back to indexUsing Salt to Optimize Mental & Physical Performance | Huberman Lab Podcast #63
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Welcome to the Huberman Lab Podcast,
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where we discuss science and science-based tools
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for everyday life.
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I'm Andrew Huberman,
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and I'm a professor of neurobiology and ophthalmology
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at Stanford School of Medicine.
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Today, we are going to discuss salt,
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also referred to as sodium.
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Now, most of us think of salt
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as something that we put on and in our food,
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maybe something to avoid,
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maybe some of you are actually trying to get more salt,
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some of you are trying to get less salt.
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We all seem to associate salt
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with things like blood pressure, et cetera.
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Today, we're going to go down
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a different set of avenues related to salt.
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We will certainly cover how salt regulates blood pressure.
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We are also going to talk about
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how the brain regulates our appetite for salt
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or our aversion for salt.
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We are also going to talk about
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how our sensing of salty tastes
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actually mediates how much sugar we crave
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and whether or not we ingest more or less sugar
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than we actually need.
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So what you're going to learn today
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is that the so-called salt system,
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meaning the cells and connections in our brain and body
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that mediate salt craving and avoidance
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are regulating many, many aspects of our health
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and our ability to perform in various contexts,
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things like athletic performance,
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things like cognitive performance.
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We're also going to talk about aging and dementia
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and avoiding aging and dementia
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and what role salt and salt avoidance might play in that.
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We're going to touch on some themes
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that for some of you might seem controversial
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and indeed, if they are controversial,
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I'll be sure to highlight them as such.
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I'm going to cover a lot of new data
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that point to the possibility,
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I want to emphasize the possibility that for some people,
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more salt might help them in terms of health,
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cognitive and bodily functioning.
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And for other people, less salt is going to be better.
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I'm going to talk about what the various parameters are.
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I'm going to give you some guidelines
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that in concert with your physician
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who you should absolutely talk to
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before adding or changing anything
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to your diet or supplementation regime
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can help you arrive at a salt intake
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that's going to optimize your mental,
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physical health and performance.
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So we're going to cover neurobiology,
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we're going to cover hormone biology,
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we're going to talk about liver function,
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we're going to talk about kidney function
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and of course, brain function.
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I'm excited to share this information with you today.
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I'm certain you're going to come away
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with a lot of information and actionable items.
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I'm pleased to announce
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that I'm hosting two live events this May.
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The first live event will take place
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in Seattle, Washington on May 17th.
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The second live event will take place in Portland, Oregon
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Presale tickets for these two events
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are now available at hubermanlab.com slash tour.
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I should mention that while I do hope to visit other cities
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in the near future to do more live events,
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right now, these are the only two live events
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I have scheduled, at least for the next six months.
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So once again, if you go to hubermanlab.com slash tour,
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you can access the presale tickets.
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I hope to see you at these live events
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and as always, thank you for your interest in science.
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Before we dive into the topic of today's episode,
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I want to highlight a really exciting new study.
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This is a study from Diego Bohor's lab at Duke University.
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The Bohor's lab studies interactions
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between the gut and the brain
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and has made some incredible discoveries
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of the so-called neuropod cells.
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Neuropod cells are neurons, nerve cells
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that reside in our gut and that detect things
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like fatty acids, amino acids,
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and some neuropod cells sense sugar.
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Previous work from this laboratory has shown
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that when we ingest sugar,
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these neuropod cells respond to that sugar
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and send electrical signals up a little wire
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that we call an axon through the vagus nerve,
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for those of you that want to know, and into the brain
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and through subsequent stations of neural processing,
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evoke the release of dopamine.
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Dopamine is a molecule known to promote craving
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and motivation and indeed action.
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And what these neuropod cells that send sugar
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are thought to do is to promote seeking
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and consumption eating of more sugary foods.
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Now, the incredible thing is that it's all subconscious.
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This is a taste system in the gut
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that is not available to your conscious awareness.
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Now, of course, when you ingest sweet foods,
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you taste them on your mouth too.
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And so part of the reason that you crave sweet foods perhaps
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is because they taste good to you.
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And the other reason is that these neuropod cells
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are driving a chemical craving
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below your conscious detection.
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So they're really two systems.
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Your gut is sensing at a subconscious level, what's in it
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and sending signals to your brain that work in concert
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in parallel with the signals coming from your mouth
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and your experience of the taste of the food.
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Now, that alone is incredible
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and has been the subject of many important landmark papers
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over the last decade or so.
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You can imagine how the system would be very important
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for things like hidden sugars,
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when nowadays in a lot of processed foods,
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they're putting hidden sugars,
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they're putting a lot of things that cause your gut
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to send signals to your brain
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that make you crave more of those foods.
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So for those of you that really love sugar,
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just understand it's not just about how that sugar tastes.
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The new study from the Borjas lab
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deserves attention, I believe.
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This is a paper published just recently,
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February 25th, this year, 2022 in Nature Neuroscience,
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an excellent journal.
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And the title of the paper is the preference
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for sugar over sweetener depends on a gut sensor cell.
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The Borjas lab has now discovered a neuropod cell,
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meaning a category of neurons,
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that can distinguish between sweet things in the gut
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that contain calories, for instance, sugar,
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and things in the gut that are sweet
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but do not contain calories, artificial sweeteners
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like aspartame, sucralose, and so forth.
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There are also, of course,
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non-artificial non-caloric sweeteners
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like stevia, monk fruit, et cetera.
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They did not explore the full gallery
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of artificial sweeteners.
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What they did find, however,
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ought to pertain to all forms
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of sweet non-caloric substances.
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What they discovered was that there is a signature pattern
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of signals sent from the gut to the brain
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when we ingest artificial or non-caloric sweeteners.
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This is important because what it says is that
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at a subconscious level,
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the gut can distinguish between sweet things
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that contain calories and sweet things that do not.
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Now, what the downstream consequences of this sensing is
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or what they are, isn't yet clear.
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Now, I believe everyone should be aware
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of these kinds of studies for a couple of reasons.
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First of all, it's important to understand
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that what you crave, meaning the foods you crave
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and the drinks you crave,
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is in part due to your conscious experience
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of the taste of those things,
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but also due to biochemical and neural events
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that start in the body and impinge on your brain
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and cause you to seek out certain things,
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even though you might not know
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why you're seeking out more sugar.
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You find that you're craving a lot of sugar
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or you're craving a lot of foods with artificial sweeteners
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and you don't necessarily know why.
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Now, artificial sweeteners themselves
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are a somewhat controversial topic.
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I want to highlight that.
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Some months back, I described a study from Yale University
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about how one can condition the insulin system.
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Insulin is involved in mobilizing a blood sugar
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and so forth in the body, as many of you know,
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and I described some studies that were done
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from Yale University School of Medicine,
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looking at how artificial sweeteners
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can actually evoke an insulin response
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under certain conditions.
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Now, a couple of key things.
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I got a little bit of pushback after covering those studies
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and I encourage pushback all the time.
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Pushback is one of those things
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that forces all of us to drill deeper into a topic.
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I want to be clear.
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First of all, I am not one to demonize artificial sweeteners.
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There is evidence in animal models, in animal models,
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that artificial sweeteners can disrupt the gut microbiome,
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but those were fairly high doses of artificial sweeteners
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and it's unclear if the same thing pertains to humans.
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Still unclear, I should say,
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has not been investigated thoroughly.
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Some people don't like the taste of artificial sweeteners.
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Some people find that they really help them
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avoid excessive caloric intake.
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Some people believe, and yet I should emphasize,
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there still isn't evidence
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that they can adjust the insulin response in all people.
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I just want to repeat that three times
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so that people are clear on that fact.
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What these new data emphasize, however,
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is that we need to understand how artificial sweeteners
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are consumed at the level of the gut,
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or I should say registered at the level of the gut
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and how that changes brain function.
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Because one thing that I'm familiar with
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and that many people report
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is that when they first taste artificial sweeteners,
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they taste sort of not right to them.
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They don't like the taste,
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but over time, they actually start to crave that taste.
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I've experienced this.
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I used to drink a lot of diet sodas
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when I was in graduate school, so this would be aspartame,
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and I found that I actually needed them.
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Now, maybe it was the caffeine.
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Maybe I just liked the sweet taste or the carbonation.
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We actually have a drive for carbonation,
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which is the topic of a future episode,
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but when I finally quit them
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for reasons that were independent of any fear
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of artificial sweeteners,
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I found that I didn't like the taste.
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Nowadays, I only occasionally drink a diet soda.
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I usually do that if I'm on a plane
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and there's nothing else available to me,
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so I don't demonize them.
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I might drink one every once in a while, no big deal.
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I also want to be clear.
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I consume stevia on a number of different supplements
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and foods that I consume.
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Stevia, of course, is a plant-based non-caloric sweetener,
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so I myself consume artificial sweeteners.
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Many people hate them.
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Many people like them and find them useful
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for their nutrition and, in fact,
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to keep their caloric intake
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in a range that's right for them,
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and many people, like myself, are curious about them
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and somewhat wary of them
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and yet continue to consume them in small amounts.
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I think most people probably fall into that category.
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I should also mention that many food manufacturers
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put artificial sweeteners, such as sucralose, et cetera,
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into foods, and it's always been unclear
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as to why they might want to do that,
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and yet we know that the sweet taste consumption,
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even if it doesn't contain calories,
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can drive more craving of sweet food,
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so there may be a logic or a strategy to why they do that.
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Again, a topic for exploration on today's podcast
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and in future podcasts,
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because where we're headed today is a discussion
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about how salt and salt sensing,
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both consciously and unconsciously,
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can adjust our craving for other things
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like sugar and water and so on.
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So I want to highlight this beautiful work
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from the Moraes lab.
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I will put a link to the study.
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I want to open this as a chapter for further exploration.
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I like to think that the listeners of this podcast
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are looking for answers where we have answers,
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but are also, I would hope,
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excited about some of the new and emerging themes
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in what we call nutritional neurobiology,
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and indeed the Moraes lab really stands
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as one of the premier laboratories out there
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that's looking at how foods, as consumed in the gut,
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are modifying our nervous system,
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the foods we crave, and how we utilize those foods.
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Before we begin, I'd like to emphasize
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that this podcast is separate
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from my teaching and research roles at Stanford.
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It is, however, part of my desire and effort
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to bring zero cost to consumer information about science
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and science-related tools to the general public.
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In keeping with that theme,
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I'd like to thank the sponsors of today's podcast.
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Our first sponsor is Athletic Greens, now called AG1.
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I've been taking AG1 since 2012,
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so I'm delighted that they're sponsoring the podcast.
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The reason I started taking AG1
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and the reason I still take AG1 once or twice a day
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is that I find it to be the best way
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to ensure I get all of my vitamins and minerals
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and the probiotics I need.
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I try and eat really well, but I'm not perfect about it,
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and with Athletic Greens, AG1,
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I cover any deficiencies I might have.
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The probiotics are particularly important to me
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because as we've talked about on many previous episodes
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and we'll talk about more on today's episode,
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the gut microbiome is supported by probiotics
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and the gut microbiome supports many biological functions
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important for immediate and long-term health,
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things like immune system function,
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things like the gut brain axis and mood and appetite
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With Athletic Greens, I make sure all of those bases
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are covered because of the probiotics.
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If you'd like to try Athletic Greens,
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you can go to athleticgreens.com slash Huberman
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to claim a special offer.
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They'll give you five free travel packs,
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which make it really easy to mix up Athletic Greens
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while you're on the road,
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and they'll give you a year's supply of vitamin D3K2.
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Vitamin D3 is crucial for many aspects
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of our immediate and long-term health,
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and many people simply are not getting enough vitamin D3,
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or the amounts they're getting are not optimal.
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K2 is important for cardiovascular health
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and for calcium regulation.
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So again, if you go to athleticgreens.com slash Huberman,
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you can claim the special offer, the five free travel packs
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and a year supply of vitamin D3K2.
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Today's episode is also brought to us by Element.
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Element is an electrolyte drink that has everything you need
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and none of the things you don't.
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That means it has salt, magnesium and potassium,
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so-called electrolytes, which are critical for neuronal
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function and a lot of other biological functions.
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As I mentioned on the podcast before, I'm a fan of salt.
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I believe in ingesting appropriate amounts of salt,
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and by appropriate, I mean,
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depending on what your background blood pressure
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happens to be, what your activity levels are,
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how much you sweat,
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what your cognitive and physical demands are.
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Today, we're going to talk about how to determine
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what those needs are.
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I'm always trying to stay on top of my hydration,
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and as you'll also learn about today,
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salt and water intake and hydration are intimately related.
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With Element, I'm sure to get the potassium, the sodium
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and the magnesium that I need,
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and I do that in a great tasting drink,
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and as I mentioned before, it has no sugar.
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If you'd like to try Element, you can go to drinkelement.com,
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that's drinklmnt.com slash Huberman
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to claim a free Element sample pack.
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You only cover the cost of shipping,
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otherwise it's completely free.
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Again, that's drinkelementlmnt.com slash Huberman
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to claim a free sample pack of Element.
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Today's episode is also brought to us by Inside Tracker.
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Inside Tracker is a personalized nutrition platform
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that analyzes data from your blood and DNA
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to help you better understand your body
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and help you reach your health goals.
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I am a big fan of getting regular blood work done,
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and I've been trying to do it
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as much as I can afford for years.
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The reason is that many of the factors
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that impact our immediate and long-term health
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can only be discovered from a quality blood test.
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With most blood tests and DNA tests, however,
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you get information back, but not a lot of information
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about what to do with those numbers.
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So if something's in high or low range,
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you might get one or two generic recommendations,
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things that you could easily look up online,
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but you're not going to get a lot of specific recommendations.
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With Inside Tracker,
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they give you a lot of specific recommendations
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as to lifestyle factors and nutrition factors,
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supplementation factors,
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or things you may want to delete from your life
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in order to bring the numbers into the ranges
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that are best for your immediate and long-term health.
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There's simply no replacement for these kinds of data,
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and your data are the most important data to you,
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and quality blood tests and DNA tests
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are the way to access them.
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If you'd like to try Inside Tracker,
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go to insidetracker.com slash Huberman
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to get 20% off any of Inside Tracker's plans.
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That's insidetracker.com slash Huberman to get 20% off.
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Okay, let's talk about salt.
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Salt has many, many important functions
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in the brain and body.
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For instance, it regulates fluid balance,
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how much fluid you desire and how much fluid you excrete.
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It also regulates your desire for salt itself,
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meaning your salt appetite.
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You have a homeostatically driven salt appetite.
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I'll talk about the mechanisms today
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and make them all very clear.
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What that means is that you crave salty things,
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beverages and foods, when your salt stores are low,
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and you tend to avoid salty beverages and foods
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when your salt stores are high,
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although that's not always the case.
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There are circumstances where you will continue
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to crave salt even though you don't need salt
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or indeed even if you need to eliminate salt
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Salt also regulates your appetite for other nutrients,
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things like sugar, things like carbohydrates.
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And today we'll explore all of that.
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Technically, salt is a mineral.
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And I should mention that when I say salt,
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I am indeed referring to sodium in most cases,
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although I will be clear to distinguish salt from sodium,
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meaning table salt from sodium.
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Most people don't realize this,
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but one gram of table salt
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contains about 388 milligrams of sodium.
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So technically we should be talking about sodium today
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I will use them interchangeably
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unless I'm referring to some specific recommendations
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or ideas about trying to define your ideal salt,
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AKA sodium intake.
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So this is important.
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I think right off the bat,
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a lot of people get themselves into a place of confusion
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and potentially even to a place of trouble
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by thinking that table salt in grams
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always equates to sodium in grams.
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And that's simply not the case.
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Today we're going to explore the neural mechanisms
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by which we regulate our salt appetite
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and the way that the brain and body interact
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in the context of salt seeking, salt avoidance,
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how to determine when we need more salt,
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when we need less salt.
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We'll talk about kidney function.
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We'll get into all of it
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and we're going to do it very systematically.
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So let's start in the brain.
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We all harbor small sets of neurons.
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We call these sets of neurons nuclei,
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meaning little clusters of neurons
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that sense the levels of salt in our brain and body.
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There are a couple of brain regions that do this
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and these brain regions are very, very special.
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Special because they lack biological fences around them
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that other brain areas have.
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And those fences, or I should say that fence
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goes by a particular name.
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And that name is the blood brain barrier or BBB.
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Most substances that are circulating around in your body
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do not have access to the brain.
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In particular, large molecules
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can't just pass into the brain.
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The brain is a privileged organ in this sense.
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There are a couple of other organs that are privileged
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and that have very strict barriers,
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very particular fences, if you will.
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And those other organs include things
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like the ovaries and testes.
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And that makes sense for the following reason.
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First of all, the brain, at least most of the brain
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cannot regenerate after injury.
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You just simply can't replace brain cells after injury.
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I know people get really excited about neurogenesis,
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the birth of new neurons,
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and indeed neurogenesis has been demonstrated
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And to some extent it exists in humans in a few places.
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For instance, the olfactory bulb
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where neurons are responsible
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for detecting odorants in the environment,
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for smell that is.
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And in a little sub region of the hippocampus,
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a memory area, there's probably some neurogenesis.
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But the bulk of really good data out there
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point to the fact that in humans,
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there's not much turnover of neurons.
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What that means is that the neurons you're born with
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are the ones that you're going to be using
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most if not all of your life.
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In fact, you're born with many more neurons
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than you'll have later.
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And there's a process of naturally occurring cell death
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called apoptosis that occurs during development.
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So you actually are born with many more neurons
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than you have later in life.
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And that's the reflection of a normal healthy process
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of nerve cell elimination.
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So the estimates vary,
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but anywhere from a third to maybe even a half
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or even two thirds of neurons,
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depending on the brain area,
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just going to die across development.
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That might sound terrible,
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but that's actually one of the ways
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in which you go from being kind of like a little potato bug
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flopping around helplessly in your crib
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to being an organism that can walk and talk
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and articulate and calculate math
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or do whatever it is that you do for a living.
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So the brain has a set of elements,
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these nerve cells and other cells,
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and it needs to use those for the entire lifespan.
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So having a BBB, a blood-brain barrier around the brain
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is absolutely critical.
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The ovaries and testes have a barrier for,
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we assume the reason that they contain the genetic material
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by which we can pass on our genes to our offspring progeny,
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meaning make children,
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and those children will have our genes
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or at least half of them.
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The other half from the partner, of course.
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If the cells within the ovaries and testes are mutated,
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well, then you can get mutations and offspring.
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So that's very costly in the evolutionary sense.
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So it makes sense that you would have
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a barrier from the blood.
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So if you ingest what's called a mutagen,
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if you ingest something that can mutate the genes of cells,
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you can imagine why there would be a premium
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on not allowing those mutagens to get into the brain,
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the ovaries or the testes, okay?
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So the brain has this BBB,
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this blood-brain barrier around it,
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which makes it very, very hard for substances
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to pass into the brain unless those substances
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are very small or those substances and molecules
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are critically required for brain function.
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However, there are a couple of regions in the brain
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that have a fence around them, but that fence is weaker.
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Okay, it's sort of like going from a really big wall,
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thick electronic 24-hour surveillance fence
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where nothing can pass through except only
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the exclusive cargo that's allowed to go through
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to having a little cyclone fence
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with a couple of holes in it,
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or it's a kind of a picket fence that's falling over
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and substances can move freely from the blood
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circulating in the body into the brain.
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And it turns out that the areas of the brain
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that monitor salt balance and other features
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of what's happening in the body at the level
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of what we call osmolarity, at the concentration of salt
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reside in these little sets of neurons
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that sit just on the other side of these weak fences.
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And the most important and famous of these
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for the sake of today's conversation is one called OVLT.
link |
OVLT stands for the organum vasculosum
link |
of the lateral terminalis.
link |
It is what's called a circumventricular organ.
link |
Why circumventricular?
link |
Well, not to bog you down with neuroanatomy,
link |
but your brain is a big squishy mass of neurons
link |
and other cell types, but it has to be nourished.
link |
And through the middle of that brain,
link |
there is a tube, there's a hollow that creates spaces.
link |
And those spaces are called ventricles.
link |
The ventricles are spaces in which cerebral spinal fluid
link |
circulates and it nourishes the brain.
link |
It does a number of other things as well.
link |
The circumventricular organs are areas of the brain
link |
that are near that circulating fluid.
link |
And that circulating fluid has access to the bloodstream
link |
and the bloodstream has access to it.
link |
And this structure that I'm referring to OVLT,
link |
organum vasculosum of the lateral terminalis,
link |
has neurons that can sense the contents of the blood
link |
and to some extent, the cerebral spinal fluid.
link |
There are a couple other brain areas
link |
that can do this as well.
link |
They go also by the name of circumventricular organs.
link |
And I'll talk about the names of some of those other areas.
link |
But for today, and I think for sake
link |
of most of the discussion,
link |
understand that the OVLT is special.
link |
Because it doesn't have this thick barrier fence,
link |
which sounds like a bad thing.
link |
And yet it's a terrific border detector.
link |
The neurons in that region are able to pay attention
link |
to what's passing through in the bloodstream
link |
and can detect, for instance,
link |
if the levels of sodium in the bloodstream are too low,
link |
if the level of blood pressure in the body
link |
is too low or too high,
link |
and then the OVLT can send signals to other brain areas.
link |
And then those other brain areas
link |
can do things like release hormones
link |
that can go and act on tissues
link |
in what we call the periphery in the body.
link |
And for instance, have the kidneys secrete more urine
link |
to get rid of salt, that's excessive salt in the body,
link |
or have the kidneys hold on to urine
link |
to hold on to whatever water or fluid that one might need.
link |
So before I go any deeper into this pathway,
link |
just understand that the OVLT has a very limited barrier.
link |
It can detect things in the bloodstream.
link |
And this incredible area of the brain
link |
almost single-handedly sets off the cascades of things
link |
that allow you to regulate your salt balance,
link |
which turns out to be absolutely critical,
link |
not just for your ability to think
link |
and for your neurons to work, but indeed for all of life.
link |
If the OVLT doesn't function correctly,
link |
you're effectively dead or dead soon.
link |
So this is a very important brain region.
link |
So let's talk about the function of the OVLT
link |
and flesh out some of the other aspects of its circuitry,
link |
of its communication with other brain areas
link |
and with the body.
link |
In the context of something that we are all familiar with,
link |
Have you ever wondered just why you get thirsty?
link |
Well, it's because neurons in your OVLT
link |
are detecting changes in your bloodstream,
link |
which detect global changes within your body.
link |
And in response to that,
link |
your OVLT sets off certain events within your brain and body
link |
that make you either want to drink more fluid
link |
or to stop drinking fluid.
link |
There are two main kinds of thirst.
link |
The first one is called osmotic thirst.
link |
And the second is called hypovolemic thirst.
link |
Osmotic thirst has to do with the concentration of salt
link |
in your bloodstream.
link |
So let's say you ingest something very, very salty.
link |
Let's say you ingest a big bag of,
link |
I confess I don't eat these very often,
link |
but I really like those kettle potato chips
link |
and they're pretty salty.
link |
I've never actually measured how much sodium is in them.
link |
I'm sure the information is there.
link |
Every once in a while,
link |
if I'm particularly interested in doing so,
link |
I'll just down a bag of those things.
link |
And I really like them and they're very salty,
link |
but they almost always make me feel thirsty.
link |
And the reason is that by eating those,
link |
I've ingested a lot of sodium.
link |
Again, not a frequent occurrence for me,
link |
but happens every now and again.
link |
And I don't have too much shame about that
link |
because I think I have a pretty healthy relationship
link |
to food and I enjoy them.
link |
And I understand that it will drive salt levels
link |
up in my bloodstream.
link |
And that will cause me to be thirsty.
link |
Because neurons in the OVLT come in two main varieties.
link |
One variety senses the osmolarity of the blood
link |
that's getting across that weak little fence
link |
that we talked about before.
link |
And when the osmolarity,
link |
meaning the salt concentration in the blood is high,
link |
it activates these specific neurons in the OVLT.
link |
I mean it causes them to send electrical potentials,
link |
literally send electrical signals to other brain areas.
link |
And those other brain areas
link |
inspire a number of different downstream events.
link |
So what are those other brain areas?
link |
Well, the OVLT signals to an area
link |
called the supraoptic nucleus.
link |
The name and why it's called the supraoptic nucleus
link |
is not necessarily important.
link |
It also signals to the so-called paraventricular nucleus,
link |
another nucleus that sits near the ventricles
link |
and can monitor the qualities,
link |
the chemical qualities of the cerebral spinal fluid,
link |
as well as probably the bloodstream as well.
link |
And the consequence of that communication
link |
is that a particular hormone is eventually released
link |
from the posterior pituitary.
link |
Now the pituitary is a gland
link |
that sits near the roof of your mouth.
link |
It releases all sorts of things like growth hormone
link |
and luteinizing hormone.
link |
Luteinizing hormone will stimulate things like estrogen
link |
and testosterone production and release
link |
from the ovaries and testes and so on.
link |
The pituitary has a bunch of different compartments
link |
and functions, but what's really cool about the pituitary
link |
is that certain regions of the pituitary
link |
actually contain the axons, the wires of neurons,
link |
and the neurons reside in the brain.
link |
And so the supraoptic nucleus gets a signal from the OVLT.
link |
The signal is purely in the form of electrical activity.
link |
Remember, neurons aren't talking to one another
link |
about what's happening out there.
link |
They're not saying, hey, there's too much salt
link |
in the bloodstream, let's do something about it.
link |
All they receive are so-called action potential,
link |
waves of electricity.
link |
The neurons in the supraoptic nucleus
link |
then release their own electrical signals
link |
within the pituitary and some of those neurons
link |
and nearby neurons are capable of releasing hormones
link |
as well as electrical signals.
link |
So from the pituitary, there's a hormonal signal
link |
that's released called vasopressin.
link |
Vasopressin also goes by the name antidiuretic hormone
link |
and antidiuretic hormone has the capacity
link |
to either restrict the amount of urine that we secrete
link |
or when that system is turned off
link |
to increase the amount of urine that we secrete.
link |
So there's a complicated set of cascades that's evoked
link |
by having high salt concentration in the blood.
link |
There's also a complicated set of cascades that are evoked
link |
by having low concentrations of sodium in the blood.
link |
But the pathway is nonetheless the same.
link |
It's OVLT is detecting those osmolarity changes,
link |
communicating to the supraoptic nucleus.
link |
Supraoptic nucleus is either causing the release of
link |
or is releasing vasopressin, antidiuretic hormone,
link |
or that system is shut off
link |
so that the antidiuretic hormone is not secreted,
link |
which would allow urine to flow more freely, right?
link |
Antidiuretic means anti-release of urine.
link |
And by shutting that off,
link |
you're going to cause the release of urine.
link |
You're sort of allowing a system to flow, so to speak.
link |
The second category of thirst is hypovolemic thirst.
link |
Hypovolemic thirst occurs when there's a drop
link |
in blood pressure, okay?
link |
So the OVLT, as I mentioned before,
link |
can sense osmolarity based on the fact
link |
that it has these neurons that can detect
link |
how much salt is in the bloodstream.
link |
But the OVLT also harbors neurons
link |
that are of the baroreceptor, mechanoreceptor category.
link |
Now, more on baroreceptors and mechanoreceptors later,
link |
but baroreceptors are essentially a receptor,
link |
meaning a protein that's in a cell
link |
that responds to changes in blood pressure.
link |
So there are a number of things that can cause decreases
link |
in blood pressure.
link |
Some of those include, for instance,
link |
if you lose a lot of blood, right?
link |
If you're bleeding quite a lot,
link |
or in some cases, if you vomit quite a lot,
link |
or if you have extensive diarrhea,
link |
or any combination of those.
link |
And there are other things that can reduce blood volume,
link |
and we will talk about some of those later.
link |
But in the classic case of hypovolemic thirst,
link |
one is simply losing blood,
link |
and therefore blood pressure goes down.
link |
So very simple to imagine in your mind,
link |
you have these pipes,
link |
which are the arteries, veins, and capillaries,
link |
and when you lose some blood volume,
link |
the pressure in those arteries,
link |
veins, and capillaries goes down.
link |
OVLT has neurons that can sense that reduction
link |
in blood pressure because of the presence
link |
of baroreceptors in OVLT.
link |
There are other elements that also play into the response
link |
to what we call hypovolemic thirst.
link |
For instance, the kidney will secrete
link |
something called renin.
link |
Renin will activate something called angiotensin II
link |
from the lungs of all things.
link |
And angiotensin II itself can act on OVLT,
link |
organum vasculosum and lateral terminalis,
link |
which in turn will create thirst.
link |
the osmolarity sensing system,
link |
meaning osmotic thirst,
link |
and in hypovolemic thirst,
link |
where blood pressure has dropped,
link |
the end result is a desire to drink more.
link |
And that desire to drink more comes through a variety
link |
of pathways that are both direct and indirect,
link |
include vasopressin and don't include vasopressin.
link |
But I think for just sake of general example,
link |
and even for those of you that don't have any biology
link |
background or physiology background,
link |
just understand that there are two main types of thirst.
link |
Both types of thirst, osmotic thirst and hypovolemic thirst,
link |
are not just about seeking water,
link |
but they also are about seeking salt.
link |
In very general terms,
link |
can help retain water.
link |
Now that doesn't mean that salt always retains water.
link |
If you have excessive amounts of salt,
link |
will you retain excessive amounts of water?
link |
Well, sort of, as we'll soon learn, it's all contextual.
link |
But for most cases,
link |
we can say that by having salt in our system,
link |
our brain and our body can function normally,
link |
provided the levels of salt are adequate
link |
and not too high or too low.
link |
And thirst, while we often think of it as just a way
link |
to bring fluid into our body,
link |
is designed as a kind of a interoceptive perception.
link |
What I mean by that,
link |
and interoception, as many of you know now
link |
from listening to this podcast,
link |
is a pang of attention or a recognition, rather,
link |
a conscious recognition of the events
link |
going on within our body.
link |
So when we are thirsty,
link |
it's a certain form of interoception.
link |
We go, oh, I need something, or I crave something.
link |
You may not know exactly what you need,
link |
but when you are thirsty, you're not just seeking water.
link |
You're also seeking to balance your osmolarity,
link |
which means you may be seeking salty fluids or foods.
link |
In some cases, you'll try and accomplish this by eating.
link |
Or it may be that you're trying to avoid,
link |
or you will be inspired to avoid salty fluids and foods.
link |
But if you want to understand sodium
link |
and its roles in the body, you have to understand thirst.
link |
And if you want to understand thirst,
link |
you have to understand how fluid balance
link |
is regulated in the body.
link |
That's not surprising at all.
link |
But sodium and water work together
link |
in order to generate what we call thirst.
link |
Sodium and water work together
link |
in order to either retain water
link |
or inspire us to let go of water, to urinate.
link |
So before we can dive into the specifics around salt
link |
and how to use salt for performance
link |
and various recommendations and things to avoid,
link |
we need to drill a little bit deeper
link |
into this fluid balance mechanism in the body.
link |
And for that reason, we have to pay
link |
at least a little bit of attention to the kidney.
link |
The kidney is an incredible organ.
link |
And one of the reasons the kidney is so amazing
link |
is that it's responsible for both retaining, holding onto,
link |
or allowing the release of various substances from the body.
link |
Substances like glucose or amino acids, urea, uric acid,
link |
salt, potassium, magnesium.
link |
It's basically a filter,
link |
but it's a very, very intelligent filter.
link |
I mean, intelligent meaning it doesn't have its own mind,
link |
but the way it works is really beautiful.
link |
Basically, blood enters the kidney
link |
and it goes through a series of tubes,
link |
which are arranged into loops.
link |
If you want to look more into this,
link |
there's the beautiful loop of Henle
link |
and other aspects of the kidney design
link |
that allow certain substances to be retained
link |
and other substances to be released,
link |
depending on how concentrated
link |
those substances are in the blood.
link |
The kidney responds to a number of hormonal signals,
link |
including vasopressin, in order to, for instance,
link |
antidiuretic hormone, in order to hold on to more fluid,
link |
if that's what your brain and body need.
link |
And it responds to other hormonal signals as well.
link |
So it's a pretty complex organ.
link |
Nonetheless, there's a key point,
link |
which I already mentioned,
link |
that I think most people don't realize,
link |
that this is actually something that I like to tell kids
link |
when I meet them, provided that they're of appropriate age.
link |
I'll say, oftentimes when kids learn that I'm a scientist,
link |
they'll ask a question about something related to science
link |
and hopefully, for my sake,
link |
it's something about neuroscience.
link |
But one thing that I'll tell kids, I'll say,
link |
do you know that your urine,
link |
your pee is actually filtered blood?
link |
And occasionally that will really terrify a kid,
link |
but that also occasionally really terrifies an adult.
link |
But indeed, your urine is filtered blood.
link |
They see blood gets into the kidney,
link |
the kidney is going to filter out certain things,
link |
certain things are going to be allowed to pass through
link |
and others are not, okay?
link |
So the way the kidney is designed is that about 90%
link |
of the stuff that's absorbed from the blood
link |
is going to be absorbed early in this series of tubes.
link |
And only a small percentage is going to be regulated
link |
or worked out as you get into what's called
link |
the distal kidney.
link |
Distal just means the furthest part away, okay?
link |
The proximal is up close.
link |
So like your shoulder is proximal
link |
to your midline of your body and your hand is distal.
link |
So in biological terms, you hear about proximal distal,
link |
which just means near or far from.
link |
So just to give a really simple example,
link |
let's say that you are very low on fluid.
link |
You haven't had much to drink in a while.
link |
Maybe you're walking around on a hot day.
link |
Chances are that the neurons in your OVLT
link |
will sense the increase in osmolarity, right?
link |
The concentration of salt is going to be increased
link |
relative to the fluid volume that's circulating.
link |
This of course assumes that you haven't excreted
link |
a lot of sodium for one reason or another,
link |
but that increase in osmolarity is detected by the OVLT.
link |
The OVLT is going to signal a bunch of different cascades
link |
through the super optic nucleus, et cetera.
link |
And then vasopressin is going to be released
link |
into the bloodstream and vasopressin,
link |
again also called antidiuretic hormone,
link |
is going to act on the kidney and change the kidney's
link |
function in a couple of different ways,
link |
some mechanical, some chemical, okay?
link |
In order to make sure that your kidney
link |
does not release much water,
link |
doesn't make you want to urinate.
link |
And in fact, even if you would try to urinate,
link |
your body's going to tend to hold on to its fluid stores.
link |
Okay, so very simple, straightforward example.
link |
We can also give the other example whereby
link |
if you were ingesting a lot, a lot, a lot of water,
link |
and it's not a particularly hot day
link |
and you're not sweating very much,
link |
let's assume your salt intake is constant
link |
or is low for whatever reason,
link |
well then the osmolarity, the salt concentration
link |
in your blood is going to be lower.
link |
Your OVLT will detect that
link |
because of these osmo-sensing neurons in your OVLT,
link |
your OVLT will fail to signal to the super optic nucleus
link |
and there will not be the release
link |
of vasopressin antidiuretic hormone
link |
and you can excrete all the water
link |
that your body wants to excrete,
link |
meaning you'll be able to urinate,
link |
there's no holding on to water at the level of the kidney.
link |
Okay, very simple examples,
link |
but hopefully it illustrates how events within the blood,
link |
meaning the concentration of salt
link |
relative to the amount of fluid, right?
link |
That's what osmolarity is, is detected by the OVLT.
link |
The brain then communicates to the pituitary.
link |
The pituitary sends a hormone out into the blood
link |
and the hormone acts on the kidney
link |
to either hold onto or let go of fluid,
link |
meaning to prevent you from wanting to urinate
link |
or from stimulating you to want to urinate.
link |
Very, very simple kind of yes, no type situation here.
link |
There's a lot of nuance to this in reality.
link |
There are a lot of other hormones in this pathway,
link |
but I think for at least this stage of the discussion,
link |
this should be sufficient.
link |
Some of you may have noticed
link |
that a molecule we've been talking a lot about today,
link |
vasopressin, was also mentioned on a previous episode
link |
of the Huberman Lab Podcast,
link |
but in a very different context.
link |
The molecule I'm referring to is vasopressin
link |
and as I mentioned, it's a hormone involved in antidiuresis,
link |
meaning preventing urination.
link |
It's an antidiuretic,
link |
but we also talked about vasopressin in the context
link |
of desire, love, and attachment.
link |
We talked about it in the context of monogamy
link |
and non-monogamy in a species of animal
link |
called the prairie vole.
link |
You can check out that episode.
link |
I believe vasopressin and the non-monogamous prairie voles
link |
are mentioned in the timestamp,
link |
so it should be easy to find.
link |
Vasopressin is made at multiple locations
link |
in the nervous system, mainly the super optic nucleus,
link |
and indeed, it's also involved in aspects
link |
of sexual behavior and mating.
link |
Now, it does that through mechanisms that are distinct
link |
from its antidiuretic effects.
link |
In fact, there are people who take vasopressin
link |
as an aphrodisiac.
link |
Now, I'm certainly not suggesting people do that,
link |
but I have all the confidence in the world
link |
that the moment I talk about vasopressin,
link |
someone in the comments is going to say,
link |
what do you think about vasopressin nasal sprays
link |
and this kind of thing?
link |
Vasopressin and indeed oxytocin,
link |
another hormone that's involved in pair bonding
link |
and various aspects of brain and body function,
link |
are available as nasal sprays
link |
that can get up into the deep recesses of the brain
link |
and it can impact some of these core,
link |
what we call hypothalamic functions,
link |
these primitive drives and hypothalamic functions.
link |
I would encourage a lot of caution,
link |
maybe even extreme caution in recreational use
link |
of things like vasopressin and oxytocin,
link |
unless you are working with an MD, excuse me,
link |
and they prescribe it,
link |
or they really know what they're doing.
link |
These are powerful hormones
link |
that have a lot of different effects on the brain and body.
link |
The way that vasopressin, meaning antidiuretic hormone,
link |
prevents the release of fluid as urine from the body
link |
is pretty interesting.
link |
It acts directly on the kidney.
link |
So as I mentioned before, blood flows into the kidney,
link |
a number of things are retained
link |
in the early part of the kidney.
link |
Vasopressin acts at a fairly distal,
link |
meaning kind of end game,
link |
part of the loops of tubes through the kidney,
link |
and it increases the permeability of those tubes.
link |
In other words, it makes sure that the fluid
link |
that would otherwise pass into a collecting duct
link |
and then go out to the bladder
link |
never actually makes it to the bladder.
link |
I point this out because what antidiuretic hormone does
link |
is it prevents the bladder from filling at all.
link |
It's not as if it locks fluid in the bladder
link |
and prevents you from urinating.
link |
I think the way I've been describing things up until now
link |
and the way you'll hear about antidiuretic hormone,
link |
it might sound like it kind of locks up the bladder,
link |
prevents you from being able to urinate,
link |
but you have a full bladder.
link |
That would be very uncomfortable.
link |
That's not the way it works.
link |
It actually causes the tubes headed towards the bladder
link |
from the kidney to become permeable,
link |
meaning to allow fluid to go back into the bloodstream,
link |
into the rest of the body,
link |
so that fluid never actually fills the bladder
link |
and so you never feel the urge to urinate.
link |
Now, this is an episode about salt.
link |
A key thing to understand about the kidney
link |
is that the kidney uses sodium in order to conserve water,
link |
which has everything to do with the fact
link |
that sodium can actually hold water.
link |
Put differently, water tends to follow sodium.
link |
So where we have sodium, we tend to have water
link |
and sodium when it's concentrated can hold on to water.
link |
And that's one of the main ways
link |
that the kidney holds on to water in the body.
link |
And as we'll soon learn,
link |
there is no simple and direct formula to say, for instance,
link |
okay, if salt levels are high, a lot of water is retained.
link |
And if salt levels are low, a lot of water is released.
link |
On the one hand, that can be true,
link |
but it's also the case because these systems are homeostatic,
link |
meaning they're always seeking balance,
link |
both within system, within the salt system,
link |
and between systems, the salt and water system,
link |
it's also the case often that if we have enough sodium,
link |
well, then we can secrete sodium and some water will follow.
link |
Or if we don't have enough sodium, then yes, indeed,
link |
because we're not holding on to water,
link |
more fluid can be excreted.
link |
But if that condition of low sodium lasts long enough,
link |
then we start to retain water
link |
because the body recognizes, ah, salt is low
link |
and water is being excreted
link |
and eventually a system will kick in to retain water.
link |
So I'd love to give you a simple black and white
link |
yes or no answer for low sodium, high sodium,
link |
moderate sodium and water balance, but it's all contextual.
link |
And when I say contextual, I mean,
link |
it will depend on blood pressure, hypertension,
link |
pre-hypertension if that's there, maybe normal tension,
link |
hormone levels, exercise, et cetera, et cetera.
link |
A pretty good example of how complicated this can all be
link |
is one that some of you may be familiar with.
link |
It's pretty well known that during certain phases
link |
of the menstrual cycle, when estrogen and progesterone
link |
and other hormones are fluctuating,
link |
that water can be retained in the body.
link |
It's what's called edema or a swelling sometimes.
link |
So the common assumption, and indeed it can be true,
link |
that when estrogen levels are high,
link |
there's water retention in the body.
link |
Also in males, if estrogen levels are high,
link |
there can be water retention in the body.
link |
This is one of the reasons why athletes
link |
and in particular bodybuilders who take anabolic steroids
link |
like testosterone, which can be converted into estrogens,
link |
sometimes they'll walk around,
link |
they look like they were partially inflated,
link |
they look like they're going to pop,
link |
and it looks like a swelling of the skin,
link |
not just because they have large muscles.
link |
And that's not always, but often water retention
link |
due to testosterone conversion into estrogen.
link |
Now, that all sounds consistent, right?
link |
Estrogen levels fluctuated in the menstrual cycle,
link |
in males where there's an increase in estrogen,
link |
there's retention of water,
link |
but actually estrogen acts as a diuretic.
link |
So one would think, okay, when estrogen levels go up,
link |
there should be a lot of fluid excreted.
link |
But I bring up this example to point out
link |
that it's a very complicated and dynamic balance
link |
between hormones and salt and fluid.
link |
You can't draw a one-to-one relationship there.
link |
And that turns out to be a very important point,
link |
and we can use that not as a way
link |
to further complicate things,
link |
but as a way to understand under which context,
link |
less sodium intake or more sodium intake can be beneficial.
link |
So that's where I'd like to turn our attention now.
link |
So how much salt do we need and what can we trust
link |
in terms of trying to guide our ingestion of salt?
link |
First of all, I want to be very, very clear
link |
that there are a number of people out there
link |
that have pre-hypertension or hypertension.
link |
You need to know if you have pre-hypertension
link |
You need to know if you have normal tension,
link |
meaning normal blood pressure.
link |
Everyone should know their blood pressure
link |
is an absolutely crucial measurement
link |
that has a lot of impact on your immediate
link |
and long-term health outcomes.
link |
It informs a lot about what you should do.
link |
Should you be doing more cardiovascular exercise?
link |
Should you be ingesting more or less salt?
link |
Should you be adjusting any number
link |
of different lifestyle factors?
link |
So you need to know that.
link |
And without knowing what your blood pressure is,
link |
I can't give a one-size-fits-all recommendation.
link |
And indeed, I'm not going to give medical recommendations.
link |
I'm simply going to spell out what I know about the research,
link |
which hopefully will point you in the direction
link |
of figuring out what's right for you
link |
in terms of salt and indeed fluid intake.
link |
There is a school of thought
link |
that everybody is consuming too much salt.
link |
And I do want to highlight the fact that there are dozens,
link |
if not hundreds of quality papers that point to the fact
link |
that a quote-unquote high salt diet can be bad
link |
for various organs and tissues in the body,
link |
including the brain.
link |
It just so happens that because fluid balance,
link |
both inside and outside of cells is crucial,
link |
not just for your heart and for your lungs
link |
and for your liver and for all the organs of your body,
link |
but also for your brain,
link |
that if the salt concentration inside of cells
link |
in your brain becomes too high, neurons suffer, right?
link |
They will draw fluid into those cells
link |
because water tends to follow salt, as I mentioned before,
link |
and those cells can swell.
link |
You can literally get swelling of brain tissue.
link |
Conversely, if salt levels are too low inside of cells
link |
in any tissue of the body, but in the brain included,
link |
then the cells of the body and brain can shrink
link |
because water is pulled into the extracellular space
link |
And indeed, under those conditions,
link |
brain function can suffer.
link |
And indeed, the overall health of the brain can suffer.
link |
So there are many reports out there indicating,
link |
both in experimental models and to some extent in humans,
link |
that overconsumption of salt is bad
link |
for brain function and longevity.
link |
And yet there's also decent evidence
link |
in both animal models and humans
link |
that if salt consumption is too low,
link |
then brain health and longevity will suffer,
link |
as will other organs and tissues of the body.
link |
So like most things in biology,
link |
you don't want things too high or too low.
link |
Now, I would say that the vast majority of studies out there
link |
point to the fact that a high salt diet
link |
is detrimental to brain health and function.
link |
Most of the studies have focused on that aspect
link |
of salt balance and its consequences on brain function.
link |
One critical issue with many of those studies, however,
link |
is that the high salt diet is often coupled
link |
to other elements of diet that are also unhealthy,
link |
things like excessively high levels of carbohydrates
link |
or fats or combinations of carbohydrates and fats.
link |
And so while I know there are many burning questions
link |
out there about how much salt one needs
link |
if they are on a low carbohydrate diet,
link |
or if they are fasting, or if they are on a vegan diet,
link |
there have simply not been many studies
link |
that have explored the low, moderate,
link |
and high salt conditions
link |
on a backdrop of very controlled nutrition.
link |
And that's probably reflective of the fact
link |
that there are not a lot
link |
of very well-controlled nutrition studies out there.
link |
There are some, of course,
link |
but it's very hard to get people to adhere
link |
to nutritional plans in a very strict way,
link |
and to do that for sufficient periods of time
link |
that would allow the various health outcomes to occur.
link |
Nonetheless, there's some interesting reports
link |
that indicate that the amount of salt intake
link |
can indeed predict health outcomes,
link |
or what we call hazardous events,
link |
things like cardiovascular events and stroke and so forth.
link |
And what's interesting is that indeed a lower,
link |
I'm not saying low, right,
link |
because I don't believe that you want your diet
link |
to be truly low in anything except perhaps poison,
link |
but a lower salt diet can reduce
link |
the number of these so-called hazardous events,
link |
but it's a somewhat of a shallow U-shaped function
link |
such that yes, indeed,
link |
a high salt intake can be very detrimental
link |
for your health, both in terms of cardiovascular events,
link |
stroke, and other deleterious health events,
link |
but somewhere in the middle
link |
that actually sits quite to the right,
link |
meaning higher than what is typically recommended
link |
can actually reduce the number of these hazardous events.
link |
At least some reports point to that.
link |
And so I want to emphasize
link |
what one of those particular reports says,
link |
and I also want to be sure to counter it
link |
from the perspective of the context
link |
that that study was set in,
link |
because again, my goal here is not to give you
link |
a strict set of recommendations at all,
link |
is to point you to the literature,
link |
try and make that literature as clear as possible
link |
and allow you to evaluate for yourself.
link |
And I don't just say that to protect us,
link |
I say that to protect you,
link |
because indeed you are responsible
link |
for your health and your health choices.
link |
So the paper that I'm referring to,
link |
it's a very interesting one.
link |
We of course never want to put too much weight
link |
on any one report,
link |
but this is a paper that was published in 2011
link |
in the Journal of the American Medical Association.
link |
The title of the paper is
link |
Urinary Sodium and Potassium Excretion
link |
and a Risk of Cardiovascular Events.
link |
We have not talked much about potassium yet,
link |
but sodium and potassium tend to work in concert
link |
in the brain and body
link |
in order to regulate various physiological functions
link |
and we'll talk more about potassium as time goes on.
link |
The key plot or set of data in this study,
link |
for those of you that want to look it up,
link |
we will link to it.
link |
And there are a lot of data in here,
link |
but it's figure one,
link |
which is basically evaluating
link |
the amount of urinary excretion of sodium,
link |
which is a somewhat indirect,
link |
but nonetheless valuable measure
link |
of how much sodium people were ingesting.
link |
And plotted against that
link |
is what they call the hazard ratio.
link |
And the hazard ratio points to
link |
the composite of cardiovascular death stroke,
link |
myocardial infarction,
link |
and an infarct is an injury
link |
and hospitalization for congestive heart failure.
link |
And what it points to is the fact that the hazard ratio
link |
is low-ish at sodium excretion
link |
of about two grams per day,
link |
but then continues to go down
link |
until about 4.5 to five grams per day.
link |
Remember, this is sodium excretion,
link |
so it's reflective of how much sodium was in the body,
link |
which is reflective of how much sodium was ingested.
link |
And then the hazard ratio increases fairly dramatically,
link |
a very steep slope,
link |
heading anywhere from seven to eight to 10
link |
and out towards 12 grams of sodium excretion per day.
link |
So the simplest way to interpret these data
link |
are that at fairly low levels of sodium,
link |
meaning at about two grams per day,
link |
you run fewer health risks,
link |
but the number of risks continues to decline
link |
as you move towards four and five grams per day.
link |
And then as you increase your salt intake further,
link |
then the risk dramatically increases.
link |
So no study is holy,
link |
nor is any figure in any study
link |
or any collection of studies holy.
link |
Rather, we always want to look at what the bulk of data
link |
in a particular field reveal.
link |
Nonetheless, I think the plot that we described,
link |
meaning the graph that we described is pretty interesting
link |
in light of the 2020 to 2025 dietary recommendations
link |
for Americans, which is that people consume
link |
no more than 2.3 grams,
link |
meaning 2,300 milligrams of sodium per day.
link |
That's about a half a teaspoon of salt per day.
link |
Now, most people are probably consuming more than that
link |
because of the fact that they are ingesting processed foods
link |
and processed foods tend to have more salt in them
link |
than non-processed foods.
link |
Now, of course, that's not always the case, right?
link |
Sea salt is not a processed food in most cases.
link |
And there are a lot of unprocessed foods
link |
that can be high in sodium,
link |
but processed foods in particular
link |
tend to have a lot of sodium.
link |
You can see this simply by looking at the packaging
link |
of any number of different foods.
link |
But if we were to take this number of 2.3 grams,
link |
that's the recommended cutoff for ingestion of sodium,
link |
it actually falls in a portion of the curve
link |
that we were talking about a moment ago
link |
that indeed is associated
link |
with low incidents of hazardous outcomes,
link |
cardiovascular events, stroke, et cetera.
link |
But according to that plot,
link |
the ingestion of four or five grams of sodium,
link |
almost double or more sodium than is currently recommended,
link |
is associated with even lower numbers of hazardous events.
link |
So we need to think about this
link |
and we need to explore it in the context
link |
of other studies, of course.
link |
And we need to evaluate it in terms of this thing
link |
that we've been going back to again and again,
link |
which is context, right?
link |
These recommendations of 2.3 gram per day cutoff
link |
is in the context of a landscape
link |
where some people do indeed have hypertension
link |
or pre-hypertension.
link |
The incidence of hypertension has gone up dramatically
link |
in the last 100 years and seems to continue to go up.
link |
Whether or not that's because of increased salt intake
link |
or whether or not it's because of increased salt intake
link |
and other things such as highly processed foods,
link |
Again, pointing to the challenge
link |
in doing these epidemiological studies
link |
and really parsing what aspects of a change
link |
in some health metric is due to, for instance,
link |
the ingestion of more sugars versus more salts
link |
or simply because of the ingestion of more salts.
link |
It's a complicated, almost barbed wire topic by now,
link |
but we can start to pull apart that barbed wire tangle
link |
and start to evaluate some of the other people
link |
in other conditions that exist out there,
link |
maybe for you, that actually warrant more sodium intake
link |
and where more sodium intake might actually be beneficial.
link |
So again, I want to be very, very clear
link |
that you need to know your blood pressure.
link |
If you have high blood pressure or you're pre-hypertensive,
link |
you should be especially cautious about doing anything
link |
that increases your blood pressure.
link |
And as always, you want to, of course,
link |
talk to your doctor about doing anything
link |
that could adjust your health in any direction.
link |
But nonetheless, there are some important papers
link |
that have been published in recent years.
link |
I want to point to one of them in particular.
link |
This is a paper that was published
link |
in the journal Autonomic Neuroscience, Basic and Clinical,
link |
because this paper, like several other papers,
link |
ask the question, and indeed they asked the question
link |
in the title, it's a review, dietary sodium and health,
link |
how much is too much for those with orthostatic disorders?
link |
Now, orthostatic disorders come
link |
in a bunch of different varieties,
link |
and we're going to talk about those in a moment,
link |
but there are a number of people out there
link |
that have low blood pressure, right?
link |
People that get dizzy when they stand up,
link |
people that are feeling chronically fatigued,
link |
and in some cases, not all, those groups can actually benefit
link |
from increasing their sodium intake.
link |
Several episodes ago on the Huberman Lab Podcast,
link |
I gave it what it's just clearly what we call anecdata,
link |
which is not even really data, it's just anecdotal data,
link |
of an individual who was always feeling hungry
link |
and craving sugar, and based on the fact
link |
that they also had low blood pressure,
link |
I had them talk to a physician and they got permission
link |
to try a little mini experiment on themselves,
link |
and so they did, and that mini experiment was,
link |
anytime they felt like they were craving sugar
link |
or they were feeling a little lightheaded and dizzy,
link |
rather than reaching for something with caloric intake,
link |
they took a little bit of sea salt,
link |
a little pinch of sea salt, and put it into some water
link |
and drank it, or in the case of this individual,
link |
they would actually take a little sea salt packet
link |
and they would actually just down a sea salt packet,
link |
and for them, that provided tremendous relief
link |
for their dizziness, but that, of course,
link |
was in the context of somewhat abnormally
link |
low blood pressure, so I don't think that they are alone
link |
in the fact that many people out there suffer
link |
from a low blood pressure condition, many people out there
link |
suffer from a high blood pressure condition,
link |
so know your blood pressure and understand
link |
that blood pressure in part is regulated
link |
by your sodium intake and your sodium balance, why?
link |
Well, because of the osmolarity of blood
link |
that we talked about before,
link |
where if you have a certain concentration of sodium,
link |
meaning sufficient sodium in your bloodstream,
link |
that will tend to draw water into the bloodstream
link |
and essentially the pipes that are your capillaries,
link |
arteries, and veins will be full,
link |
the blood pressure will get up to your head,
link |
whereas some people, their blood pressure is low
link |
because the osmolarity of their blood is low,
link |
and that can have a number of downstream consequences,
link |
I should also mention it can be the consequence itself
link |
of challenges or even deficits in kidney function,
link |
but all of these organs are working together,
link |
so the encouragement here is not necessarily
link |
to ingest more sodium, it's to know your blood pressure
link |
and to address whether or not an increase in sodium intake
link |
would actually benefit your blood pressure
link |
in a way that could relieve some of the dizziness
link |
and other symptoms of things like orthostatic disorders,
link |
but of course, to do that in a safe context
link |
and to never play games with your blood sugar
link |
or your blood osmolarity that could set your system
link |
down a cascade of negative events,
link |
let's look at what the current recommendations are
link |
for people that suffer from orthostatic disorders
link |
like orthostatic hypo, meaning too low tension,
link |
orthostatic hypotension, postural tachycardia syndrome,
link |
sometimes referred to as POTS, P-O-T-S,
link |
or idiopathic orthostatic tachycardia and SYNCOPE,
link |
these have the incredibly elaborate names,
link |
those groups are often told to increase their salt intake
link |
in order to combat their symptoms,
link |
the American Society of Hypertension recommends
link |
anywhere from 6,000 to 10,000, these are very high levels,
link |
so this is six grams to 10 grams of salt per day,
link |
keeping in mind, again, that salt is not the same as sodium,
link |
so that equates to about 2,400 to 4,000 milligrams
link |
of sodium per day, again, if you want to learn more
link |
about this and get more of the citations,
link |
I'll refer you back to this study on dietary sodium
link |
and health, how much is too much
link |
for those with orthostatic disorders,
link |
we will put a link to this in the caption show notes,
link |
so that's not just in the US, the salt recommendations
link |
from the Canadian Cardiovascular Society
link |
are 10,000 milligrams of salt per day,
link |
so four grams of sodium is what that equates to,
link |
and on and on and on for things like POTS
link |
for these postural syndromes that result from,
link |
or I should say from the syndromes
link |
that involve low blood pressure
link |
when people stand up or in certain postures,
link |
so I point out this paper
link |
and I point out these higher salt recommendations
link |
to emphasize, again, that context is vital, right,
link |
that people with high blood pressure
link |
are going to need certain amounts of salt intake,
link |
people with lower blood pressure
link |
and maybe with some of these postural orthostatic syndromes
link |
are going to need higher amounts of salt,
link |
and for most people out there,
link |
you're going to need to evaluate how much salt intake
link |
is going to allow your brain and body to function optimally,
link |
and there are some fairly straightforward ways
link |
to explore that, and there's some ways to explore that
link |
in the context of what you already know
link |
about thirst and salt appetite
link |
that can make that exploration
link |
one in which it's not going to be a constant
link |
wandering around in the dark
link |
and where you can figure out what's right for you.
link |
For most people, a moderate increase in salt intake
link |
is not going to be detrimental
link |
provided that you consume enough fluids,
link |
in particular, water, okay,
link |
meaning if you happen to overeat salt a bit,
link |
you will get thirsty, you will ingest more water,
link |
and you will excrete the excess sodium.
link |
There is evidence that the body can store sodium
link |
in various organs.
link |
That storage of sodium may or may not be
link |
a detrimental thing.
link |
In general, excess storage of sodium
link |
in tissues and organs of the brain and body
link |
is not thought to be good for long-term health,
link |
so eating much more sodium than you need
link |
for long periods of time is indeed bad for you.
link |
Earlier, I mentioned that salt
link |
and your hunger and thirst for salt
link |
is homeostatically regulated,
link |
and indeed, that's the case,
link |
much like temperature is homeostatically regulated.
link |
What that means is if you pay attention to it,
link |
if your salt levels are low,
link |
you will tend to crave salt
link |
and salty beverages and salty foods,
link |
and in most cases, you should probably follow that craving
link |
provided those salty beverages and salty foods
link |
are not bringing in a lot of other things
link |
or anything, ideally, that's bad for you,
link |
so I think it's fair to say
link |
that whether or not you're vegan, vegetarian,
link |
carnivore, omnivore,
link |
that we should all try to limit
link |
our ingestion of processed foods.
link |
My read of the literature is that, sure,
link |
some processed foods are acceptable for us
link |
and aren't going to kill us outright,
link |
but that for most people in the world,
link |
eating fewer processed foods
link |
is just going to be a good thing to do,
link |
so following your salt hunger and thirst, in most cases,
link |
is going to be beneficial
link |
provided that it's in the context
link |
of eating healthy non-processed foods
link |
on whatever backdrop of nutritional
link |
and dietary recommendations is right for you.
link |
I simply can't tell you what to eat and what not to eat
link |
because I acknowledge the fact that some people are vegans
link |
because of ethical reasons related to animals,
link |
or some people are vegans
link |
because of reasons related to the climate
link |
and the environment.
link |
Other people do it for specific health reasons.
link |
Likewise, I know plenty of people that eat meat
link |
and avoid vegetables, believe it or not,
link |
and I know people that eat both,
link |
and they do this often each, I should say,
link |
all citing literature that supports their particular camp
link |
and their particular view.
link |
It's not a territory I want to get into,
link |
but with respect to salt intake
link |
and the fact that salt intake is homeostatically regulated,
link |
it is the case that if you're craving salt,
link |
you probably need it.
link |
So for those of you that are sweating excessively,
link |
or even if you're in a very hot environment
link |
and you're not exercising and you're just losing,
link |
you're losing water and salt from your system,
link |
remember also that you can be in a very cold environment,
link |
very cold, dry environments often go together,
link |
and you can be losing a lot of fluids from your body
link |
and you will crave fluids and salt even though it's cold
link |
and you're not actually noticeably perspiring.
link |
So if you're exercising a lot,
link |
if you're in a particular cold, dry environment
link |
or a particular hot environment,
link |
you ought to be ingesting sufficient amounts
link |
of salt and fluid.
link |
A rule of thumb for exercise-based replenishment of fluid
link |
comes from what I, some episodes back,
link |
referred to as the Galpin equation.
link |
The Galpin equation, I named it after Andy Galpin,
link |
and I think that is the appropriate attribution there.
link |
Andy Galpin is an exercise physiologist
link |
at Cal State Fullerton, I believe,
link |
and he's going to be a podcast guest
link |
here on the Huberman Lab Podcast.
link |
He's an exceptional muscle physiologist.
link |
He also lives in the practical realm
link |
where he gives recommendations about exercise
link |
to expert athletes, as well as the everyday person.
link |
So the Galpin equation is based on the fact
link |
that we lose about one to five pounds of water per hour,
link |
which can definitely impact our mental capacity
link |
and our physical performance.
link |
And the reason that loss of water from our system
link |
impacts mental capacity and physical performance
link |
has a lot to do with literally the changes
link |
in the volume of those cells, the size of those cells,
link |
based on how much sodium is contained
link |
in or outside those cells,
link |
and something that I've alluded to before on the podcast
link |
and I'll talk about more in a moment,
link |
which is that neurons signal to one another
link |
by way of electricity
link |
through something called the action potential,
link |
and that actually requires sodium and potassium
link |
So the Galpin equation suggests
link |
that we start exercise hydrated with electrolytes,
link |
not just with water.
link |
So that means water that has some sodium,
link |
potassium, and magnesium.
link |
There are simple low cost ways to do that we'll talk about.
link |
And the formula for hydration,
link |
the so-called Galpin equation is your body weight in pounds
link |
divided by 30 equals the ounces of fluid
link |
you should drink every 15 minutes.
link |
That may turn out to be more fluid
link |
than you can comfortably consume
link |
during the activity that you're performing.
link |
Now, the Galpin equation is mainly designed for exercise,
link |
but I think is actually a very good rule of thumb
link |
for any time that you need to engage mental capacity,
link |
not just physical performance.
link |
Your body weight in pounds divided by 30
link |
equals the ounces of fluid you should drink every 15 minutes
link |
does not necessarily mean you have to ingest it
link |
every 15 minutes on the dot.
link |
And I think many activities, physical activities,
link |
but also cognitive activities like Zoom meetings
link |
or in-person meetings or lecturing or running or cycling
link |
are going to make it complicated
link |
to ingest the appropriate amount of fluid
link |
every 15 minutes on the dot.
link |
I'm not going to speak for Andy, for Dr. Galpin,
link |
but I think he would probably agree
link |
that these are averages to shoot for
link |
and that unless you're hyper neurotic,
link |
the idea is to make sure that you're entering the activity,
link |
cognitive or physical, sufficiently hydrated,
link |
and that throughout that activity,
link |
you're hydrating regularly.
link |
And it points to the fact
link |
that most people are probably under hydrating,
link |
but not just under hydrating
link |
from the perspective of not ingesting enough water,
link |
that they're probably not getting enough electrolytes
link |
as well, sodium, potassium, and magnesium.
link |
So I've said two somewhat contradictory things.
link |
On the one hand, I said, follow your salt appetite,
link |
follow your salt thirst.
link |
If you're craving salt,
link |
ingest some salt until you stop craving the salt.
link |
On the other hand, I've given you this
link |
fairly specific recommendation based on the Galpin equation
link |
that you should ingest your body weight in pounds
link |
divided by 30, that's how many ounces of fluid
link |
you should drink every 15 minutes,
link |
which I'm guessing for most people is going to be more fluid
link |
than they're currently drinking on average.
link |
And so how could it be that you can have a recommendation
link |
for what's optimal that's different
link |
than the amount that you would reflexively drink?
link |
And it has to do with the fact
link |
that a lot of the hormone systems like vasopressin,
link |
antidiuretic hormone, other hormones like aldosterone,
link |
and a lot of the neural and hormonal signals
link |
that govern salt and water balance
link |
are fairly slow to kick in.
link |
So for instance, if you eat a fairly salty meal
link |
and you sense that salt, you'll probably,
link |
meaning you detect it and perceive it,
link |
because the food tastes salty,
link |
you'll probably want to drink
link |
a fair amount of fluid with it.
link |
Whereas if some of the salt is disguised by other flavors,
link |
something that we'll talk about in a few minutes
link |
when we talk about the neural representation
link |
of things like salty and sweet,
link |
well, then you might not notice that something's salty,
link |
and then a few minutes or hours after ingesting that meal,
link |
you might feel very, very tired.
link |
You might even wonder whether or not
link |
it's because of some blood sugar effect.
link |
Maybe it's a crash in blood sugar, you might think,
link |
or something else related to that meal,
link |
or maybe you think it's because of
link |
some other event in your life,
link |
but actually what has happened is you're dehydrated
link |
because you didn't recognize
link |
that you needed to drink more fluids.
link |
So I want to acknowledge the contradiction
link |
in the idea that everything is homostatically regulated,
link |
and therefore you are aware of what you need,
link |
and the counterargument that ah,
link |
you need to follow these strict recommendations,
link |
it's actually going to be somewhere in between.
link |
And of course, your body and brain can start to adapt
link |
to certain levels of salt intake.
link |
There's a now fairly famous study that was done in Germany,
link |
which looked at different phases of salt intake,
link |
meaning they had subjects ingest
link |
either 12 grams of salt per day or nine grams per day
link |
or six grams per day for fairly long periods of time,
link |
and they collected urine for testing.
link |
This was actually a very controlled study.
link |
I'm just going to paraphrase
link |
from the National Institutes of Health report on this study
link |
because they did a very nice writeup of it.
link |
And they say that a big surprise of these results
link |
is that whatever the level of salt that was consumed,
link |
sodium was stored and released from the subjects bodies
link |
in fairly regular weekly and monthly patterns,
link |
meaning people tended to adapt
link |
to a certain level of salt intake,
link |
and then it led to a fairly constant amount
link |
of salt retention and urine fluid excretion.
link |
And that's because of the various hormones like aldosterone,
link |
which regulates sodium excretion from the kidney
link |
and glucocorticoids,
link |
which we'll talk about more in a moment,
link |
which help regulate metabolism.
link |
Glucocorticoids are released from the adrenal glands,
link |
which ride the top of the kidneys.
link |
And there's a very close relationship
link |
between the stress system, glucocorticoids,
link |
and the salt system.
link |
So the reason why your salt appetite
link |
isn't a perfect readout of how much salt you should ingest
link |
and why it might be helpful
link |
to follow some of these formulas like the Galpin equation,
link |
especially if you're engaging in exercise,
link |
where you're going to be perspiring, of course,
link |
is that your body will tend to adapt
link |
to a certain amount of salt intake over time,
link |
and then your appetite for salt
link |
won't necessarily be the best indication
link |
of how much salt you should ingest or avoid.
link |
Before I move on, I want to really reemphasize the fact
link |
that inside of the Galpin equation,
link |
there is that mention of every 15 minutes,
link |
and people have come back to me again and again
link |
about this saying,
link |
I can't drink that much water every 15 minutes.
link |
It's too much volume of fluid in my stomach.
link |
I can't run with that, et cetera.
link |
Remember, these are averages.
link |
So that's what you want to average
link |
around a particular activity.
link |
These are not strict recommendations
link |
where a buzzer goes off and every 15 minutes,
link |
you have to chug that exact amount
link |
of electrolyte-containing solution.
link |
Another key feature of the study
link |
that I was referring to before,
link |
which incidentally was published
link |
in the Journal of Clinical Investigation,
link |
is that the body regulates its salt and water balance
link |
not just by excreting sodium,
link |
but by retaining or releasing water.
link |
And this is because of the relationship
link |
between sodium and water that we were talking about before.
link |
And the advantage of this mechanism they state,
link |
here I'm paraphrasing,
link |
is that the long-term maintenance of body fluids
link |
is not as dependent on external water as once believed.
link |
What the system probably evolved to do
link |
was to adjust to different levels of sodium availability
link |
in the environment.
link |
And that raises a really key element of salt
link |
and its importance in human history
link |
and human evolution and human health.
link |
We haven't talked too much about this,
link |
and there are several very good books
link |
about the history of salt.
link |
You know, salt was a very valuable
link |
and heavily sought-after substance
link |
throughout much of human history,
link |
so much so that there are actually written reports
link |
of people being paid for labor in the form of salt.
link |
And, you know, salt, when it's scarce,
link |
has been quite expensive in certain regions of the world,
link |
especially regions located further away from the sea.
link |
And a friend of mine who has deep roots
link |
within the culinary community told me about traveling
link |
to some somewhat impoverished areas of Europe
link |
some years ago and going into homes
link |
where in the middle of the kitchen table,
link |
there was a fish, a salty fish,
link |
hanging from a thread above the table.
link |
And that because of a lack of availability of table salt,
link |
the common practice was to take any food
link |
that needed some salt for additional flavoring
link |
and to actually rub that food on this salty fish
link |
or to squeeze the fish a bit onto the food substance
link |
in order to get salt from it.
link |
So, you know, that's a very kind of extreme example.
link |
Nowadays, we kind of take salt for granted
link |
and most of the discussion out there is about excess salt.
link |
But as I'm pointing out that, you know,
link |
salt for a long time has been a very sought-after commodity
link |
and one that people really cherished for their health.
link |
In the episode that I did on metabolism,
link |
I talked about the relationship between salt and iodine.
link |
If you're interested in iodine
link |
and whether or not iodized salt or non-iodized salt
link |
is best or required,
link |
I'd encourage you to listen to that episode,
link |
which was about, again, metabolism.
link |
Some people may need more iodine intake.
link |
Some people perhaps do not.
link |
Some people might even want to ingest things like kelp.
link |
Some people might not.
link |
So please listen to that episode
link |
if you're interested in the iodine aspects of salt,
link |
which have direct impact on thyroid hormone
link |
and thyroid function, which of course relates to metabolism.
link |
Nowadays, there's a lot of interest in
link |
and even a kind of proliferation
link |
of what I call fancy salts.
link |
So whether or not you should be ingesting sea salts
link |
or whether or not common table salt will suffice.
link |
In most cases, for what we're discussing here,
link |
common table salt is fine,
link |
but I should point out that sea salt
link |
often contains other minerals, which can be very useful,
link |
and we will do entire episodes on those other minerals.
link |
So sea salt can contain, you know,
link |
dozens or more of minerals,
link |
some of which can be quite valuable to our health,
link |
others of which are less important
link |
and only need to be consumed in trace amounts,
link |
but you're not going to get many minerals, if any,
link |
from common table salt,
link |
and that's why in addition to the pretty colors
link |
and perhaps some people report
link |
that they actually taste better,
link |
some of these so-called fancy salts or sea salts,
link |
you might want to consume a more advanced form of salt,
link |
Although I suppose it's actually
link |
the more primitive form of salt
link |
if it's actually the one that comes from the ocean.
link |
So we've all heard about how excess salt,
link |
it's bad for blood pressure,
link |
damage the heart, the brain, et cetera.
link |
I do want to give some voice to situations
link |
where too little salt can actually cause problems,
link |
and this has everything to do with the nervous system.
link |
So without getting into excessive amounts of detail,
link |
the kidneys, as we talked about before,
link |
are going to regulate salt and fluid balance.
link |
The adrenal glands, which ride atop the kidneys,
link |
are going to make glucocorticoids like aldosterone,
link |
and those are going to directly impact
link |
things like fluid balance.
link |
And in part, they do that by regulating
link |
how much craving for and tolerance
link |
of salty solutions we have.
link |
And there's some really nice studies
link |
that have looked at so-called adrenalectomies.
link |
Now, this is an extreme case,
link |
and it's typically done in animal models,
link |
but it illustrates the role of the adrenals
link |
in salt preference.
link |
Basically, when the glucocorticoid system,
link |
meaning the release of these particular hormones
link |
from the adrenal glands,
link |
is eliminated by adrenalectomy,
link |
ectomy means removal,
link |
then the threshold for what's considered too salty
link |
really shifts, okay?
link |
So typically, when the adrenals are intact,
link |
a animal or a human will prefer a mildly salty
link |
to moderately salty solution if given a choice.
link |
And at some point, it's so salty
link |
that it just feels aversive.
link |
Just like taking a gulp of seawater
link |
is almost always aversive.
link |
I can't think of an instance where it's not aversive,
link |
and actually drinking seawater can kill you
link |
because of the high osmolarity of seawater.
link |
You certainly don't want to drink seawater.
link |
Under conditions where the adrenals are missing,
link |
animals and humans will tend to prefer
link |
a higher sodium concentration fluid,
link |
and they will be willing to tolerate ingesting
link |
very high concentrations of sodium.
link |
Now, that's a very crude experiment
link |
and not one that you want to do, I promise you.
link |
But I mention it because it illustrates
link |
the very direct relationship between the stress system,
link |
which is the glucocorticoid system,
link |
and the salt craving system.
link |
And this actually makes sense.
link |
Earlier, as we were talking about hypovolemic thirst,
link |
when there's a loss of blood pressure from,
link |
usually due to a loss of blood from the body,
link |
there's a salt craving in order
link |
to bring that blood volume back up,
link |
because by ingesting salt,
link |
you bring fluid into the bloodstream,
link |
you're increasing that blood pressure
link |
and you can restore the blood that's lost.
link |
Now, there are many examples where if sodium levels
link |
get too low in the bloodstream,
link |
either because people are ingesting too little salt
link |
or they are ingesting too much water
link |
and therefore excreting too much salt,
link |
that it can cause stress and anxiety.
link |
There's some really nice data that point to the fact
link |
that low dietary sodium can actually exacerbate anxiety
link |
And to some extent,
link |
there's evidence for this in humans as well.
link |
And that should not come as a surprise.
link |
The whole basis for a relationship
link |
between the adrenal system, these glucocorticoids,
link |
things like aldosterone, and the craving for sodium,
link |
is that the stress system is a generic system
link |
designed to deal with various challenges to the organism,
link |
to you or to me or to an animal.
link |
And those challenges can arrive in many different forms.
link |
They can be an infection, it can be famine,
link |
it can be lack of water and so on.
link |
But in general, the stress response
link |
is one of elevated heart rate, elevated blood pressure,
link |
and an ability to maintain movement
link |
and resistance to that challenge, okay?
link |
I've said this before, but I'll emphasize it again.
link |
There's this common misperception that stress makes us sick.
link |
And indeed, if stress lasts too long,
link |
it has a number of negative effects on our health.
link |
But more often than not, if we're pushing, pushing, pushing,
link |
we're studying or taking care of somebody
link |
or traveling like crazy,
link |
we don't tend to get sick under those conditions.
link |
But as soon as we stop,
link |
as soon as we reduce our adrenaline output,
link |
as soon as we reduce our glucocorticoid output
link |
from our adrenals, then we will get sick.
link |
That's a very common occurrence.
link |
And it's because stress actually activates our immune system
link |
in the short term.
link |
So I'd like to try and dispel this myth
link |
that stress actually suppresses the immune system,
link |
at least not in the short term.
link |
For long-term stress, it's a different issue.
link |
You don't want long-term ongoing stress,
link |
especially if several weeks or more.
link |
Nonetheless, it makes sense that bringing sodium
link |
into the body would be at least one way
link |
that we would be wired to counteract
link |
or to resist stressors, right?
link |
Stressors being the things on the outside coming at us.
link |
So it could be stressful relationships,
link |
stressful job situation, and again, infection and so on.
link |
It's clear from a number of studies
link |
that if sodium levels are too low,
link |
that our ability to meet stress challenges is impaired.
link |
Now, that doesn't mean
link |
to place your sodium intake cosmically high,
link |
but it does point to the fact that if you're feeling anxious,
link |
perhaps from low blood pressure,
link |
which can also give symptoms of anxiety,
link |
as we talked about before,
link |
but even if it's independent of low blood pressure,
link |
that slightly increasing sodium intake,
link |
again, I would encourage people to do this
link |
not in the context of processed foods and drinks,
link |
but ideally in the form of maybe a little bit
link |
of sea salt and water or salting one's food
link |
a little bit more, that that can stabilize blood pressure
link |
and one's ability to lean into stressors and challenges.
link |
And I say this because I think that most people assume
link |
that adding salt is always bad,
link |
when in fact that's simply not the case.
link |
There are conditions such as
link |
when we are under stress challenge,
link |
when there is a natural craving for more sodium,
link |
and that natural craving for more sodium
link |
is hardwired into us as a way to meet that challenge.
link |
So it's hard for me to know whether or not people out there,
link |
especially the listeners of this podcast,
link |
are getting too much, just enough, or too little sodium.
link |
So I can't know that, I'm shouting into a tunnel here.
link |
You have to decide how much sodium you are ingesting.
link |
But I think that there's some, for most people,
link |
especially people who are not hypertensive, prehypertensive,
link |
there's some wiggle room to explore
link |
whether more intake of sodium could actually be beneficial
link |
for suppressing some of the anxiety responses
link |
that they might feel under conditions of stress.
link |
Again, more studies need to be done.
link |
Certainly more studies in humans need to be done,
link |
but the relationship between stress and sodium intake
link |
and the fact that additional sodium intake may be beneficial
link |
and indeed is naturally stimulated by stress
link |
shouldn't be necessarily looked at as a pathological event.
link |
I know when some people get stressed,
link |
they crave salty foods.
link |
That's actually a hardwired biological phenomenon
link |
that you see not just in humans, but in animals,
link |
because this is a very primitive mechanism
link |
whereby your body is preparing
link |
to meet any additional challenges and stressors.
link |
Now, we can't have a discussion about sodium
link |
without having a discussion about the other electrolytes,
link |
magnesium and potassium.
link |
Magnesium is important enough
link |
and an extensive enough topic
link |
that we should probably do an entire episode
link |
just on magnesium.
link |
For purposes of today's discussion,
link |
I just will briefly touch on some of the forms of magnesium
link |
that we've discussed on the podcast before
link |
in different contexts.
link |
I want to emphasize that many people
link |
are probably getting enough magnesium in their diet
link |
that they don't need to supplement magnesium.
link |
Some people, however, opt to supplement magnesium
link |
in ways that can support them.
link |
And there are many different forms of magnesium.
link |
And just in very brief passing,
link |
I'll just say that there is some evidence
link |
that you can reduce muscle soreness from exercise
link |
by ingestion of magnesium malate, M-A-L-A-T-E.
link |
I've talked before about magnesium threnate,
link |
T-H-R-E-N-O-A-T-E, magnesium threnate
link |
for sake of promoting the transition into sleep
link |
and for depth of sleep.
link |
And perhaps, again, highlighted perhaps,
link |
because right now it's mainly animal studies
link |
and ongoing human studies, but the data aren't all in,
link |
perhaps magnesium threnate can be used
link |
as a way to support cognitive function and longevity.
link |
That was discussed in the episode
link |
with Dr. Jack Feldman from UCLA.
link |
Typically magnesium threnate is taken 30 or 60 minutes
link |
before bedtime in order to encourage sleep.
link |
You can go to our neural network newsletter
link |
and look for the one on sleep,
link |
and you can see the recommendations,
link |
or I should say the options for that,
link |
because again, you should always check with your physician.
link |
Those aren't strict across the board recommendations.
link |
And then there are other forms of magnesium,
link |
magnesium bisglycinate,
link |
which is a somewhat of an alternative to threnate,
link |
not known to have cognitive enhancing effects,
link |
but seems at least on par with magnesium threnate
link |
in terms of promoting transition
link |
into in-depth of sleep and so on.
link |
There are other forms of magnesium, magnesium citrate,
link |
which has other functions.
link |
Actually magnesium citrate is a fairly effective laxative,
link |
not known to promote sleep and things of that sort.
link |
So a lot of different forms of magnesium,
link |
and there's still other forms out there.
link |
Many people are not getting enough magnesium,
link |
Okay, so that's magnesium.
link |
Anytime we're talking about sodium balance,
link |
we have to take into consideration potassium,
link |
because the way that the kidney works
link |
and the way that sodium balance is regulated,
link |
both in the body and the brain,
link |
is that sodium and potassium are working in close concert
link |
There are a lot of different recommendations
link |
about ratios out there,
link |
and they range widely from two to one ratio
link |
of potassium to sodium.
link |
I've heard it in the other direction too.
link |
I've heard a two to one sodium to potassium.
link |
The recommendations vary.
link |
One of the sponsors of this podcast, for instance, Element,
link |
which I've talked about in this episode and before,
link |
the ratio there is a gram of sodium
link |
to 200 milligrams of potassium, 60 milligrams of magnesium.
link |
So there they've opted for a five to one ratio
link |
of sodium to potassium.
link |
And of course, many people opt to make their own
link |
hydration electrolyte formulas.
link |
They'll put sea salt into some water,
link |
maybe even ingest a potassium tablet.
link |
It all depends on the context.
link |
An important contextual element is your diet.
link |
So for instance, carbohydrates hold water in the body.
link |
So regardless of how much salt
link |
and how much fluid you're ingesting,
link |
if you're ingesting carbohydrate and you drink fluids,
link |
water, some of that fluid is going to be retained
link |
Now, for people that are following low carbohydrate diets,
link |
one of the most immediate effects of a low carbohydrate diet
link |
is that you're going to excrete more water.
link |
And so under those conditions,
link |
you're also going to lose not just water,
link |
but you'll probably also lose sodium and potassium.
link |
And so some people, many people in fact,
link |
find that when they are on a lower or low carbohydrate diet,
link |
then they need to make sure that they're getting enough
link |
sodium and enough potassium.
link |
And some people do that by taking 99 milligram
link |
potassium tablets every time they eat.
link |
Some people do that by ingesting more foods
link |
that contain potassium.
link |
And of course, some people who are on low carbohydrate diets
link |
do ingest vegetables or other forms of food
link |
that carry along with them potassium.
link |
So it's quite variable from person to person.
link |
I mean, you can imagine if carbohydrate holds water,
link |
water and salt balance and potassium go hand in hand
link |
and hand that if you're on a low carbohydrate diet
link |
that you might need to adjust your salt intake and potassium
link |
and conversely, that if you're on a carbohydrate rich diet
link |
or a moderate carbohydrate diet,
link |
then you may need to ingest less sodium and less potassium.
link |
And in fact, a certain amount of water
link |
is probably coming in through the foods you eat as well.
link |
So I don't say all this to confuse you.
link |
Again, I say this because it all depends on the context.
link |
I'll give yet another context that I think
link |
is fairly common nowadays,
link |
which is many people are following a pattern of eating
link |
that more or less resembles intermittent fasting
link |
or at least time restricted feeding.
link |
So they're eating between particular feeding windows.
link |
And then in the certain parts of the 24 hour cycle,
link |
but during certain parts of their waking cycle,
link |
they're also actively avoiding food banking on,
link |
I think either the possible, I want to say possible
link |
longevity promoting effects of intermittent fasting
link |
or, and or I should say,
link |
they are banking on the fact that for many people,
link |
not eating is easier than portion control
link |
for certain parts of the day.
link |
And so they find it beneficial to limit calories overall
link |
to a given amount, depending on what their goals are
link |
by not consuming food for certain periods of the day.
link |
But usually during those periods of the day,
link |
they're consuming fluids.
link |
And oftentimes those fluids include not just water,
link |
but caffeine and caffeine is a diuretic.
link |
It actually causes the excretion of fluids from the body
link |
in part because it causes the excretion of sodium.
link |
All of that to say that if you're somebody who,
link |
for instance, eats your first meal around noon
link |
or one or 2 p.m. and you're fasting
link |
for the early part of the day
link |
and you're drinking coffee or tea
link |
or ingesting a lot of water,
link |
you are going to be excreting sodium
link |
along with that water.
link |
And so many people, including myself,
link |
find that it's useful,
link |
especially when I'm drinking caffeine
link |
during that so-called fasting or non-food intake
link |
part of time-restricted feeding,
link |
that I'm making sure to get enough salt
link |
either in the form of something like Element,
link |
an electrolyte drink,
link |
or putting some sea salt into some water,
link |
or certainly anytime one is ingesting caffeine,
link |
replacing some of the lost water
link |
by increasing one's water intake.
link |
There are some simple rules of thumb around this
link |
that I think can get most people into a place
link |
where they're more comfortable and functioning better,
link |
which is for every ounce of coffee or tea that you drink,
link |
I should say caffeinated coffee or tea that you drink,
link |
that you consume one and a half times as much water.
link |
So let's say you have an eight-ounce coffee.
link |
Try and drink about, you don't have to be exact,
link |
but try and drink about a 12-ounce glass of water,
link |
and you might want to put a tiny bit of sodium into that.
link |
By tiny bit, I just mean a tiny pinch of sodium.
link |
Because remember, even if we're talking about
link |
increasing the amount of sodium intake overall,
link |
the total amount of sodium contained in salt
link |
is sufficiently high that even just a quarter teaspoon
link |
is going to really start to move that number up
link |
towards that range that's still within the safe range,
link |
but if you keep doing that all day long,
link |
you're very quickly going to get into
link |
that excessive salt intake range
link |
that is deleterious for health.
link |
So again, if you're consuming more caffeine,
link |
you're going to be excreting water and salt and potassium,
link |
and so you're going to have to find ways
link |
to bring water, salt, and potassium back in.
link |
Again, this has to be evaluated
link |
for each of your own individual situations.
link |
If you're exercising fasted,
link |
and you're doing that after drinking caffeine,
link |
then before, during, and certainly after exercise,
link |
you're going to want to replenish the fluids
link |
and electrolytes that you lost, including sodium.
link |
So you can imagine how this all starts
link |
to become pretty dizzying,
link |
and yet it doesn't have to be dizzying.
link |
We can provide some useful ranges
link |
that for most people will work.
link |
And so let's talk about what those ranges are,
link |
and I'm going to point you to a resource
link |
that explores what those ranges are
link |
in these various contexts of nutrition, exercise, and so on.
link |
The resource is a book that was authored
link |
by Dr. James D. Nicolantonio.
link |
He's not a medical doctor.
link |
He's a scientist, studies cardiovascular physiology,
link |
as well, I believe, as a doctor of pharmacy,
link |
and the title of the book is The Salt Fix.
link |
The Salt Fix is an interesting read
link |
because it points to, first of all,
link |
the history of salt in society and as it relates to health.
link |
It actually emphasizes some of the major missteps,
link |
maybe even pretty drastic errors that have been made
link |
in terms of trying to interpret the role
link |
that salt has in various diseases,
link |
and emphasizes some of the ways
link |
in which perhaps increasing salt
link |
can actually improve health outcomes.
link |
And I think it strikes a pretty nice balance
link |
between what's commonly known about salt
link |
and what I believe ought to be known about salt,
link |
or at least taken into consideration.
link |
The book does provide certain recommendations,
link |
and I actually reached out to the author.
link |
I've never met him in person or talked to him directly.
link |
And I asked him outright, I said,
link |
how much salt do you recommend people take on average?
link |
And he gave, of course, the appropriate caveats
link |
about pre-hypertension, hypertension, et cetera,
link |
but made a recommendation, which I'll just share with you.
link |
And if you want to learn more
link |
about the support for this recommendation,
link |
you can check out his book.
link |
The recommendation he made was anywhere
link |
from eight to 12 grams of salt a day,
link |
which corresponds to 3.2 to 4.8 grams of sodium.
link |
So going back to the current recommendations
link |
that we talked about before, 2.3 grams of sodium per day,
link |
this is about one and a half times
link |
to double the amount of sodium
link |
that's currently recommended in most circles.
link |
And then what this corresponds to
link |
is about one and a half to two teaspoons of salt per day
link |
to arrive at that 3.2 to 4.8 grams of sodium.
link |
Again, this is the recommendation that was passed along
link |
for most people, most conditions
link |
barring specific health issues.
link |
Now, what was also interesting is he pointed to
link |
a sodium to potassium ratio,
link |
which is four grams of potassium.
link |
And he also mentioned 400 milligrams of magnesium
link |
and pointed out, and I generally agree here
link |
that many people are deficient in magnesium.
link |
So again, that was a 3.2 to 4.8 grams of sodium,
link |
four grams of potassium.
link |
You might think, well, gosh, that's a one and a half
link |
to two times the current recommendation,
link |
but we can go back to that study
link |
that was mentioned earlier in the episode,
link |
that 2011 study where I described this
link |
sort of J-shaped curve in which when you look at the
link |
occurrence of these negative health events,
link |
they were fairly low at low sodium intake,
link |
lower still at slightly higher sodium intake,
link |
much in line with the recommendations that are made
link |
or that Dr. D. Nicolantonio passed along to me.
link |
And then they increased quite,
link |
those health risks increase quite substantially as one moves
link |
out past six grams of sodium,
link |
seven grams of sodium per day.
link |
That's when things really do seem to get hazardous
link |
and really it makes sense, I think,
link |
given the consensus around this
link |
to really avoid very high salt intake.
link |
So the salt fix describes the rationale
link |
behind those recommendations.
link |
The salt fix also describes in quite beautiful detail
link |
the relationship between salt intake, potassium intake,
link |
and the relationship to the sugar consumption system.
link |
I'd like to pick up on this idea of the relationship
link |
between salt and sugar,
link |
because I think that one key aspect of the way
link |
that salt can work and can benefit us or can harm us
link |
has to do with the way that sodium and sugar are regulated
link |
and actually perceived by the brain
link |
and how under conditions of certain levels of sodium intake,
link |
we might be inspired to seek more sugar
link |
or to crave sweets more or less.
link |
we've been talking about salt as a substance
link |
and a way to regulate fluid balance
link |
and blood volume and so on.
link |
We haven't talked a lot about salt as a taste
link |
or the taste of things that are salty.
link |
And yet we know that we have salt receptors,
link |
meaning neurons that fire action potentials
link |
when salty substances are detected much in the same way
link |
that we have sweet detectors and bitter detectors
link |
and we have detectors of umami,
link |
the savory flavor on our tongue.
link |
And earlier at the beginning of the episode,
link |
I talked about the fact that we have sweet receptors,
link |
neurons that respond to the presence of sugar
link |
or even non-caloric sweet things in the gut
link |
and that signals up to the brain through the vagus nerve
link |
and those signals converge on pathways
link |
that relate to dopamine and so on.
link |
Well, we also have salt sensors at various locations
link |
throughout our digestive tract,
link |
although the sensation and the taste of salt
link |
actually exerts a very robust effect
link |
on certain areas of the brain
link |
that can either make us crave more or sate,
link |
meaning fulfill our desire for salt.
link |
And you can imagine why this would be important.
link |
Your brain actually has to register
link |
whether or not you're bringing in salt
link |
in order to know whether or not
link |
you are going to crave salt more or not.
link |
And beautiful work that's been done by the Zucker Lab,
link |
Z-U-K-E-R, Zucker Lab at Columbia University,
link |
as well as many other labs have used imaging techniques
link |
and other techniques such as molecular biology
link |
to define these so-called parallel pathways.
link |
Parallel meaning pathways that represent sweet
link |
or the presence of sweet taste in the mouth and gut.
link |
Parallel pathways, meaning neural circuits
link |
that represent the presence of salty tastes
link |
in the mouth and gut and so on.
link |
And that those go into the brain,
link |
move up through brain stem centers
link |
and up to the neocortex,
link |
indeed where our seat of our conscious perception is
link |
to give us a sense and a perception of the components
link |
of the foods that we happen to be ingesting
link |
and a sense and a perception of the fluids
link |
and the components of those fluids
link |
that we happen to be ingesting.
link |
Now, parallel pathways, as I'm describing them,
link |
are a fundamental feature of every sensory system,
link |
not just the taste system, but also the visual system.
link |
We have parallel pathways for perceiving dark objects
link |
versus light objects, for perceiving red versus green,
link |
This is a fundamental feature of how we are built
link |
and how our nervous system works.
link |
And in the taste system, much like in these other systems,
link |
these pathways are indeed parallel,
link |
but they converge and they can influence one another.
link |
And I think the simplest way to put this
link |
is in the context first of the visual system,
link |
whereby your ability to detect the color red
link |
has everything to do with the fact
link |
that you have neurons in your eye
link |
that absorb long wavelengths of light that we call reds,
link |
red wavelengths of light,
link |
which are longer wavelengths than say blue light,
link |
which is shorter wavelength.
link |
But it is really the comparison of the electrical activity
link |
of the neurons that absorb red light
link |
with the activity of the neurons that absorb green light,
link |
which actually gives you the perception of red.
link |
So that might seem a little counterintuitive,
link |
but indeed it's not.
link |
It's actually because something is red
link |
and has less greenness
link |
that we perceive it as more red than the green.
link |
And this is actually the way
link |
that your entire nervous system works,
link |
is that we aren't really good
link |
at evaluating absolute levels of anything
link |
in the context of perception.
link |
It's only by comparison.
link |
And actually there's a fun experiment that you can do.
link |
I think you could probably find it easily online.
link |
You could also do this experiment at home.
link |
You can stare at something that's red
link |
or green for that matter for a while.
link |
So you make an active decision to not blink
link |
and to stare at something that's red.
link |
And then you look away from that thing
link |
and you'll actually see a green after image
link |
of that red object.
link |
Conversely, if you look at something that's green for a while
link |
and you stare at it and you look away,
link |
you will see the red after image of that thing.
link |
Now the taste system doesn't have
link |
quite the same aftertaste type effect,
link |
but nonetheless, the pathways,
link |
the parallel pathways for salty
link |
and the parallel pathways for sweet and bitter and so on
link |
can actually interact.
link |
And this has important relevance
link |
in the context of food choices and sugar craving.
link |
One of the things that's commonplace nowadays
link |
is in many processed foods, there is a business,
link |
literally a business of putting so-called hidden sugars.
link |
And these hidden sugars are not always
link |
in the form of caloric sugars.
link |
They're sometimes in the form of artificial sweeteners
link |
into various foods.
link |
And you might say, well, why would they put more sugar
link |
into a food and then disguise the sugary taste
link |
given that sweet tastes often compel people
link |
to eat more of these things?
link |
Well, it's a way actually of bypassing
link |
some of the homeostatic mechanisms for sweet.
link |
Even though we might think that the more sweet stuff we eat,
link |
the more sweet stuff we crave,
link |
in general, people have a threshold whereby they say,
link |
okay, I've had enough sugary stuff.
link |
You can actually experience this
link |
if you ever feel like something is really, really sweet.
link |
Take a little sip of water
link |
with a little bit of lemon juice in it or vinegar
link |
and it will quickly quench
link |
that overly sweet sensation or perception.
link |
It will disappear almost immediately.
link |
There's actually a practice in fancy meals
link |
of cleansing the palate
link |
through the ingestion of different foods.
link |
And that's the same idea that you're cleansing the palate.
link |
You're actually neutralizing the previous taste
link |
so then they can bring yet another dish
link |
to overindulge you in decadence and so forth.
link |
So these sensory systems interact in this way.
link |
By putting sugars into foods
link |
and hiding the sugary taste of those foods,
link |
those foods, even if they contain artificial sweeteners,
link |
can activate the sorts of neurons
link |
that we talked about at the beginning of the episode,
link |
like the neuropod cells
link |
that will then signal to the brain to release more dopamine
link |
and make you crave more of that food.
link |
Whereas had you been able to perceive
link |
the true sweetness of that food,
link |
you might've consumed less and indeed that's what happens.
link |
So these hidden sugars are kind of diabolical.
link |
Why am I talking about all of this
link |
in the context of an episode on salt?
link |
Well, as many of you have probably noticed,
link |
a lot of foods out there
link |
contain a salty-sweet combination,
link |
and it's that combination of salty and sweet
link |
which can actually lead you to consume more
link |
of the salty-sweet food than you would have
link |
if it had just been sweet or it had just been salty.
link |
And that's because both sweet taste and salty taste
link |
have a homeostatic balance.
link |
So if you ingest something that's very, very salty,
link |
pretty soon your appetite for salty foods will be reduced.
link |
But if you mask some of that with sweet,
link |
well, because of the interactions of these parallel pathways
link |
you somewhat shut down your perception
link |
of how much salt you're ingesting,
link |
or conversely, by ingesting some salt with sweet foods,
link |
you mask some of the sweetness
link |
of the sweet foods that you're tasting
link |
and you will continue to indulge in those foods.
link |
So salty-sweet interactions can be very diabolical,
link |
they can also be very tasty,
link |
but they can be very diabolical
link |
in terms of inspiring you to eat more of a particular food
link |
than you would otherwise
link |
if you were just following your homeostatic salt
link |
or your homeostatic sugar balance systems.
link |
And the beautiful imaging work
link |
that's been done by the Zucker Lab and other labs
link |
has actually been able to reveal
link |
how some of this might work by showing, for instance,
link |
that a certain ensemble, meaning a certain group of neurons,
link |
is activated by a sweet taste
link |
and a non-overlapping distinct set of neurons just nearby,
link |
sitting cheek to jowl with those other neurons,
link |
would be activated by salty tastes
link |
and yet others by bitter taste, et cetera.
link |
So there's a separate map
link |
of these different parallel pathways,
link |
but that when foods or fluids are ingested
link |
that are both salty and sweet,
link |
you get a yet entirely different
link |
ensemble of neurons activated.
link |
So your brain, whether or not it's for your visual system
link |
or your auditory system or your taste system,
link |
has a way of representing the pure form of taste,
link |
salty, sweet, bitter, et cetera,
link |
and has a way of representing their combinations.
link |
And food manufacturers have exploited this to large degree.
link |
I mention all of this because if you're somebody
link |
who's looking to explore either increasing
link |
or decreasing your sodium intake for health benefits,
link |
for performance benefits,
link |
in many ways, it is useful to do that
link |
in the context of a fairly pure,
link |
meaning unprocessed food intake background,
link |
whether or not that's keto, carnivore, omnivore,
link |
intermittent fasting or what have you,
link |
it doesn't really matter.
link |
But the closer that foods are to their basic form and taste,
link |
meaning not combinations of large amounts of ingredients
link |
and certainly avoiding highly processed foods,
link |
the more quickly you're going to be able to hone in
link |
on your specific salt appetite and salt needs,
link |
which as I've pointed out numerous times
link |
throughout this episode are going to vary
link |
from person to person, depending on nutrition,
link |
depending on activity, depending on hormone status,
link |
or even portion of your menstrual cycle for that matter.
link |
So if you want to hone in
link |
on the appropriate amount of sodium for you,
link |
yes, blood pressure is going to be an important metric
link |
to pay attention to as you go along.
link |
And the parameters for healthy blood pressure ranges
link |
are readily available online.
link |
So I'll let you refer to those
link |
in order to determine those for yourself.
link |
But in determining whether or not increasing
link |
your salt intake might be beneficial
link |
for, for instance, for reducing anxiety a bit
link |
or for increasing blood pressure
link |
to offset some of these postural syndromes
link |
where you get dizzy, et cetera,
link |
for improving sports performance or cognitive performance,
link |
I can only recommend that you do this
link |
in a fairly clean context
link |
where you're not trying to do this
link |
by ingesting a bunch of salty foods
link |
or salty sweet foods, et cetera.
link |
And indeed, many people find, and it's reviewed a bit,
link |
and some of the data are reviewed in the book,
link |
The Salt Fix, that when people increase their salt intake
link |
in a backdrop of relatively unprocessed foods,
link |
that sugar cravings can indeed be vastly reduced.
link |
And that makes sense given the way
link |
that these neural pathways for salty and sweet interact.
link |
Now, thus far, I've already covered quite a lot of material,
link |
but I would be completely remiss
link |
if I didn't emphasize the crucial role
link |
that sodium plays in the way that neurons function.
link |
In fact, sodium is one of the key elements
link |
that allows neurons to function at all.
link |
And that's by way of engaging
link |
what we call the action potential.
link |
The action potential is the firing
link |
of electrical activity by neurons.
link |
Neurons can engage electrical activity
link |
in a number of different ways.
link |
They have graded potentials, they have gap junctions.
link |
There's a whole landscape
link |
of different electrophysiologies of neurons
link |
that I don't want to go into just yet.
link |
At least not in this episode.
link |
But the action potential is the fundamental way
link |
in which neurons communicate with one another.
link |
They're sometimes called spikes.
link |
It's just kind of nomenclature that neuroscientists use.
link |
I'm just going to briefly describe the action potential
link |
and the role that sodium plays.
link |
And this will involve a little bit of chemistry,
link |
but I promise it will be accessible to anyone,
link |
even if you don't have a chemistry or a physics background
link |
or electrophysiology background.
link |
Neurons have an inside and an outside.
link |
And inside are things like your genetic material.
link |
They have a bunch of things floating around in there
link |
that allow those cells to function.
link |
And they tend to have this wire extending out of them,
link |
sometimes a very long wire,
link |
sometimes a short one that we call the axon.
link |
And at the end of that wire, that axon,
link |
they release little packets of chemicals
link |
that either cause the next neuron to fire action potentials
link |
or prevent the next neuron from firing action potential.
link |
So they kind of vomit out these little packets of chemicals
link |
that either inspire or suppress action potentials
link |
The way that that whole process occurs
link |
is that a given neuron needs to change
link |
its electrical activity.
link |
So normally neurons are hanging out
link |
and they have what we call a negative charge.
link |
And the reason they have a negative charge
link |
is that the inside of the cell
link |
has things floating around in it,
link |
like potassium, a little bit of sodium
link |
and some stuff like chloride.
link |
These are literally just,
link |
just imagine these as little balls of stuff.
link |
And if they have a negative charge on them,
link |
then the inside of the cell
link |
is going to tend to be more negative.
link |
And outside of the cell, it turns out
link |
you're going to have a bunch of stuff
link |
that's positively charged.
link |
And one of the main factors
link |
in creating that positive charge is sodium.
link |
Sodium carries a positive charge.
link |
So you have neurons that you can just imagine,
link |
for sake of this discussion,
link |
you can just imagine as a sphere
link |
with a little wire sticking out of it.
link |
They, you can put a little minus on the inside for negative.
link |
You can put a little plus on the outside for positive.
link |
And when that neuron is stimulated by another neuron,
link |
if the stimulation, the electrical stimulation
link |
is sufficiently high,
link |
meaning enough little packets of neurotransmitter
link |
have been vomited onto its surface
link |
at sufficient concentration,
link |
what happens is little pores, little spaces,
link |
little gaps open up in the membrane of that cell
link |
that separates the inside from the outside.
link |
And because it's positive,
link |
there's a lot of positive charge outside
link |
and there's a lot of negative inside.
link |
It's like a boulder running downhill.
link |
All this stuff tends to rush downhill.
link |
It tries to create even amounts of charge.
link |
So it's negative on the inside, positive on the outside.
link |
And what happens is sodium rushes into the cell,
link |
carrying a lot of charge into the cell.
link |
And as a consequence,
link |
the charge of that cell goes from negative,
link |
actually very negative, to quite positive.
link |
And if it hits a certain threshold of positive charge
link |
because of all the sodium ions going into the cell,
link |
then it fires what's called an action potential.
link |
And it vomits out its own set of chemicals
link |
onto the next neuron.
link |
And so it sets off a chain of one neuron
link |
goes from negative to positive,
link |
vomits out chemicals onto the next one.
link |
The next neuron that binds to receptors or enters the cell
link |
and that cell goes from negative to positive charge,
link |
vomits its contents onto the next cell
link |
and so on and so forth.
link |
Sodium rushing into the cell, therefore,
link |
is the way that the action potential is stimulated.
link |
In other words, sodium is the way
link |
that neurons communicate with one another.
link |
Now, the neurons don't stay in a positive charge,
link |
otherwise they would just keep vomiting out their contents.
link |
But they need to maintain some of that
link |
and they need to go back to preparing to do it
link |
the next time and the next time by resting a bit.
link |
And it turns out that the way they restore their charge
link |
is by pushing that sodium back out of the cell,
link |
there are mechanisms in place to do that,
link |
things like the so-called sodium potassium pump.
link |
There's a change in the levels of potassium
link |
across the cell membrane and so on and so forth.
link |
If you want to look at a demonstration of this,
link |
you can put into a web browser the action potential.
link |
You'll find some beautiful descriptions there
link |
on YouTube and elsewhere.
link |
Maybe some time on Instagram,
link |
I'll do a description with a diagram
link |
because I realize a number of people
link |
are just listening to this.
link |
I can't do that here.
link |
I won't do that here because I want everyone
link |
to be able to get the same amount of material
link |
regardless of whether or not they're watching
link |
and or listening to this.
link |
But the point I'd like to make,
link |
at least as it relates to this episode on salt,
link |
is that having sufficient levels of salt in your system
link |
allows your brain to function,
link |
allows your nervous system to function at all.
link |
Again, this is the most basic aspect
link |
of nervous system function.
link |
And there are cases where this whole system gets disrupted.
link |
And that brings us to the topic of sodium and water balance.
link |
As many of you have probably heard,
link |
but hopefully if you haven't,
link |
you'll take this message seriously.
link |
If you drink too much water,
link |
especially in a short amount of time,
link |
you can actually kill yourself, right?
link |
And we certainly don't want that to happen.
link |
If you ingest a lot of water in a very short period of time,
link |
something called the hypernatremia,
link |
you will excrete a lot of sodium very quickly
link |
and your ability to regulate kidney function
link |
will be disrupted.
link |
But in addition to that,
link |
your brain can actually stop functioning.
link |
So people have actually consumed water to excess,
link |
especially after sports events and so forth.
link |
And if that water doesn't contain sufficient electrolytes,
link |
you can actually shut down neurons' ability
link |
to function at all by disrupting this balance
link |
of sodium and potassium
link |
and the amount of extracellular sodium
link |
and neurons' ability to signal to one another
link |
through action potentials.
link |
And I can't emphasize the importance
link |
of action potentials enough.
link |
They are the way that I can lift my pen right now.
link |
They're the way that I can speak.
link |
They're the way that you breathe.
link |
They literally control all aspects
link |
of your nervous system function.
link |
Now, it takes quite a lot of water intake
link |
before you excrete enough sodium
link |
that your nervous system is going to shut down.
link |
And I certainly don't want to give the impression
link |
that simply by ingesting more sodium,
link |
your neurons will work better,
link |
but it absolutely is the case
link |
that if you don't ingest enough sodium,
link |
that your neurons won't function as well as they could,
link |
and that if your sodium levels are made too low
link |
by hemorrhage or by ingesting so much water, fluid,
link |
that you excrete excess amounts of sodium
link |
or through any other mechanism, that is,
link |
then indeed your neurons won't be able
link |
to fire action potentials,
link |
and your brain and nervous system simply won't work.
link |
And that's one of the primary reasons
link |
why dehydration leads to confusion
link |
and dizziness and lack of coordination.
link |
And I've talked about this a bit
link |
in the episode on endurance,
link |
but there are instances in which competitive athletes
link |
have come into the stadium to finish a final lap
link |
of a long endurance race and are completely disoriented
link |
and actually can't find their way to the finish line.
link |
It might sound like kind of a silly, crazy example,
link |
but there are examples of people having severe mental issues
link |
and physical issues post-exercise
link |
when that exercise involved a ton of sweating
link |
or hot environments or insufficient ingestion of fluids
link |
and electrolytes because included
link |
in the electrolyte formula, of course, is sodium.
link |
And as you just learned,
link |
sodium is absolutely crucial for neurons to function.
link |
So to briefly recap some of what I've talked about today,
link |
we talked about how the brain monitors
link |
the amount of salt in your brain and body
link |
and how that relates to thirst
link |
and the drive to consume more fluid and or salty fluids.
link |
We also talked a little bit about the hormones
link |
that come from the brain and operate at the level
link |
of the kidney in order to either retain
link |
or allow water to leave your system.
link |
We talked a little bit about the function
link |
of the kidney itself, a beautiful organ.
link |
We talked about the relationship between salt intake
link |
and various health parameters
link |
and how a particular range of salt intake might be optimal
link |
depending on the context in which
link |
that range is being consumed,
link |
meaning depending on whether or not you're hypertensive,
link |
pre-hypertensive, or normal tension.
link |
We talked about fluid intake and electrolyte intake,
link |
so sodium, potassium, and magnesium
link |
in the context of athletic or sports performance,
link |
but also in terms of maintaining cognitive function.
link |
Talked about the Galpin equation,
link |
which you could easily adapt to your body weight
link |
and to your circumstances.
link |
Of course, adjusting the amount of fluid
link |
and electrolyte intake upwards if you're exercising
link |
or working in very hot environments,
link |
downwards maybe if you're in less hot environments
link |
where you're sweating less and so on.
link |
We also talked about the relationship
link |
between the stress system and the salt craving system
link |
and why those two systems interact
link |
and why for some people who may suffer a bit from anxiety
link |
or under conditions of stress,
link |
increasing salt intake provided it's done
link |
through healthy means might actually be beneficial.
link |
We also talked about conditions
link |
in which increasing salt intake might be beneficial
link |
for offsetting low blood pressure
link |
and some of these postural syndromes
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that can lead people to dizziness and so forth.
link |
These are things that have to be explored
link |
on an individual basis and of course have to be explored
link |
with the support of your doctor.
link |
I mentioned the salt fix,
link |
which I think is an interesting read,
link |
keeping in mind that a lot of the information in there
link |
runs counter to the typical narrative
link |
that you hear around salt,
link |
but nonetheless has some very interesting points
link |
that you might want to consider
link |
and certainly will broaden your view of the history of
link |
and the applications of salt
link |
as it relates to a great number
link |
of health and performance metrics.
link |
We also talked about the perception of salt,
link |
meaning the perception of salty tastes
link |
and how the perception of salty tastes
link |
and the perception of other tastes like sweet
link |
can interact with one another
link |
to drive things like increased sugar intake
link |
when you're not even aware of it.
link |
And indeed how the combination of salty and sweet tastes
link |
can bias you towards craving more,
link |
for instance, processed foods
link |
and why that might be a good thing to avoid.
link |
And of course, we talked about salt
link |
and its critical role in the action potential,
link |
the fundamental way in which
link |
the nervous system functions at all.
link |
So my hope for you in listening to this episode
link |
is that you consider a question and that question is
link |
what salt intake is best for you
link |
and that you place that question
link |
in the context of your fluid intake,
link |
you place that in the context of the diet you're following,
link |
the amount of caffeine you might be ingesting
link |
and the diuretic effects of caffeine
link |
and crucially that you place that in the context
link |
of the electrolytes more generally,
link |
meaning sodium, potassium, and magnesium.
link |
Someday there will be an online program or an app I imagine
link |
where one could put a bunch of different parameters in
link |
about their particular health status,
link |
their particular diet, their particular exercise, et cetera.
link |
Maybe it would all be run by AI algorithm or something
link |
where it would monitor all of that for us
link |
and then it would spit out for us a precise amount of sodium
link |
that we should take in each day.
link |
Unfortunately, no such tool or device exists right now
link |
and so all of us have to figure out
link |
the appropriate amount of sodium intake for ourselves
link |
and that has to be done
link |
under these contextual considerations.
link |
Who knows, maybe one of you will design such an app
link |
or such a device, I think it would be very useful.
link |
If nothing else, today's discussion ought to illuminate
link |
the fact that some strict recommendation of salt intake
link |
cannot be made universally across the board for everybody.
link |
There's just simply no way that could be done
link |
and yet I think most of what we've learned about salt
link |
in the general discussions around health
link |
are that it's this evil substance.
link |
Nothing could be further from the truth.
link |
It's an incredible substance.
link |
Our physiology is dependent on it.
link |
Our cognition is dependent on it.
link |
Indeed, our mental and physical health and our performance
link |
in essentially all aspects of life is dependent on it
link |
and I hope I've been able to illuminate
link |
some of the beautiful ways in which the brain
link |
and the bodily organs interact
link |
in order to help us regulate this thing
link |
that we call sodium balance
link |
and the fact that we have neurons in our brain
link |
that are both tuned to the levels of salt in our body
link |
and positioned in a location in the brain
link |
that allows them to detect the levels of salt in our body
link |
and to drive the intake of more or less salt
link |
and more or less fluid and other electrolytes
link |
really just points to the beauty of the system
link |
that we've all evolved
link |
that allows us to interact with our environment
link |
and make adjustments according to the context
link |
of our daily and ongoing life.
link |
If you're learning from and are enjoying this podcast,
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please subscribe to our YouTube channel.
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That's a terrific zero cost way to support us.
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In addition, please subscribe to the podcast
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And on Apple, you have the opportunity
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The best place to leave us comments, however,
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That's the best way to support this podcast.
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We also have a Patreon.
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During today's episode and on many previous episodes
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of the Huberman Lab Podcast, we discuss supplements.
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While supplements aren't necessary for everybody,
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many people derive tremendous benefit from them
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for things like enhancing sleep and focus and so on.
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One issue with supplements, however,
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is that the quality of supplements varies tremendously
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from one brand to the next.
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For that reason, we've partnered with Thorne, T-H-O-R-N-E,
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because Thorne supplements are of the absolute
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is what's actually contained in that product.
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They've partnered with all the major sports teams
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and with the Mayo Clinic, so trust is very, very high
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with respect to the quality of Thorne products.
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If you'd like to see the Thorne supplements that I take,
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you can go to Thorne, that's thorne.com slash the letter U
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slash Huberman, and you can get 20% off
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In addition, if you navigate deeper into the Thorne site
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There, I cover science and science-based tools
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but sometimes is distinct from the content of this podcast.
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Thank you once again for joining me today
link |
to discuss the neuroscience and the physiology around salt
link |
and its many incredible influences on our brain and body.
link |
And last, but certainly not least,
link |
thank you for your interest in science.
link |
And I'll see you next time.