Using Salt to Optimize Mental & Physical Performance

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

00:00:02.260 | where we discuss science and science-based tools

00:00:04.880 | for everyday life.

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

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

00:00:12.960 | at Stanford School of Medicine.

00:00:14.840 | Today, we are going to discuss salt,

00:00:17.320 | also referred to as sodium.

00:00:19.640 | Most of us think of salt

00:00:21.600 | as something that we put on and in our food,

00:00:24.320 | maybe something to avoid,

00:00:25.760 | maybe some of you are actually trying to get more salt,

00:00:27.780 | some of you are trying to get less salt.

00:00:29.880 | We all seem to associate salt

00:00:31.440 | with things like blood pressure, et cetera.

00:00:33.420 | Today, we're going to go down

00:00:34.840 | a different set of avenues related to salt.

00:00:37.040 | We will certainly cover how salt regulates blood pressure.

00:00:40.320 | We are also going to talk about

00:00:41.840 | how the brain regulates our appetite for salt

00:00:44.960 | or our aversion for salt.

00:00:47.220 | We are also going to talk about

00:00:48.520 | how our sensing of salty tastes

00:00:51.440 | actually mediates how much sugar we crave

00:00:54.600 | and whether or not we ingest more or less sugar

00:00:57.360 | than we actually need.

00:00:59.000 | So what you're going to learn today

00:01:00.420 | is that the so-called salt system,

00:01:02.460 | meaning the cells and connections in our brain and body

00:01:05.440 | that mediate salt craving and avoidance

00:01:07.880 | are regulating many, many aspects of our health

00:01:11.500 | and our ability to perform in various contexts,

00:01:13.940 | things like athletic performance,

00:01:15.280 | things like cognitive performance.

00:01:17.520 | We're also going to talk about aging and dementia

00:01:19.800 | and avoiding aging and dementia

00:01:21.360 | and what role salt and salt avoidance might play in that.

00:01:25.480 | We're going to touch on some themes

00:01:26.840 | that for some of you might seem controversial

00:01:28.920 | and indeed, if they are controversial,

00:01:30.560 | I'll be sure to highlight them as such.

00:01:32.480 | I'm going to cover a lot of new data

00:01:34.240 | that point to the possibility,

00:01:35.940 | I want to emphasize the possibility that for some people,

00:01:38.960 | more salt might help them in terms of health,

00:01:42.020 | cognitive and bodily functioning.

00:01:44.040 | And for other people, less salt is going to be better.

00:01:47.400 | I'm going to talk about what the various parameters are.

00:01:49.500 | I'm going to give you some guidelines

00:01:50.720 | that in concert with your physician,

00:01:53.200 | who you should absolutely talk to

00:01:54.400 | before adding or changing anything

00:01:56.020 | to your diet or supplementation regime

00:01:57.880 | can help you arrive at a salt intake

00:01:59.880 | that's going to optimize your mental,

00:02:01.280 | physical health and performance.

00:02:03.280 | So we're going to cover neurobiology,

00:02:04.500 | we're going to cover hormone biology,

00:02:06.320 | we're going to talk about liver function,

00:02:07.620 | we're going to talk about kidney function

00:02:09.560 | and of course, brain function.

00:02:11.400 | I'm excited to share this information with you today.

00:02:13.560 | I'm certain you're going to come away

00:02:14.480 | with a lot of information and actionable items.

00:02:18.040 | I'm pleased to announce

00:02:18.960 | that I'm hosting two live events this May.

00:02:21.340 | The first live event will take place

00:02:22.800 | in Seattle, Washington on May 17th.

00:02:25.400 | The second live event will take place in Portland, Oregon

00:02:27.920 | on May 18th.

00:02:29.880 | Presale tickets for these two events are now available

00:02:32.320 | at hubermanlab.com/tour.

00:02:35.200 | I should mention that while I do hope to visit other cities

00:02:38.460 | in the near future to do more live events,

00:02:40.440 | right now, these are the only two live events

00:02:42.500 | I have scheduled, at least for the next six months.

00:02:44.960 | So once again, if you go to hubermanlab.com/tour,

00:02:47.560 | you can access the presale tickets.

00:02:49.440 | I hope to see you at these live events

00:02:51.320 | and as always, thank you for your interest in science.

00:02:54.320 | Before we dive into the topic of today's episode,

00:02:57.120 | I want to highlight a really exciting new study.

00:02:59.760 | This is a study from Diego Bohor's lab at Duke University.

00:03:04.140 | The Bohor's lab studies interactions

00:03:06.500 | between the gut and the brain

00:03:08.840 | and has made some incredible discoveries

00:03:11.200 | of the so-called neuropod cells.

00:03:13.320 | Neuropod cells are neurons, nerve cells

00:03:15.840 | that reside in our gut and that detect things

00:03:19.060 | like fatty acids, amino acids,

00:03:21.280 | and some neuropod cells sense sugar.

00:03:24.360 | Previous work from this laboratory has shown

00:03:26.880 | that when we ingest sugar,

00:03:29.220 | these neuropod cells respond to that sugar

00:03:32.840 | and send electrical signals up a little wire

00:03:35.280 | that we call an axon through the vagus nerve,

00:03:37.740 | for those of you that want to know, and into the brain

00:03:40.920 | and through subsequent stations of neural processing,

00:03:44.000 | evoke the release of dopamine.

00:03:46.400 | Dopamine is a molecule known to promote craving

00:03:49.880 | and motivation and indeed action.

00:03:52.500 | And what these neuropod cells that send sugar

00:03:54.620 | are thought to do is to promote seeking and consumption,

00:03:58.140 | eating of more sugary foods.

00:04:00.920 | Now, the incredible thing is that it's all subconscious.

00:04:03.560 | This is a taste system in the gut

00:04:06.060 | that is not available to your conscious awareness.

00:04:09.560 | Now, of course, when you ingest sweet foods,

00:04:11.320 | you taste them on your mouth too.

00:04:12.880 | And so part of the reason that you crave sweet foods perhaps

00:04:16.040 | is because they taste good to you.

00:04:17.800 | And the other reason is that these neuropod cells

00:04:20.800 | are driving a chemical craving

00:04:23.280 | below your conscious detection.

00:04:24.760 | So they're really two systems.

00:04:26.360 | Your gut is sensing at a subconscious level what's in it

00:04:31.360 | and sending signals to your brain that work in concert

00:04:34.040 | in parallel with the signals coming from your mouth

00:04:36.400 | and your experience of the taste of the food.

00:04:38.640 | Now, that alone is incredible and has been the subject

00:04:41.440 | of many important landmark papers

00:04:43.180 | over the last decade or so.

00:04:45.420 | You can imagine how the system would be very important

00:04:47.940 | for things like hidden sugars,

00:04:49.260 | when nowadays in a lot of processed foods,

00:04:51.580 | they're putting hidden sugars,

00:04:53.640 | they're putting a lot of things that cause your gut

00:04:57.060 | to send signals to your brain

00:04:58.800 | that make you crave more of those foods.

00:05:01.160 | So for those of you that really love sugar,

00:05:02.780 | just understand it's not just about how that sugar tastes.

00:05:06.440 | The new study from the Borjas lab

00:05:07.980 | deserves attention, I believe.

00:05:09.940 | This is a paper published just recently,

00:05:11.900 | February 25th, this year, 2022 in Nature Neuroscience,

00:05:15.720 | an excellent journal.

00:05:16.760 | And the title of the paper is the preference for sugar

00:05:19.440 | over sweetener depends on a gut sensor cell.

00:05:22.520 | The Borjas lab has now discovered a neuropod cell,

00:05:25.960 | meaning a category of neurons that can distinguish

00:05:29.120 | between sweet things in the gut that contain calories,

00:05:34.120 | for instance, sugar, and things in the gut that are sweet,

00:05:40.160 | but do not contain calories.

00:05:41.960 | Artificial sweeteners like aspartame, sucralose,

00:05:44.240 | and so forth.

00:05:45.780 | There are also, of course,

00:05:46.700 | non-artificial non-caloric sweeteners like stevia,

00:05:49.780 | monk fruit, et cetera.

00:05:51.360 | They did not explore the full gallery

00:05:53.280 | of artificial sweeteners.

00:05:54.640 | What they did find, however,

00:05:56.440 | ought to pertain to all forms

00:05:58.440 | of sweet non-caloric substances.

00:06:01.400 | What they discovered was that there is a signature pattern

00:06:03.860 | of signals sent from the gut to the brain

00:06:06.680 | when we ingest artificial or non-caloric sweeteners.

00:06:11.040 | This is important because what it says

00:06:12.680 | is that at a subconscious level,

00:06:14.260 | the gut can distinguish between sweet things

00:06:16.300 | that contain calories and sweet things that do not.

00:06:18.600 | Now, what the downstream consequences of this sensing is,

00:06:23.400 | or what they are, isn't yet clear.

00:06:26.400 | Now, I believe everyone should be aware

00:06:27.840 | of these kinds of studies for a couple of reasons.

00:06:30.640 | First of all, it's important to understand

00:06:33.040 | that what you crave, meaning the foods you crave

00:06:35.460 | and the drinks you crave,

00:06:36.780 | is in part due to your conscious experience

00:06:39.280 | of the taste of those things,

00:06:40.800 | but also due to biochemical and neural events

00:06:44.200 | that start in the body and impinge on your brain

00:06:47.560 | and cause you to seek out certain things,

00:06:50.680 | even though you might not know

00:06:52.000 | why you're seeking out more sugar.

00:06:53.560 | You find that you're craving a lot of sugar

00:06:55.520 | or you're craving a lot of foods with artificial sweeteners

00:06:58.080 | and you don't necessarily know why.

00:06:59.880 | Now, artificial sweeteners themselves

00:07:01.520 | are a somewhat controversial topic.

00:07:03.340 | I want to highlight that.

00:07:05.060 | Some months back, I described a study from Yale University

00:07:08.800 | about how one can condition the insulin system.

00:07:11.760 | Insulin is involved in mobilizing a blood sugar

00:07:13.960 | and so forth in the body, as many of you know,

00:07:15.840 | and I described some studies that were done

00:07:18.640 | from Yale University School of Medicine,

00:07:20.400 | looking at how artificial sweeteners

00:07:22.280 | can actually evoke an insulin response

00:07:26.120 | under certain conditions.

00:07:29.000 | Now, a couple of key things.

00:07:30.760 | I got a little bit of pushback after covering those studies,

00:07:34.380 | and I encourage pushback all the time.

00:07:37.360 | Pushback is one of those things that forces all of us

00:07:39.440 | to drill deeper into a topic.

00:07:41.280 | I want to be clear.

00:07:42.120 | First of all, I am not one to demonize artificial sweeteners.

00:07:45.680 | There is evidence in animal models, in animal models,

00:07:49.340 | that artificial sweeteners can disrupt the gut microbiome,

00:07:53.240 | but those were fairly high doses of artificial sweeteners,

00:07:55.700 | and it's unclear if the same thing pertains to humans.

00:07:57.960 | Still unclear, I should say,

00:07:59.360 | has not been investigated thoroughly.

00:08:01.420 | Some people don't like the taste of artificial sweeteners.

00:08:03.580 | Some people do.

00:08:04.440 | Some people find that they really help them

00:08:06.400 | avoid excessive caloric intake.

00:08:08.440 | Some people believe, and yet I should emphasize,

00:08:11.200 | there still isn't evidence

00:08:12.500 | that they can adjust the insulin response in all people.

00:08:15.280 | I just want to repeat that three times

00:08:16.600 | so that people are clear on that fact.

00:08:18.740 | What these new data emphasize, however,

00:08:21.900 | is that we need to understand how artificial sweeteners

00:08:25.580 | are consumed at the level of the gut,

00:08:27.120 | or I should say, registered at the level of the gut,

00:08:29.120 | and how that changes brain function,

00:08:31.880 | because one thing that I'm familiar with,

00:08:33.320 | and that many people report,

00:08:34.480 | is that when they first taste artificial sweeteners,

00:08:37.220 | they taste sort of not right to them.

00:08:39.260 | They don't like the taste,

00:08:40.140 | but over time, they actually start to crave that taste.

00:08:42.860 | I've experienced this.

00:08:43.700 | I used to drink a lot of diet sodas

00:08:45.000 | when I was in graduate school, so this would be aspartame,

00:08:47.960 | and I found that I actually needed them.

00:08:50.700 | Now, maybe it was the caffeine.

00:08:51.780 | Maybe I just liked the sweet taste or the carbonation.

00:08:53.760 | We actually have a drive for carbonation,

00:08:56.200 | which is the topic of a future episode,

00:08:58.260 | but when I finally quit them,

00:09:01.060 | for reasons that were independent of any fear

00:09:03.400 | of artificial sweeteners,

00:09:04.600 | I found that I didn't like the taste.

00:09:07.300 | Nowadays, I only occasionally drink a diet soda.

00:09:10.420 | I usually do that if I'm on a plane

00:09:11.620 | and there's nothing else available to me,

00:09:12.900 | so I don't demonize them.

00:09:14.260 | I might drink one every once in a while, no big deal.

00:09:17.180 | I also want to be clear.

00:09:18.140 | I consume stevia on a number of different supplements

00:09:21.100 | and foods that I consume.

00:09:22.460 | Stevia, of course, is a plant-based non-caloric sweetener,

00:09:25.300 | so I myself consume artificial sweeteners.

00:09:27.540 | Many people hate them.

00:09:28.860 | Many people like them and find them useful

00:09:31.440 | for their nutrition and in fact to keep their caloric intake

00:09:34.460 | in a range that's right for them,

00:09:36.260 | and many people like myself are curious about them

00:09:39.940 | and somewhat wary of them

00:09:41.860 | and yet continue to consume them in small amounts.

00:09:44.180 | I think most people probably fall into that category.

00:09:46.380 | I should also mention that many food manufacturers

00:09:48.820 | put artificial sweeteners, such as sucralose, et cetera,

00:09:52.820 | into foods, and it's always been unclear

00:09:56.220 | as to why they might want to do that,

00:09:58.180 | and yet we know that the sweet taste consumption,

00:10:02.220 | even if it doesn't contain calories,

00:10:03.600 | can drive more craving of sweet food,

00:10:06.700 | so there may be a logic or a strategy to why they do that.

00:10:09.620 | Again, a topic for exploration on today's podcast

00:10:12.300 | and in future podcasts because where we're headed today

00:10:15.160 | is a discussion about how salt and salt sensing,

00:10:18.800 | both consciously and unconsciously,

00:10:20.740 | can adjust our craving for other things

00:10:22.860 | like sugar and water and so on.

00:10:25.300 | So I want to highlight this beautiful work

00:10:26.960 | from the Morres Lab.

00:10:27.800 | We'll put a link to the study.

00:10:29.340 | I want to open this as a chapter for further exploration.

00:10:32.500 | I like to think that the listeners of this podcast

00:10:35.060 | are looking for answers where we have answers,

00:10:36.960 | but are also, I would hope,

00:10:38.680 | excited about some of the new and emerging themes

00:10:41.200 | in what we call nutritional neurobiology,

00:10:43.540 | and indeed the Morres Lab really stands

00:10:45.920 | as one of the premier laboratories out there

00:10:48.400 | that's looking at how foods as consumed in the gut

00:10:52.020 | are modifying our nervous system, the foods we crave,

00:10:54.800 | and how we utilize those foods.

00:10:56.820 | Before we begin, I'd like to emphasize that this podcast

00:10:59.360 | is separate from my teaching and research roles at Stanford.

00:11:02.020 | It is, however, part of my desire and effort

00:11:04.320 | to bring zero cost to consumer information about science

00:11:06.880 | and science-related tools to the general public.

00:11:09.700 | In keeping with that theme,

00:11:10.720 | I'd like to thank the sponsors of today's podcast.

00:11:13.340 | Our first sponsor is Athletic Greens, now called AG1.

00:11:17.020 | I've been taking AG1 since 2012,

00:11:19.340 | so I'm delighted that they're sponsoring the podcast.

00:11:21.640 | The reason I started taking AG1

00:11:23.100 | and the reason I still take AG1 once or twice a day

00:11:25.900 | is that I find it to be the best way

00:11:28.160 | to ensure I get all of my vitamins and minerals

00:11:30.560 | and the probiotics I need.

00:11:32.520 | I try and eat really well, but I'm not perfect about it,

00:11:35.560 | and with Athletic Greens, AG1,

00:11:38.300 | I cover any deficiencies I might have.

00:11:40.720 | The probiotics are particularly important to me

00:11:43.120 | because as we've talked about on many previous episodes

00:11:45.880 | and we'll talk about more on today's episode,

00:11:47.800 | the gut microbiome is supported by probiotics

00:11:50.260 | and the gut microbiome supports many biological functions

00:11:53.440 | important for immediate and long-term health,

00:11:55.320 | things like immune system function,

00:11:56.860 | things like the gut brain axis

00:11:58.480 | and mood and appetite and so forth.

00:12:00.480 | With Athletic Greens,

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00:12:39.560 | Today's episode is also brought to us by Element.

00:12:42.200 | Element is an electrolyte drink that has everything you need

00:12:45.320 | and none of the things you don't.

00:12:47.760 | That means it has salt, magnesium, and potassium,

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00:12:52.940 | function and a lot of other biological functions.

00:12:57.080 | As I mentioned on the podcast before, I'm a fan of salt.

00:13:00.200 | I believe in ingesting appropriate amounts of salt,

00:13:02.420 | and by appropriate, I mean,

00:13:03.560 | depending on what your background blood pressure

00:13:05.720 | happens to be, what your activity levels are,

00:13:07.580 | how much you sweat,

00:13:08.800 | what your cognitive and physical demands are.

00:13:10.640 | Today, we're going to talk about how to determine

00:13:13.120 | what those needs are.

00:13:14.660 | I'm always trying to stay on top of my hydration,

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00:13:50.880 | Today's episode is also brought to us by Inside Tracker.

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00:15:06.920 | Okay, let's talk about salt.

00:15:08.320 | Salt has many, many important functions

00:15:10.160 | in the brain and body.

00:15:11.600 | For instance, it regulates fluid balance,

00:15:14.200 | how much fluid you desire and how much fluid you excrete.

00:15:18.680 | It also regulates your desire for salt itself,

00:15:22.160 | meaning your salt appetite.

00:15:24.040 | You have a homeostatically driven salt appetite.

00:15:28.020 | I'll talk about the mechanisms today

00:15:29.360 | and make them all very clear.

00:15:31.280 | What that means is that you crave salty things,

00:15:34.360 | beverages and foods, when your salt stores are low,

00:15:37.460 | and you tend to avoid salty beverages and foods

00:15:40.760 | when your salt stores are high,

00:15:42.320 | although that's not always the case.

00:15:43.880 | There are circumstances where you will continue

00:15:46.000 | to crave salt, even though you don't need salt,

00:15:48.560 | or indeed, even if you need to eliminate salt

00:15:51.880 | from your system.

00:15:52.740 | Salt also regulates your appetite for other nutrients,

00:15:56.720 | things like sugar, things like carbohydrates.

00:15:59.360 | And today we'll explore all of that.

00:16:01.500 | Technically, salt is a mineral.

00:16:04.000 | And I should mention that when I say salt,

00:16:06.480 | I am indeed referring to sodium in most cases,

00:16:09.120 | although I will be clear to distinguish salt from sodium,

00:16:11.860 | meaning table salt from sodium.

00:16:14.040 | Most people don't realize this,

00:16:16.020 | but one gram of table salt

00:16:18.580 | contains about 388 milligrams of sodium.

00:16:22.900 | So technically we should be talking about sodium today

00:16:25.680 | and not salt.

00:16:26.520 | I will use them interchangeably

00:16:27.980 | unless I'm referring to some specific recommendations

00:16:31.860 | or ideas about trying to define your ideal salt,

00:16:36.300 | AKA sodium intake, okay?

00:16:38.280 | So this is important.

00:16:39.240 | I think right off the bat, a lot of people get themselves

00:16:42.360 | into a place of confusion

00:16:43.740 | and potentially even to a place of trouble

00:16:46.100 | by thinking that table salt in grams

00:16:49.180 | always equates to sodium in grams,

00:16:51.840 | and that's simply not the case.

00:16:53.900 | Today we're going to explore the neural mechanisms

00:16:56.920 | by which we regulate our salt appetite

00:17:00.600 | and the way that the brain and body interact

00:17:02.780 | in the context of salt seeking, salt avoidance,

00:17:06.220 | how to determine when we need more salt,

00:17:08.020 | when we need less salt.

00:17:09.460 | We'll talk about kidney function.

00:17:11.280 | We'll get into all of it,

00:17:12.320 | and we're going to do it very systematically.

00:17:14.080 | So let's start in the brain.

00:17:16.240 | We all harbor small sets of neurons.

00:17:19.800 | We call these sets of neurons nuclei,

00:17:21.780 | meaning little clusters of neurons

00:17:24.320 | that sense the levels of salt in our brain and body.

00:17:27.740 | There are a couple brain regions that do this,

00:17:31.000 | and these brain regions are very, very special,

00:17:33.180 | special because they lack biological fences around them

00:17:37.760 | that other brain areas have.

00:17:39.340 | And those fences, or I should say that fence

00:17:42.340 | goes by a particular name,

00:17:43.460 | and that name is the blood-brain barrier or BBB.

00:17:47.680 | Most substances that are circulating around in your body

00:17:50.580 | do not have access to the brain,

00:17:52.540 | in particular large molecules,

00:17:54.460 | can't just pass into the brain.

00:17:56.500 | The brain is a privileged organ in this sense.

00:17:58.960 | There are a couple other organs that are privileged

00:18:00.840 | and that have very strict barriers,

00:18:03.180 | very particular fences, if you will,

00:18:05.800 | and those other organs include things like the ovaries

00:18:07.980 | and testes, and that makes sense for the following reason.

00:18:11.220 | First of all, the brain, at least most of the brain,

00:18:15.300 | cannot regenerate after injury.

00:18:18.000 | You just simply can't replace brain cells after injury.

00:18:20.500 | I know people get really excited about neurogenesis,

00:18:22.820 | the birth of new neurons,

00:18:23.940 | and indeed neurogenesis has been demonstrated

00:18:26.620 | in animal models, and to some extent,

00:18:28.420 | it exists in humans in a few places.

00:18:30.480 | For instance, the olfactory bulb,

00:18:32.420 | where neurons are responsible for detecting odorants

00:18:35.840 | in the environment for smell, that is,

00:18:37.440 | and in a little sub-region of the hippocampus,

00:18:39.820 | a memory area, there's probably some neurogenesis,

00:18:42.780 | but the bulk of really good data out there

00:18:44.700 | point to the fact that in humans,

00:18:46.400 | there's not much turnover of neurons.

00:18:48.660 | What that means is that the neurons you're born with

00:18:51.160 | are the ones that you're going to be using

00:18:53.580 | most if not all of your life.

00:18:56.240 | In fact, you're born with many more neurons

00:18:58.260 | than you'll have later,

00:18:59.560 | and there's a process of naturally occurring cell death

00:19:02.040 | called apoptosis that occurs during development.

00:19:04.380 | So you actually are born with many more neurons

00:19:06.420 | than you have later in life,

00:19:07.340 | and that's the reflection of a normal, healthy process

00:19:10.540 | of nerve cell elimination.

00:19:13.020 | So the estimates vary, but anywhere from 1/3

00:19:17.100 | to maybe even 1/2 or even 2/3 of neurons,

00:19:19.440 | depending on the brain area,

00:19:20.280 | just going to die across development.

00:19:22.040 | That might sound terrible,

00:19:23.160 | but that's actually one of the ways in which you go

00:19:24.780 | from being kind of like a little potato bug

00:19:26.840 | flopping around helplessly in your crib

00:19:28.780 | to being an organism that can walk and talk

00:19:31.140 | and articulate and calculate math

00:19:34.180 | or do whatever it is that you do for a living.

00:19:36.540 | So the brain has a set of elements,

00:19:39.900 | these nerve cells and other cells,

00:19:41.480 | and it needs to use those for the entire lifespan.

00:19:44.560 | So having a BBB, a blood-brain barrier around the brain

00:19:47.200 | is absolutely critical.

00:19:49.100 | The ovaries and testes have a barrier

00:19:51.340 | for we assume the reason that they contain

00:19:54.840 | the genetic material by which we can pass on our genes

00:19:58.540 | to our offspring progeny,

00:19:59.780 | meaning make children and those children will have our genes

00:20:02.620 | or at least half of them.

00:20:04.540 | The other half from the partner, of course.

00:20:06.700 | If the cells within the ovaries and testes are mutated,

00:20:12.900 | well, then you can get mutations and offspring.

00:20:14.720 | So that's very costly in the evolutionary sense.

00:20:17.080 | So it makes sense that you would have

00:20:18.420 | a barrier from the blood.

00:20:19.820 | So if you ingest what's called a mutagen,

00:20:21.700 | if you ingest something that can mutate the genes of cells,

00:20:25.040 | you can imagine why there would be a premium

00:20:28.900 | on not allowing those mutagens to get into the brain,

00:20:31.720 | the ovaries or the testes.

00:20:33.500 | So the brain has this BBB,

00:20:34.940 | this blood-brain barrier around it,

00:20:36.440 | which makes it very, very hard for substances

00:20:38.180 | to pass into the brain unless those substances

00:20:40.040 | are very small or those substances and molecules

00:20:44.140 | are critically required for brain function.

00:20:46.900 | However, there are a couple of regions in the brain

00:20:50.640 | that have a fence around them, but that fence is weaker.

00:20:55.580 | It's sort of like going from a really big wall,

00:20:57.820 | thick electronic 24-hour surveillance fence

00:21:02.260 | where nothing can pass through

00:21:03.440 | except only the exclusive cargo that's allowed to go through

00:21:06.940 | to having a little cyclone fence with a couple holes in it,

00:21:09.680 | or it's a kind of a picket fence that's falling over,

00:21:12.260 | and substances can move freely in from the blood

00:21:15.420 | circulating in the body into the brain.

00:21:17.580 | And it turns out that the areas of the brain

00:21:19.400 | that monitor salt balance and other features

00:21:22.820 | of what's happening in the body

00:21:24.540 | at the level of what we call osmolarity,

00:21:27.540 | at the concentration of salt,

00:21:30.100 | reside in these little sets of neurons

00:21:34.520 | that sit just on the other side of these weak fences.

00:21:37.420 | And the most important and famous of these

00:21:39.780 | for the sake of today's conversation is one called OVLT.

00:21:43.500 | OVLT stands for the organum vasculosum

00:21:46.300 | of the lateral terminalis.

00:21:48.020 | It is what's called a circumventricular organ.

00:21:50.660 | Why circumventricular?

00:21:51.820 | Well, not to bog you down with neuroanatomy,

00:21:54.180 | but your brain is a big squishy mass of neurons

00:21:57.820 | and other cell types, but it has to be nourished.

00:22:00.840 | And through the middle of that brain, there is a tube,

00:22:04.560 | there's a hollow that creates spaces,

00:22:06.860 | and those spaces are called ventricles.

00:22:08.900 | The ventricles are spaces in which cerebral spinal fluid

00:22:12.780 | circulates and it nourishes the brain.

00:22:15.040 | It does a number of other things as well.

00:22:17.780 | The circumventricular organs are areas of the brain

00:22:21.500 | that are near that circulating fluid,

00:22:23.780 | and that circulating fluid has access to the bloodstream

00:22:26.580 | and the bloodstream has access to it.

00:22:28.220 | And this structure that I'm referring to, OVLT,

00:22:31.260 | organum vasculosum of the lateral terminalis,

00:22:33.420 | has neurons that can sense the contents of the blood

00:22:38.420 | and to some extent, the cerebral spinal fluid.

00:22:41.140 | There are a couple other brain areas

00:22:42.560 | that can do this as well.

00:22:44.300 | They go also by the name of circumventricular organs.

00:22:47.820 | And I'll talk about the names of some of those other areas.

00:22:50.100 | But for today, and I think for sake

00:22:52.300 | of most of the discussion, understand that the OVLT

00:22:54.620 | is special, why?

00:22:55.960 | Because it doesn't have this thick barrier fence,

00:22:58.700 | which sounds like a bad thing,

00:23:00.360 | and yet it's a terrific border detector.

00:23:04.440 | The neurons in that region are able to pay attention

00:23:08.340 | to what's passing through in the bloodstream

00:23:10.860 | and can detect, for instance, if the levels of sodium

00:23:13.780 | in the bloodstream are too low,

00:23:15.260 | if the level of blood pressure in the body

00:23:17.300 | is too low or too high, and then the OVLT can send signals

00:23:21.460 | to other brain areas, and then those other brain areas

00:23:24.620 | can do things like release hormones

00:23:26.700 | that can go and act on tissues

00:23:28.540 | in what we call the periphery in the body,

00:23:31.500 | and for instance, have the kidneys secrete more urine

00:23:36.020 | to get rid of salt, that's excessive salt in the body,

00:23:39.380 | or have the kidneys hold on to urine

00:23:41.780 | to hold on to whatever water or fluid that one might need.

00:23:45.100 | So before I go any deeper into this pathway,

00:23:47.020 | just understand that the OVLT has a very limited barrier.

00:23:50.460 | It can detect things in the bloodstream,

00:23:52.380 | and this incredible area of the brain almost single-handedly

00:23:57.340 | sets off the cascades of things that allow you

00:24:00.220 | to regulate your salt balance,

00:24:02.020 | which turns out to be absolutely critical,

00:24:04.080 | not just for your ability to think

00:24:05.660 | and for your neurons to work, but indeed for all of life.

00:24:08.420 | If the OVLT doesn't function correctly,

00:24:10.320 | you're effectively dead or dead soon.

00:24:12.700 | So this is a very important brain region.

00:24:14.980 | So let's talk about the function of the OVLT

00:24:17.100 | and flesh out some of the other aspects of its circuitry,

00:24:20.340 | of its communication with other brain areas

00:24:22.300 | and with the body in the context of something

00:24:24.160 | that we are all familiar with, which is thirst.

00:24:27.060 | Have you ever wondered just why you get thirsty?

00:24:29.900 | Well, it's because neurons in your OVLT

00:24:33.340 | are detecting changes in your bloodstream,

00:24:35.540 | which detect global changes within your body,

00:24:38.500 | and in response to that, your OVLT sets off certain events

00:24:43.500 | within your brain and body that make you

00:24:45.500 | either want to drink more fluid or to stop drinking fluid.

00:24:50.060 | There are two main kinds of thirst.

00:24:52.360 | The first one is called osmotic thirst,

00:24:54.860 | and the second is called hypovolemic thirst.

00:24:57.800 | Osmotic thirst has to do with the concentration of salt

00:25:01.820 | in your bloodstream.

00:25:03.200 | So let's say you ingest something very, very salty.

00:25:05.460 | Let's say you ingest a big bag of,

00:25:08.200 | I confess I don't eat these very often,

00:25:09.840 | but I really like those kettle potato chips,

00:25:11.720 | and they're pretty salty.

00:25:12.620 | I've never actually measured how much sodium is in them.

00:25:14.620 | I'm sure the information is there.

00:25:15.720 | Every once in a while, I'm particularly interested

00:25:20.220 | in doing so, I'll just down a bag of those things,

00:25:22.400 | and I really like them, and they're very salty,

00:25:24.320 | but they almost always make me feel thirsty,

00:25:26.500 | and the reason is that by eating those,

00:25:28.920 | I've ingested a lot of sodium.

00:25:30.280 | Again, not a frequent occurrence for me,

00:25:32.500 | but happens every now and again,

00:25:34.780 | and I don't have too much shame about that

00:25:36.560 | because I think I have a pretty healthy relationship

00:25:38.900 | to food, and I enjoy them,

00:25:40.840 | and I understand that it will drive salt levels

00:25:44.220 | up in my bloodstream, and that will cause me to be thirsty,

00:25:48.500 | but why, why?

00:25:49.460 | Because neurons in the OVLT come in two main varieties.

00:25:53.780 | One variety senses the osmolarity of the blood

00:25:57.760 | that's getting across that weak little fence

00:25:59.880 | that we talked about before,

00:26:01.380 | and when the osmolarity,

00:26:03.020 | meaning the salt concentration in the blood is high,

00:26:06.360 | it activates these specific neurons in the OVLT,

00:26:09.300 | and by activates, I mean,

00:26:10.340 | it causes them to send electrical potentials,

00:26:13.160 | literally send electrical signals to other brain areas,

00:26:17.660 | and those other brain areas inspire

00:26:19.620 | a number of different downstream events.

00:26:21.920 | So what are those other brain areas?

00:26:23.920 | Well, the OVLT signals to an area

00:26:27.840 | called the supraoptic nucleus.

00:26:30.320 | The name and why it's called the supraoptic nucleus

00:26:33.240 | is not necessarily important.

00:26:34.940 | It also signals to the so-called paraventricular nucleus,

00:26:37.840 | another nucleus that sits near the ventricles

00:26:39.780 | and can monitor the qualities, the chemical qualities

00:26:44.020 | of the cerebral spinal fluid,

00:26:45.500 | as well as probably the bloodstream as well.

00:26:48.320 | And the consequence of that communication

00:26:53.320 | is that a particular hormone is eventually released

00:26:57.180 | from the posterior pituitary.

00:26:59.680 | Now, the pituitary is a gland

00:27:02.780 | that sits near the roof of your mouth.

00:27:05.080 | It releases all sorts of things like growth hormone

00:27:07.960 | and luteinizing hormone, luteinizing hormone

00:27:10.180 | will stimulate things like estrogen

00:27:11.860 | and testosterone production and release

00:27:14.980 | from the ovaries and testes and so on.

00:27:17.600 | The pituitary has a bunch of different compartments

00:27:19.480 | and functions, but what's really cool about the pituitary

00:27:22.580 | is that certain regions of the pituitary

00:27:24.500 | actually contain the axons, the wires of neurons,

00:27:27.460 | and the neurons reside in the brain.

00:27:29.560 | And so the supraoptic nucleus gets a signal from the OVLT.

00:27:34.560 | The signal is purely in the form of electrical activity.

00:27:37.400 | Remember, neurons aren't talking in one another

00:27:39.420 | about what's happening out there.

00:27:40.760 | They're not saying, hey, there's too much salt

00:27:43.640 | in the bloodstream, let's do something about it.

00:27:45.460 | All they receive are so-called action potential,

00:27:47.840 | waves of electricity.

00:27:49.480 | The neurons in the supraoptic nucleus

00:27:51.820 | then release their own electrical signals

00:27:56.020 | within the pituitary and some of those neurons

00:27:59.240 | and nearby neurons are capable of releasing hormones

00:28:02.700 | as well as electrical signals.

00:28:05.360 | So from the pituitary, there's a hormonal signal

00:28:08.200 | that's released called vasopressin.

00:28:10.960 | Vasopressin also goes by the name antidiuretic hormone

00:28:15.560 | and antidiuretic hormone has the capacity

00:28:19.760 | to either restrict the amount of urine that we secrete

00:28:23.820 | or when that system is turned off

00:28:26.120 | to increase the amount of urine that we secrete.

00:28:29.620 | So there's a complicated set of cascades

00:28:32.840 | that's evoked by having high salt concentration in the blood.

00:28:35.920 | There's also a complicated set of cascades

00:28:38.240 | that are evoked by having low concentrations

00:28:40.600 | of sodium in the blood.

00:28:42.200 | But the pathway is nonetheless the same.

00:28:44.180 | It's OVLT is detecting those osmolarity changes,

00:28:47.840 | communicating to the supraoptic nucleus.

00:28:49.680 | Supraoptic nucleus is either causing the release of

00:28:54.340 | or is releasing vasopressin, antidiuretic hormone,

00:28:57.800 | or that system is shut off so that the antidiuretic hormone

00:29:02.360 | is not secreted,

00:29:03.480 | which would allow urine to flow more freely, right?

00:29:06.240 | Antidiuretic means anti-release of urine.

00:29:10.440 | And by shutting that off,

00:29:12.720 | you're going to cause the release of urine.

00:29:15.920 | You're sort of allowing a system to flow, so to speak.

00:29:18.720 | The second category of thirst is hypovolemic thirst.

00:29:22.960 | Hypovolemic thirst occurs

00:29:24.720 | when there's a drop in blood pressure, okay?

00:29:27.800 | So the OVLT, as I mentioned before, can sense osmolarity

00:29:32.540 | based on the fact that it has these neurons

00:29:34.440 | that can detect how much salt is in the bloodstream.

00:29:37.100 | But the OVLT also harbors neurons

00:29:41.440 | that are of the baroreceptor, mechanoreceptor category.

00:29:46.440 | Now, more on baroreceptors and mechanoreceptors later,

00:29:50.820 | but baroreceptors are essentially a receptor,

00:29:55.840 | meaning a protein that's in a cell

00:29:58.220 | that responds to changes in blood pressure.

00:30:01.540 | So there are a number of things

00:30:02.760 | that can cause decreases in blood pressure.

00:30:04.920 | Some of those include, for instance,

00:30:07.200 | if you lose a lot of blood, right?

00:30:08.900 | If you're bleeding quite a lot,

00:30:10.600 | or in some cases, if you vomit quite a lot,

00:30:14.240 | or if you have extensive diarrhea,

00:30:16.420 | or any combination of those.

00:30:17.800 | And there are other things that can reduce blood volume,

00:30:20.680 | and we will talk about some of those later.

00:30:23.240 | But in the classic case of hypovolemic thirst,

00:30:27.440 | one is simply losing blood,

00:30:29.440 | and therefore blood pressure goes down.

00:30:31.180 | So very simple to imagine in your mind.

00:30:33.040 | You have these pipes,

00:30:33.880 | which are the arteries, veins, and capillaries,

00:30:35.320 | and when you lose some blood volume,

00:30:37.240 | the pressure in those arteries, veins,

00:30:39.420 | and capillaries goes down.

00:30:40.800 | OVLT has neurons that can sense that reduction

00:30:44.180 | in blood pressure because of the presence

00:30:46.440 | of baroreceptors in OVLT.

00:30:49.560 | There are other elements that also play into the response

00:30:54.400 | to what we call hypovolemic thirst.

00:30:57.560 | For instance, the kidney will secrete

00:31:00.400 | something called renin.

00:31:02.080 | Renin will activate something called angiotensin II

00:31:05.720 | from the lungs of all things, amazing.

00:31:08.280 | And angiotensin II itself can act on OVLT,

00:31:12.120 | organ and vasculosin and lateral terminalis,

00:31:14.300 | which in turn will create thirst, okay?

00:31:18.800 | So in both cases, right, the osmolarity sensing system,

00:31:23.420 | meaning osmotic thirst, and in hypovolemic thirst,

00:31:26.080 | where blood pressure has dropped,

00:31:27.800 | the end result is a desire to drink more.

00:31:31.700 | And that desire to drink more comes through a variety

00:31:34.140 | of pathways that are both direct and indirect,

00:31:36.400 | include vasopressin and don't include vasopressin.

00:31:38.800 | But I think for just sake of general example,

00:31:42.240 | and even for those of you that don't have

00:31:43.560 | any biology background or physiology background,

00:31:46.520 | just understand that there are two main types of thirst.

00:31:49.920 | Both types of thirst, osmotic thirst and hypovolemic thirst,

00:31:54.060 | are not just about seeking water,

00:31:56.240 | but they also are about seeking salt.

00:31:58.660 | In very general terms, salt, AKA sodium,

00:32:03.480 | can help retain water.

00:32:06.900 | Now that doesn't mean that salt always retains water.

00:32:10.100 | If you have excessive amounts of salt,

00:32:11.920 | will you retain excessive amounts of water?

00:32:14.000 | Well, sort of, as we'll soon learn, it's all contextual.

00:32:17.240 | But for most cases, we can say that

00:32:20.920 | by having salt in our system,

00:32:23.520 | our brain and our body can function normally,

00:32:25.800 | provided the levels of salt are adequate

00:32:28.360 | and not too high or too low.

00:32:30.640 | And thirst, while we often think of it

00:32:34.200 | as just a way to bring fluid into our body,

00:32:36.680 | is designed as a kind of a interoceptive perception.

00:32:41.560 | What I mean by that, interoception, as many of you know now

00:32:44.440 | from listening to this podcast, is a paying of attention

00:32:47.360 | or a recognition, rather, a conscious recognition

00:32:50.040 | of the events going on within our body.

00:32:52.440 | So when we are thirsty,

00:32:54.080 | it's a certain form of interoception.

00:32:56.000 | We go, oh, I need something or I crave something.

00:32:58.600 | You may not know exactly what you need,

00:33:00.200 | but when you are thirsty, you're not just seeking water,

00:33:03.500 | you're also seeking to balance your osmolarity,

00:33:07.000 | which means you may be seeking salty fluids or foods.

00:33:12.000 | In some cases, you'll try and accomplish this by eating,

00:33:15.500 | or it may be that you're trying to avoid

00:33:17.760 | or you will be inspired to avoid salty fluids and foods.

00:33:21.640 | But if you want to understand sodium

00:33:24.680 | and its roles in the body, you have to understand thirst.

00:33:26.960 | And if you want to understand thirst,

00:33:28.220 | you have to understand how fluid balance

00:33:31.280 | is regulated in the body.

00:33:32.240 | That's not surprising at all.

00:33:34.280 | But sodium and water work together

00:33:37.520 | in order to generate what we call thirst.

00:33:39.600 | Sodium water work together in order to either retain water

00:33:43.640 | or inspire us to let go of water to urinate.

00:33:46.880 | So before we can dive into the specifics around salt

00:33:50.440 | and how to use salt for performance

00:33:52.040 | and various recommendations and things to avoid,

00:33:55.420 | we need to drill a little bit deeper

00:33:57.400 | into this fluid balance mechanism in the body.

00:34:00.240 | And for that reason, we have to pay

00:34:01.920 | at least a little bit of attention to the kidney.

00:34:04.180 | The kidney is an incredible organ.

00:34:06.680 | And one of the reasons the kidney is so amazing

00:34:08.920 | is that it's responsible for both retaining,

00:34:11.860 | holding onto, or allowing the release

00:34:14.420 | of various substances from the body.

00:34:16.720 | Substances like glucose or amino acids, urea, uric acid,

00:34:21.720 | salt, potassium, magnesium.

00:34:26.140 | It's basically a filter,

00:34:27.580 | but it's a very, very intelligent filter.

00:34:31.120 | I mean, intelligent, meaning it doesn't have its own mind,

00:34:33.480 | but the way it works is really beautiful.

00:34:36.320 | Basically, blood enters the kidney

00:34:39.480 | and it goes through a series of tubes,

00:34:42.620 | which are arranged into loops.

00:34:44.300 | If you want to look more into this,

00:34:45.560 | there's the beautiful loop of Henle

00:34:48.120 | and other aspects of the kidney design

00:34:51.080 | that allow certain substances to be retained

00:34:55.460 | and other substances to be released

00:34:56.920 | depending on how concentrated those substances are

00:34:59.260 | in the blood.

00:35:02.180 | The kidney responds to a number of hormonal signals,

00:35:04.560 | including vasopressin, in order to, for instance,

00:35:08.200 | antidiuretic hormone, in order to hold on to more fluid,

00:35:11.540 | if that's what your brain and body need.

00:35:14.020 | And it responds to other hormonal signals as well.

00:35:17.760 | So it's a pretty complex organ.

00:35:19.960 | Nonetheless, there's a key point,

00:35:22.580 | which I already mentioned

00:35:23.580 | that I think most people don't realize.

00:35:25.260 | This is actually something that I like to tell kids

00:35:27.180 | when I meet them, provided that they're of appropriate age.

00:35:29.200 | I'll say, oftentimes when kids learn that I'm a scientist,

00:35:33.040 | they'll ask a question about something related to science,

00:35:36.480 | and hopefully for my sake,

00:35:38.360 | it's something about neuroscience.

00:35:40.520 | But one thing that I'll tell kids, I'll say,

00:35:42.280 | you know, do you know that your urine,

00:35:44.760 | your pee is actually filtered blood?

00:35:47.160 | And occasionally that will really terrify a kid,

00:35:49.480 | but that also occasionally really terrifies an adult.

00:35:53.000 | But indeed, your urine is filtered blood.

00:35:55.480 | They see blood gets into the kidney,

00:35:57.140 | the kidney is going to filter out certain things,

00:35:58.800 | certain things are going to be allowed to pass through

00:36:00.280 | and others are not, okay?

00:36:02.460 | So the way the kidney is designed is that about 90%

00:36:07.080 | of the stuff that's absorbed from the blood

00:36:09.480 | is going to be absorbed early in this series of tubes.

00:36:12.460 | And only a small percentage is going to be regulated

00:36:16.760 | or worked out as you get into what's called

00:36:18.240 | the distal kidney.

00:36:19.520 | Distal just means the furthest part away, okay?

00:36:23.240 | The proximal is up close.

00:36:25.500 | So like your shoulder is proximal

00:36:27.000 | to your midline of your body and your hand is distal.

00:36:29.840 | So in biological terms, you hear about proximal distal,

00:36:32.000 | which just means near or far from.

00:36:34.320 | So just to give a really simple example,

00:36:36.120 | let's say that you are very low on fluid.

00:36:39.920 | You haven't had much to drink in a while,

00:36:41.360 | maybe you're walking around on a hot day.

00:36:43.420 | Chances are that the neurons in your OVLT

00:36:48.120 | will sense the increase in osmolarity, right?

00:36:51.300 | The concentration of salt is going to be increased

00:36:54.500 | relative to the fluid volume that's circulating.

00:36:58.140 | This of course assumes that you haven't excreted

00:37:00.180 | a lot of sodium for one reason or another,

00:37:02.280 | but that increase in osmolarity is detected by the OVLT.

00:37:05.880 | The OVLT is going to signal a bunch of different cascades

00:37:09.460 | through the super optic nucleus, et cetera.

00:37:11.580 | And then vasopressin is going to be released

00:37:13.700 | into the bloodstream and vasopressin,

00:37:16.000 | again also called antidiuretic hormone,

00:37:18.340 | is going to act on the kidney and change

00:37:21.460 | the kidney's function in a couple of different ways,

00:37:24.900 | some mechanical, some chemical, okay,

00:37:28.200 | in order to make sure that your kidney

00:37:30.620 | does not release much water,

00:37:32.880 | doesn't make you want to urinate.

00:37:35.260 | And in fact, even if you would try to urinate,

00:37:37.300 | your body's going to tend to hold on to its fluid stores.

00:37:40.060 | Okay, so very simple, straightforward example.

00:37:42.960 | We can also give the other example

00:37:44.380 | whereby if you are ingesting a lot, a lot, a lot of water,

00:37:47.820 | and it's not a particularly hot day

00:37:49.780 | and you're not sweating very much,

00:37:51.460 | let's assume your salt intake is constant

00:37:53.460 | or is low for whatever reason,

00:37:55.740 | well then the osmolarity, the salt concentration

00:37:58.900 | in your blood is going to be lower.

00:38:00.300 | Your OVLT will detect that

00:38:02.580 | because of these osmosensing neurons in your OVLT.

00:38:06.800 | Your OVLT will fail to signal to the super optic nucleus

00:38:11.800 | and there will not be the release

00:38:14.820 | of vasopressin antidiuretic hormone

00:38:16.940 | and you can excrete all the water

00:38:19.980 | that your body wants to excrete,

00:38:22.180 | meaning you'll be able to urinate,

00:38:23.460 | there's no holding on to water at the level of the kidney.

00:38:25.740 | Okay, very simple examples,

00:38:27.140 | but hopefully it illustrates how events within the blood,

00:38:29.840 | meaning the concentration of salt

00:38:31.160 | relative to the amount of fluid, right?

00:38:33.540 | That's what osmolarity is, is detected by the OVLT.

00:38:37.360 | The brain then communicates to the pituitary.

00:38:39.940 | The pituitary sends a hormone out into the blood

00:38:42.100 | and the hormone acts on the kidney

00:38:44.220 | to either hold onto or let go of fluid,

00:38:48.380 | meaning to prevent you from wanting to urinate

00:38:51.040 | or from stimulating you to want to urinate.

00:38:54.120 | Very, very simple kind of yes/no type situation here.

00:38:57.580 | There's a lot of nuance to this in reality.

00:38:59.540 | There are a lot of other hormones in this pathway,

00:39:01.100 | but I think for at least this stage of the discussion,

00:39:04.100 | this should be sufficient.

00:39:05.300 | Some of you may have noticed

00:39:06.900 | that a molecule we've been talking a lot about today,

00:39:09.340 | vasopressin, was also mentioned on a previous episode

00:39:12.780 | of the Huberman Lab Podcast,

00:39:13.980 | but in a very different context.

00:39:16.100 | The molecule I'm referring to is vasopressin,

00:39:18.300 | and as I mentioned, it's a hormone involved in anti-diuresis,

00:39:23.300 | meaning preventing urination.

00:39:26.220 | It's an anti-diuretic.

00:39:28.140 | But we also talked about vasopressin

00:39:30.540 | in the context of desire, love, and attachment.

00:39:33.740 | We talked about it in the context of monogamy

00:39:35.940 | and non-monogamy in a species of animal

00:39:38.180 | called the prairie vole.

00:39:39.900 | You can check out that episode.

00:39:41.860 | I believe vasopressin and the non-monogamous prairie voles

00:39:45.900 | are mentioned in the timestamp, so it should be easy to find.

00:39:49.660 | Vasopressin is made at multiple locations

00:39:53.660 | in the nervous system, mainly the super optic nucleus,

00:39:56.740 | and indeed, it's also involved

00:39:59.260 | in aspects of sexual behavior and mating.

00:40:03.180 | Now, it does that through mechanisms

00:40:05.700 | that are distinct from its anti-diuretic effects.

00:40:10.480 | In fact, there are people who take vasopressin

00:40:14.860 | as an aphrodisiac.

00:40:16.460 | Now, I'm certainly not suggesting people do that,

00:40:19.080 | but I have all the confidence in the world

00:40:22.320 | that the moment I talk about vasopressin,

00:40:23.820 | someone in the comments is going to say,

00:40:24.920 | "What do you think about vasopressin nasal sprays

00:40:26.960 | and this kind of thing?"

00:40:28.160 | Vasopressin and indeed oxytocin,

00:40:30.420 | another hormone that's involved in pair bonding

00:40:33.840 | and various aspects of brain and body function,

00:40:36.520 | are available as nasal sprays

00:40:39.300 | that can get up into the deep recesses of the brain

00:40:42.240 | and can impact some of these core,

00:40:44.580 | what we call hypothalamic functions,

00:40:46.080 | these primitive drives and hypothalamic functions.

00:40:48.560 | I would encourage a lot of caution,

00:40:51.720 | maybe even extreme caution in recreational use

00:40:54.500 | of things like vasopressin and oxytocin,

00:40:56.700 | unless you are working with an MD, excuse me,

00:40:59.740 | and they prescribe it or they really know what they're doing,

00:41:01.840 | these are powerful hormones

00:41:03.600 | that have a lot of different effects on the brain and body.

00:41:06.500 | The way that vasopressin, meaning antidiuretic hormone,

00:41:09.860 | prevents the release of fluid as urine from the body

00:41:13.820 | is pretty interesting.

00:41:15.080 | It acts directly on the kidney.

00:41:17.200 | So as I mentioned before, blood flows into the kidney,

00:41:19.700 | a number of things are retained

00:41:21.020 | in the early part of the kidney.

00:41:22.860 | Vasopressin acts at a fairly distal,

00:41:25.540 | meaning kind of end game,

00:41:28.920 | part of the loops of tubes through the kidney,

00:41:32.020 | and it increases the permeability of those tubes.

00:41:35.420 | In other words, it makes sure that the fluid

00:41:37.480 | that would otherwise pass into a collecting duct

00:41:40.320 | and then go out to the bladder

00:41:41.580 | never actually makes it to the bladder.

00:41:43.940 | I point this out because what antidiuretic hormone does

00:41:46.940 | is it prevents the bladder from filling at all.

00:41:49.120 | It's not as if it locks fluid in the bladder

00:41:51.340 | and prevents you from urinating.

00:41:52.860 | I think the way I've been describing things up until now

00:41:55.060 | and the way you'll hear about antidiuretic hormone,

00:41:56.980 | it might sound like it kind of locks up the bladder,

00:41:59.380 | prevents you from being able to urinate,

00:42:01.200 | but you have a full bladder.

00:42:02.140 | That would be very uncomfortable.

00:42:03.180 | That's not the way it works.

00:42:04.420 | It actually causes the tubes headed towards the bladder

00:42:08.380 | from the kidney to become permeable,

00:42:10.340 | meaning to allow fluid to go back into the bloodstream

00:42:14.340 | into the rest of the body

00:42:15.300 | so that fluid never actually fills the bladder

00:42:17.220 | and so you never feel the urge to urinate.

00:42:19.400 | Now, this is an episode about salt.

00:42:21.180 | A key thing to understand about the kidney

00:42:23.920 | is that the kidney uses sodium in order to conserve water,

00:42:28.380 | which has everything to do with the fact

00:42:30.380 | that sodium can actually hold water, put differently,

00:42:35.380 | water tends to follow sodium.

00:42:37.660 | So where we have sodium, we tend to have water

00:42:40.540 | and sodium, when it's concentrated, can hold onto water.

00:42:45.380 | And that's one of the main ways

00:42:46.780 | that the kidney holds onto water in the body.

00:42:49.260 | And as we'll soon learn,

00:42:51.220 | there is no simple and direct formula to say,

00:42:54.060 | for instance, okay, if salt levels are high,

00:42:57.900 | a lot of water is retained.

00:42:59.660 | And if salt levels are low, a lot of water is released.

00:43:04.220 | On the one hand, that can be true,

00:43:06.300 | but it's also the case because these systems are homeostatic,

00:43:09.820 | meaning they're always seeking balance,

00:43:11.820 | both within system, within the salt system

00:43:14.020 | and between systems, the salt and water system,

00:43:16.940 | it's also the case often that if we have enough sodium,

00:43:21.940 | well, then we can secrete sodium and some water will follow.

00:43:25.940 | Or if we don't have enough sodium,

00:43:28.460 | then yes, indeed, because we're not holding onto water,

00:43:33.220 | more fluid can be excreted.

00:43:35.320 | But if that condition of low sodium lasts long enough,

00:43:39.780 | then we start to retain water

00:43:41.280 | because the body recognizes, ah, salt is low

00:43:44.260 | and water is being excreted.

00:43:46.100 | And eventually a system will kick in to retain water.

00:43:49.300 | So I'd love to give you a simple black and white,

00:43:52.000 | yes or no answer for low sodium, high sodium,

00:43:54.420 | moderate sodium and water balance, but it's all contextual.

00:43:57.900 | And when I say contextual, I mean,

00:43:59.300 | it will depend on blood pressure, hypertension,

00:44:02.800 | prehypertension if that's there, maybe normal tension,

00:44:06.580 | hormone levels, exercise, et cetera, et cetera.

00:44:10.300 | A pretty good example of how complicated this can all be

00:44:12.580 | is one that some of you may be familiar with.

00:44:15.140 | It's pretty well known that during certain phases

00:44:18.180 | of the menstrual cycle, when estrogen and progesterone

00:44:21.340 | and other hormones are fluctuating,

00:44:23.120 | that water can be retained in the body.

00:44:26.140 | There's, it's what's called edema or a swelling sometimes.

00:44:29.480 | So the common assumption, and indeed it can be true,

00:44:32.820 | that when estrogen levels are high,

00:44:34.800 | there's water retention in the body.

00:44:37.640 | Also in males, if estrogen levels are high,

00:44:39.800 | there can be water retention in the body.

00:44:41.240 | This is one of the reasons why athletes

00:44:44.060 | and in particular bodybuilders who take anabolic steroids

00:44:46.700 | like testosterone, which can be converted into estrogens,

00:44:49.300 | sometimes they'll look, they'll walk around,

00:44:50.820 | they look like they were partially inflated,

00:44:52.380 | they look like they're going to pop,

00:44:53.540 | and it looks like a swelling of the skin,

00:44:55.660 | not just because they have large muscles.

00:44:57.120 | And that's not always, but often water retention

00:45:00.140 | due to testosterone conversion into estrogen.

00:45:03.460 | Now that all sounds consistent, right?

00:45:05.860 | Estrogen levels fluctuated in the menstrual cycle,

00:45:08.300 | in males where there's an increase in estrogen,

00:45:10.220 | there's retention of water,

00:45:11.520 | but actually estrogen acts as a diuretic.

00:45:14.820 | So one would think, okay, when estrogen levels go up,

00:45:17.300 | there should be a lot of fluid excreted.

00:45:19.180 | But I bring up this example to point out

00:45:21.260 | that it's a very complicated and dynamic balance

00:45:23.560 | between hormones and salt and fluid.

00:45:25.880 | You can't draw a one-to-one relationship there.

00:45:28.520 | And that turns out to be a very important point.

00:45:30.760 | And we can use that not as a way

00:45:33.040 | to further complicate things,

00:45:34.420 | but as a way to understand under which context

00:45:39.180 | less sodium intake or more sodium intake can be beneficial.

00:45:43.260 | So that's where I'd like to turn our attention now.

00:45:45.260 | So how much salt do we need and what can we trust

00:45:48.660 | in terms of trying to guide our ingestion of salt?

00:45:53.180 | First of all, I want to be very, very clear

00:45:55.340 | that there are a number of people out there

00:45:57.520 | that have pre-hypertension or hypertension.

00:46:00.500 | You need to know

00:46:01.340 | if you have pre-hypertension or hypertension.

00:46:03.500 | You need to know if you have normal tension,

00:46:06.180 | meaning normal blood pressure.

00:46:07.880 | Everyone should know their blood pressure

00:46:10.560 | is an absolutely crucial measurement

00:46:12.500 | that has a lot of impact

00:46:14.420 | on your immediate and long-term health outcomes.

00:46:17.360 | It informs a lot about what you should do.

00:46:19.420 | Should you be doing more cardiovascular exercise?

00:46:21.580 | Should you be ingesting more or less salt?

00:46:24.240 | Should you be adjusting any number

00:46:25.740 | of different lifestyle factors?

00:46:27.340 | So you need to know that.

00:46:28.740 | And without knowing what your blood pressure is,

00:46:31.340 | I can't give a one-size-fits-all recommendation.

00:46:34.420 | And indeed, I'm not going to give medical recommendations.

00:46:36.800 | I'm simply going to spell out what I know about the research,

00:46:39.940 | which hopefully will point you in the direction

00:46:41.300 | of figuring out what's right for you

00:46:42.940 | in terms of salt and indeed fluid intake.

00:46:45.500 | There is a school of thought

00:46:46.980 | that everybody is consuming too much salt.

00:46:50.380 | And I do want to highlight the fact that there are dozens,

00:46:54.520 | if not hundreds of quality papers that point to the fact

00:46:57.860 | that a quote unquote high salt diet

00:47:01.460 | can be bad for various organs and tissues in the body,

00:47:05.500 | including the brain.

00:47:06.580 | It just so happens that because fluid balance,

00:47:11.540 | both inside and outside of cells is crucial,

00:47:14.260 | not just for your heart and for your lungs

00:47:16.840 | and for your liver and for all the organs of your body,

00:47:19.300 | but also for your brain,

00:47:20.820 | that if the salt concentration inside of cells in your brain

00:47:25.820 | becomes too high, neurons suffer, right?

00:47:29.740 | They will draw fluid into those cells

00:47:32.020 | because water tends to follow salt, as I mentioned before,

00:47:36.260 | and those cells can swell.

00:47:38.940 | You can literally get swelling of brain tissue.

00:47:41.180 | Conversely, if salt levels are too low inside of cells

00:47:45.440 | in any tissue of the body, but in the brain included,

00:47:50.000 | then the cells of the body and brain can shrink

00:47:54.840 | because water is pulled into the extracellular space

00:47:59.320 | away from cells.

00:48:00.560 | And indeed under those conditions,

00:48:03.040 | brain function can suffer.

00:48:05.260 | And indeed the overall health of the brain can suffer.

00:48:08.000 | So there are many reports out there

00:48:10.840 | indicating both in experimental models

00:48:13.700 | and to some extent in humans

00:48:15.360 | that overconsumption of salt

00:48:17.200 | is bad for brain function and longevity.

00:48:19.720 | And yet there is also decent evidence

00:48:23.000 | in both animal models and humans

00:48:25.020 | that if salt consumption is too low,

00:48:28.200 | then brain health and longevity will suffer

00:48:31.220 | as will other organs and tissues of the body.

00:48:33.880 | So like most things in biology,

00:48:35.380 | you don't want things too high or too low.

00:48:38.720 | Now, I would say that the vast majority of studies out there

00:48:42.100 | point to the fact that a high salt diet

00:48:45.420 | is detrimental to brain health and function.

00:48:48.500 | Most of the studies have focused on that aspect

00:48:52.060 | of salt balance and its consequences on brain function.

00:48:55.440 | One critical issue with many of those studies, however,

00:49:00.940 | is that the high salt diet is often coupled

00:49:04.120 | to other elements of diet that are also unhealthy.

00:49:07.820 | Things like excessively high levels of carbohydrates

00:49:10.720 | or fats or combinations of carbohydrates and fats.

00:49:14.040 | And so while I know there are many burning questions

00:49:16.440 | out there about how much salt one needs

00:49:18.840 | if they are on a low carbohydrate diet

00:49:20.920 | or if they are fasting or if they are on a vegan diet,

00:49:24.260 | there have simply not been many studies

00:49:26.860 | that have explored the low, moderate,

00:49:29.480 | and high salt conditions

00:49:31.420 | on a backdrop of very controlled nutrition.

00:49:34.280 | And that's probably reflective of the fact

00:49:36.400 | that there are not a lot

00:49:38.000 | of very well-controlled nutrition studies out there.

00:49:40.200 | There are some, of course,

00:49:41.960 | but it's very hard to get people to adhere

00:49:44.080 | to nutritional plans in a very strict way

00:49:46.400 | and to do that for sufficient periods of time

00:49:48.960 | that would allow the various health outcomes to occur.

00:49:52.600 | Nonetheless, there's some interesting reports

00:49:55.360 | that indicate that the amount of salt intake

00:49:58.920 | can indeed predict health outcomes

00:50:03.360 | or what we call hazardous events,

00:50:06.320 | things like cardiovascular events and stroke and so forth.

00:50:09.200 | And what's interesting is that indeed a lower,

00:50:13.760 | I'm not saying low, right?

00:50:15.480 | Because I don't believe that you want your diet

00:50:16.800 | to be truly low in anything except perhaps poison,

00:50:21.040 | but a lower salt diet can reduce the number

00:50:26.040 | of these so-called hazardous events,

00:50:28.680 | but it's a somewhat of a shallow U-shaped function

00:50:32.940 | such that yes, indeed, a high salt intake

00:50:37.940 | can be very detrimental for your health,

00:50:40.900 | both in terms of cardiovascular events,

00:50:42.620 | stroke and other deleterious health events,

00:50:46.200 | but somewhere in the middle that actually sits

00:50:49.460 | quite to the right, meaning higher

00:50:52.400 | than what is typically recommended for salt intake

00:50:55.800 | can actually reduce the number of these hazardous events.

00:50:58.760 | At least some reports point to that.

00:51:00.920 | And so I want to emphasize

00:51:02.120 | what one of those particular reports says,

00:51:05.640 | and I also want to be sure to counter it

00:51:07.540 | from the perspective of the context

00:51:09.800 | that that study was set in.

00:51:10.880 | Because again, my goal here is not to give you

00:51:13.040 | a strict set of recommendations at all,

00:51:16.060 | is to point you to the literature,

00:51:18.040 | try and make that literature as clear as possible

00:51:19.880 | and allow you to evaluate for yourself.

00:51:21.920 | And I don't just say that to protect us,

00:51:23.600 | I say that to protect you because indeed you are responsible

00:51:26.720 | for your health and your health choices.

00:51:28.560 | So the paper that I'm referring to

00:51:30.600 | is a very interesting one.

00:51:32.320 | We of course never want to put too much weight

00:51:34.920 | on any one report, but this is a paper

00:51:37.440 | that was published in 2011

00:51:39.400 | in the journal of the American Medical Association.

00:51:41.900 | The title of the paper is urinary sodium

00:51:44.340 | and potassium excretion and a risk of cardiovascular events.

00:51:48.020 | We have not talked much about potassium yet,

00:51:50.460 | but sodium and potassium tend to work in concert

00:51:53.580 | in the brain and body in order to regulate

00:51:55.820 | various physiological functions and health.

00:51:57.540 | And we'll talk more about potassium as time goes on.

00:52:00.340 | The key plot or set of data in this study,

00:52:05.340 | for those of you that want to look it up,

00:52:06.740 | we will link to it.

00:52:08.440 | And there are a lot of data in here,

00:52:10.080 | but is figure one, which is basically evaluating

00:52:14.200 | the amount of urinary excretion of sodium,

00:52:17.260 | which is a somewhat indirect,

00:52:19.360 | but nonetheless valuable measure

00:52:21.200 | of how much sodium people were ingesting.

00:52:24.300 | And plotted against that is what they call the hazard ratio.

00:52:28.220 | And the hazard ratio points to the composite

00:52:32.040 | of cardiovascular death, stroke, myocardial infarction,

00:52:35.240 | and an infarct as an injury and hospitalization

00:52:37.940 | for congestive heart failure.

00:52:39.860 | And what it points to is the fact that the hazard ratio

00:52:43.640 | is low-ish at sodium excretion of about two grams per day,

00:52:48.640 | but then continues to go down

00:52:52.920 | until about 4.5 to five grams per day.

00:52:57.920 | Remember, this is sodium excretion,

00:52:59.840 | so it's reflective of how much sodium was in the body,

00:53:02.840 | which is reflective of how much sodium was ingested.

00:53:05.120 | And then the hazard ratio increases fairly dramatically,

00:53:09.080 | a very steep slope,

00:53:10.800 | heading anywhere from seven to eight to 10

00:53:14.520 | and out towards 12 grams of sodium excretion per day.

00:53:18.120 | So the simplest way to interpret these data

00:53:20.600 | are that at fairly low levels of sodium,

00:53:24.800 | meaning at about two grams per day,

00:53:27.640 | you run fewer health risks,

00:53:29.920 | but the number of risks continues to decline

00:53:31.880 | as you move towards four and five grams per day.

00:53:34.520 | And then as you increase your salt intake further,

00:53:37.560 | then the risk dramatically increases.

00:53:40.840 | So no study is holy,

00:53:42.080 | nor is any figure in any study

00:53:44.780 | or any collection of studies holy.

00:53:47.760 | Rather, we always want to look at

00:53:49.280 | what the bulk of data in a particular field reveal.

00:53:52.640 | Nonetheless, I think that the plot that we described,

00:53:54.900 | meaning the graph that we described is pretty interesting

00:53:57.560 | in light of the 2020 to 2025 dietary recommendations

00:54:02.560 | for Americans, which is that people consume

00:54:06.100 | no more than 2.3 grams,

00:54:08.760 | meaning 2,300 milligrams of sodium per day.

00:54:12.480 | That's about a half a teaspoon of salt per day.

00:54:17.480 | Now, most people are probably consuming more than that

00:54:22.360 | because of the fact that they are ingesting processed foods

00:54:26.380 | and processed foods tend to have more salt in them

00:54:29.640 | than non-processed foods.

00:54:30.780 | Now, of course, that's not always the case, right?

00:54:33.000 | Sea salt is not a processed food in most cases.

00:54:35.460 | And there are a lot of unprocessed foods

00:54:39.120 | that can be high in sodium,

00:54:41.040 | but processed foods in particular

00:54:42.780 | tend to have a lot of sodium.

00:54:43.780 | You can see this simply by looking at the packaging

00:54:46.360 | of any number of different foods.

00:54:48.080 | But if we were to take this number of 2.3 grams,

00:54:52.840 | that's the recommended cutoff

00:54:55.720 | for ingestion of sodium.

00:54:57.400 | It actually falls in a portion of the curve

00:55:01.060 | that we were talking about a moment ago

00:55:02.780 | that indeed is associated with low incidents

00:55:06.780 | of hazardous outcomes, cardiovascular events,

00:55:10.380 | stroke, et cetera.

00:55:11.740 | But according to that plot,

00:55:15.320 | the ingestion of four or five grams of sodium,

00:55:19.400 | almost double or more sodium than is currently recommended,

00:55:24.460 | is associated with even lower numbers of hazardous events.

00:55:29.280 | So we need to think about this

00:55:30.640 | and we need to explore it in the context

00:55:32.480 | of other studies, of course.

00:55:34.500 | And we need to evaluate it in terms of this thing

00:55:37.920 | that we've been going back to again and again,

00:55:40.360 | which is context, right?

00:55:42.360 | These recommendations of 2.3 gram per day cutoff

00:55:46.540 | is in the context of a landscape

00:55:48.200 | where some people do indeed have hypertension

00:55:51.360 | or pre-hypertension.

00:55:53.400 | The incidence of hypertension has gone up dramatically

00:55:55.760 | in the last 100 years and seems to continue to go up.

00:56:00.080 | Whether or not that's because of increased salt intake

00:56:04.560 | or whether or not it's because of increased salt intake

00:56:07.280 | and other things such as highly processed foods,

00:56:10.380 | that isn't clear.

00:56:11.260 | Again, pointing to the challenge

00:56:13.120 | in doing these epidemiological studies

00:56:14.880 | and really parsing what aspects of a change

00:56:17.820 | in some health metric is due to, for instance,

00:56:20.880 | the ingestion of more sugars versus more salts

00:56:23.080 | or simply because of the ingestion of more salts.

00:56:25.720 | It's a complicated, almost barbed wire topic by now,

00:56:29.380 | but we can start to pull apart that barbed wire tangle

00:56:32.520 | and start to evaluate some of the other people

00:56:35.560 | in other conditions that exist out there, maybe for you,

00:56:40.520 | that actually warrant more sodium intake

00:56:43.760 | and where more sodium intake might actually be beneficial.

00:56:46.680 | So again, I want to be very, very clear

00:56:48.600 | that you need to know your blood pressure.

00:56:50.120 | If you have high blood pressure or you're pre-hypertensive,

00:56:52.820 | you should be especially cautious about doing anything

00:56:55.140 | that increases your blood pressure.

00:56:57.140 | And as always, you want to, of course, talk to your doctor

00:56:59.380 | about doing anything that could adjust your health

00:57:01.300 | in any direction.

00:57:02.660 | But nonetheless, there are some important papers

00:57:05.700 | that have been published in recent years.

00:57:08.180 | I want to point to one of them in particular.

00:57:10.100 | This is a paper that was published

00:57:12.340 | in the journal Autonomic Neuroscience, Basic and Clinical,

00:57:15.940 | because this paper, like several other papers,

00:57:19.460 | ask the question, and indeed they ask the question

00:57:21.700 | in the title, it's a review, dietary sodium and health,

00:57:24.580 | how much is too much for those with orthostatic disorders?

00:57:28.620 | Now, orthostatic disorders come in a bunch

00:57:30.740 | of different varieties, and we're going to talk about those

00:57:32.580 | in a moment, but there are a number of people out there

00:57:35.240 | that have low blood pressure, right?

00:57:37.380 | People that get dizzy when they stand up,

00:57:39.960 | people that are feeling chronically fatigued,

00:57:42.780 | and in some cases, not all, those groups can actually benefit

00:57:46.500 | from increasing their sodium intake.

00:57:48.620 | Several episodes ago on the Huberman Lab Podcast,

00:57:51.220 | I gave it what, it's just clearly what we call anecdata,

00:57:55.020 | which is not even really data, it's just anecdotal data,

00:57:58.260 | of an individual who was always feeling hungry

00:58:02.220 | and craving sugar, and based on the fact

00:58:04.900 | that they also had low blood pressure,

00:58:07.480 | I had them talk to a physician and they got permission

00:58:10.080 | to try a little mini experiment on themselves,

00:58:12.980 | and so they did, and that mini experiment was,

00:58:15.020 | anytime they felt like they were craving sugar

00:58:17.640 | or they were feeling a little lightheaded and dizzy,

00:58:19.400 | rather than reaching for something with caloric intake,

00:58:22.120 | they took a little bit of sea salt,

00:58:23.440 | a little pinch of sea salt, and put it into some water

00:58:26.600 | and drank it, or in the case of this individual,

00:58:29.660 | they would actually take a little sea salt packet

00:58:31.260 | and they would actually just down a sea salt packet,

00:58:33.080 | and for them, that provided tremendous relief

00:58:35.720 | for their dizziness, but that, of course,

00:58:38.360 | was in the context of somewhat abnormally low blood pressure,

00:58:42.680 | so I don't think that they are alone in the fact

00:58:45.200 | that many people out there suffer

00:58:46.840 | from a low blood pressure condition, many people out there

00:58:50.980 | suffer from a high blood pressure condition,

00:58:52.720 | so know your blood pressure and understand

00:58:54.760 | that blood pressure in part is regulated

00:58:57.720 | by your sodium intake and your sodium balance, why?

00:59:01.420 | Well, because of the osmolarity of blood

00:59:03.840 | that we talked about before,

00:59:05.360 | where if you have a certain concentration of sodium,

00:59:09.840 | meaning sufficient sodium in your bloodstream,

00:59:12.140 | that will tend to draw water into the bloodstream

00:59:13.960 | and essentially the pipes that are your capillaries,

00:59:16.160 | arteries, and veins will be full,

00:59:18.600 | the blood pressure will get up to your head,

00:59:20.520 | whereas some people, their blood pressure is low

00:59:22.880 | because the osmolarity of their blood is low,

00:59:26.040 | and that can have a number of downstream consequences,

00:59:28.920 | I should also mention it can be the consequence itself

00:59:32.360 | of challenges or even deficits in kidney function,

00:59:37.120 | but all of these organs are working together,

00:59:39.320 | so the encouragement here is not necessarily

00:59:41.880 | to ingest more sodium, it's to know your blood pressure

00:59:44.200 | and to address whether or not an increase in sodium intake

00:59:47.840 | would actually benefit your blood pressure

00:59:50.080 | in a way that could relieve some of the dizziness

00:59:52.680 | and other symptoms of things like orthostatic disorders,

00:59:56.540 | but of course, to do that in a safe context

00:59:59.780 | and to never play games with your blood sugar

01:00:01.920 | or your blood osmolarity that could set your system

01:00:04.320 | down a cascade of negative events,

01:00:06.180 | let's look at what the current recommendations are

01:00:09.960 | for people that suffer from orthostatic disorders

01:00:12.960 | like orthostatic hypo, meaning too low tension,

01:00:15.960 | orthostatic hypotension, postural tachycardia syndrome,

01:00:19.240 | sometimes referred to as POTS, P-O-T-S,

01:00:23.220 | or idiopathic orthostatic tachycardia and SYNCOPE,

01:00:26.800 | these have the incredibly elaborate names,

01:00:29.040 | those groups are often told to increase their salt intake

01:00:33.200 | in order to combat their symptoms,

01:00:34.720 | the American Society of Hypertension recommends

01:00:37.560 | anywhere from 6,000 to 10,000, these are very high levels,

01:00:42.480 | so this is six grams to 10 grams of salt per day,

01:00:45.820 | keeping in mind, again, that salt is not the same as sodium,

01:00:50.820 | so that equates to about 2,400 to 4,000 milligrams

01:00:54.560 | of sodium per day, again, if you want to learn more

01:00:57.300 | about this and get more of the citations,

01:00:59.160 | I'll refer you back to this study on dietary sodium

01:01:02.140 | and health, how much is too much

01:01:03.320 | for those with orthostatic disorders,

01:01:04.640 | we will put a link to this in the caption show notes,

01:01:07.720 | so that's not just in the US, the salt recommendations

01:01:11.660 | from the Canadian Cardiovascular Society

01:01:13.660 | are 10,000 milligrams of salt per day,

01:01:15.980 | so four grams of sodium is what that equates to,

01:01:19.120 | and on and on and on for things like POTS

01:01:22.480 | for these postural syndromes that result from,

01:01:25.280 | or I should say from the syndromes

01:01:27.080 | that involve low blood pressure when people stand up

01:01:30.140 | or in certain postures, so I point out this paper

01:01:33.800 | and I point out these higher salt recommendations

01:01:36.800 | to emphasize, again, that context is vital, right?

01:01:40.800 | That people with high blood pressure are going to need

01:01:43.060 | certain amounts of salt intake,

01:01:44.860 | people with lower blood pressure,

01:01:47.280 | and maybe with some of these postural orthostatic syndromes

01:01:50.740 | are going to need higher amounts of salt,

01:01:53.100 | and for most people out there,

01:01:55.660 | you're going to need to evaluate how much salt intake

01:01:58.180 | is going to allow your brain and body to function optimally,

01:02:00.960 | and there are some fairly straightforward ways

01:02:03.640 | to explore that, and there's some ways to explore that

01:02:06.220 | in the context of what you already know

01:02:08.220 | about thirst and salt appetite that can make

01:02:11.260 | that exploration one in which it's not going

01:02:13.820 | to be a constant wandering around in the dark

01:02:16.000 | and where you can figure out what's right for you.

01:02:18.240 | For most people, a moderate increase in salt intake

01:02:21.520 | is not going to be detrimental provided

01:02:23.540 | that you consume enough fluids, in particular water, okay?

01:02:28.540 | Meaning if you happen to overeat salt a bit,

01:02:31.100 | you will get thirsty, you will ingest more water,

01:02:34.460 | and you will excrete the excess sodium.

01:02:37.900 | There is evidence that the body can store sodium

01:02:40.580 | in various organs.

01:02:42.540 | That storage of sodium may or may not be

01:02:45.700 | a detrimental thing.

01:02:47.260 | In general, excess storage of sodium in tissues

01:02:50.500 | and organs of the brain and body is not thought

01:02:52.820 | to be good for long-term health,

01:02:55.740 | so eating much more sodium than you need

01:02:58.980 | for long periods of time is indeed bad for you.

01:03:01.720 | Earlier, I mentioned that salt and your hunger

01:03:07.460 | and thirst for salt is homeostatically regulated,

01:03:11.000 | and indeed that's the case,

01:03:11.900 | much like temperature is homeostatically regulated.

01:03:14.980 | What that means is if you pay attention to it,

01:03:18.520 | if your salt levels are low, you will tend to crave salt

01:03:23.720 | and salty beverages and salty foods,

01:03:26.140 | and in most cases, you should probably follow that craving

01:03:30.700 | provided those salty beverages and salty foods

01:03:33.040 | are not bringing in a lot of other things

01:03:36.180 | or anything, ideally, that's bad for you.

01:03:38.860 | So I think it's fair to say that whether or not

01:03:41.540 | you're vegan, vegetarian, carnivore, omnivore,

01:03:44.580 | that we should all try to limit our ingestion

01:03:49.280 | of processed foods.

01:03:50.360 | My read of the literature is that, sure,

01:03:53.900 | some processed foods are acceptable for us

01:03:56.660 | and aren't going to kill us outright,

01:03:58.700 | but that for most people in the world,

01:04:00.820 | eating fewer processed foods is just going

01:04:02.900 | to be a good thing to do.

01:04:04.760 | So following your salt hunger and thirst, in most cases,

01:04:09.740 | is going to be beneficial provided that it's in the context

01:04:14.400 | of eating healthy non-processed foods

01:04:17.400 | on whatever backdrop of nutritional

01:04:19.360 | and dietary recommendations is right for you.

01:04:21.180 | I simply can't tell you what to eat and what not to eat

01:04:24.580 | because I acknowledge the fact that some people are vegans

01:04:29.620 | because of ethical reasons related to animals,

01:04:33.260 | or some people are vegans because of reasons related

01:04:37.340 | to the climate and the environment.

01:04:40.060 | Other people do it for specific health reasons.

01:04:43.740 | Likewise, I know plenty of people that eat meat

01:04:46.700 | and avoid vegetables, believe it or not,

01:04:48.360 | and I know people that eat both,

01:04:49.800 | and they do this often each, I should say,

01:04:52.980 | all citing literature that supports their particular camp

01:04:56.060 | and their particular view.

01:04:57.360 | It's not a territory I want to get into,

01:04:59.860 | but with respect to salt intake and the fact

01:05:02.080 | that salt intake is homeostatically regulated,

01:05:05.760 | it is the case that if you're craving salt,

01:05:09.080 | you probably need it.

01:05:10.780 | So for those of you that are sweating excessively,

01:05:13.060 | or even if you're in a very hot environment

01:05:16.360 | and you're not exercising and you're just losing,

01:05:19.420 | you're losing water and salt from your system,

01:05:22.080 | remember also that you can be in a very cold environment,

01:05:24.580 | very cold, dry environments often go together,

01:05:27.720 | and you can be losing a lot of fluids from your body

01:05:30.240 | and you will crave fluids and salt even though it's cold

01:05:32.860 | and you're not actually noticeably perspiring.

01:05:36.800 | So if you're exercising a lot,

01:05:38.440 | if you're in a particular cold, dry environment

01:05:40.800 | or a particular hot environment,

01:05:42.460 | you ought to be ingesting sufficient amounts

01:05:44.820 | of salt and fluid.

01:05:46.460 | A rule of thumb for exercise-based replenishment of fluid

01:05:50.960 | comes from what I, some episodes back,

01:05:53.980 | referred to as the Galpin equation.

01:05:56.660 | The Galpin equation, I named it after Andy Galpin,

01:06:00.400 | and I think that is the appropriate attribution there.

01:06:03.100 | Andy Galpin is an exercise physiologist

01:06:06.540 | at Cal State Fullerton, I believe,

01:06:09.500 | and he's going to be a podcast guest

01:06:11.800 | here on the Huberman Lab Podcast.

01:06:13.140 | He's an exceptional muscle physiologist.

01:06:15.040 | He also lives in the practical realm

01:06:16.980 | where he gives recommendations about exercise

01:06:20.780 | to expert athletes, as well as the everyday person.

01:06:24.280 | So the Galpin equation is based on the fact

01:06:26.420 | that we lose about one to five pounds of water per hour,

01:06:31.060 | which can definitely impact our mental capacity

01:06:34.060 | and our physical performance.

01:06:35.920 | And the reason that loss of water from our system

01:06:39.580 | impacts mental capacity and physical performance

01:06:41.780 | has a lot to do with literally the changes

01:06:45.180 | in the volume of those cells, the size of those cells,

01:06:47.880 | based on how much sodium is contained

01:06:49.420 | in or outside those cells,

01:06:50.820 | and something that I've alluded to before on the podcast,

01:06:53.620 | and I'll talk about more in a moment,

01:06:55.700 | which is that neurons signal to one another

01:06:59.080 | by way of electricity

01:07:00.640 | through something called the action potential,

01:07:02.140 | and that actually requires sodium and potassium

01:07:04.860 | and magnesium.

01:07:06.020 | So the Galpin equation suggests

01:07:07.540 | that we start exercise hydrated with electrolytes,

01:07:10.700 | not just with water.

01:07:12.260 | So that means water that has some sodium,

01:07:15.720 | potassium, and magnesium.

01:07:18.200 | There are simple low cost ways to do that, we'll talk about.

01:07:21.420 | And the formula for hydration,

01:07:23.900 | the so-called Galpin equation is your body weight in pounds

01:07:27.960 | divided by 30 equals the ounces of fluid

01:07:31.660 | you should drink every 15 minutes.

01:07:34.180 | That may turn out to be more fluid

01:07:36.300 | than you can comfortably consume

01:07:37.920 | during the activity that you're performing.

01:07:39.860 | Now, the Galpin equation is mainly designed for exercise,

01:07:44.860 | but I think is actually a very good rule of thumb

01:07:49.060 | for any time that you need to engage mental capacity,

01:07:52.260 | not just physical performance.

01:07:53.840 | Your body weight in pounds divided by 30

01:07:57.660 | equals the ounces of fluid you should drink every 15 minutes

01:08:00.920 | does not necessarily mean you have to ingest it

01:08:03.440 | every 15 minutes on the dot.

01:08:06.220 | And I think many activities, physical activities,

01:08:10.460 | but also cognitive activities like Zoom meetings

01:08:14.600 | or in-person meetings or lecturing or running or cycling

01:08:20.660 | are going to make it complicated

01:08:23.340 | to ingest the appropriate amount of fluid

01:08:25.660 | every 15 minutes on the dot.

01:08:27.860 | I'm not going to speak for Andy, for Dr. Galpin,

01:08:30.740 | but I think he would probably agree

01:08:32.740 | that these are averages to shoot for

01:08:35.940 | and that unless you're hyper neurotic,

01:08:38.660 | the idea is to make sure that you're entering the activity,

01:08:42.000 | cognitive or physical, sufficiently hydrated,

01:08:46.100 | and that throughout that activity,

01:08:47.660 | you're hydrating regularly.

01:08:48.820 | And it points to the fact that most people

01:08:50.880 | are probably under hydrating,

01:08:53.140 | but not just under hydrating from the perspective

01:08:56.100 | of not ingesting enough water,

01:08:58.020 | that they're probably not getting enough electrolytes

01:09:00.460 | as well, sodium, potassium, and magnesium.

01:09:03.420 | So I've said two somewhat contradictory things.

01:09:05.780 | On the one hand, I said, follow your salt appetite,

01:09:09.980 | follow your salt thirst.

01:09:11.020 | If you're craving salt,

01:09:12.860 | ingest some salt until you stop craving the salt.

01:09:16.260 | On the other hand, I've given you this

01:09:19.140 | fairly specific recommendation

01:09:21.500 | based on the Galpin equation that you should ingest

01:09:24.840 | your body weight in pounds divided by 30.

01:09:26.900 | That's how many ounces of fluid

01:09:28.040 | you should drink every 15 minutes,

01:09:29.660 | which I'm guessing for most people is going to be more fluid

01:09:32.020 | than they're currently drinking on average.

01:09:34.380 | And so how could it be that you can have a recommendation

01:09:37.020 | for what's optimal that's different

01:09:38.980 | than the amount that you would reflexively drink?

01:09:42.060 | And it has to do with the fact

01:09:43.420 | that a lot of the hormone systems like vasopressin,

01:09:46.860 | antidiuretic hormone, other hormones like aldosterone,

01:09:50.180 | and a lot of the neural and hormonal signals

01:09:53.520 | that govern salt and water balance

01:09:55.720 | are fairly slow to kick in.

01:09:58.020 | So for instance, if you eat a fairly salty meal

01:10:01.500 | and you sense that salt, you'll probably,

01:10:04.060 | meaning you detect it and perceive it,

01:10:05.900 | because the food tastes salty,

01:10:07.460 | you'll probably want to drink

01:10:09.060 | a fair amount of fluid with it.

01:10:10.520 | Whereas if some of the salt is disguised by other flavors,

01:10:13.680 | something that we'll talk about in a few minutes

01:10:15.060 | when we talk about the neural representation

01:10:17.280 | of things like salty and sweet,

01:10:20.200 | well, then you might not notice that something's salty,

01:10:22.640 | and then a few minutes or hours after ingesting that meal,

01:10:26.220 | you might feel very, very tired.

01:10:27.760 | You might even wonder whether or not

01:10:29.960 | it's because of some blood sugar effect.

01:10:32.520 | Maybe it's a crash in blood sugar, you might think,

01:10:35.000 | or something else related to that meal,

01:10:36.640 | or maybe you think it's because of

01:10:38.460 | some other event in your life,

01:10:39.820 | but actually what has happened is you're dehydrated

01:10:43.040 | because you didn't recognize

01:10:44.180 | that you needed to drink more fluids.

01:10:46.060 | So I want to acknowledge the contradiction

01:10:50.080 | in the idea that everything is homostatically regulated

01:10:52.760 | and therefore you are aware of what you need.

01:10:55.780 | And the counterargument that,

01:10:58.480 | ah, you need to follow these strict recommendations,

01:11:00.440 | it's actually going to be somewhere in between.

01:11:02.560 | And of course, your body and brain can start to adapt

01:11:04.560 | to certain levels of salt intake.

01:11:06.420 | There's a now fairly famous study that was done in Germany,

01:11:11.420 | which looked at different phases of salt intake,

01:11:16.800 | meaning they had subjects ingest

01:11:19.860 | either 12 grams of salt per day or nine grams per day

01:11:22.560 | or six grams per day for fairly long periods of time.

01:11:26.240 | And they collected urine for testing.

01:11:28.360 | This was actually a very controlled study.

01:11:30.180 | I'm just going to paraphrase

01:11:31.220 | from the National Institutes of Health report on this study

01:11:35.240 | because they did a very nice writeup of it.

01:11:37.960 | And they say that a big surprise of these results

01:11:41.380 | is that whatever the level of salt that was consumed,

01:11:44.420 | sodium was stored and released from the subjects bodies

01:11:48.620 | in fairly regular weekly and monthly patterns,

01:11:52.400 | meaning people tended to adapt

01:11:53.840 | to a certain level of salt intake.

01:11:55.820 | And then it led to a fairly constant amount

01:11:59.300 | of salt retention and urine fluid excretion.

01:12:03.360 | And that's because of the various hormones like aldosterone,

01:12:06.640 | which regulates sodium excretion from the kidney

01:12:08.680 | and glucocorticoids, which we'll talk about more in a moment

01:12:11.400 | which help regulate metabolism.

01:12:13.000 | Glucocorticoids are released from the adrenal glands,

01:12:16.000 | which ride the top of the kidneys.

01:12:17.800 | And there's a very close relationship

01:12:19.320 | between the stress system, glucocorticoids

01:12:22.080 | and the salt system.

01:12:23.640 | So the reason why your salt appetite

01:12:27.360 | isn't a perfect readout of how much salt you should ingest

01:12:30.680 | and why it might be helpful

01:12:31.760 | to follow some of these formulas like the Galpin equation,

01:12:34.220 | especially if you're engaging in exercise,

01:12:36.960 | where you're going to be perspiring, of course,

01:12:39.520 | is that your body will tend to adapt

01:12:41.860 | to a certain amount of salt intake over time.

01:12:43.640 | And then your appetite for salt

01:12:45.160 | won't necessarily be the best indication

01:12:47.520 | of how much salt you should ingest or avoid.

01:12:50.180 | Before I move on, I want to really reemphasize the fact

01:12:55.360 | that inside of the Galpin equation,

01:12:57.800 | there is that mention of every 15 minutes

01:13:00.280 | and people have come back to me again and again

01:13:02.580 | about this saying,

01:13:03.420 | "I can't drink that much water every 15 minutes.

01:13:05.320 | It's too much volume of fluid in my stomach.

01:13:08.160 | I can't run with that," et cetera.

01:13:09.400 | Remember, these are averages.

01:13:11.740 | So that's what you want to average

01:13:13.280 | around a particular activity.

01:13:14.620 | These are not strict recommendations

01:13:16.040 | where a buzzer goes off and every 15 minutes,

01:13:17.780 | you have to chug that exact amount

01:13:19.440 | of electrolyte containing solution.

01:13:21.280 | Another key feature of the study

01:13:23.520 | that I was referring to before,

01:13:26.000 | which incidentally was published

01:13:27.360 | in the Journal of Clinical Investigation,

01:13:29.360 | is that the body regulates its salt and water balance

01:13:32.820 | not just by excreting sodium,

01:13:35.560 | but by retaining or releasing water.

01:13:38.120 | And this is because of the relationship

01:13:39.480 | between sodium and water that we were talking about before.

01:13:42.200 | And the advantage of this mechanism,

01:13:44.160 | they state here I'm paraphrasing,

01:13:45.800 | is that the long-term maintenance of body fluids

01:13:48.240 | is not as dependent on external water as once believed.

01:13:53.200 | What the system probably evolved to do

01:13:55.520 | was to adjust to different levels of sodium availability

01:13:58.420 | in the environment.

01:13:59.640 | And that raises a really key element of salt

01:14:04.080 | and its importance in human history

01:14:06.280 | and human evolution and human health.

01:14:08.400 | We haven't talked too much about this,

01:14:09.600 | and there are several very good books

01:14:12.280 | about the history of salt.

01:14:13.540 | You know, salt was a very valuable

01:14:17.160 | and heavily sought-after substance

01:14:19.640 | throughout much of human history,

01:14:21.600 | so much so that there are actually written reports

01:14:24.840 | of people being paid for labor in the form of salt.

01:14:28.680 | And, you know, salt, when it's scarce,

01:14:32.280 | has been quite expensive in certain regions of the world,

01:14:34.940 | especially regions located further away from the sea.

01:14:38.420 | And a friend of mine who has deep roots

01:14:41.320 | within the culinary community told me about

01:14:44.280 | traveling to some somewhat impoverished areas

01:14:48.460 | of Europe some years ago and going into homes

01:14:52.440 | where in the middle of the kitchen table,

01:14:55.540 | there was a fish, a salty fish,

01:14:57.840 | hanging from a thread above the table.

01:15:01.960 | And that because of a lack of availability of table salt,

01:15:05.400 | the common practice was to take any food

01:15:07.800 | that needed some salt for additional flavoring

01:15:10.040 | and to actually rub that food on this salty fish

01:15:13.200 | or to squeeze the fish a bit onto the food substance

01:15:17.440 | in order to get salt from it.

01:15:19.200 | So, you know, that's a very kind of extreme example.

01:15:22.640 | Nowadays, we kind of take salt for granted

01:15:24.500 | and most of the discussion out there is about excess salt.

01:15:27.640 | But as I'm pointing out that, you know,

01:15:29.920 | salt for a long time has been a very sought-after commodity

01:15:34.440 | and one that people really cherished for their health.

01:15:37.080 | In the episode that I did on metabolism,

01:15:40.640 | I talked about the relationship between salt and iodine.

01:15:43.320 | If you're interested in iodine

01:15:45.000 | and whether or not iodized salt or non-iodized salt

01:15:47.400 | is best or required,

01:15:49.500 | I'd encourage you to listen to that episode,

01:15:51.280 | which was about, again, metabolism.

01:15:53.640 | Some people may need more iodine intake.

01:15:55.960 | Some people perhaps do not.

01:15:57.340 | Some people might even want to ingest things like kelp.

01:15:59.640 | Some people might not.

01:16:00.920 | So please listen to that episode

01:16:02.520 | if you're interested in the iodine aspects of salt,

01:16:05.020 | which have direct impact on thyroid hormone

01:16:07.840 | and thyroid function, which of course relates to metabolism.

01:16:10.840 | Nowadays, there's a lot of interest in

01:16:13.720 | and even a kind of proliferation of what I call fancy salts.

01:16:17.120 | So whether or not you should be ingesting sea salts

01:16:19.280 | or whether or not common table salt will suffice.

01:16:23.600 | In most cases, for what we're discussing here,

01:16:26.280 | common table salt is fine,

01:16:28.600 | but I should point out that sea salt

01:16:30.480 | often contains other minerals, which can be very useful,

01:16:33.280 | and we will do entire episodes on those other minerals.

01:16:35.720 | So sea salt can contain, you know,

01:16:38.840 | dozens or more of minerals,

01:16:40.640 | some of which can be quite valuable to our health,

01:16:43.680 | others of which are less important

01:16:45.960 | and only need to be consumed in trace amounts,

01:16:47.960 | but you're not going to get many minerals, if any,

01:16:50.760 | from common table salt,

01:16:52.320 | and that's why in addition to the pretty colors

01:16:55.240 | and perhaps some people report

01:16:57.000 | that they actually taste better,

01:16:59.060 | some of these so-called fancy salts or sea salts,

01:17:01.920 | you might want to consume a more advanced form of salt,

01:17:05.420 | if you will.

01:17:06.260 | Although I suppose it's actually

01:17:07.240 | the more primitive form of salt

01:17:08.580 | if it's actually the one that comes from the ocean.

01:17:10.580 | So we've all heard about how excess salt,

01:17:12.500 | it's bad for blood pressure,

01:17:14.160 | damage the heart, the brain, et cetera.

01:17:16.400 | I do want to give some voice to situations

01:17:19.620 | where too little salt can actually cause problems,

01:17:22.880 | and this has everything to do with the nervous system.

01:17:25.520 | So without getting into excessive amounts of detail,

01:17:28.640 | the kidneys, as we talked about before,

01:17:32.060 | are going to regulate salt and fluid balance.

01:17:34.760 | The adrenal glands, which ride atop the kidneys,

01:17:38.360 | are going to make glucocorticoids like aldosterone,

01:17:41.160 | and those are going to directly impact things like

01:17:44.840 | fluid balance, and in part, they do that by regulating

01:17:48.700 | how much craving for and tolerance of salty solutions

01:17:53.540 | we have, and there's some really nice studies

01:17:56.560 | that have looked at so-called adrenalectomies.

01:17:59.360 | Now, this is an extreme case,

01:18:00.800 | and it's typically done in animal models,

01:18:02.820 | but it illustrates the role of the adrenals

01:18:05.840 | in salt preference.

01:18:08.040 | Basically, when the glucocorticoid system,

01:18:11.660 | meaning the release of these particular hormones

01:18:14.080 | from the adrenal glands, is eliminated by adrenalectomy,

01:18:18.320 | ectomy means removal, then the threshold

01:18:21.460 | for what's considered too salty really shifts, okay?

01:18:24.800 | So typically, when the adrenals are intact,

01:18:29.200 | a animal or a human will prefer a mildly salty

01:18:34.180 | to moderately salty solution if given a choice,

01:18:37.880 | and then at some point, it's so salty

01:18:39.620 | that it just feels aversive.

01:18:40.980 | Just like taking a gulp of seawater

01:18:42.740 | is almost always aversive.

01:18:44.160 | I can't think of an instance where it's not aversive,

01:18:46.280 | and actually drinking seawater can kill you

01:18:47.920 | because of the high osmolarity of seawater.

01:18:51.000 | You certainly don't want to drink seawater.

01:18:53.720 | Under conditions where the adrenals are missing,

01:18:56.440 | animals and humans will tend to prefer

01:19:00.820 | a higher sodium concentration fluid,

01:19:04.060 | and they will be willing to tolerate ingesting

01:19:06.640 | very high concentrations of sodium.

01:19:08.880 | Now, that's a very crude experiment

01:19:10.640 | and not one that you want to do, I promise you,

01:19:13.900 | but I mention it because it illustrates

01:19:17.100 | the very direct relationship between the stress system,

01:19:20.760 | which is the glucocorticoid system,

01:19:22.740 | and the salt craving system, and this actually makes sense.

01:19:26.880 | Earlier, as we were talking about hypovolemic thirst,

01:19:29.000 | when there's a loss of blood pressure

01:19:31.200 | from usually due to a loss of blood from the body,

01:19:34.400 | there's a salt craving in order

01:19:35.900 | to bring that blood volume back up,

01:19:37.420 | because by ingesting salt,

01:19:38.900 | you bring fluid into the bloodstream,

01:19:41.000 | you're increasing that blood pressure,

01:19:42.480 | and you can restore the blood that's lost.

01:19:44.800 | Now, there are many examples where if sodium levels

01:19:47.900 | get too low in the bloodstream,

01:19:50.660 | either because people are ingesting too little salt,

01:19:54.020 | or they are ingesting too much water

01:19:56.360 | and therefore excreting too much salt,

01:19:59.020 | that it can cause stress and anxiety.

01:20:02.500 | There's some really nice data that point to the fact

01:20:04.460 | that low dietary sodium can actually exacerbate anxiety

01:20:09.220 | in animal models, and to some extent,

01:20:12.140 | there's evidence for this in humans as well,

01:20:14.580 | and that should not come as a surprise.

01:20:16.780 | The whole basis for a relationship

01:20:20.200 | between the adrenal system, these glucocorticoids,

01:20:22.660 | things like aldosterone, and the craving for sodium,

01:20:25.780 | is that the stress system is a generic system designed

01:20:30.340 | to deal with various challenges to the organism,

01:20:33.860 | to you, or to me, or to an animal,

01:20:36.320 | and those challenges can arrive in many different forms.

01:20:39.920 | It can be an infection, it can be famine,

01:20:43.260 | it can be lack of water, and so on,

01:20:45.500 | but in general, the stress response

01:20:48.900 | is one of elevated heart rate, elevated blood pressure,

01:20:52.020 | and an ability to maintain movement

01:20:54.260 | and resistance to that challenge, okay?

01:20:57.060 | I've said this before, but I'll emphasize it again,

01:21:00.140 | there's this common misperception that stress makes us sick,

01:21:03.140 | and indeed, if stress lasts too long,

01:21:05.220 | it has a number of negative effects on our health,

01:21:08.100 | but more often than not, if we're pushing, pushing, pushing,

01:21:12.340 | we're studying or taking care of somebody

01:21:14.060 | or traveling like crazy,

01:21:16.100 | we don't tend to get sick under those conditions,

01:21:18.620 | but as soon as we stop,

01:21:20.820 | as soon as we reduce our adrenaline output,

01:21:22.960 | as soon as we reduce our glucocorticoid output

01:21:25.700 | from our adrenals, then we will get sick.

01:21:28.080 | That's a very common occurrence,

01:21:29.620 | and it's because stress actually activates our immune system

01:21:33.300 | in the short term, so I'd like to try and dispel this myth

01:21:36.920 | that stress actually suppresses the immune system,

01:21:39.420 | at least not in the short term.

01:21:40.900 | For long-term stress, it's a different issue.

01:21:43.100 | You don't want long-term ongoing stress,

01:21:45.300 | especially if several weeks or more.

01:21:47.100 | Nonetheless, it makes sense that bringing sodium

01:21:52.640 | into the body would be at least one way

01:21:55.660 | that we would be wired to counteract

01:21:57.860 | or to resist stressors, right?

01:22:01.060 | Stressors being the things on the outside coming at us,

01:22:04.240 | so it could be stressful relationships,

01:22:05.820 | stressful job situation, again, infection, and so on.

01:22:09.540 | It's clear from a number of studies

01:22:12.860 | that if sodium levels are too low,

01:22:15.800 | that our ability to meet stress challenges is impaired.

01:22:19.560 | Now, that doesn't mean to place your sodium intake cosmically

01:22:22.900 | high, but it does point to the fact

01:22:25.420 | that if you're feeling anxious,

01:22:27.580 | perhaps from low blood pressure,

01:22:29.280 | which can also give symptoms of anxiety,

01:22:31.020 | as we talked about before,

01:22:32.300 | but even if it's independent of low blood pressure,

01:22:35.560 | that slightly increasing sodium intake,

01:22:38.540 | again, I would encourage people to do this

01:22:40.580 | not in the context of processed foods and drinks,

01:22:42.780 | but ideally in the form of maybe a little bit

01:22:44.840 | of sea salt and water or salting one's food

01:22:47.300 | a little bit more, that that can stabilize blood pressure

01:22:51.980 | and one's ability to lean into stressors and challenges.

01:22:55.420 | And I say this because I think that most people assume

01:22:58.380 | that adding salt is always bad,

01:23:00.980 | when in fact that's simply not the case.

01:23:03.560 | There are conditions such as

01:23:05.240 | when we are under stress challenge,

01:23:06.860 | when there is a natural craving for more sodium,

01:23:10.080 | and that natural craving for more sodium

01:23:12.260 | is hardwired into us as a way to meet that challenge.

01:23:16.100 | So it's hard for me to know whether or not

01:23:18.420 | people out there, especially the listeners of this podcast

01:23:20.740 | are getting too much, just enough or too little sodium.

01:23:24.820 | So I can't know that, I'm shouting into a tunnel here.

01:23:27.240 | You have to decide how much sodium you are ingesting.

01:23:30.300 | But I think that there's some, for most people,

01:23:34.080 | especially people who are not hypertensive, prehypertensive,

01:23:36.740 | there's some wiggle room to explore

01:23:38.880 | whether more intake of sodium could actually be beneficial

01:23:42.840 | for suppressing some of the anxiety responses

01:23:45.260 | that they might feel under conditions of stress.

01:23:47.260 | Again, more studies need to be done.

01:23:49.100 | Certainly more studies in humans need to be done,

01:23:51.880 | but the relationship between stress and sodium intake

01:23:54.620 | and the fact that additional sodium intake may be beneficial

01:23:58.620 | and indeed is naturally stimulated by stress

01:24:03.140 | shouldn't be necessarily looked at as a pathological event.

01:24:06.720 | I know when some people get stressed,

01:24:08.020 | they crave salty foods.

01:24:09.300 | That's actually a hardwired biological phenomenon

01:24:12.160 | that you see, not just in humans, but in animals,

01:24:14.580 | because this is a very primitive mechanism

01:24:16.980 | whereby your body is preparing

01:24:18.900 | to meet any additional challenges and stressors.

01:24:21.840 | Now, we can't have a discussion about sodium

01:24:23.700 | without having a discussion about the other electrolytes,

01:24:26.540 | magnesium and potassium.

01:24:28.020 | Magnesium is important enough

01:24:30.540 | and an extensive enough topic

01:24:32.160 | that we should probably do an entire episode

01:24:33.620 | just on magnesium.

01:24:34.860 | For purposes of today's discussion,

01:24:37.900 | I just will briefly touch on some of the forms of magnesium

01:24:41.760 | that we've discussed on the podcast before

01:24:43.780 | in different contexts.

01:24:45.640 | I want to emphasize that many people

01:24:47.500 | are probably getting enough magnesium in their diet

01:24:50.620 | that they don't need to supplement magnesium.

01:24:53.560 | Some people, however, opt to supplement magnesium

01:24:56.760 | in ways that can support them.

01:24:58.500 | And there are many different forms of magnesium.

01:25:00.580 | And just in very brief passing,

01:25:03.520 | I'll just say that there is some evidence

01:25:07.200 | that you can reduce muscle soreness from exercise

01:25:11.340 | by ingestion of magnesium malate, M-A-L-A-T-E.

01:25:15.740 | I've talked before about magnesium threnate,

01:25:20.020 | T-H-R-E-N-O-A-T-E, magnesium threnate,

01:25:24.260 | for sake of promoting the transition into sleep

01:25:27.100 | and for depth of sleep.

01:25:28.080 | And perhaps, again, highlighted perhaps,

01:25:30.620 | because right now it's mainly animal studies

01:25:32.980 | and ongoing human studies, but the data aren't all in,

01:25:35.740 | perhaps magnesium threnate can be used

01:25:38.740 | as a way to support cognitive function and longevity.

01:25:42.900 | That was discussed in the episode

01:25:44.140 | with Dr. Jack Feldman from UCLA.

01:25:46.160 | Typically, magnesium threnate is taken 30 to 60 minutes

01:25:51.120 | before bedtime in order to encourage sleep.

01:25:53.000 | You can go to our neural network newsletter

01:25:54.620 | and look for the one on sleep,

01:25:56.340 | and you can see the recommendations,

01:25:58.060 | or I should say the options for that,

01:26:00.940 | because again, you should always check with your physician.

01:26:03.140 | Those aren't strict across the board recommendations.

01:26:05.940 | And then there are other forms of magnesium,

01:26:07.560 | magnesium bisglycinate,

01:26:09.000 | which is somewhat of an alternative to threonate,

01:26:12.620 | not known to have cognitive enhancing effects,

01:26:14.540 | but seems at least on par with magnesium threnate

01:26:18.660 | in terms of promoting transition into in-depth of sleep

01:26:21.460 | and so on.

01:26:22.780 | There are other forms of magnesium, magnesium citrate,

01:26:25.580 | which has other functions.

01:26:27.500 | Actually, magnesium citrate is a fairly effective laxative,

01:26:32.420 | not known to promote sleep and things of that sort.

01:26:36.120 | So a lot of different forms of magnesium,

01:26:37.580 | and there's still other forms out there.

01:26:39.780 | Many people are not getting enough magnesium,

01:26:41.700 | many people are.

01:26:42.620 | Okay, so that's magnesium.

01:26:44.060 | Anytime we're talking about sodium balance,

01:26:47.520 | we have to take into consideration potassium,

01:26:49.880 | because the way that the kidney works

01:26:52.000 | and the way that sodium balance is regulated

01:26:53.820 | both in the body and the brain

01:26:55.260 | is that sodium and potassium

01:26:57.060 | are working in close concert with one another.

01:26:59.860 | There are a lot of different recommendations

01:27:01.380 | about ratios out there,

01:27:03.800 | and they range widely from two to one ratio

01:27:07.420 | of potassium to sodium.

01:27:09.780 | I've heard it in the other direction too.

01:27:11.860 | I've heard a two to one sodium to potassium.

01:27:15.180 | The recommendations vary.

01:27:16.500 | One of the sponsors of this podcast, for instance, Element,

01:27:19.460 | which I've talked about in this episode and before,

01:27:21.960 | the ratio there is a gram of sodium

01:27:23.820 | to 200 milligrams of potassium, 60 milligrams of magnesium.

01:27:27.500 | So there they've opted for a five to one ratio

01:27:32.380 | of sodium to potassium.

01:27:34.400 | And of course, many people opt

01:27:35.440 | to make their own hydration electrolyte formulas.

01:27:37.720 | They'll put sea salt into some water,

01:27:39.280 | maybe even ingest a potassium tablet.

01:27:41.400 | It all depends on the context.

01:27:43.120 | An important contextual element is your diet.

01:27:46.180 | So for instance, carbohydrates hold water in the body.

01:27:49.280 | So regardless of how much salt

01:27:50.620 | and how much fluid you're ingesting,

01:27:52.080 | if you're ingesting carbohydrate and you drink fluids,

01:27:55.420 | water, some of that fluid is going to be retained

01:27:58.260 | in the body.

01:27:59.100 | Now, for people that are following low carbohydrate diets,

01:28:02.260 | one of the most immediate effects of a low carbohydrate diet

01:28:05.540 | is that you're going to excrete more water.

01:28:07.400 | And so under those conditions,

01:28:09.080 | you're also going to lose not just water,

01:28:11.260 | but you'll probably also lose sodium and potassium.

01:28:13.740 | And so some people, many people in fact,

01:28:16.840 | find that when they are in a lower or low carbohydrate diet,

01:28:20.280 | then they need to make sure

01:28:21.320 | that they're getting enough sodium and enough potassium.

01:28:24.300 | And some people do that

01:28:25.180 | by taking 99 milligram potassium tablets

01:28:27.420 | every time they eat.

01:28:28.400 | Some people do that by ingesting more foods

01:28:31.620 | that contain potassium.

01:28:33.780 | And of course, some people who are on low carbohydrate diets

01:28:36.580 | do ingest vegetables or other forms of food

01:28:40.660 | that carry along with them potassium.

01:28:42.880 | So it's quite variable from person to person.

01:28:47.220 | I mean, you can imagine if carbohydrate holds water,

01:28:50.260 | water and salt balance and potassium go hand in hand

01:28:53.660 | and hand, that if you're on a low carbohydrate diet

01:28:56.500 | that you might need to adjust your salt intake and potassium.

01:28:58.980 | And conversely, that if you're on a carbohydrate rich diet

01:29:02.100 | or a moderate carbohydrate diet,

01:29:03.380 | then you may need to ingest less sodium and less potassium.

01:29:06.320 | And in fact, a certain amount of water

01:29:08.100 | is probably coming in through the foods you eat as well.

01:29:10.680 | So I don't say all this to confuse you.

01:29:12.660 | Again, I say this because it all depends on the context.

01:29:17.540 | I'll give yet another context

01:29:18.900 | that I think is fairly common nowadays,

01:29:21.420 | which is many people are following a pattern of eating

01:29:24.980 | that more or less resembles intermittent fasting

01:29:27.940 | or at least time restricted feeding.

01:29:29.420 | So they're eating between particular feeding windows.

01:29:32.420 | And then in the certain parts of the 24 hour cycle,

01:29:35.300 | not just sleep,

01:29:36.300 | but during certain parts of their waking cycle,

01:29:38.060 | they're also actively avoiding food.

01:29:40.440 | Banking on, I think either the possible,

01:29:44.060 | I want to say possible longevity promoting effects

01:29:47.240 | of intermittent fasting or, and or I should say,

01:29:50.960 | they are banking on the fact that for many people

01:29:53.620 | not eating is easier than portion control

01:29:56.100 | for certain parts of the day.

01:29:57.100 | And so they find it beneficial to limit calories overall

01:30:01.040 | to a given amount, depending on what their goals are,

01:30:03.880 | by not consuming food for certain periods of the day.

01:30:07.840 | But usually during those periods of the day,

01:30:09.340 | they're consuming fluids.

01:30:10.620 | And oftentimes those fluids include not just water,

01:30:12.740 | but caffeine and caffeine is a diuretic.

01:30:15.360 | It actually causes the excretion of fluids from the body

01:30:18.580 | in part because it causes the excretion of sodium.

01:30:22.040 | All of that to say that if you're somebody who,

01:30:25.440 | for instance, eats your first meal around noon

01:30:27.940 | or one or 2 p.m. and you're fasting

01:30:29.840 | for the early part of the day and you're drinking coffee

01:30:32.140 | or tea or ingesting a lot of water,

01:30:35.400 | you are going to be excreting sodium along with that water.

01:30:39.060 | And so many people, including myself, find that it's useful,

01:30:42.420 | especially when I'm drinking caffeine

01:30:45.100 | during that so-called fasting or non-food intake part

01:30:49.080 | of time restricted feeding,

01:30:51.240 | that I'm making sure to get enough salt

01:30:53.420 | either in the form of something like Element,

01:30:56.200 | an electrolyte drink,

01:30:57.160 | or putting some sea salt into some water,

01:30:59.360 | or certainly anytime one is ingesting caffeine,

01:31:03.680 | replacing some of the lost water

01:31:05.580 | by increasing one's water intake.

01:31:07.700 | There are some simple rules of thumb around this

01:31:10.520 | that I think can get most people into a place

01:31:13.300 | where they're more comfortable and functioning better,

01:31:15.900 | which is for every ounce of coffee or tea that you drink,

01:31:20.300 | I should say caffeinated coffee or tea that you drink,

01:31:22.720 | that you consume one and a half times as much water.

01:31:26.240 | So let's say you have an eight ounce coffee,

01:31:28.960 | try and drink about, you don't have to be exact,

01:31:30.760 | but try and drink about a 12 ounce glass of water.

01:31:33.560 | And you might want to put a tiny bit of sodium into that.

01:31:35.760 | By tiny bit, I just mean a tiny pinch of sodium.

01:31:37.960 | Because remember, even if we're talking about

01:31:40.360 | increasing the amount of sodium intake overall,

01:31:43.720 | the total amount of sodium contained in salt

01:31:47.000 | is sufficiently high that even just a quarter teaspoon

01:31:50.140 | is going to really start to move that number up

01:31:51.900 | towards that range that's still within the safe range.

01:31:54.620 | But you're going to, if you keep doing that all day long,

01:31:57.100 | you're very quickly going to get into that

01:31:58.460 | excessive salt intake range that is deleterious for health.

01:32:01.860 | So again, if you're consuming more caffeine,

01:32:03.500 | you're going to be excreting water and salt and potassium.

01:32:06.280 | And so you're going to have to find ways

01:32:07.580 | to bring water, salt, and potassium back in.

01:32:09.620 | Again, this has to be evaluated

01:32:11.520 | for each of your own individual situations.

01:32:14.100 | If you're exercising fasted,

01:32:17.060 | and you're doing that after drinking caffeine,

01:32:19.700 | then before, during, and certainly after exercise,

01:32:23.480 | you're going to want to replenish the fluids

01:32:25.220 | and electrolytes that you lost, including sodium.

01:32:28.300 | So you can imagine how this all starts

01:32:30.300 | to become pretty dizzying,

01:32:31.880 | and yet it doesn't have to be dizzying.

01:32:33.420 | We can provide some useful ranges

01:32:35.080 | that for most people will work.

01:32:37.260 | And so let's talk about what those ranges are.

01:32:39.020 | And I'm going to point you to a resource

01:32:40.660 | that explores what those ranges are

01:32:42.380 | in these various contexts of nutrition, exercise, and so on.

01:32:45.820 | The resource is a book that was authored by Dr. James D.

01:32:50.180 | Nicolantonio.

01:32:51.620 | He's not a medical doctor.

01:32:53.060 | He's a scientist that studies cardiovascular physiology,

01:32:58.060 | as well, I believe, as a doctor of pharmacy.

01:33:00.660 | And the title of the book is "The Salt Fix."

01:33:02.740 | "The Salt Fix" is an interesting read

01:33:04.220 | because it points to, first of all,

01:33:06.340 | the history of salt in society and as it relates to health.

01:33:11.340 | It actually emphasizes some of the major missteps,

01:33:14.740 | maybe even pretty drastic errors that have been made

01:33:17.980 | in terms of trying to interpret the role

01:33:20.320 | that salt has in various diseases

01:33:24.260 | and emphasizes some of the ways

01:33:26.940 | in which perhaps increasing salt

01:33:29.480 | can actually improve health outcomes.

01:33:31.700 | And I think it strikes a pretty nice balance

01:33:33.820 | between what's commonly known about salt

01:33:36.820 | and what I believe ought to be known about salt,

01:33:40.340 | or at least taken into consideration.

01:33:43.300 | The book does provide certain recommendations,

01:33:46.540 | and I actually reached out to the author.

01:33:48.620 | I've never met him in person or talked to him directly.

01:33:51.300 | And I asked him outright, I said,

01:33:54.980 | "How much salt do you recommend people take on average?"

01:33:59.240 | And he gave, of course, the appropriate caveats

01:34:02.980 | about pre-hypertension, hypertension, et cetera,

01:34:05.440 | but made a recommendation which I'll just share with you.

01:34:09.940 | And if you want to learn more

01:34:11.300 | about the support for this recommendation,

01:34:13.580 | you can check out his book.

01:34:14.860 | The recommendation he made was anywhere

01:34:17.120 | from eight to 12 grams of salt a day,

01:34:19.520 | which corresponds to 3.2 to 4.8 grams of sodium.

01:34:24.520 | So going back to the current recommendations

01:34:28.960 | that we talked about before, 2.3 grams of sodium per day,

01:34:32.220 | this is about 1 1/2 times to double the amount of sodium

01:34:37.220 | that's currently recommended in most circles.

01:34:40.900 | And then what this corresponds to

01:34:42.300 | is about 1 1/2 to two teaspoons of salt per day

01:34:46.260 | to arrive at that 3.2 to 4.8 grams of sodium.

01:34:49.080 | Again, this is the recommendation that was passed along

01:34:52.900 | for most people, most conditions,

01:34:54.940 | barring specific health issues.

01:34:58.740 | Now, what was also interesting is he pointed

01:35:00.260 | to a sodium to potassium ratio,

01:35:03.300 | which is four grams of potassium.

01:35:06.380 | And he also mentioned 400 milligrams of magnesium

01:35:08.900 | and pointed out, and I generally agree here

01:35:11.140 | that many people are deficient in magnesium.

01:35:14.040 | So again, that was a 3.2 to 4.8 grams of sodium,

01:35:18.880 | four grams of potassium.

01:35:21.020 | You might think, well, gosh,

01:35:21.980 | that's a 1 1/2 to two times the current recommendation,

01:35:24.840 | but we can go back to that study

01:35:27.620 | that was mentioned earlier in the episode,

01:35:29.380 | that 2011 study where I described this sort

01:35:32.780 | of J-shaped curve in which when you look

01:35:35.940 | at the occurrence of these negative health events,

01:35:39.340 | they were fairly low at low sodium intake,

01:35:42.460 | lower still at slightly higher sodium intake,

01:35:45.500 | much in line with the recommendations that are made

01:35:48.540 | or that Dr. D. Nicolantonio passed along to me.

01:35:52.980 | And then they increased quite,

01:35:54.660 | those health risks increased quite substantially

01:35:57.480 | as one moves out past six grams of sodium,

01:36:00.860 | seven grams of sodium per day.

01:36:02.100 | That's when things really do seem to get hazardous.

01:36:05.900 | And really it makes sense, I think,

01:36:08.580 | given the consensus around this

01:36:10.200 | to really avoid very high salt intake.

01:36:12.300 | So the salt fix describes the rationale

01:36:17.180 | behind those recommendations.

01:36:19.180 | The salt fix also describes in quite beautiful detail

01:36:23.380 | the relationship between salt intake, potassium intake,

01:36:27.500 | and the relationship to the sugar consumption system.

01:36:31.020 | I'd like to pick up on this idea of the relationship

01:36:33.220 | between salt and sugar,

01:36:35.940 | because I think that one key aspect

01:36:38.620 | of the way that salt can work and can benefit us

01:36:41.340 | or can harm us has to do with the way that sodium

01:36:44.860 | and sugar are regulated and actually perceived by the brain

01:36:49.100 | and how under conditions of certain levels of sodium intake,

01:36:52.600 | we might be inspired to seek more sugar

01:36:54.660 | or to crave sweets more or less.

01:36:56.820 | So up until now, we've been talking about salt

01:36:58.620 | as a substance and a way to regulate fluid balance

01:37:01.900 | and blood volume and so on.

01:37:04.220 | We haven't talked a lot about salt as a taste

01:37:06.300 | or the taste of things that are salty.

01:37:08.920 | And yet we know that we have salt receptors,

01:37:12.280 | meaning neurons that fire action potentials

01:37:16.320 | when salty substances are detected,

01:37:18.780 | much in the same way that we have sweet detectors

01:37:20.920 | and bitter detectors, and we have detectors of umami,

01:37:24.680 | the savory flavor on our tongue.

01:37:27.140 | And earlier at the beginning of the episode,

01:37:29.120 | I talked about the fact that we have sweet receptors,

01:37:33.020 | neurons that respond to the presence of sugar

01:37:35.440 | or even non-caloric sweet things in the gut,

01:37:38.820 | and that signals up to the brain through the vagus nerve,

01:37:42.120 | and those signals converge on pathways

01:37:44.020 | that relate to dopamine and so on.

01:37:45.920 | Well, we also have salt sensors at various locations

01:37:48.920 | throughout our digestive tract,

01:37:51.020 | although the sensation and the taste of salt

01:37:53.600 | actually exerts a very robust effect

01:37:56.640 | on certain areas of the brain

01:37:59.000 | that can either make us crave more or sate,

01:38:03.200 | meaning fulfill our desire for salt.

01:38:06.040 | And you can imagine why this would be important.

01:38:07.900 | Your brain actually has to register

01:38:09.240 | whether or not you're bringing in salt

01:38:11.680 | in order to know whether or not

01:38:13.360 | you are going to crave salt more or not.

01:38:16.520 | And beautiful work that's been done by the Zucker Lab,

01:38:19.560 | Z-U-K-E-R, Zucker Lab at Columbia University,

01:38:22.400 | as well as many other labs,

01:38:23.880 | have used imaging techniques and other techniques

01:38:26.200 | such as molecular biology

01:38:27.400 | to define these so-called parallel pathways.

01:38:29.400 | Parallel meaning pathways that represent sweet

01:38:32.960 | or the presence of sweet taste in the mouth and gut.

01:38:35.960 | Parallel pathways, meaning neural circuits

01:38:37.800 | that represent the presence of salty tastes

01:38:39.980 | in the mouth and gut and so on.

01:38:41.880 | And that those go into the brain,

01:38:44.440 | move up through brain stem centers

01:38:46.680 | and up to the neocortex,

01:38:48.200 | indeed where our seat of our conscious perception is,

01:38:50.600 | to give us a sense and a perception

01:38:53.400 | of the components of the foods

01:38:56.600 | that we happen to be ingesting

01:38:57.960 | and a sense and a perception of the fluids

01:39:00.740 | and the components of those fluids

01:39:02.060 | that we happen to be ingesting.

01:39:04.040 | Now, parallel pathways, as I'm describing them,

01:39:06.900 | are a fundamental feature of every sensory system,

01:39:10.700 | not just the taste system, but also the visual system.

01:39:13.360 | We have parallel pathways for perceiving dark objects

01:39:15.760 | versus light objects,

01:39:16.760 | for perceiving red versus green, et cetera.

01:39:19.840 | This is a fundamental feature of how we are built

01:39:22.580 | and how our nervous system works.

01:39:24.260 | And in the taste system, much like in these other systems,

01:39:28.680 | these pathways are indeed parallel,

01:39:31.320 | but they converge and they can influence one another.

01:39:34.480 | And I think the simplest way to put this

01:39:36.520 | is in the context first of the visual system,

01:39:38.520 | whereby your ability to detect the color red

01:39:42.280 | has everything to do with the fact

01:39:43.840 | that you have neurons in your eye

01:39:45.760 | that absorb long wavelengths of light that we call reds,

01:39:49.360 | red wavelengths of light,

01:39:50.560 | which are longer wavelengths than say blue light,

01:39:53.920 | just shorter wavelength.

01:39:55.200 | But it is really the comparison of the electrical activity

01:39:58.160 | of the neurons that absorb red light

01:40:00.320 | with the activity of the neurons that absorb green light,

01:40:03.460 | which actually gives you the perception of red.

01:40:05.720 | So that might seem a little counterintuitive,

01:40:07.940 | but indeed it's not.

01:40:09.260 | It's actually because something is red

01:40:12.700 | and has less greenness that we perceive it

01:40:15.680 | as more red than the green.

01:40:18.320 | And this is actually the way

01:40:19.600 | that your entire nervous system works,

01:40:21.640 | is that we aren't really good at evaluating absolute levels

01:40:25.280 | of anything in the context of perception.

01:40:27.040 | It's only by comparison.

01:40:29.440 | And actually there's a fun experiment that you can do.

01:40:31.480 | I think you could probably find it easily online.

01:40:33.680 | You could also do this experiment at home.

01:40:35.080 | You can stare at something that's red

01:40:37.040 | or green for that matter for a while.

01:40:40.140 | So you make an active decision to not blink

01:40:44.240 | and to stare at something that's red.

01:40:45.960 | And then you look away from that thing

01:40:47.900 | and you'll actually see a green after image

01:40:50.400 | of that red object.

01:40:51.800 | Conversely, if you look at something that's green for a while

01:40:54.240 | and you stare at it and you look away,

01:40:55.400 | you will see the red after image of that thing.

01:40:58.700 | Now the taste system doesn't have quite the same

01:41:01.540 | after taste type effect, but nonetheless,

01:41:05.500 | the pathways, the parallel pathways for salty

01:41:08.720 | and the parallel pathways for sweet and bitter and so on

01:41:12.240 | can actually interact.

01:41:13.480 | And this has important relevance

01:41:14.840 | in the context of food choices and sugar craving.

01:41:18.500 | One of the things that's commonplace nowadays

01:41:21.300 | is in many processed foods, there is a business, literally,

01:41:25.360 | a business of putting so-called hidden sugars.

01:41:28.260 | And these hidden sugars are not always

01:41:29.740 | in the form of caloric sugars.

01:41:31.100 | They're sometimes in the form of artificial sweeteners

01:41:33.660 | into various foods.

01:41:35.220 | And you might say, well, why would they put more sugar

01:41:38.300 | into a food and then disguise the sugary taste

01:41:41.140 | given that sweet tastes often compel people

01:41:43.420 | to eat more of these things?

01:41:44.940 | Well, it's a way actually of bypassing

01:41:47.740 | some of the homeostatic mechanisms for sweet.

01:41:50.980 | Even though we might think that the more sweet stuff we eat,

01:41:53.340 | the more sweet stuff we crave,

01:41:55.140 | in general, people have a threshold whereby they say,

01:41:57.340 | okay, I've had enough sugary stuff.

01:41:59.940 | You can actually experience this

01:42:01.620 | if you ever feel like something is really, really sweet.

01:42:04.340 | Take a little sip of water

01:42:06.420 | with a little bit of lemon juice in it or vinegar,

01:42:08.180 | and it will quickly quench that overly sweet sensation

01:42:11.940 | or perception.

01:42:12.780 | It will disappear almost immediately.

01:42:14.720 | There's actually a practice in fancy meals

01:42:17.220 | of cleansing the palate

01:42:19.140 | through the ingestion of different foods.

01:42:20.960 | And that's the same idea that you're cleansing the palate.

01:42:22.660 | You're actually neutralizing the previous taste

01:42:24.940 | so then they can bring yet another dish

01:42:26.940 | to overindulge you in decadence and so forth.

01:42:30.140 | So these sensory systems interact in this way.

01:42:32.680 | By putting sugars into foods

01:42:36.940 | and hiding the sugary taste of those foods,

01:42:40.100 | those foods, even if they contain artificial sweeteners,

01:42:43.620 | can activate the sorts of neurons

01:42:45.500 | that we talked about at the beginning of the episode,

01:42:47.140 | like the neuropod cells that will then signal to the brain

01:42:50.300 | to release more dopamine

01:42:51.340 | and make you crave more of that food.

01:42:52.940 | Whereas had you been able to perceive

01:42:55.420 | the true sweetness of that food,

01:42:57.720 | you might've consumed less,

01:42:59.100 | and indeed that's what happens.

01:43:00.380 | So these hidden sugars are kind of diabolical.

01:43:03.300 | Why am I talking about all of this

01:43:05.020 | in the context of an episode on salt?

01:43:07.820 | Well, as many of you have probably noticed,

01:43:10.500 | a lot of foods out there contain a salty-sweet combination,

01:43:15.420 | and it's that combination of salty and sweet,

01:43:18.300 | which can actually lead you to consume more

01:43:20.340 | of the salty-sweet food than you would have

01:43:24.780 | if it had just been sweet or it had just been salty.

01:43:28.260 | And that's because both sweet taste and salty taste

01:43:32.540 | have a homeostatic balance.

01:43:34.400 | So if you ingest something that's very, very salty,

01:43:36.540 | pretty soon your appetite for salty foods will be reduced.

01:43:39.360 | But if you mask some of that with sweet,

01:43:41.800 | well, because of the interactions

01:43:44.460 | of these parallel pathways,

01:43:45.920 | you somewhat shut down your perception

01:43:48.260 | of how much salt you're ingesting.

01:43:50.640 | Or conversely, by ingesting some salt with sweet foods,

01:43:53.900 | you mask some of the sweetness of the sweet foods

01:43:56.500 | that you're tasting,

01:43:57.340 | and you will continue to indulge in those foods.

01:43:58.940 | So salty-sweet interactions can be very diabolical.

01:44:03.060 | They can also be very tasty,

01:44:04.420 | but they can be very diabolical in terms of inspiring you

01:44:06.900 | to eat more of a particular food than you would otherwise

01:44:10.180 | if you were just following your homeostatic salt

01:44:13.340 | or your homeostatic sugar balance systems.

01:44:16.680 | And the beautiful imaging work that's been done

01:44:18.780 | by the Zucker Lab and other labs

01:44:20.420 | has actually been able to reveal

01:44:21.820 | how some of this might work by showing, for instance,

01:44:24.500 | that a certain ensemble,

01:44:26.720 | meaning a certain group of neurons,

01:44:28.300 | is activated by a sweet taste

01:44:30.580 | and a non-overlapping distinct set of neurons just nearby,

01:44:34.240 | sitting cheek to jowl with those other neurons,

01:44:37.100 | would be activated by salty tastes

01:44:39.300 | and yet others by bitter taste, et cetera.

01:44:41.180 | So there's a separate map of these different

01:44:43.380 | parallel pathways,

01:44:44.560 | but that when foods or fluids are ingested

01:44:47.780 | that are both salty and sweet,

01:44:50.020 | you get a yet entirely different

01:44:52.740 | ensemble of neurons activated.

01:44:54.740 | So your brain, whether or not it's for your visual system

01:44:58.540 | or your auditory system or your taste system,

01:45:00.580 | has a way of representing the pure form of taste,

01:45:03.420 | salty, sweet, bitter, et cetera,

01:45:05.040 | and has a way of representing their combinations.

01:45:07.780 | And food manufacturers have exploited this to large degree.

01:45:12.060 | I mention all of this because if you're somebody

01:45:14.140 | who's looking to explore either increasing

01:45:17.600 | or decreasing your sodium intake for health benefits,

01:45:21.020 | for performance benefits,

01:45:22.940 | in many ways, it is useful to do that

01:45:25.620 | in the context of a fairly pure,

01:45:28.140 | meaning unprocessed food intake background,

01:45:30.940 | whether or not that's keto, carnivore, omnivore,

01:45:33.860 | intermittent fasting, or what have you,

01:45:36.420 | it doesn't really matter.

01:45:37.540 | But the closer that foods are to their basic form and taste,

01:45:42.020 | meaning not combinations of large amounts of ingredients

01:45:46.300 | and certainly avoiding highly processed foods,

01:45:49.100 | the more quickly you're going to be able to hone in

01:45:51.700 | on your specific salt appetite and salt needs,

01:45:54.860 | which as I've pointed out numerous times

01:45:56.940 | throughout this episode are going to vary

01:45:58.220 | from person to person, depending on nutrition,

01:46:00.320 | depending on activity, depending on hormone status,

01:46:02.900 | or even portion of your menstrual cycle for that matter.

01:46:06.020 | So if you want to hone in

01:46:07.900 | on the appropriate amount of sodium for you,

01:46:09.800 | yes, blood pressure is going to be an important metric

01:46:12.740 | to pay attention to as you go along.

01:46:14.320 | And the parameters for healthy blood pressure ranges

01:46:16.720 | are readily available online.

01:46:18.220 | So I'll let you refer to those

01:46:19.940 | in order to determine those for yourself.

01:46:21.860 | But in determining whether or not

01:46:23.620 | increasing your salt intake might be beneficial for,

01:46:27.640 | for instance, for reducing anxiety a bit

01:46:29.500 | or for increasing blood pressure

01:46:31.160 | to offset some of these postural syndromes

01:46:33.560 | where you get dizzy, et cetera,

01:46:34.900 | for improving sports performance or cognitive performance,

01:46:37.800 | I can only recommend that you do this

01:46:41.460 | in a fairly clean context

01:46:43.580 | where you're not trying to do this

01:46:44.700 | by ingesting a bunch of salty foods

01:46:46.580 | or salty sweet foods, et cetera.

01:46:48.540 | And indeed many people find, and it's reviewed a bit,

01:46:51.380 | and some of the data are reviewed in the book,

01:46:53.600 | The Salt Fix, that when people increase their salt intake

01:46:57.820 | in a backdrop of relatively unprocessed foods,

01:47:01.580 | that sugar cravings can indeed be vastly reduced.

01:47:04.420 | And that makes sense given the way

01:47:06.160 | that these neural pathways for salty and sweet interact.

01:47:09.000 | Now, thus far, I've already covered quite a lot of material,

01:47:12.900 | but I would be completely remiss

01:47:15.380 | if I didn't emphasize the crucial role

01:47:17.980 | that sodium plays in the way that neurons function.

01:47:21.660 | In fact, sodium is one of the key elements

01:47:24.580 | that allows neurons to function at all.

01:47:27.300 | And that's by way of engaging

01:47:28.620 | what we call the action potential.

01:47:30.620 | The action potential is the firing of electrical activity

01:47:35.600 | by neurons.

01:47:37.320 | Neurons can engage electrical activity

01:47:39.740 | in a number of different ways.

01:47:40.880 | They have graded potentials, they have gap junctions.

01:47:44.180 | There's a whole landscape

01:47:45.740 | of different electrophysiologies of neurons

01:47:48.980 | that I don't want to go into just yet,

01:47:51.600 | at least not in this episode.

01:47:53.300 | But the action potential is the fundamental way

01:47:55.940 | in which neurons communicate with one another.

01:47:58.620 | They're sometimes called spikes.

01:48:00.700 | It's just kind of nomenclature that neuroscientists use.

01:48:04.260 | I'm just going to briefly describe the action potential

01:48:06.420 | and the role that sodium plays.

01:48:08.340 | And this will involve a little bit of chemistry,

01:48:10.800 | but I promise it will be accessible to anyone,

01:48:13.120 | even if you don't have a chemistry or a physics background

01:48:15.360 | or electrophysiology background.

01:48:16.960 | Neurons have an inside and an outside,

01:48:20.820 | and inside are things like your genetic material.

01:48:25.620 | They have a bunch of things floating around in there

01:48:27.800 | that allow those cells to function,

01:48:29.740 | and they tend to have this wire extending out of them,

01:48:32.780 | sometimes a very long wire,

01:48:33.920 | sometimes a short one that we call the axon.

01:48:36.100 | And at the end of that wire, that axon,

01:48:39.200 | they release little packets of chemicals

01:48:42.460 | that either cause the next neuron to fire action potentials

01:48:47.120 | or prevent the next neuron from firing action potential.

01:48:49.900 | So they kind of vomit out these little packets of chemicals

01:48:53.860 | that either inspire or suppress action potentials

01:48:57.760 | in other neurons.

01:48:58.780 | The way that that whole process occurs

01:49:03.780 | is that a given neuron needs to change

01:49:07.480 | its electrical activity.

01:49:08.540 | So normally neurons are hanging out

01:49:11.980 | and they have what we call a negative charge.

01:49:13.860 | And the reason they have a negative charge

01:49:16.300 | is that the inside of the cell

01:49:18.220 | has things floating around in it,

01:49:19.620 | like potassium, a little bit of sodium,

01:49:22.420 | and some stuff like chloride.

01:49:23.900 | These are literally just,

01:49:25.060 | just imagine these as little balls of stuff.

01:49:28.460 | And if they have a negative charge on them,

01:49:31.520 | then the inside of the cell

01:49:32.600 | is going to tend to be more negative.

01:49:34.040 | And outside of the cell, it turns out,

01:49:36.120 | you're going to have a bunch of stuff

01:49:38.600 | that's positively charged.

01:49:40.680 | And one of the main factors

01:49:42.700 | in creating that positive charge is sodium.

01:49:44.940 | Sodium carries a positive charge.

01:49:47.080 | So you have neurons that you can just imagine,

01:49:50.440 | for sake of this discussion,

01:49:52.160 | you can just imagine as a sphere

01:49:53.620 | with a little wire sticking out of it,

01:49:55.660 | they, you can put a little minus on the inside for negative.

01:49:58.700 | You can put a little plus on the outside for positive.

01:50:01.260 | And when that neuron is stimulated by another neuron,

01:50:05.980 | if the stimulation,

01:50:07.100 | the electrical stimulation is sufficiently high,

01:50:09.900 | meaning enough little packets of neurotransmitter

01:50:14.620 | have been vomited onto its surface

01:50:17.220 | at sufficient concentration,

01:50:19.220 | what happens is little pores, little spaces,

01:50:24.000 | little gaps open up in the membrane of that cell

01:50:28.700 | that separates the inside from the outside.

01:50:31.800 | And because it's positive,

01:50:34.100 | there's a lot of positive charge outside,

01:50:35.900 | and there's a lot of negative inside,

01:50:38.320 | it's like a boulder running downhill.

01:50:40.460 | All this stuff tends to rush downhill.

01:50:42.540 | It tries to create even amounts of charge.

01:50:44.700 | So it's negative on the inside, positive on the outside.

01:50:47.180 | And what happens is sodium rushes into the cell,

01:50:51.420 | carrying a lot of charge into the cell.

01:50:53.540 | And as a consequence,

01:50:55.040 | the charge of that cell goes from negative,

01:50:57.540 | actually very negative, to quite positive.

01:51:00.280 | And if it hits a certain threshold of positive charge

01:51:03.820 | because of all the sodium ions going into the cell,

01:51:07.380 | then it fires what's called an action potential.

01:51:10.300 | And it vomits out its own set of chemicals

01:51:13.540 | onto the next neuron.

01:51:14.420 | And so it sets off a chain of,

01:51:16.360 | one neuron goes from negative to positive,

01:51:18.960 | vomits out chemicals onto the next one.

01:51:20.600 | The next one, the next neuron that binds to receptors

01:51:24.420 | or enters the cell,

01:51:26.200 | and that cell goes from negative to positive charge,

01:51:30.020 | vomits its contents onto the next cell,

01:51:32.140 | and so on and so forth.

01:51:33.480 | Sodium rushing into the cell, therefore,

01:51:37.840 | is the way that the action potential is stimulated.

01:51:41.240 | In other words, sodium is the way

01:51:44.280 | that neurons communicate with one another.

01:51:46.740 | Now, the neurons don't stay in a positive charge,

01:51:50.020 | otherwise they would just keep vomiting out their contents.

01:51:52.500 | [imitates vomiting]

01:51:53.680 | But they need to maintain some of that,

01:51:55.060 | and they need to go back to preparing to do it

01:51:56.940 | the next time and the next time by resting a bit.

01:51:59.340 | And it turns out that the way they restore their charge

01:52:02.020 | is by pushing that sodium back out of the cell.

01:52:06.580 | There are mechanisms in place to do that,

01:52:08.280 | things like the so-called sodium-potassium pump.

01:52:11.220 | There's a change in the levels of potassium

01:52:14.520 | across the cell membrane and so on and so forth.

01:52:16.600 | If you want to look at a demonstration of this,

01:52:18.000 | you can put into a web browser the action potential.

01:52:22.840 | You'll find some beautiful descriptions there

01:52:24.560 | on YouTube and elsewhere.

01:52:26.560 | Maybe some time on Instagram,

01:52:28.320 | I'll do a description with a diagram,

01:52:30.280 | 'cause I realize a number of people

01:52:31.660 | are just listening to this.

01:52:33.000 | I can't do that here, I won't do that here,

01:52:35.480 | 'cause I want everyone to be able

01:52:36.520 | to get the same amount of material

01:52:37.840 | regardless of whether or not they're watching

01:52:39.200 | and/or listening to this.

01:52:40.860 | But the point I'd like to make,

01:52:43.680 | at least as it relates to this episode on salt,

01:52:45.760 | is that having sufficient levels of salt in your system

01:52:49.840 | allows your brain to function,

01:52:51.260 | allows your nervous system to function at all.

01:52:53.360 | Again, this is the most basic aspect

01:52:55.400 | of nervous system function.

01:52:57.080 | And there are cases where this whole system gets disrupted.

01:53:02.080 | And that brings us to the topic of sodium and water balance.

01:53:06.040 | As many of you have probably heard,

01:53:08.440 | but hopefully if you haven't,

01:53:10.700 | you'll take this message seriously.

01:53:13.060 | If you drink too much water,

01:53:15.780 | especially in a short amount of time,

01:53:17.740 | you can actually kill yourself, right?

01:53:20.360 | And we certainly don't want that to happen.

01:53:22.700 | If you ingest a lot of water

01:53:25.740 | in a very short period of time,

01:53:27.320 | something called the hypernatremia,

01:53:29.060 | you will excrete a lot of sodium very quickly,

01:53:32.740 | and your ability to regulate kidney function

01:53:35.040 | will be disrupted.

01:53:36.140 | But in addition to that,

01:53:37.620 | your brain can actually stop functioning.

01:53:39.600 | So people have actually consumed water to excess,

01:53:43.520 | especially after sports events and so forth.

01:53:45.820 | And if that water doesn't contain sufficient electrolytes,

01:53:49.220 | you can actually shut down neurons' ability

01:53:51.380 | to function at all by disrupting

01:53:54.020 | this balance of sodium and potassium

01:53:56.460 | and the amount of extracellular sodium

01:53:58.380 | and neurons' ability to signal to one another

01:54:01.820 | through action potentials.

01:54:03.300 | And I can't emphasize the importance

01:54:04.800 | of action potentials enough.

01:54:06.060 | They are the way that I can lift my pen.

01:54:07.780 | Right now, they're the way that I can speak.

01:54:09.180 | They're the way that you breathe.

01:54:10.740 | They literally control all aspects

01:54:12.620 | of your nervous system function.

01:54:14.380 | Now, it takes quite a lot of water intake

01:54:16.100 | before you excrete enough sodium

01:54:18.020 | that your nervous system is going to shut down.

01:54:20.060 | And I certainly don't want to give the impression

01:54:21.640 | that simply by ingesting more sodium,

01:54:23.260 | your neurons will work better.

01:54:24.900 | But it absolutely is the case

01:54:26.300 | that if you don't ingest enough sodium,

01:54:28.780 | that your neurons won't function as well as they could,

01:54:31.500 | and that if your sodium levels are made too low

01:54:35.580 | by hemorrhage or by ingesting so much water, fluid,

01:54:40.580 | that you excrete excess amounts of sodium

01:54:44.300 | or through any other mechanism, that is,

01:54:46.860 | then indeed your neurons won't be able

01:54:48.800 | to fire action potentials,

01:54:49.860 | and your brain and nervous system simply won't work.

01:54:52.300 | And that's one of the primary reasons

01:54:53.720 | why dehydration leads to confusion and dizziness

01:54:57.020 | and lack of coordination.

01:54:58.820 | And I've talked about this a bit

01:55:00.460 | in the episode on endurance,

01:55:01.940 | but there are instances in which competitive athletes

01:55:05.760 | have come into the stadium to finish a final lap

01:55:08.020 | of a long endurance race and are completely disoriented

01:55:10.840 | and actually can't find their way to the finish line.

01:55:12.860 | It might sound like kind of a silly, kind of crazy example,

01:55:15.460 | but there are examples of people having severe mental issues

01:55:20.440 | and physical issues post-exercise

01:55:22.940 | when that exercise involved a ton of sweating

01:55:25.180 | or hot environments or insufficient ingestion of fluids

01:55:28.220 | and electrolytes,

01:55:29.380 | because included in the electrolyte formula, of course,

01:55:31.900 | is sodium.

01:55:32.740 | And as you just learned,

01:55:33.700 | sodium is absolutely crucial for neurons to function.

01:55:36.940 | So to briefly recap some of what I've talked about today,

01:55:40.740 | we talked about how the brain monitors the amount of salt

01:55:43.780 | in your brain and body and how that relates to thirst

01:55:47.180 | and the drive to consume more fluid and/or salty fluids.

01:55:51.740 | We also talked a little bit about the hormones

01:55:53.880 | that come from the brain and operate

01:55:55.080 | at the level of the kidney in order to either retain

01:55:58.940 | or allow water to leave your system.

01:56:02.700 | We talked a little bit about the function

01:56:04.040 | of the kidney itself, a beautiful organ.

01:56:06.860 | We talked about the relationship between salt intake

01:56:11.080 | and various health parameters

01:56:12.900 | and how a particular range of salt intake might be optimal

01:56:17.900 | depending on the context

01:56:20.820 | in which that range is being consumed,

01:56:22.360 | meaning depending on whether or not you're hypertensive,

01:56:25.500 | pre-hypertensive, or normal tension.

01:56:27.880 | We talked about fluid intake and electrolyte intake,

01:56:30.300 | so sodium, potassium, and magnesium

01:56:32.000 | in the context of athletic or sports performance,

01:56:35.280 | but also in terms of maintaining cognitive function.

01:56:37.560 | Talked about the Galpin equation,

01:56:39.160 | which you could easily adapt to your body weight

01:56:41.940 | and to your circumstances.

01:56:43.900 | Of course, adjusting the amount of fluid

01:56:46.840 | and electrolyte intake upwards if you're exercising

01:56:51.040 | or working in very hot environments,

01:56:53.020 | downwards maybe if you're in less hot environments

01:56:56.100 | where you're sweating less and so on.

01:56:57.840 | We also talked about the relationship

01:56:59.260 | between the stress system and the salt craving system

01:57:02.860 | and why those two systems interact

01:57:05.380 | and why for some people who may suffer a bit from anxiety

01:57:10.300 | or under conditions of stress,

01:57:12.260 | increasing salt intake provided it's done

01:57:14.340 | through healthy means might actually be beneficial.

01:57:18.020 | We also talked about conditions

01:57:19.260 | in which increasing salt intake might be beneficial

01:57:22.380 | for offsetting low blood pressure

01:57:24.940 | and some of these postural syndromes

01:57:26.620 | that can lead people to dizziness and so forth.

01:57:29.080 | These are things that have to be explored

01:57:30.580 | on an individual basis and of course have to be explored

01:57:34.000 | with the support of your doctor.

01:57:35.900 | I mentioned the salt fix,

01:57:37.440 | which I think is an interesting read.

01:57:39.280 | Keeping in mind that a lot of the information in there

01:57:41.420 | runs counter to the typical narrative

01:57:43.600 | that you hear around salt,

01:57:45.040 | but nonetheless has some very interesting points

01:57:47.260 | that you might want to consider

01:57:48.880 | and certainly will broaden your view of the history of

01:57:52.560 | and the applications of salt

01:57:54.200 | as it relates to a great number of health

01:57:57.000 | and performance metrics.

01:57:58.400 | We also talked about the perception of salt,

01:58:00.760 | meaning the perception of salty tastes

01:58:02.780 | and how the perception of salty tastes

01:58:04.360 | and the perception of other tastes like sweet

01:58:06.580 | can interact with one another

01:58:08.220 | to drive things like increased sugar intake

01:58:11.140 | when you're not even aware of it.

01:58:12.720 | And indeed how the combination of salty and sweet tastes

01:58:16.500 | can bias you towards craving more, for instance,

01:58:19.760 | processed foods and why that might be a good thing to avoid.

01:58:22.780 | And of course we talked about salt

01:58:24.640 | and its critical role in the action potential,

01:58:27.220 | the fundamental way in which the nervous system

01:58:29.140 | functions at all.

01:58:30.460 | So my hope for you in listening to this episode

01:58:33.040 | is that you consider a question

01:58:35.280 | and that question is what salt intake is best for you

01:58:39.520 | and that you place that question

01:58:41.060 | in the context of your fluid intake,

01:58:44.120 | you place that in the context of the diet you're following,

01:58:47.160 | the amount of caffeine you might be ingesting

01:58:50.360 | and the diuretic effects of caffeine

01:58:52.520 | and crucially that you place that

01:58:54.780 | in the context of the electrolytes more generally,

01:58:58.120 | meaning sodium, potassium, and magnesium.

01:59:01.320 | Someday there will be an online program or an app I imagine

01:59:05.220 | where one could put a bunch of different parameters in

01:59:08.880 | about their particular health status,

01:59:12.560 | their particular diet, their particular exercise, et cetera.

01:59:15.440 | Maybe it would all be run by AI algorithm or something

01:59:18.300 | where it would monitor all of that for us.

01:59:20.040 | And then it would spit out for us a precise amount of sodium

01:59:23.940 | that we should take in each day.

01:59:25.760 | Unfortunately, no such tool or device exists right now.

01:59:29.360 | And so all of us have to figure out

01:59:32.000 | the appropriate amount of sodium intake for ourselves.

01:59:34.920 | And that has to be done

01:59:36.360 | under these contextual considerations.

01:59:39.240 | Who knows, maybe one of you will design such an app

01:59:41.540 | or such a device.

01:59:42.640 | I think it would be very useful.

01:59:44.240 | If nothing else,

01:59:46.900 | today's discussion ought to illuminate the fact

01:59:49.680 | that some strict recommendation of salt intake

01:59:53.880 | cannot be made universally across the board for everybody.

01:59:56.760 | There's just simply no way that could be done.

01:59:59.360 | And yet I think most of what we've learned about salt

02:00:03.240 | in the general discussions around health

02:00:05.680 | are that it's this evil substance.

02:00:07.940 | Nothing could be further from the truth.

02:00:09.340 | It's an incredible substance.

02:00:10.980 | Our physiology is dependent on it.

02:00:13.480 | Our cognition is dependent on it.

02:00:16.200 | Indeed, our mental and physical health and our performance

02:00:18.920 | in essentially all aspects of life is dependent on it.

02:00:21.960 | And I hope I've been able to illuminate

02:00:24.180 | some of the beautiful ways in which the brain

02:00:26.040 | and the bodily organs interact

02:00:27.880 | in order to help us regulate this thing

02:00:29.640 | that we call sodium balance.

02:00:31.080 | And the fact that we have neurons in our brain

02:00:33.180 | that are both tuned to the levels of salt in our body

02:00:37.520 | and positioned in a location in the brain

02:00:40.120 | that allows them to detect the levels of salt in our body

02:00:42.920 | and to drive the intake of more or less salt

02:00:46.120 | and more or less fluid and other electrolytes

02:00:48.880 | really just points to the beauty of the system

02:00:51.460 | that we've all evolved

02:00:52.760 | that allows us to interact with our environment

02:00:54.700 | and make adjustments according to the context

02:00:57.140 | of our daily and ongoing life.

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02:03:35.540 | Thank you once again for joining me today

02:03:37.440 | to discuss the neuroscience and the physiology

02:03:40.660 | around salt and its many incredible influences

02:03:43.640 | on our brain and body.

02:03:45.140 | And last, but certainly not least,

02:03:47.520 | thank you for your interest in science.

02:03:49.380 | [upbeat music]

02:03:51.960 | [MUSIC PLAYING]

Using Salt to Optimize Mental & Physical Performance | Huberman Lab Podcast #63

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