:02.240 | both times.

01:14:03.560 | First, they got a big increase in growth hormone

01:14:05.260 | and then less if they did sauna again.

01:14:07.560 | If they had people do exercise and then sauna,

01:14:10.240 | what they found was exercise could stimulate growth hormone,

01:14:12.840 | but then following it with sauna did not allow you

01:14:15.560 | to get twice as much growth hormone.

01:14:18.520 | In general, anytime you release growth hormone,

01:14:21.000 | you reduce the likelihood

01:14:22.440 | that you're going to release growth hormone again

01:14:25.160 | later that day.

01:14:26.240 | And this partially explains that earlier study

01:14:28.240 | where if people did this growth hormone promoting protocol

01:14:31.360 | on day one, but then on day three,

01:14:32.960 | they didn't see quite as big an effect.

01:14:34.360 | And on day seven, they didn't see quite as big effect.

01:14:36.880 | All it basically boils down to is that

01:14:39.240 | if you really want to crank out the most amount

01:14:41.260 | of growth hormone in response to sauna,

01:14:43.600 | do it fasted or at least not having ingested any food

01:14:46.480 | in the two or three hours before.

01:14:48.180 | You don't have to be deep into a fast.

01:14:50.360 | And the whole notion of what breaks a fast

01:14:52.100 | is kind of an interesting conversation

01:14:53.600 | because it's contextual, right?

01:14:55.320 | Will a sip of coffee break your fast?

01:14:57.000 | Well, maybe, probably not.

01:14:59.060 | Will one grain of sugar break your fast?

01:15:01.320 | No.

01:15:02.160 | Will an entire candy bar break your fast?

01:15:04.960 | Yes, it has to do with where your blood glucose is

01:15:07.460 | when you ingest that particular food item,

01:15:09.240 | not so much what that food item is per se.

01:15:12.120 | But the bottom line here is if you want to crank out

01:15:14.200 | the most amount of growth hormone,

01:15:15.840 | wait a couple of hours after eating

01:15:17.320 | before getting into the sauna,

01:15:18.680 | or maybe do it before dinner and then prepare dinner,

01:15:21.920 | do the sauna before dinner that is,

01:15:23.700 | then prepare dinner, then eat dinner,

01:15:25.520 | and then make sure that you wait a few hours

01:15:27.540 | before going to sleep.

01:15:28.620 | You're going to have to arrange your schedule accordingly.

01:15:31.380 | I know most people can't arrange their schedule perfectly

01:15:34.460 | just to get growth hormone increases,

01:15:35.940 | nor do I think people should approach

01:15:37.380 | health protocols that way.

01:15:38.740 | I think for 90% of people, 90% of the time,

01:15:42.140 | just getting into the sauna once or twice

01:15:45.560 | or three times a week is going to be beneficial

01:15:47.620 | for the number of reasons that I described earlier.

01:15:50.180 | And you don't want to obsess too much

01:15:52.320 | about the exact conditions you need

01:15:54.060 | in order to get the greatest effect

01:15:55.740 | out of that sauna treatment.

01:15:57.160 | These are just some additional tweaks

01:15:58.680 | related to food intake and low-level hypoglycemia

01:16:02.520 | and exercise that if you wanted to leverage, you could.

01:16:05.300 | So if decreases in body temperature

01:16:06.920 | tend to aid the transition to sleep

01:16:09.000 | and getting out of a hot sauna

01:16:10.780 | tends to promote decreases in body temperature,

01:16:13.300 | it makes sense why you would want to put your sauna exposure

01:16:16.940 | or other deliberate heat exposure

01:16:18.220 | in the second half of your day

01:16:19.600 | and maybe even right before sleep.

01:16:21.360 | Now, regardless of what time of day you do sauna

01:16:24.240 | or how frequently you do it,

01:16:25.700 | you're going to want to hydrate after going in the sauna.

01:16:29.280 | When you go in the sauna, you lose water.

01:16:31.500 | And when you lose water, you need to replace it.

01:16:34.040 | Why?

01:16:34.880 | Well, you need water for all your cells,

01:16:36.180 | but you also need electrolytes.

01:16:37.380 | So make sure that you're replacing the water

01:16:39.420 | that you lose in the sauna.

01:16:41.140 | Now there's no exact formula of how much water to drink

01:16:43.740 | and whether or not you need electrolytes

01:16:45.440 | in that water or not.

01:16:46.520 | It's going to depend on how much you sweat,

01:16:48.000 | meaning how heat adapted you are.

01:16:49.400 | It's going to depend on how much salt you tend to excrete

01:16:51.860 | in your sweat, huge amount of variation.

01:16:54.620 | But in general, one way to approach this would be

01:16:57.060 | to make sure that you drink at least 16 ounces of water

01:17:00.760 | for every 10 minutes that you happen to be in the sauna.

01:17:04.120 | You could do that before and during and after,

01:17:06.860 | you could do it during and after, or you could do it after.

01:17:09.940 | Now, there are other reasons to do deliberate heat exposure

01:17:12.600 | that have nothing to do with cardiovascular effects,

01:17:15.160 | nothing to do with growth hormone or anything of that sort,

01:17:18.240 | but rather have to do with improvements

01:17:20.100 | in mood and mental health.

01:17:21.820 | In fact, the data related to sauna

01:17:25.100 | and other forms of deliberate heat exposure improving mood

01:17:27.780 | are very impressive, both at the mechanistic level

01:17:31.020 | and in terms of the long-term consequences

01:17:33.700 | that people experience.

01:17:35.220 | First of all, we need to ask,

01:17:36.260 | how is it that deliberate heat exposure

01:17:38.360 | can improve our mood and wellbeing?

01:17:40.180 | Well, it turns out that it improves mood and wellbeing,

01:17:43.340 | but it also improves our capacity to feel good

01:17:47.200 | in response to things

01:17:48.300 | that would ordinarily make us feel somewhat good.

01:17:51.820 | Now, this is not a situation

01:17:53.520 | where you're going to be walking around,

01:17:55.500 | grinning ear to ear in response to nothing at all,

01:17:58.500 | simply because you went in a sauna.

01:18:00.180 | What I'm talking about is the upregulation of pathways,

01:18:04.140 | meaning chemical pathways in your brain and body

01:18:06.820 | that allow you to experience pleasure in all its fullness.

01:18:10.060 | So here's how this whole deliberate heat exposure

01:18:12.160 | sauna mood thing works.

01:18:14.020 | Many of you have probably heard of endorphins.

01:18:17.380 | Endorphins are a category of molecules

01:18:19.780 | that are made naturally in your brain and body

01:18:22.140 | and that are released in response

01:18:23.860 | to different forms of stressors.

01:18:26.580 | That's right, in response to stressors.

01:18:28.160 | So if ever you've gone out on a long run

01:18:30.500 | and at some point in that run,

01:18:31.580 | you feel like you're aching and your joints hurt,

01:18:33.660 | or maybe you have shin splints and you push through that,

01:18:36.580 | part of the reason that you experience a lack of pain

01:18:40.660 | at some point usually,

01:18:42.400 | or you experience a euphoria during or after that exercise

01:18:46.340 | is the exercise induced effects on endorphin release,

01:18:50.240 | or rather to be more specific,

01:18:52.100 | I should say the exercise induced consequences

01:18:55.700 | on the stress system,

01:18:56.860 | which in turn trigger the release of endorphin.

01:18:59.740 | In other words, when we experience short-term

01:19:02.660 | or acute stress, the endorphin system is activated.

01:19:06.780 | Now the endorphin system is not just about feeling good,

01:19:10.100 | believe it or not, it's also about feeling bad.

01:19:12.700 | And there are two general categories of endorphins.

01:19:14.980 | The first are the ones that you normally hear about,

01:19:17.100 | endorphins, things that bind, for instance,

01:19:19.460 | to receptors like the mu opioid receptor.

01:19:22.540 | Opioids are not just prescribed compounds

01:19:25.580 | or unfortunately drugs of abuse, which they are, right?

01:19:29.500 | We have this opioid crisis in the United States

01:19:31.500 | and elsewhere, which is a very serious and tragic thing,

01:19:34.700 | but we make endogenous opioids.

01:19:37.260 | We make endorphins that naturally act as pain relievers

01:19:40.800 | and that make us feel mildly euphoric.

01:19:43.640 | We also make endorphins such as dynorphin,

01:19:47.160 | that's D-Y-N-O-R-P-H-I-N, dynorphin,

01:19:52.160 | that actually make us feel worse in response to stressors.

01:19:56.000 | When we get into a hot sauna

01:19:59.440 | or a hot environment of any kind,

01:20:01.720 | dynorphins are liberated in the brain and body.

01:20:04.880 | And I should mention that dynorphins are made

01:20:06.680 | by many neurons in many different areas of the brain.

01:20:10.280 | So you might think, well, why would I want that?

01:20:12.560 | Why would I want to release dynorphin into my brain and body?

01:20:15.020 | Well, first of all,

01:20:15.860 | when you get into an uncomfortably hot situation,

01:20:19.220 | uncomfortably hot scenario, oh gosh,

01:20:21.480 | this is sounding terrible,

01:20:22.500 | in a deliberately hot environment that you are using

01:20:26.480 | to try and trigger some sort of biological

01:20:28.740 | or psychological benefit, I should say,

01:20:31.080 | the discomfort that you feel,

01:20:33.860 | the desire to get out of that environment

01:20:36.340 | is in part the consequence of the release of dynorphin.

01:20:40.640 | It's also the consequence of the activation

01:20:42.700 | of that sympathetic nervous system.

01:20:43.920 | Remember the preoptic area can communicate with the amygdala

01:20:46.920 | and trigger that kind of fight or flight mode.

01:20:48.800 | I want to get out of the sauna.

01:20:49.800 | This is really, really hot.

01:20:51.200 | But dynorphin is also liberated

01:20:53.440 | from a certain number of neurons.

01:20:55.600 | Dynorphin binds to what's called the kappa receptor.

01:20:59.720 | The kappa receptor binds dynorphin

01:21:02.720 | and triggers pathways in the brain and body

01:21:05.100 | that lead to agitation, to stress,

01:21:07.780 | and believe it or not, to a general sense of pain.

01:21:10.660 | This is why you want to get out of the hot sauna.

01:21:13.180 | And remember, if it's unsafe levels of hot,

01:21:15.580 | then you should get out of that sauna

01:21:17.400 | or other hot environment.

01:21:19.200 | But if you're working in a range

01:21:21.220 | or you're exposing yourself to a range of heat

01:21:23.020 | that's uncomfortable but safe to be in,

01:21:25.380 | dynorphin will be liberated from these neurons,

01:21:27.920 | bind to the kappa receptor.

01:21:30.220 | And as a downstream consequence of that,

01:21:33.620 | there will be an increase in the receptors

01:21:35.820 | that bind the other endorphins,

01:21:38.820 | the endorphins that make you feel soothed,

01:21:40.740 | that make you feel happy,

01:21:41.900 | and that make you feel mild euphoria.

01:21:44.500 | So there've been a number of studies showing

01:21:45.780 | that initially deliberate heat exposure

01:21:48.020 | by sauna or otherwise causes the release of dynorphin.

01:21:51.220 | In fact, I think it's fair to say

01:21:52.700 | that every time we get into a hot environment

01:21:55.100 | that's uncomfortable or a cold environment

01:21:56.920 | that's uncomfortable, dynorphin is likely released

01:21:59.220 | and binding to the kappa receptor.

01:22:00.920 | But over time, that binding of dynorphin

01:22:04.980 | to the kappa receptor leads to downstream changes

01:22:08.260 | in the way that the feel-good endorphins,

01:22:10.740 | things like endorphin binding to the mu opioid receptor,

01:22:13.660 | and there are still other feel-good endorphins, so to speak,

01:22:17.480 | that system becomes much more efficient

01:22:20.340 | such that people feel an elevation

01:22:22.240 | in their baseline level of mood.

01:22:24.060 | And when a good or happy event comes along,

01:22:27.920 | they feel a heightened level of happiness or joy or awe

01:22:31.900 | or improved mood in response to that.

01:22:34.180 | This is not unlike the effects of caffeine

01:22:36.760 | on the dopamine receptor that I've described previously.

01:22:39.060 | And for those of you that aren't familiar with it,

01:22:41.320 | many of you drink caffeine and love it.

01:22:44.260 | Part of the reason you love it is because of the release

01:22:46.620 | of certain neurochemicals like norepinephrine, et cetera,

01:22:50.080 | the energy that it gives you, maybe the taste,

01:22:51.980 | I would hope as well.

01:22:53.260 | But caffeine ingestion also causes increases

01:22:56.420 | in dopamine receptor concentration and efficacy.

01:22:59.300 | In other words, it allows the receptors for dopamine

01:23:01.880 | to work better so that for a given amount

01:23:04.680 | of dopamine release,

01:23:05.600 | you experience more pleasure and motivation.

01:23:08.820 | This is a similar mechanism,

01:23:10.120 | but within the endorphin pathway.

01:23:11.900 | So what does it mean?

01:23:12.860 | It means that a little bit of discomfort

01:23:15.360 | as a consequence of deliberate heat exposure,

01:23:17.380 | while in the short term, doesn't feel good by definition,

01:23:21.380 | it is activating pathways that are allowing

01:23:23.500 | the feel-good molecules and neural circuitries

01:23:27.120 | that exist in your brain and body

01:23:28.640 | to increase their efficiency,

01:23:31.360 | placing you in a better position to be joyful

01:23:33.460 | in response to the events of life.

01:23:35.220 | I confess I'm very excited about the data

01:23:37.020 | on deliberate heat exposure and improvements

01:23:40.180 | in the chemical systems that underlie good mood.

01:23:44.100 | And just to underscore this further,

01:23:46.340 | the dynorphin system is not unique to heat-induced stress.

01:23:51.340 | In fact, there are beautiful studies and reviews out there

01:23:55.180 | about the role of dynorphin in stress and depression,

01:23:58.820 | in stress and alcoholism,

01:24:01.480 | just as a brief aside and in the future,

01:24:03.520 | we will do a whole episode on alcohol and alcoholism,

01:24:07.300 | but turns out that chronic alcohol use

01:24:09.220 | and alcoholism causes changes in dopamine receptors

01:24:12.900 | that make it very difficult for people to achieve pleasure

01:24:16.820 | through things other than alcohol and even alcohol.

01:24:19.560 | That's kind of the really diabolical nature of addiction,

01:24:22.860 | which is the thing that initially brings pleasure,

01:24:24.900 | eventually is just required to maintain baseline levels

01:24:27.760 | of dopamine.

01:24:28.840 | And I've talked before and Dr. Anna Lemke,

01:24:31.040 | when she was a guest on this podcast,

01:24:33.440 | talked about the pleasure playing balance

01:24:36.180 | that exists within the dopamine system.

01:24:38.380 | And it's beautifully described in her book,

01:24:39.680 | "Dopamine Nation," by the way,

01:24:41.380 | excellent book I recommend to all people, addicts or not.

01:24:45.140 | Well, in that context of pleasure and pain,

01:24:49.180 | it's very clear what the pleasure molecule is.

01:24:51.460 | It's actually a molecule more related to motivation

01:24:53.800 | and that's dopamine.

01:24:55.580 | The pain molecule, however, appears to be dynorphin.

01:24:59.620 | And the fact that dynorphin is dysregulated

01:25:03.400 | in stress and depression and alcoholism

01:25:05.240 | and the relationship between dynorphin and dopamine

01:25:07.640 | is something that we should all take very seriously.

01:25:09.960 | And for that reason, I'm very excited about the fact

01:25:12.940 | that deliberate heat exposure can leverage

01:25:16.440 | the dynorphin system in a short-term and acute way

01:25:19.780 | that allows mood to improve after the sauna exposure.

01:25:23.620 | So for those of you that don't like heat exposure,

01:25:26.620 | keep in mind that a lot of the observed positive effects

01:25:31.220 | on our biology relate to metabolism,

01:25:33.740 | cardiovascular function, but also mental health.

01:25:36.860 | And along those lines, there's a wonderful study,

01:25:40.500 | again, published in 2018.

01:25:42.260 | I don't know why, I guess 2018 was a big year

01:25:44.300 | for deliberate heat exposure studies.

01:25:47.360 | The title of this study is "Sauna Bathing

01:25:50.860 | "and Risk of Psychotic Disorders."

01:25:52.740 | And this was a prospective cohort study.

01:25:55.140 | Again, we'll provide a link to this study.

01:25:57.200 | It's a really interesting study that explored

01:25:58.980 | the relationship between mental health,

01:26:01.260 | so people suffering from various forms of psychosis,

01:26:04.260 | schizophrenia and other forms of psychosis, and use of sauna.

01:26:07.980 | So essentially what this study did is they looked

01:26:10.320 | at a very large number of subjects,

01:26:11.980 | more than 2000 subjects who had no history

01:26:14.800 | of psychotic disorders.

01:26:16.220 | They were classified into three groups

01:26:17.740 | based on their frequency of sauna use,

01:26:20.220 | either once a week, two to three times per week,

01:26:23.120 | or four to seven times per week.

01:26:24.860 | This should call to mind that earlier study

01:26:27.480 | on all-risk mortality and cardiovascular event risk.

01:26:31.780 | And then they explored the hazard ratio

01:26:35.180 | for psychosis specifically, meaning how likely it was

01:26:38.380 | that people would develop psychotic symptoms

01:26:40.540 | or full-blown psychotic illness

01:26:43.900 | according to their frequency of sauna session.

01:26:45.980 | So again, this isn't causal, this is correlative.

01:26:48.780 | And according to the data in this study,

01:26:50.820 | what they concluded is that there was a strong

01:26:53.120 | and inverse independent association

01:26:55.340 | between frequent sauna bathing and the future risk

01:26:57.700 | of psychotic disorders in this population.

01:27:00.780 | Now, this does not mean that going into a sauna

01:27:03.820 | seven times per week is going to prevent people

01:27:05.920 | from becoming schizophrenic necessarily,

01:27:08.320 | or from having a psychotic episode necessarily.

01:27:10.740 | And of course, frequent sauna use will be related

01:27:14.160 | to other health promoting activities.

01:27:16.800 | But in this study, as in the previous study,

01:27:19.200 | they went to great lengths in order to try

01:27:21.140 | and limit those so-called confounding variables.

01:27:24.320 | Now, of course, this is just one study.

01:27:26.160 | And again, it's correlative, not causal,

01:27:28.560 | but based on the large number of subjects they included,

01:27:31.380 | plus the rigor of the statistical analysis,

01:27:34.320 | we're starting to see a general picture

01:27:36.080 | that using the sorts of sauna protocols

01:27:38.800 | that I've described throughout this episode,

01:27:41.520 | five to 20 minutes or so, done one to seven times per week,

01:27:46.880 | is associated with a general improvement

01:27:49.960 | in cardiovascular health,

01:27:51.280 | a general improvement in mental health.

01:27:54.440 | And it really points to the fact that yes,

01:27:57.120 | sauna done acutely for three or four times a day,

01:28:01.180 | 30 minutes each session separated by cooling,

01:28:03.520 | maybe getting into cold bath.

01:28:04.920 | Sure, that can potently increase growth hormone,

01:28:08.160 | but done on a more regular basis can reduce cortisol,

01:28:11.260 | improve heart health, improve mental health.

01:28:13.920 | And for that reason, and the fact that for most people,

01:28:17.520 | it is conceivable to come up with a way

01:28:19.220 | that you could get into deliberate heat exposure

01:28:21.080 | for a minimum of cost, right?

01:28:22.880 | It's a hot bath, or if you had to resort to bundling up

01:28:26.680 | and going for a jog, this sort of thing,

01:28:28.200 | or if you have access to it, a sauna of some sort,

01:28:31.960 | that we're really talking about a stimulus

01:28:34.920 | to initiate a large number of different biological cascades

01:28:38.480 | that wick out to improve multiple aspects

01:28:42.280 | of brain and body health.

01:28:43.580 | So up until now, I've been talking about whole body heating.

01:28:46.900 | So for instance, putting your whole body into the sauna,

01:28:49.660 | which of course is what most people do,

01:28:51.880 | or getting into a hot tub or hot bath up to your neck,

01:28:55.000 | or in the cases where we were talking

01:28:56.440 | about deliberate cold exposure

01:28:57.840 | as a means to increase core body temperature and metabolism,

01:29:01.720 | getting into an ice bath or cold water of some sort

01:29:05.180 | up to your neck or into a cold shower, et cetera.

01:29:08.160 | Now I'd like to talk about deliberately heating

01:29:10.120 | or cooling specific parts of the body,

01:29:12.980 | meaning certain surface areas of your body

01:29:16.280 | as a means to get effects on those particular areas,

01:29:19.460 | as well as at the whole body level.

01:29:21.680 | Numerous times throughout this episode,

01:29:23.000 | I've talked about the dangers of overheating.

01:29:25.060 | So what should you do if you think you

01:29:27.120 | or someone else is hyperthermic, is too hot?

01:29:30.360 | Well, if you understand just a little bit

01:29:32.400 | about the cooling and heating systems of your shell and core,

01:29:36.600 | there are some terrific tools that you can use

01:29:38.580 | in order to cool off your core quickly.

01:29:41.240 | And remember the core consists of the nervous system,

01:29:43.360 | the spinal cord and the viscera,

01:29:44.740 | which are really the organs you're trying to protect.

01:29:47.140 | So being able to cool off the core of your body quickly

01:29:50.940 | can be very beneficial.

01:29:52.160 | And in some cases, it could even save your life.

01:29:54.440 | There is a way to more quickly heat or cool the body.

01:29:58.020 | And that's through specific elements of your shell,

01:30:01.540 | meaning particular skin surfaces.

01:30:03.700 | I've talked extensively about this in the episode on cold.

01:30:06.720 | It was also covered in the episode with my guest,

01:30:09.720 | Dr. Craig Heller from the biology department at Stanford.

01:30:12.660 | It relates to the so-called glabrous skin surfaces

01:30:16.520 | on the upper half of our face,

01:30:19.080 | palms of our hands and the bottoms of our feet.

01:30:20.760 | And for those of you that heard this before,

01:30:23.100 | I encourage you to continue to listen nonetheless,

01:30:25.060 | because today I'm going to talk about specifically

01:30:27.380 | how to heat the body or cool the body

01:30:30.180 | through these glabrous skin surfaces.

01:30:32.700 | Very briefly, the mechanism is as follows.

01:30:35.640 | The palms of our hands, the bottoms of our feet

01:30:37.260 | and the upper half of our face,

01:30:39.660 | overlies specific types of vasculature,

01:30:42.580 | meaning specific types of veins and arteries

01:30:46.540 | that don't have capillaries between them.

01:30:48.940 | And as a consequence, heat and cold can move very quickly

01:30:53.940 | from the palms of the hands, the bottoms of the feet

01:30:57.100 | and the upper half of our face

01:30:58.500 | and change our core body temperature.

01:31:01.580 | There's a name for these particular vascular structures.

01:31:04.400 | They're called AVAs or arteriovenous astomoses.

01:31:08.160 | Basically, veins and arteries interacting directly

01:31:12.040 | without capillaries in between,

01:31:14.140 | which allows cooling of blood or heating of blood

01:31:18.020 | much more quickly than is possible

01:31:20.760 | by applying colder heat elsewhere on the body

01:31:23.420 | where capillaries intervene between veins and arteries.

01:31:26.460 | These AVAs, arteriovenous astomoses can be leveraged

01:31:29.860 | to cool off your core body temperature very quickly.

01:31:32.240 | The key thing is to get the palms of your hands,

01:31:35.180 | the bottoms of your feet and the upper half of your face

01:31:37.020 | in contact with a cold surface or fluid

01:31:40.540 | that is cold enough to cool the blood

01:31:44.000 | and the core of your body,

01:31:45.700 | but not so cold that it constricts the veins

01:31:49.820 | just below the palms of your hands,

01:31:51.660 | the bottoms of your feet or the upper half of your face.

01:31:54.080 | So not placing ice packs necessarily,

01:31:57.660 | but maybe placing cool towels on the bottoms of the feet,

01:32:00.920 | the palms of the hands and the upper half of the face

01:32:02.620 | and as they warm up, replacing those with other cool towels.

01:32:05.980 | The exact temperature will depend

01:32:07.260 | on how hot you happen to be.

01:32:08.900 | I can't know that

01:32:09.860 | without knowing your particular circumstances.

01:32:12.140 | If you'd like to learn more

01:32:13.380 | about how to cool off your core very quickly

01:32:16.200 | and some of the details and some of the technologies

01:32:18.340 | that are being developed to do that,

01:32:20.020 | please see the episode I did with Craig Heller

01:32:21.840 | or the episode on cold.

01:32:23.260 | If you don't want to go to those episodes,

01:32:25.020 | here's a good procedure that you could use.

01:32:27.180 | You could grab, for instance,

01:32:28.780 | a package of frozen broccoli or frozen blueberries.

01:32:32.120 | If someone is really, really warm,

01:32:33.420 | make sure they take off their shoes and socks,

01:32:34.840 | get their feet on top of those,

01:32:36.100 | ideally get some into their hands as well,

01:32:38.140 | get some cool compresses and get them onto people's face.

01:32:41.160 | You could of course also put a cool compress

01:32:44.080 | on the back of the neck and the top of the head.

01:32:45.920 | That would be an especially good idea

01:32:47.560 | if someone were hyperthermic

01:32:48.780 | because of the way that cooling of the brain occurs

01:32:51.580 | under conditions of hyperthermia.

01:32:53.680 | But the key point here is that just putting cold compresses

01:32:57.540 | or cold materials onto somebody's torso

01:32:59.520 | is not going to be as efficient

01:33:00.980 | as cooling those glabber skin surfaces,

01:33:02.720 | the bottoms of the feet, the palms of the hands

01:33:04.400 | and the upper half of their face.

01:33:06.660 | Similarly, or I suppose to be more accurate,

01:33:09.180 | I should say conversely,

01:33:10.420 | there are times when it is desirable

01:33:13.060 | to heat the core of the body.

01:33:15.440 | And once again, just simply throwing a hot towel

01:33:18.180 | over somebody is not going to be the most efficient way.

01:33:21.140 | If someone is hypothermic, they're too cold,

01:33:25.120 | it is not a problem to cover them with a blanket,

01:33:27.760 | but ideally what you do is you use some warm object

01:33:33.300 | or warm fluid to warm the bottoms of their feet,

01:33:36.740 | their hands and the upper half of their face.

01:33:38.800 | Of course, not so warm that you burn those skin surfaces.

01:33:41.880 | This has actually been examined in studies

01:33:43.440 | from the Heller lab.

01:33:44.560 | Turns out that for instance, to get people out of anesthesia,

01:33:48.300 | it is beneficial to warm their core body temperature.

01:33:51.440 | And of course there is fever,

01:33:52.940 | which you should know is an adaptive response.

01:33:55.660 | While fever is uncomfortable,

01:33:57.660 | and in fact often involves a mismatch

01:33:59.560 | between our perception of our shell

01:34:01.160 | and a perception of our core temperature,

01:34:03.120 | in other words,

01:34:04.040 | there are times when our body temperature is really high,

01:34:05.880 | we have a fever and yet we're shivering, we're cold.

01:34:08.040 | And that's because under conditions of fever,

01:34:10.340 | the immune system liberates certain molecules that impact

01:34:15.060 | and in some ways intentionally disrupt the preoptic area,

01:34:19.180 | the POA and the way it normally functions

01:34:21.600 | so that it can override peripheral signals

01:34:24.160 | and simply try and heat the body

01:34:25.740 | and kill whatever pathogen has infected the body.

01:34:29.640 | So for those of you that think about fever

01:34:32.520 | is always a bad thing, it's not.

01:34:34.520 | Now, of course, we don't want our core body temperature

01:34:36.680 | to go so high that tissues of the brain and body are damaged.

01:34:39.640 | This is one reason why if a fever ever goes above 103,

01:34:43.520 | you need to start getting a little bit worried, 104.

01:34:46.440 | There are times when you need to call an ambulance

01:34:48.600 | or go to a hospital.

01:34:49.740 | You really need to employ cooling methods of the sort

01:34:52.400 | that I talked about before to prevent hyperthermia.

01:34:55.040 | Of course, safe ranges for body temperature

01:34:57.560 | vary between infants and adults.

01:34:59.760 | So you can look those up online

01:35:01.120 | depending on the person's age, what is a safe range,

01:35:03.180 | what is not, but keep in mind that if you are taking

01:35:06.160 | compounds, pills to reduce your fever,

01:35:08.360 | you're actually short-circuiting the protective mechanism

01:35:11.620 | for burning up the pathogen.

01:35:13.400 | And that's because most pathogens, bacteria and viruses

01:35:16.920 | don't survive well at high temperatures.

01:35:18.820 | In fact, in laboratories,

01:35:19.840 | if we want to preserve a virus for use,

01:35:21.660 | we put it into a freezer.

01:35:23.080 | If we want to kill a virus, we heat inoculate it.

01:35:26.480 | So in many ways, fever is your natural form

01:35:28.800 | of heat inoculation designed to kill pathogens

01:35:31.200 | of various kinds.

01:35:32.440 | Now, last, but certainly not least,

01:35:33.940 | I want to refer to the study that I described

01:35:35.880 | at the very beginning of this episode

01:35:38.280 | involving what's called local hyperthermia

01:35:41.480 | in order to trigger a number of biological processes

01:35:44.320 | in fat tissue, in order to convert white fat to beige fat,

01:35:49.160 | which is the metabolically active form of fat.

01:35:52.200 | Many of you, or at least some of you should be familiar

01:35:54.500 | with the fact that deliberate cold exposure

01:35:57.080 | can increase brown fat stores,

01:35:59.440 | these mitochondrial dense fat stores

01:36:01.680 | that can in turn allow a person to feel more comfortable

01:36:05.260 | in cold temperatures, water or otherwise,

01:36:07.800 | and increase core metabolism.

01:36:10.320 | I talked about this in the episode on cold,

01:36:12.180 | but very briefly, the general protocol again,

01:36:14.480 | is to get 11 minutes total per week of uncomfortable,

01:36:17.640 | yet safe, deliberate cold exposure,

01:36:19.320 | either through ice bath, cold shower,

01:36:21.860 | cold immersion up to the neck,

01:36:23.920 | or some other form of cold exposure.

01:36:27.360 | That triggers increases in brown fat,

01:36:29.180 | that's been beautifully shown by Dr. Susanna Soberg,

01:36:32.740 | and that increase in brown fat in turn

01:36:34.940 | increases core metabolism and one's ability

01:36:37.300 | to feel comfortable in cold temperatures.

01:36:40.060 | This was a study done in humans,

01:36:42.400 | and there's now ample evidence from animal models

01:36:44.940 | to support that this is a general phenomenon

01:36:47.100 | that I think most people could use and benefit from.

01:36:50.340 | Local hyperthermia is a distinctly different phenomenon.

01:36:53.420 | It involves heating a particular surface of the body

01:36:56.660 | as a way to convert the white fat at that location

01:37:00.300 | to beige fat, which in turn leads to more systemic increases

01:37:04.660 | in thermogenesis and increases in metabolism,

01:37:07.940 | and believe it or not, in fat loss.

01:37:09.760 | Now, the study that I'm referring to

01:37:11.140 | is a very recent study that was published again

01:37:13.060 | in this terrific apex journal, Cell, Cell Press Journal,

01:37:17.100 | and again, one of the three top journals,

01:37:19.060 | Nature Science and Cell are the three top journals.

01:37:21.160 | Top because they're the most competitive,

01:37:23.460 | but also generally, not always,

01:37:25.680 | but generally the most stringent

01:37:27.060 | in terms of the review process.

01:37:28.340 | Papers that make it into these three journals

01:37:30.400 | generally are of very, very high quality,

01:37:32.580 | and certainly enough people see them

01:37:33.720 | that if they're not of high quality,

01:37:35.260 | they get shot down pretty quickly

01:37:36.540 | in a short amount of time,

01:37:37.740 | whereas papers in other journals can sometimes

01:37:39.740 | last a long time before they're ever replicated, et cetera.

01:37:43.840 | The title of this paper is Local Hyperthermia Therapy

01:37:46.820 | Induces Browning of White Fat and Treats Obesity.

01:37:50.820 | This was a study that was performed on mice and humans

01:37:54.400 | in the same study.

01:37:55.900 | What the study involved was heating of a local patch of skin

01:37:59.100 | to 41 degrees Celsius,

01:38:00.640 | which is 105.8 degrees Fahrenheit,

01:38:04.360 | but not damaging the skin, okay?

01:38:06.720 | So the methods of heating did not involve

01:38:10.180 | placing something on the skin that would damage it.

01:38:11.980 | In fact, in the study on the mice,

01:38:13.460 | they use this kind of clever molecular chicanery

01:38:17.440 | in order to do it,

01:38:18.280 | and in humans, they used a thermocouple

01:38:20.200 | that would allow them to heat the skin up just locally,

01:38:23.760 | in particular locations on the body

01:38:25.020 | that I'll talk about in a moment.

01:38:27.020 | They refer to this process as LHT or local heat therapy.

01:38:32.020 | The reason they did this is worth considering.

01:38:36.980 | It's long been known from clinical data,

01:38:40.300 | and in fact, from a bit of research data,

01:38:42.420 | that people that experience burn on a small or unfortunately,

01:38:47.820 | in some circumstances, significant portion of their body,

01:38:50.940 | experience overall decreases in body fat

01:38:54.580 | and increases in metabolism that can last many years.

01:38:58.420 | Now, of course, is not reasonable,

01:39:01.120 | nor would one ever want to induce burn

01:39:03.440 | in order to induce fat loss,

01:39:05.420 | but the observed increases in metabolism and fat loss

01:39:08.600 | in response to skin surface burn couldn't be explained

01:39:12.820 | by reductions in activity related to the burn, for instance.

01:39:17.180 | And in fact, there are molecular pathways

01:39:19.540 | related to something called UCP-1,

01:39:22.120 | which is uncoupling protein one.

01:39:24.060 | I talked about this also in the cold episode,

01:39:25.820 | but don't worry if you didn't see that episode

01:39:27.640 | or if you choose not to.

01:39:28.780 | UCP-1 has the ability to increase mitochondrial function

01:39:33.780 | in ways that increase core body temperature overall,

01:39:37.200 | in particular in beige and brown fat,

01:39:39.880 | which are these fat cells

01:39:41.380 | that exist generally along our spine,

01:39:44.020 | and in particular in the upper part of our back

01:39:46.140 | and around our neck and clavicles,

01:39:47.960 | and they're responsible for acting as a sort of a candle,

01:39:51.860 | or I should say the fuel or the fat of a candle

01:39:55.940 | that can be burned up to manufacture heat in the body.

01:40:00.260 | So if you normally think about fat

01:40:02.300 | and you think about blubbery fat,

01:40:03.560 | you're thinking about white fat,

01:40:05.100 | which again is just a storage site.

01:40:06.660 | Beige fat and brown fat exist at just a few locations,

01:40:09.680 | mainly internally around our spinal cord and our clavicles,

01:40:13.060 | and those fat stores are responsible

01:40:15.160 | for generating heat in our body,

01:40:16.580 | so they are very metabolically active form of fat.

01:40:20.560 | Small children have a lot of brown fat and beige fat,

01:40:23.800 | in particular because very young children can't shiver,

01:40:26.980 | and a number of you probably didn't know that,

01:40:28.660 | but very young children can't shiver,

01:40:30.360 | so they need some way to generate heat

01:40:31.860 | in order to make sure that they stay alive

01:40:33.480 | if they were ever to get cold.

01:40:35.020 | This is also probably the reason why little kids

01:40:37.140 | can run around on a cold day outside without their shirt on

01:40:39.700 | and they don't even seem to notice

01:40:40.840 | whereas adults are freezing cold.

01:40:43.060 | As we get older, the amount of beige and brown fat

01:40:45.740 | tends to either reduce or shrink or disappear entirely,

01:40:50.740 | it's still debated, which happens,

01:40:53.000 | but we know that white fat can be converted

01:40:55.840 | to this more metabolically active form of beige fat

01:40:59.860 | by deliberate cold exposure,

01:41:01.960 | according to the protocol I talked about earlier,

01:41:03.860 | and now it seems, based on this new study,

01:41:07.340 | that local heating of skin tissue can also induce UCP-1

01:41:12.480 | and the effects of UCP-1 on increasing mitochondria,

01:41:15.540 | and in fact, that local hyperthermia,

01:41:19.240 | 41 degrees Celsius, that is 105.8 degrees Fahrenheit,

01:41:23.160 | can actually induce the conversion

01:41:25.840 | of white fat to beige fat.

01:41:27.960 | Now that's pretty interesting,

01:41:28.980 | and I can already predict the way this is probably going to go

01:41:31.260 | in the kind of wellness and biohacking

01:41:33.360 | and longevity communities.

01:41:34.360 | I'm sure that pretty soon there are going to be

01:41:36.560 | people putting heating pads on different fat pads of theirs

01:41:39.520 | on their body, trying to reduce

01:41:40.880 | or at least convert the white fat into beige fat,

01:41:43.560 | and who knows, maybe that'll work.

01:41:44.720 | There have not been many controlled studies of this yet.

01:41:47.280 | This is the first, at least to my knowledge,

01:41:49.680 | of such studies looking at this in non-burn conditions.

01:41:53.560 | Nonetheless, the data are mechanistically

01:41:56.200 | even more interesting than this whole business about UCP-1,

01:41:59.560 | and here's why.

01:42:00.460 | Local hyperthermia,

01:42:03.400 | using the protocol that I described before,

01:42:05.600 | resulted in the increase of a promoter,

01:42:09.520 | which is essentially a mechanism by which certain genes

01:42:12.980 | regulate their activity.

01:42:14.920 | This is a DNA binding of something called HSF-1.

01:42:18.960 | We don't have to go too deep into the mechanism here

01:42:21.040 | or the nomenclature,

01:42:21.880 | but HSF stands for heat shock factor one,

01:42:25.240 | and HSF-1 binding to a particular location in the genome

01:42:30.240 | allowed for a different molecule with a very long name.

01:42:36.140 | I'll just tell it to you for fun,

01:42:37.320 | but you can just let the numbers and letters stream by.

01:42:40.280 | It's not important.

01:42:41.120 | HNRNPA2B1 shortened to A2B1,

01:42:45.360 | which frankly is not that short to begin with.

01:42:47.460 | A2B1 is still a name that should be meaningless

01:42:49.920 | to most everybody, but here's what's really cool.

01:42:52.360 | A2B1 is directly involved in glucose and lipid metabolism

01:42:57.080 | and regulates the genes that control

01:42:59.820 | glucose and lipid metabolism.

01:43:01.720 | So here we have a situation where local heating of skin

01:43:04.580 | converted a metabolically sluggish or inactive cell type,

01:43:08.180 | the white fat cell, into the metabolically charging,

01:43:13.180 | so to speak, beige fat cell,

01:43:15.960 | which in turn led to systemic,

01:43:18.340 | meaning body-wide increases in metabolism

01:43:20.700 | through two mechanism.

01:43:21.780 | One mechanism is this increase in UCP-1,

01:43:24.800 | which for those of you that want to know,

01:43:25.980 | UCP-1 causes shifts in the way that potential energy

01:43:30.020 | is pushed from the protons through the mitochondria,

01:43:33.340 | basically more mitochondrial function,

01:43:34.900 | which means more ATP, which means cells are more active,

01:43:37.360 | AKA increased metabolism,

01:43:39.480 | and increases in things like heat shock factor one

01:43:42.140 | and A2B1, which are involved in lipid and glucose metabolism

01:43:45.780 | and regulation.

01:43:46.880 | So I want to be very clear.

01:43:48.900 | This study does not say that spot reduction is possible

01:43:52.100 | with local heating of tissue.

01:43:54.040 | I just can see it now that once this paper gets out

01:43:56.880 | into the press, people are going to say,

01:43:58.680 | oh, heating up a certain patch of skin is going to burn fat

01:44:01.540 | or convert fat to some other cell type at that location.

01:44:04.540 | Sorry, that's not the way it works.

01:44:06.300 | They did observe increases in beige fat cells

01:44:11.300 | at certain locations in the body,

01:44:13.560 | but those increases in beige fat occurred

01:44:16.100 | where beige fat cells always reside,

01:44:18.720 | around the spine, the upper neck, the clavicles, and so on.

01:44:22.400 | This is exciting because it provides

01:44:24.220 | yet another potential mechanism

01:44:26.100 | in addition to deliberate cold exposure

01:44:28.740 | to increase beige fat, meaning the metabolically active form

01:44:32.480 | of fat cell.

01:44:34.020 | It also nicely provides a mechanism,

01:44:36.520 | or at least a potential mechanism for the observation

01:44:40.480 | that burn either small patch of skin being burned,

01:44:44.460 | or again, sadly, large patches of skin being burned,

01:44:48.460 | leading to these very extreme and very long lasting increases

01:44:53.460 | in body fat loss and metabolism.

01:44:56.540 | What, if anything, should you do with this information?

01:44:58.900 | Well, first of all, I want to very much caution people

01:45:02.580 | about putting anything so hot

01:45:05.060 | that it can damage the surface of your skin onto your skin.

01:45:08.180 | That would be a terrible idea.

01:45:10.020 | However, I do predict a time not too far from now

01:45:14.660 | where people will start to explore

01:45:17.000 | the use of local skin heating

01:45:19.420 | as a means to increase the conversion of white to beige fat

01:45:24.300 | and in turn for beige fat stores

01:45:26.580 | to increase metabolism overall

01:45:28.160 | and maybe even improve glucose metabolism and thermogenesis.

01:45:31.640 | If you'd like more details about this study,

01:45:33.540 | we will provide a link to it in the show notes caption.

01:45:37.020 | I should mention that the study,

01:45:38.740 | at least the portion of the study that was focused on humans

01:45:41.460 | involved roughly equal numbers of males and females.

01:45:45.220 | The subjects followed their normal daily schedule,

01:45:47.780 | including time and composition of meals, they say,

01:45:49.740 | or rest and active hours, et cetera, et cetera.

01:45:52.860 | The local hyperthermia therapy was done in the following way.

01:45:55.820 | Here I'm paraphrasing from their method section,

01:45:58.140 | the subjects were seated in upright posture.

01:46:00.820 | They were wearing a standard test robe

01:46:03.360 | with the head and neck and shoulders unclothed

01:46:05.300 | and one meter away from a thermal imaging camera,

01:46:08.180 | which could basically measure the temperature

01:46:10.340 | at their skin surface to make sure

01:46:11.620 | that it remained constant across subjects and yet safe.

01:46:15.220 | The supraclavicular fat deposits,

01:46:18.900 | meaning the upper shoulders and upper back area

01:46:21.220 | were exposed to this thermal source, again,

01:46:22.940 | 41 degrees for 20 minutes, okay?

01:46:26.660 | So it was 41 degrees for 20 minutes

01:46:29.340 | and their core temperatures and skin temperatures

01:46:31.860 | were monitored before and after

01:46:34.020 | this local hyperthermic therapy.

01:46:35.900 | The subjects were exposed to this local hyperthermia therapy

01:46:39.140 | three days per week, separated by day,

01:46:41.180 | Monday, Wednesday, and Friday.

01:46:42.400 | So they had weekends off for five weeks total

01:46:46.300 | after which their data were collected.

01:46:48.220 | And the study has a number of other

01:46:49.540 | really interesting features that are sure to lead

01:46:52.000 | to increased understanding of both mechanism

01:46:54.060 | and new protocols, such as analysis of the genes

01:46:56.860 | and proteins that are activated downstream

01:46:59.500 | of this local hyperthermia therapy.

01:47:01.380 | I find these data incredibly interesting,

01:47:03.500 | in part because of the ways that local hyperthermia therapy

01:47:06.580 | mimics deliberate cold exposure therapy,

01:47:09.280 | same downstream mechanisms, UCP1

01:47:11.540 | and some of the other pathways are involved.

01:47:13.420 | And all of that points to a somewhat new,

01:47:15.600 | but certainly an important concept.

01:47:17.960 | Many of you have probably heard of hormesis,

01:47:19.760 | which is the subjecting of oneself or others, I suppose,

01:47:23.800 | to enough stress to induce an adaptation of some kind.

01:47:27.260 | So hormesis is the reason why

01:47:29.740 | if you get into cold water repeatedly,

01:47:32.400 | at first it's very painful psychologically

01:47:34.760 | and over time you get used to it.

01:47:36.300 | You never get completely used to it,

01:47:37.420 | but you get more used to it.

01:47:38.700 | Hormesis is also used to describe the adaptation

01:47:41.980 | to cardiovascular exercise

01:47:43.720 | or to the hard rep sets of resistance training

01:47:47.000 | and the growth of muscles or the strengthening of muscles

01:47:49.180 | or the improvement in cardiovascular function

01:47:50.740 | to endurance exercise and so forth.

01:47:52.980 | Hormesis is a somewhat common term nowadays.

01:47:55.100 | If you haven't heard it, now you've heard it.

01:47:57.940 | In this paper, they describe what is called mitohormesis,

01:48:01.180 | which is in essence,

01:48:02.720 | the fact that any number of different stressful stimuli,

01:48:05.660 | provided they activate UCP1

01:48:07.900 | and some of these other pathways that I just described,

01:48:10.060 | like HSF1, can induce changes in the mitochondria

01:48:13.780 | that lead to increases in metabolism.

01:48:16.340 | So it shouldn't surprise us that cold and heat

01:48:20.260 | can both lead to increases in metabolism

01:48:22.440 | and conversion of white fat to beige fat.

01:48:25.260 | It shouldn't surprise us because both pathways are stress.

01:48:28.800 | Local hyperthermia is stress.

01:48:30.920 | Burn certainly is stress.

01:48:32.800 | Sauna is a form of stress.

01:48:35.480 | Deliberate cold exposure is a form of stress.

01:48:38.320 | Exercise is a form of stress.

01:48:39.760 | And the adaptation to those stressors is not infinite.

01:48:43.360 | All of those protocols, any protocol for that matter,

01:48:46.520 | is going to be effective because it's going to converge

01:48:48.660 | on an existing internal biological mechanism.

01:48:51.700 | So there's no unique mechanism for each protocol.

01:48:55.200 | Each protocol that I've talked about today,

01:48:57.140 | whether or not it's five minutes or 20 minutes

01:48:58.900 | or four times in a day or three times per week

01:49:01.700 | or seven times per week is tickling or pushing

01:49:04.520 | or stomping, if you will, on a given pathway

01:49:07.480 | and really activating it to a mild or to severe degree.

01:49:10.660 | What I've tried to do today is to illustrate

01:49:12.800 | the general mechanisms by which heat in particular

01:49:16.160 | can activate certain biological pathways

01:49:18.420 | so that you can devise protocols

01:49:20.360 | that are going to be optimal for you and your needs.

01:49:23.100 | So just to briefly recap,

01:49:24.940 | if you want to get the greatest growth hormone increases,

01:49:28.560 | do sauna or other deliberate heat exposure fairly seldom.

01:49:33.120 | Probably no more than once per week, maybe even less.

01:49:36.240 | And do it a lot that day.

01:49:37.600 | Just make sure that you break it up into multiple sessions.

01:49:39.780 | In the study I described earlier,

01:49:40.840 | they did four sessions, 30 minutes each,

01:49:43.560 | but that was just once a week.

01:49:46.620 | If you're interested in the cardiovascular benefits

01:49:49.080 | and the potential longevity benefits of sauna,

01:49:51.600 | well, then it's clear that doing it three to four,

01:49:53.900 | maybe even seven times per week

01:49:55.140 | is going to be more beneficial

01:49:56.480 | than doing it just one or three times per week.

01:49:58.840 | It stands to reason that for those of you interested

01:50:00.640 | in the general health effects of sauna,

01:50:04.120 | about an hour per week broken up into three sessions

01:50:06.480 | makes the most sense based on my read of the data.

01:50:09.300 | And again, that range of 80 to 100 degrees Celsius

01:50:12.020 | is going to be your guide.

01:50:13.620 | And in terms of the mental health benefits,

01:50:15.760 | it seems that getting a little bit uncomfortable

01:50:18.220 | in that heat environment, sauna or otherwise,

01:50:20.980 | provided it's safe, is going to be the best way

01:50:23.540 | to access those mental health effects

01:50:25.460 | by way of increasing dynorphin, which as you recall,

01:50:29.340 | will then increase the ability of endorphin

01:50:32.240 | to have its positive effects on mood

01:50:34.260 | after you get out of the sauna

01:50:36.260 | or other deliberate heat exposure.

01:50:37.940 | And in terms of timing,

01:50:39.780 | after a workout of any kind, morning or afternoon,

01:50:43.260 | or if you're not doing it after a workout,

01:50:46.140 | certainly in the later part of the day

01:50:47.620 | is going to be most beneficial as it relates to sleep.

01:50:50.220 | But of course, there's a caveat there,

01:50:51.800 | which I will mention again,

01:50:53.200 | which is that for those of you that have no trouble sleeping

01:50:55.500 | because you're exhausted

01:50:56.340 | or you're just one of these phenomenal sleepers,

01:50:58.380 | well then do it any time of day or night.

01:51:00.780 | But for most people doing it later in the day

01:51:02.860 | is going to be more beneficial

01:51:03.980 | because of the post sauna cooling effect

01:51:06.940 | and the relationship between cooling by a degree or more

01:51:10.660 | as a way to enter sleep.

01:51:12.100 | Thank you for joining me today for my discussion

01:51:14.140 | about the science of heat and heating for health.

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The Science & Health Benefits of Deliberate Heat Exposure | Huberman Lab Podcast #69

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