Using Salt to Optimize Mental & Physical Performance | Huberman Lab Essentials

Welcome to Huberman Lab Essentials, [music] where we revisit past episodes for the most potent and actionable science-based [music] tools for mental health, physical health, and performance. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today, we are going to discuss salt, also referred to as sodium. Salt has many, many important functions in the brain and body. For instance, it regulates fluid balance, how much fluid you desire and how much fluid you excrete. Salt also regulates your appetite for other nutrients, things like sugar, things like carbohydrates. We all harbor small sets of neurons. We call these sets of neurons nuclei, meaning little clusters of neurons, that sense the levels of salt in our brain and body. There are a couple brain regions that do this, and these brain regions are very, very special. Special because they lack biological fences around them that other brain areas have. And that those fences, or I should say that fence, goes by a particular name, and that name is the blood-brain barrier, or BBB. Most substances that are circulating around in your body do not have access to the brain. In particular, large molecules can't just pass into the brain. The brain is a privileged organ in this sense. However, there are a couple of regions in the brain that have a fence around them, but that fence is weaker. And it turns out that the areas of the brain that monitor salt balance and other features of what's happening in the body at the level of what we call osmolarity, at the concentration of salt, reside in these little sets of neurons that sit just on the other side of these weak fences. And the most important and famous of these, for the sake of today's conversation, is one called OVLT. OVLT stands for the organum vasculosum of the lateral terminalis. The neurons in that region are able to pay attention to what's passing through in the bloodstream and can detect, for instance, if the levels of sodium in the bloodstream are too low, if the level of blood pressure in the body is too low or too high, and then the OVLT can send signals to other brain areas, and then those other brain areas can do things like release hormones that can go and act on tissues in what we call the periphery, in the body, for instance, have the kidneys secrete more urine to get rid of salt that's excessive salt in the body. So, let's talk about the function of the OVLT and flesh out some of the other aspects of its circuitry, of its communication with other brain areas and with the body, in the context of something that we are all familiar with, which is thirst. Have you ever wondered just why you get thirsty? Well, it's because neurons in your OVLT are detecting changes in your bloodstream, which detect global changes within your body, and in response to that, your OVLT sets off certain events within your brain and body that make you either want to drink more fluid or to stop drinking fluid. There two main kinds of thirst. The first one is called osmotic thirst, and the second is called hypovolemic thirst. Osmotic thirst has to do with the concentration of salt in your bloodstream. So, let's say you ingest something very, very salty. Let's say you ingest, you know, a big bag of, you know, I I I confess I don't eat these very often, but I really like those kettle potato chips, and I don't have too much shame about that because I think I have a pretty healthy relationship to food, and I enjoy them, and I understand that it will drive salt levels up in my bloodstream, and that will cause me to be thirsty. But why? Why? Because neurons in the OVLT come in two main varieties. One variety senses the osmolarity of the blood and when the osmolarity, meaning the salt concentration in the blood is high, it activates these specific neurons in the OVT and by activates, I mean it causes them to send electrical potentials. Literally, send electrical signals to other brain areas and those other brain areas inspire a number of different downstream events. The consequence of the that communication is that a particular hormone is eventually released from the posterior pituitary. So, from the pituitary, there's a hormonal signal that's released called vasopressin. Vasopressin also goes by the name antidiuretic hormone and antidiuretic hormone has the capacity to either restrict the amount of urine that we secrete or when that system is turned off to increase the amount of urine that we secrete. So, there's a complicated set of cascades that's evoked by having high salt concentration in the blood. There's also a complicated set of cascades that are evoked by having low concentrations of sodium in the blood. But, the pathway is nonetheless the same. It's OVT is detecting those osmolarity changes, communicating to the supraoptic nucleus. Supraoptic nucleus is either causing the release of or is releasing vasopressin antidiuretic hormone or that system is shut off so that the antidiuretic hormone is not secreted, which would allow urine to flow more freely, right? Antidiuretic means anti release of urine and by shutting that off, you are going to cause the release of urine. You're sort of allowing a system to flow, so to speak. The second category of thirst is hypovolemic thirst. Hypovolemic thirst occurs when there's a drop in blood pressure, okay? So, the OVT, as I mentioned before, can sense osmolality based on the fact that it has these neurons that can detect how much salt is in the bloodstream, but the OVLTI also harbors neurons that are of the baroreceptor mechanoreceptor category. Now, more on baroreceptors and mechanoreceptors later, but baroreceptors are essentially a receptor, a meaning a protein that's in a cell that responds to changes in blood pressure. So, there are a number of things that can cause decreases in blood pressure. Some of those include, for instance, if you lose a lot of blood, right? If you're bleeding quite a lot. Or in some cases, if you vomit quite a lot. Or if you have extensive diarrhea. Or any combination of those. Both types of thirst, osm- osmotic thirst and hypovolemic thirst, are not just about seeking water, but they also are about seeking salt. In very general terms, salt, aka sodium, can help retain water. But, sodium and water work together in order to generate what we call thirst. Sodium water work together in order to either retain water or inspire us to let go of water, to urinate. So, before we can dive into the specifics around salt and how to use salt for performance and various recommendations and things to avoid, we need to drill a little bit deeper into this fluid balance mechanism in the body. And for that reason, we have to pay at least a little bit of attention to the kidney. The kidney is an incredible organ. And one of the reasons the kidney is so amazing is that it's responsible for both retaining, holding on to, or allowing the release of various substances from the body. Basically, blood enters the kidney and it goes through a series of tubes, which are arranged into loops. If you want to look more into this, there's the the beautiful loop of Henle and other aspects of the kidney design that allow certain substances to be retained and other substances to be released depending on how concentrated those substances are in the blood. The kidney responds to a number of hormonal signals including vasopressin in order to, for instance, antidiuretic hormone in order to hold on to more fluid if that's what your brain and body need. And it responds to other hormonal signals as well. So, it's a pretty complex organ. So, the way the kidney is designed is that about 90% of the stuff that's absorbed from the blood is going to be absorbed early in this series of tubes. So, just to give a really simple example, let's say that you are very low on fluid. You haven't had much to drink in a while, maybe you're walking around on a hot day. Chances are that the neurons in your OVLT will sense the increase in osmolarity, right? The concentration of salt is going to be increased relative to the fluid volume that's circulating. This, of course, assumes that you haven't excreted a lot of sodium for one reason or another. But, that increase in osmolarity is detected by the OVLT. The OVLT is going to signal a bunch of different cascades through the supraoptic nucleus, et cetera. And then vasopressin is going to be released into the bloodstream, and vasopressin, again, also called antidiuretic hormone, is going to act on the kidney and change the kidney's function in a couple of different ways, some mechanical, some chemical, okay? In order to make sure that your kidney does not release much water, doesn't make you want to urinate, and in fact, even if you would try to urinate, your body's going to tend to hold on to its fluid stores. Okay? So, very simple, straightforward example. We can also give the other example whereby if you're ingesting a lot, a lot, a lot of water, and it's not a particularly hot day, and you're not sweating very much. Let's assume your salt intake is constant or or is low for whatever reason. Well, then the osmolarity, the salt concentration in your blood is going to be lower. Your OVL T will detect that because of these osmo sensing neurons in your OVL T. Your OVL T will fail to signal to the super optic nucleus, and there will not be the release of vasopressin antidiuretic hormone, and you can excrete all the water that your body wants to excrete. Meaning, you'll be able to urinate. There's no holding on to water at the level of the kidney. Okay. So, how much salt do we need? And what can we trust in terms of trying to guide our ingestion of salt? First of all, I want to be very, very clear that there are a number of people out there that have prehypertension or hypertension. You need to know if you have prehypertension or hypertension. You need to know if you have normal tension, meaning normal blood pressure. Everyone should know their blood pressure. It's an absolutely crucial measurement that has a lot of impact on your immediate and long-term health outcomes. It informs a lot about what you should do. Should you be doing more cardiovascular exercise? Should you be ingesting more or less salt? And without knowing what your blood pressure is, I can't give a one-size-fits-all recommendation. And indeed, I'm not going to give medical recommendations. I'm simply going to spell out what I know about the research, which hopefully will point you in the direction of figuring out what's right for you in terms of salt and indeed fluid intake. There is a school of thought that everybody is consuming too much salt. And I do want to highlight the fact that there are dozens, if not hundreds, of quality papers that point to the fact that a {quote} {end quote} high salt diet can be bad for various organs and tissues in the body, including the brain. It just so happens that because fluid balance both inside and outside of cells is crucial not just for your heart and for your lungs and for your liver and for all the organs of your body, but also for your brain, that if the salt concentration inside of cells in your brain go becomes too high, neurons suffer. Right? They will draw fluid into those cells because water tends to follow salt, as I mentioned before, and those cells can swell. You can literally get swelling of brain tissue. Conversely, if salt levels are too low inside of cells in any tissue of the body, but in the brain included, then the cells of the body and brain can shrink because water is pulled into the extracellular space away from cells. And indeed, under those conditions, brain function can suffer. And indeed, the overall health of the brain can suffer. At very low levels of sodium, meaning at about 2 g per day, you run fewer health risks, but the number of risk continues to decline as you move towards 4 and 5 g per day. And then as you increase your salt intake further, then the risk dramatically increases. Most people are probably consuming more than that because of the fact that they are ingesting processed foods and processed foods tend to have more salt in them than non-processed foods. But if we were to take this number of 2.3 g, that's the recommended cutoff for ingestion of sodium, that indeed is associated with low incidence of hazardous outcomes, cardiovascular events, stroke, et cetera. So again, I want to be very, very clear that you need to know your blood pressure. If you have high blood pressure or you're prehypertensive, you should be especially cautious about doing anything that increases your blood pressure. And as always, you want to, of course, talk to your doctor about doing anything that could adjust your health in any direction. But, there are a number of people out there that have low blood pressure, right? People that get dizzy when they stand up. People that are feeling chronically fatigued. And in some cases, not all, those groups can actually benefit from increasing their sodium intake. Why? Well, because of the osmolarity of blood that we talked about before, where if you have a certain concentration of sodium, meaning sufficient sodium in your bloodstream, that will tend to draw water into the bloodstream. And essentially, the pipes that are your capillaries, arteries, and and veins will be full. The blood pressure will get up to your head. Whereas, some people their blood pressure is low because the osmolarity of their blood is low. And that can have a number of downstream consequences. I should also mention it can be the consequence itself of challenges or or even deficits in kidney function. But, all of these organs are working together. So, the encouragement here is not necessarily to ingest more sodium. It's to know your blood pressure and to address whether or not an increase in sodium intake would actually benefit your blood pressure in a way that could relieve some of the dizziness and other symptoms of things like orthostatic disorders. Let's look at what the current recommendations are for people that suffer from orthostatic disorders like orthostatic hypo, meaning too low tension, orthostatic hypotension, postural tachycardia syndrome, sometimes referred to as POTS, P.O.T.S., or idiopathic orthostatic tachycardia and syncope. Those groups are often told to increase their salt intake in order to combat their symptoms. The American Society of Hypertension recommends anywhere from 6,000 to 10,000. These are very high levels. So, this is 6 g to 10 g of salt per day. Keeping in mind, again, that salt is not the same as sodium. So, that equates to about 2,400 to 4,000 mg of sodium per day. I point out this paper and I point out these higher salt recommendations to emphasize again that context is vital, right? That people with high blood pressure are going to need certain amounts of salt intake. People with lower blood pressure are going to need higher amounts of salt. And for most people out there, you're going to need to evaluate how much salt intake is going to allow your brain and body to function optimally. So, if you're exercising a lot, if you're in a particular cold, dry environment, or a particular hot environment, you ought to be ingesting sufficient amounts of salt and fluid. A rule of thumb for exercise-based replenishment of fluid comes from what I some episodes back referred to as the Galpin equation. The Galpin equation I named it after Andy Galpin, and I think that is the appropriate attribution there. Andy Galpin is an exercise physiologist. So, the Galpin equation is based on the fact that we lose about 1 to 5 lb of water per hour, which can definitely impact our mental capacity and our physical performance. And the reason that loss of water from our system impacts mental capacity and physical performance has a lot to do with literally the changes in the volume of those cells, the size of those cells, based on how much sodium is contained in or outside those cells. And the formula for hydration, the so-called Galpin equation, is your body weight in pounds divided by 30 equals the ounces of fluid you should drink every 15 minutes. Now, the Galpin equation is mainly designed for exercise, but I think is actually a very good rule of thumb for anytime that you need to engage mental capacity, not just physical performance. The idea is to make sure that you're entering the activity, cognitive or or physical, sufficiently hydrated. And that throughout that activity you're hydrating regularly. And it points to the fact that most people are probably under hydrating, but not just under hydrating from the perspective of not ingesting enough water, that they're probably not getting enough electrolytes as well, sodium, potassium, and magnesium. So, we've all heard about how excess salt it's bad for blood pressure, damage the heart, the brain, etc. I do want to give some voice to situations where too little salt can actually cause problems. And this has everything to do with the nervous system. So, without getting into excessive amounts of detail, the kidneys, as we talked about before, are going to regulate salt and fluid balance. The adrenal glands, which ride atop the kidneys, are going to make glucocorticoids like aldosterone, and those are going to directly impact things like fluid balance, and in part they do that by regulating how much craving for and tolerance of salty solutions uh we have. The whole basis for a relationship between the adrenal system, these glucocorticoids, things like aldosterone, and the craving for sodium, is that the stress system is a generic system designed to deal with various challenges to the organism, to you, or to me, or to an animal. And those challenges can arise in many different forms. They can be an infection, it can be famine, it can be lack of water, and so on. But, in general, the stress response is one of elevated heart rate, elevated blood pressure, and an inability to maintain movement and resistance to that challenge, okay? It's clear from a number of studies that if sodium levels are too low, that our ability to meet stress challenges is impaired. There are conditions, such as when we are under stress challenge, when there is a natural craving for more sodium, and that natural craving for more sodium is hardwired into us as a way to meet that challenge. Now, we can't have a discussion about sodium without having a discussion about the other electrolytes, magnesium and potassium. I want to emphasize that many people are probably getting enough magnesium in their diet that they don't need to supplement magnesium. Some people, however, opt to supplement magnesium in ways that can support them, and there are many different forms of magnesium and just in very brief passing, I'll just say that there is some evidence that you can reduce muscle soreness from exercise by ingestion of magnesium malate, m a l a t e. I've talked before about magnesium threonate, t h r e n o a t e, magnesium threonate, for sake of promoting the transition into sleep and for depth of sleep. And then there are other forms of magnesium, magnesium bisglycinate, which it seems at least on par with magnesium threonate in terms of promoting transition into and depth of sleep, and so on. There are other forms of magnesium, magnesium citrate, which um has other functions. Actually, magnesium citrate huh is uh is a fairly effective uh laxative. Um uh not known to promote sleep and things of that sort. So, a lot of different forms of magnesium, and there's still other forms out there. Many people are not getting enough magnesium. Many people are. Okay, so that's magnesium. Anytime we're talking about sodium balance, we have to take into consideration potassium because the way that the kidney works and the way that sodium balance is regulated both in the body and the brain is that sodium and potassium are working in close concert with one another. There are a lot of different recommendations about ratios out there, and they range widely from two to one ratio of potassium to sodium. Uh I've heard it in the other direction, too. I've heard a two to one sodium to potassium. Um the recommendations vary. Now, for people that are following low-carbohydrate diets, one of the most immediate effects of a low-carbohydrate diet is that you're going to excrete more water. And so, under those conditions, you're also going to lose not just water, but you'll probably also lose sodium and potassium. And so, some people, many people in fact, find that when they are on a lower or low-carbohydrate diet, then they need to make sure that they're getting enough sodium and enough potassium. And of course, some people who are on low-carbohydrate diets do ingest vegetables at, you know, or other forms of of food that that carry along with them potassium. So, it's quite variable from person to person. I mean, you can imagine if carbohydrate holds water, water and salt balance and potassium go hand in hand and hand, that if you're on a low-carbohydrate diet, that you might need to adjust your salt intake and potassium. And conversely, that if you're on a carbohydrate-rich diet or a moderate-carbohydrate diet, then you may need to ingest less sodium and less potassium. So, up until now, we've been talking about salt as a substance and a way to regulate fluid balance and blood volume and so on. We haven't talked a lot about salt as a taste or taste of things that are salty. And yet, we know that we have salt receptors, meaning neurons that fire action potentials when salty substances are detected, much in the same way that we have sweet detectors and bitter detectors, and we have detectors of umami, the savory flavor, on our tongue. Well, we also have salt sensors at various locations throughout our digestive tract. Although that the sensation and the taste of salt actually exerts a very robust effect on certain areas of the brain that can either make us crave more or sate, meaning fulfill, our desire for salt. And you can imagine why this would be important. Your brain actually has to register whether or not you're bringing in salt in order to know whether or not you are going to crave salt more or not. And beautiful work that's been done by the Zuker lab, z u k e r, Zuker lab at Columbia University as well as many other labs have used imaging techniques and other techniques such as molecular biology to define these so-called parallel pathways. Parallel meaning pathways that represent sweet or the presence of sweet taste in the mouth and gut. Parallel pathways meaning neural circuits that represent the presence of salty tastes in the mouth and gut and so on. And then those go into the brain, move up through brainstem centers and up to the neocortex, indeed where our seat of our conscious perception is, to give us a sense and a perception of the components of the foods that we happen to be ingesting. The pathways, the parallel pathways for salty and the parallel pathways for sweet and bitter and so on can actually interact. And this has important relevance in the context of food choices and sugar craving. One of the things that's commonplace nowadays is in many processed foods there is a business, literally, a business of putting so-called hidden sugars. And these hidden sugars are not always in the form of caloric sugars. They're sometimes in the form of artificial sweeteners into various foods. And you might say, "Well, why would they put more sugar into a food and then disguise the sugary taste given that sweet tastes often compel people to eat more of these things?" Well, it's a way actually of bypassing some of the homeostatic mechanisms for sweet. You know, even though we might think that the more sweet stuff we eat, the more sweet stuff we crave, in general people have a threshold whereby they say, "Okay, I've had enough sugary stuff." So, these sensory systems interact in this way by putting sugars into foods and hiding the sugary taste of those foods, those foods, even if they contain artificial sweeteners that will then signal to the brain to release more dopamine and make you crave more of that food. Whereas, had you been able to perceive the true sweetness of that food, you might have consumed less. And indeed, that's what happens. So, these hidden sugars are kind of diabolical. Why am I talking about all of this in the context of an episode on salt? Well, as many of you have probably noticed, a lot of foods out there contain a salty-sweet combination. And it is it's that combination of salty and sweet which can actually lead you to consume more of the salty-sweet food than you would have if if if it had just been sweet or it had just been salty. And that's because both sweet taste and salty taste have a homeostatic balance. So, if you ingest something that's very very salty, pretty soon your appetite for salty foods will be reduced. But if you mask some of that with sweet, well, because of the uh interactions of these parallel pathways, you somewhat shut down your perception of how much salt you're ingesting. Or conversely, by ingesting some salt with sweet foods, you mask some of the sweetness of the sweet foods that you're tasting, and you will continue to indulge in those foods. So, salty-sweet interactions uh can be very diabolical. They can also be very tasty, but they can be very diabolical in terms of inspiring you to eat more of a particular food than you would otherwise if you were just following your homeostatic salt or your homeostatic sugar balance systems. So, your brain has a way of representing the pure form of taste, salty, sweet, bitter, etc., and has a way of representing their combinations. And food manufacturers have have exploited this um to large degree. I mention all of this because if you're somebody who's looking to explore either increasing or decreasing your sodium intake for health benefits, for performance benefits, in many ways, it is useful to do that in the context of a fairly pure, meaning unprocessed, food intake background, whether or not that's keto, carnivore, omnivore, uh intermittent fasting, or what have you. It doesn't really matter, but the closer that foods are to their basic form and taste, meaning not com- large combinations of large amounts of ingredients, and certainly avoiding highly processed foods, the more quickly you're going to be able to hone in on your specific salt appetite and salt needs, which as I've pointed out numerous times throughout this episode are going to vary from person to person depending on nutrition, depending on activity, depending on hormone status. So, if you want to home in on the appropriate amount of sodium for you, yes, blood pressure is going to be an important metric to pay attention to as you go along. But, in determining whether or not increasing your salt intake might be beneficial for uh for instance, for reducing anxiety a bit, or for increasing blood pressure to offset some of these postural syndromes where you get dizzy, etc., for improving sports performance, or cognitive performance, and indeed many people find, and it's a reviewed a bit, and some of the data are reviewed in the book The Salt Fix, that when people increase their salt intake in a backdrop of relatively unprocessed foods, that sugar cravings can indeed be vastly reduced, and that makes sense given the way that these neural pathways for salty and sweet interact. Now, thus far, I've already covered quite a lot of material, but I would be completely remiss if I didn't emphasize the crucial role that sodium plays in the way that neurons function. In fact, sodium is one of the key elements that allows neurons to function at all. And that's by way of engaging what we call the action potential. The action potential is the fundamental way in which neurons communicate with one another. The point I'd like to make, at least as it relates to this episode on salt, is that having sufficient levels of salt in your system allows your brain to function, allows your nervous system to function at all. Again, this is the most basic aspect of nervous system function. And there are cases where this whole system gets disrupted, and that brings us to the topic of sodium and water balance. As many of you have probably heard, but hopefully, uh, if you haven't, you'll take this message seriously, if you drink too much water, especially in a short amount of time, you can actually kill yourself. All right? And we certainly don't want that to happen. If you ingest a lot of water in a very short period of time, something called hyponatremia, you will excrete a lot of sodium very quickly, and your ability to regulate kidney function will be disrupted, but in addition to that, your brain can actually stop functioning. And I've talked about this a bit in the episode on endurance, but there are instances in which, you know, competitive athletes have come into the stadium to finish a final lap of a long endurance race, and are completely disoriented, and actually can't find their way to the finish line. You know, it might sound like kind of a silly, kind of crazy example, but there are examples of people having severe mental issues and physical issues post-exercise when that exercise involved a ton of sweating, or hot environments, or insufficient ingestion of fluids and electrolytes, because included in that electrolyte formula, of course, is sodium. And as you just learned, sodium is absolutely crucial for neurons to function. So, to briefly recap some of what I've talked about today, we talked about how the brain monitors the amount of salt in your brain and body, and how that relates to thirst, and the drive to consume more fluid and or salty fluids. We also talked a little bit about the hormones that come from the brain and operate at the level of the kidney in order to either retain or allow water to leave your system. Talked a little bit about the function of the kidney itself, a beautiful organ. We talked about the relationship between salt intake and various health parameters and how a particular range of salt intake might be optimal depending on the context in which that range has been consumed. Meaning, depending on whether or not you're hypertensive, pre-hypertensive, or normal tension. We talked about fluid intake and electrolyte intake, so sodium, potassium, magnesium in the context of athletic or sports performance, but also in terms of maintaining cognitive function. Talked about the Galpin equation, which you could easily adapt to your body weight and to your circumstances. Of course, adjusting the amount of fluid and electrolyte intake upwards if you're exercising or working in very hot environments, downwards maybe if you're in less hot environments where you're sweating less and so on. We also talked about the relationship between the stress system and the salt craving system and why those two systems interact and why for some people who may suffer a bit from anxiety or under conditions of stress, increasing salt intake, provided it's done through healthy means, might actually be beneficial. We also talked about conditions in which increasing salt intake might be beneficial for offsetting low blood pressure and some of these postural syndromes that can lead people to dizziness and so forth. These are things that have to be explored on an individual basis and of course have to be explored with the support of your doctor. We also talked about the perception of salt, meaning the perception of salty taste and how the perception of salty taste and the perception of other tastes like sweet can interact with one another to drive things like increased sugar intake when you're not even aware of it and indeed how the combination of salty and sweet taste can bias you towards craving more, for instance, processed foods and why that might be a good thing to avoid. And of course, we talked about salt and its critical role in the action potential, the fundamental way in which the nervous system functions at all. So, my hope for you in listening to this episode is that you consider a question. And that question is, what salt intake is best for you? And that you place that question in the context of your fluid intake and crucially that you place that in the context of the electrolytes more generally, meaning sodium, potassium, and magnesium. And I hope I've been able to illuminate some of the beautiful ways in which the brain and the bodily organs interact in order to help us regulate this thing that we call sodium balance. And the fact that we have neurons in our brain that are both tuned to the levels of salt in our body and positioned in a location in in the brain that allows them to detect the levels of salt in our body and to drive the intake of more or less salt and more or less fluid and other electrolytes, really just points to the beauty of the system that we've all evolved that allows us to interact with our environment and make adjustments according to the context of our daily and ongoing life. And last but certainly not least, thank you for your interest in science.