Using Salt to Optimize Mental and Physical Performance

**Andrew D. Huberman** (0:00)
Welcome to the Huberman Lab podcast, where we discuss science and science-based tools for everyday life.
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. Most of us think of salt as something that we put on and in our food, maybe something to avoid. Maybe some of you are actually trying to get more salt, some of you are trying to get less salt. We all seem to associate salt with things like blood pressure, et cetera. Today, we are going to go down a different set of avenues related to salt. We will certainly cover how salt regulates blood pressure. We are also going to talk about how the brain regulates our appetite for salt or our aversion for salt. We are also going to talk about how our sensing of salty tastes actually mediates how much sugar we crave and whether or not we ingest more or less sugar than we actually need. So what you're going to learn today is that the so-called salt system, meaning the cells and connections in our brain and body that mediate salt craving and avoidance, are regulating many, many aspects of our health and our ability to perform in various contexts, things like athletic performance, things like cognitive performance. We're also going to talk about aging and dementia and avoiding aging and dementia and what role salt and salt avoidance might play in that. We're going to touch on some themes that for some of you might seem controversial. And indeed, if they are controversial, I'll be sure to highlight them as such. I'm going to cover a lot of new data that point to the possibility, I want to emphasize the possibility that for some people, more salt might help them in terms of health, cognitive and bodily functioning. And for other people, less salt is going to be better. I'm going to talk about what the various parameters are. I'm going to give you some guidelines that in concert with your physician, who you should absolutely talk to before adding or changing anything to your diet or supplementation regime can help you arrive at a salt intake that's going to optimize your mental, physical health and performance. So we're going to cover neurobiology, we're going to cover hormone biology, we're going to talk about liver function, we're going to talk about kidney function, and of course, brain function. I'm excited to share this information with you today. I'm certain you're going to come away with a lot of information and actionable items. Before we dive into the topic of today's episode, I want to highlight a really exciting new study. This is a study from Diego Borges Lab at duke University. The Borges Lab studies interactions between the gut and the brain, and has made some incredible discoveries of the so-called neuropod cells. Neuropod cells are neurons, nerve cells, that reside in our gut, and that detect things like fatty acids, amino acids, and some neuropod cells sense sugar. Previous work from this laboratory has shown that when we ingest sugar, these neuropod cells respond to that sugar and send electrical signals up a little wire that we call an axon through the vagus nerve, for those of you that want to know, and into the brain. And through subsequent stations of neural processing, evoke the release of dopamine. Dopamine is a molecule known to promote craving and motivation and indeed action. And what these neuropod cells that send sugar are thought to do is to promote seeking and consumption, eating, of more sugary foods. Now, the incredible thing is that it's all subconscious. This is a taste system in the gut that is not available to your conscious awareness. Now, of course, when you ingest sweet foods, you taste them on your mouth too. And so part of the reason that you crave sweet foods, perhaps, is because they taste good to you. And the other reason is that these neuropod cells are driving a chemical craving below your conscious detection. So they're really two systems. Your gut is sensing, at a subconscious level, what's in it and sending signals to your brain that work in concert, in parallel, with the signals coming from your mouth and your experience of the taste of the food. Now, that alone is incredible and has been the subject of many important landmark papers over the last decade or so. You can imagine how this system would be very important for things like hidden sugars, when nowadays in a lot of processed foods, they're putting hidden sugars, they're putting a lot of things that cause your gut to send signals to your brain that make you crave more of those foods. So for those of you that really love sugar, just understand it's not just about how that sugar tastes. The new study from the Borges Lab deserves attention, I believe. This is a paper published just recently, February 25th, this year, 2022, in Nature Neuroscience, an excellent journal. And the title of the paper is The preference for sugar over sweetener depends on a gut sensor cell. The Borges Lab has now discovered a neuropod cell, meaning a category of neurons, that can distinguish between sweet things in the gut that contain calories, for instance, sugar, and things in the gut that are sweet, but do not contain calories. Artificial sweeteners like aspartame, sucralose, and so forth. There are also, of course, non-artificial, non-caloric sweeteners like stevia, monk fruit, et cetera. They did not explore the full gallery of artificial sweeteners. What they did find, however, ought to pertain to all forms of sweet non-caloric substances. What they discovered was that there is a signature pattern of signals sent from the gut to the brain when we ingest artificial or non-caloric sweeteners. This is important because what it says is that at a subconscious level, the gut can distinguish between sweet things that contain calories and sweet things that do not. Now, what the downstream consequences of this sensing is or what they are isn't yet clear. Now, I believe everyone should be aware of these kinds of studies for a couple of reasons. First of all, it's important to understand that what you crave, meaning the foods you crave and the drinks you crave is in part due to your conscious experience of the taste of those things, but also due to biochemical and neural events that start in the body and impinge on your brain and cause you to seek out certain things, even though you might not know why you're seeking out more sugar. You find that you're craving a lot of sugar or you're craving a lot of foods with artificial sweeteners and you don't necessarily know why. Now, artificial sweeteners themselves are a somewhat controversial topic. I want to highlight that. Some months back, I described a study from Yale University about how one can condition the insulin system. Insulin is involved in mobilizing a blood sugar and so forth in the body, as many of you know. And I described some studies that were done from Yale University School of Medicine looking at how artificial sweeteners can actually evoke an insulin response under certain conditions. Now, a couple of key things. I got a little bit of pushback after covering those studies, and I encourage pushback all the time. Pushback is one of those things that forces all of us to drill deeper into a topic. I want to be clear. First of all, I am not one to demonize artificial sweeteners. There is evidence in animal models, in animal models, that artificial sweeteners can disrupt the gut microbiome, but those were fairly high doses of artificial sweeteners, and it's unclear if the same thing pertains to humans. Still unclear, I should say. It has not been investigated thoroughly. Some people don't like the taste of artificial sweeteners. Some people do. Some people find that they really help them avoid excessive caloric intake. Some people believe, and yet I should emphasize, there still isn't evidence that they can adjust the insulin response in all people. I just want to repeat that three times so that people are clear on that fact. What these new data emphasize, however, is that we need to understand how artificial sweeteners are consumed at the level of the gut, or I should say registered at the level of the gut and how that changes brain function. Because one thing that I'm familiar with and that many people report is that when they first taste artificial sweeteners, they taste sort of not right to them. They don't like the taste, but over time they actually start to crave that taste. I've experienced this. I used to drink a lot of diet sodas when I was in graduate school. So this would be aspartame. And I found that I actually needed them. Now, maybe it was the caffeine. Maybe I just liked the sweet taste or the carbonation. We actually have a drive for carbonation, which is a topic of a future episode. But when I finally quit them for reasons that were independent of any fear of artificial sweeteners, I found that I didn't like the taste. Nowadays, I only occasionally drink a diet soda. I usually do that if I'm on a plane and there's nothing else available to me. So I don't demonize them. I might drink one every once in a while. No big deal. I also want to be clear. I consume stevia on a number of different supplements and foods that I consume. Stevia, of course, is a plant-based non-caloric sweetener. So I myself consume artificial sweeteners. Many people hate them. Many people like them and find them useful for their nutrition and in fact, to keep their caloric intake in a range that's right for them. And many people like myself are curious about them and somewhat wary of them and yet continue to consume them in small amounts. I think most people probably fall into that category. I should also mention that many food manufacturers put artificial sweeteners such as sucralose, et cetera, into foods. And it's always been unclear as to why they might want to do that. And yet we know that the sweet taste consumption, even if it doesn't contain calories, can drive more craving of sweet food. So there may be a logic or a strategy to why they do that. Again, a topic for exploration on today's podcast and in future podcasts, because where we're headed today is a discussion about how salt and salt sensing, both consciously and unconsciously, can adjust our craving for other things like sugar and water and so on. So I want to highlight this beautiful work from the Bohoriz Lab. We'll put a link to the study. I want to open this as a chapter for further exploration. I like to think that the listeners of this podcast are looking for answers where we have answers, but are also, I would hope, excited about some of the new and emerging themes in what we call nutritional neurobiology. And indeed, the Bohoriz Lab really stands as one of the premier laboratories out there that's looking at how foods, as consumed in the gut, are modifying our nervous system, the foods we crave and how we utilize those foods. Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero cost to consumer information about science and science-related tools to the general public. In keeping with that theme, I'd like to thank the sponsors of today's podcast. Our first sponsor is Athletic Greens. Athletic Greens is an all-in-one vitamin mineral probiotic drink. I've been taking Athletic Greens since 2012, so I'm delighted that they're sponsoring the podcast. The reason I started taking Athletic Greens and the reason I still take Athletic Greens once or twice a day is that it helps me cover all of my basic nutritional needs. It makes up for any deficiencies that I might have. In addition, it has probiotics, which are vital for microbiome health. I've done a couple of episodes now on the so-called gut microbiome and the ways in which the microbiome interacts with your immune system, with your brain to regulate mood, and essentially with every biological system relevant to health throughout your brain and body. With Athletic Greens, I get the vitamins I need, the minerals I need and the probiotics to support my microbiome. If you'd like to try Athletic Greens, you can go to athleticgreens.com/huberman and claim a special offer. They'll give you five free travel packs plus a year's supply of vitamin D3K2. There are a ton of data now showing that vitamin D3 is essential for various aspects of our brain and body health. Even if we're getting a lot of sunshine, many of us are still deficient in vitamin D3 and K2 is also important because it regulates things like cardiovascular function, calcium in the body and so on. Again, go to athleticgreens.com/huberman to claim the special offer of the five free travel packs and the year's supply of vitamin D3K2. Today's episode is also brought to us by Thesis. Thesis makes what are called nootropics, which means smart drugs. Now, to be honest, I am not a fan of the term nootropics. I don't believe in smart drugs in the sense that I don't believe that there's any one substance or collection of substances that can make us smarter. I do believe based on science, however, that there are particular neural circuits and brain functions that allow us to be more focused, more alert, access creativity, be more motivated, et cetera. That's just the way that the brain works. Different neural circuits for different brain states. Thesis understands this. And as far as I know, they're the first nootropics company to create targeted nootropics for specific outcomes. I've been using Thesis for more than six months now. And I can confidently say that the nootropics have been a total game changer. My go-to formula is the clarity formula, or sometimes I'll use their energy formula before training. To get your own personalized nootropic starter kit, go online to takethesis.com/huberman. Take a three minute quiz and Thesis will send you four different formulas to try in your first month. That's takethesis.com/huberman and use the code Huberman at checkout for 10% off your first order. Today's episode is also brought to us by Element. Element is an electrolyte drink that has everything you need and none of the things you don't. That means it has salt, magnesium and potassium, the so-called electrolytes, which are critical for neuronal function and a lot of other biological functions. As I mentioned on the podcast before, I'm a fan of salt. I believe in ingesting appropriate amounts of salt. And by appropriate, I mean, depending on what your background blood pressure happens to be, what your activity levels are, how much you sweat, what your cognitive and physical demands are. Today, we're going to talk about how to determine what those needs are. I'm always trying to stay on top of my hydration. And as you'll also learn about today, salt and water intake and hydration are intimately related. With element, I'm sure to get the potassium, the sodium and the magnesium that I need. And I do that in a great tasting drink. And as I mentioned before, it has no sugar. If you'd like to try element, you can go to drinklmnt.com. That's drinklmnt.com/huberman to claim a free element sample pack. You only cover the cost of shipping. Otherwise, it's completely free. Again, that's drinklmnt.com/huberman to claim a free sample pack of element. Okay, let's talk about salt. 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. It also regulates your desire for salt itself, meaning your salt appetite. You have a homeostatically driven salt appetite. I'll talk about the mechanisms today, make them all very clear. What that means is that you crave salty things, beverages and foods, when your salt stores are low, and you tend to avoid salty beverages and foods when your salt stores are high, although that's not always the case. There are circumstances where you will continue to crave salt even though you don't need salt, or indeed, even if you need to eliminate salt from your system. Salt also regulates your appetite for other nutrients, things like sugar, things like carbohydrates. And today we'll explore all of that. Technically, salt is a mineral. And I should mention that when I say salt, I am indeed referring to sodium in most cases, although I will be clear to distinguish salt from sodium, meaning for table salt from sodium. Most people don't realize this, but one gram of table salt contains about 388 milligrams of sodium. So technically, we should be talking about sodium today and not salt. I will use them interchangeably unless I'm referring to some specific recommendations or ideas about trying to define your ideal salt, AKA sodium intake. Okay, so this is important. I think right off the bat, a lot of people get themselves into a place of confusion and potentially even to a place of trouble by thinking that table salt in grams always equates to sodium in grams. And that's simply not the case. Today, we're going to explore the neural mechanisms by which we regulate our salt appetite and the way that the brain and body interact in the context of salt seeking, salt avoidance, how to determine when we need more salt, when we need less salt. We'll talk about kidney function. We'll get into all of it. And we're going to do it very systematically. So let's start in the brain. 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 of 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 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. There are a couple of other organs that are privileged and that have very strict barriers, very particular fences, if you will. And those other organs include things like the ovaries and testes. And that makes sense for the following reason. First of all, the brain, at least most of the brain, cannot regenerate after injury. You just simply can't replace brain cells after injury. I know people get really excited about neurogenesis, the birth of new neurons. And indeed neurogenesis has been demonstrated in animal models. And to some extent it exists in humans in a few places, for instance, the olfactory bulb, where neurons are responsible for detecting odor into the environment for smell that is. And in a little sub region of the hippocampus, a memory area, there's probably some neurogenesis. But the bulk of really good data out there point to the fact that in humans, there's not much turnover of neurons. What that means is that the neurons you're born with are the ones that you're going to be using most, if not all of your life. In fact, you're born with many more neurons than you'll have later. And there's a process of naturally occurring cell death called apoptosis that occurs during development. So you actually are born with many more neurons than you have later in life. And that's the reflection of a normal, healthy process of nerve cell elimination. The estimates vary, but anywhere from a third to maybe even a half or even two thirds of neurons, depending on the brain area, just going to die across development. That might sound terrible, but that's actually one of the ways in which you go from being kind of like a little potato bug flopping around helplessly in your crib to being an organism that can walk and talk and articulate and calculate math or do whatever it is that you do for a living. So the brain has a set of elements, these nerve cells and other cells, and it needs to use those for the entire lifespan. So having a BBB, a blood brain barrier around the brain is absolutely critical. The ovaries and testes have a barrier for, we assume, the reason that they contain the genetic material by which we can pass on our genes to our offspring, progeny, meaning make children, and those children will have our genes, or at least half of them, the other half from the partner, of course.