Improve Your Lymphatic System for Overall Health & Appearance

Andrew Huberman: Welcome to the Huberman Lab podcast, where we discuss science and science-based tools for everyday life.

Andrew Huberman: I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today, we are discussing the lymphatic system.

Andrew Huberman: For many of you, the lymphatic system probably sounds a little bit esoteric. And for many of you, the lymphatic system may even drop notions of people talking about lymphatic clearance, or doing bizarre-seeming types of very light massage, or jade rollers, or bouncing on trampolines. And I must say, in researching this episode, I came to three general conclusions that I think are important to point out right now.

Andrew Huberman: First of all, your lymphatic system is absolutely essential to your immediate and long-term health. It's an incredible system that is serving you right now as you listen to this, and it's a system that you need to support. The second conclusion is that the lymphatic system is somewhat cryptic, and it doesn't get as much attention as, say, the cardiovascular system, or your brain and nervous system, or even the gut microbiome.

Andrew Huberman: And then the third conclusion is that the lymphatic system, and what is sometimes just generally referred to as "lymphatics," often get kind of a bad rap. And the reason is that a lot of the practices that are out there in the wellness space and health space that relate to lymphatics can often seem a little bit goofy, or odd, or kind of new agey, or woo, things like rebounding, like bouncing on a trampoline, or shaking, things of that sort. And to some extent, they look odd, because typically those aren't behaviors that most people engage in every day.

Andrew Huberman: But once you understand the structure and function of the lymphatic system, which you soon will, you'll realize why things like rebounding, things like treading water, things like specific ways of breathing actually serve the lymphatic system quite well, and there's a real basis for why those practices actually work. So, those are three general points about the lymphatic system to keep in mind today as we move forward. Another thing to keep in mind is that the lymphatic system is directly related to your appearance.

Andrew Huberman: Later, you'll learn why if you were to stay up for one night and not get any sleep, or even just get a poor night's sleep, and you look at your face in the morning, you look very different after a poor night's sleep than you do after a great night's sleep. Sometimes you even look very different immediately upon waking after a great night's sleep as opposed to a couple of hours later. Many people wake up with kind of bags under their eyes. They look kind of groggy. They look much older. And then a couple of hours later, they look fresh, and that stuff is all cleared away, and certainly not by doing anything cosmetic in terms of makeup or anything.

Andrew Huberman: That transition from bags under the eyes, feeling a heaviness in the face, the eyes tired, a sort of lack of life in the face and eyes, and then later, just a couple of hours, looking vibrant, the face looking very fresh and ready for the day, that has everything to do with what's called a "lymphatic clearance," and the lymphatic system of the face and neck.

Andrew Huberman: So today you're going to learn how the lymphatic system works, you're going to learn how to support your lymphatic system for your immediate and long-term health as well as for appearance, and you're going to learn about if you were to have, say, an injury to the body, or, God forbid, if you were suffering from cancer, how you could support your lymphatic system.

Andrew Huberman: And in talking about all of this, you'll be able to make sense of why it is that things like lymphatic massage or the various tools and treatments that are out there may actually work, and why some of them perhaps should be avoided. And as a final point, you're also going to realize by the end of today's episode that the lymphatic system is one of the major reasons why exercise supports longevity, and heart health, and brain health, and all the other things that we've heard that exercise can provide.

Andrew Huberman: The point here is that your lymphatic system sits central to everything we care about in terms of immediate and long-term health, and as you'll soon see, it's also just a really cool system.

Andrew Huberman: 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, today's episode does include sponsors.

Andrew Huberman: Okay, let's get into the lymphatic system. But in order to get into the lymphatic system, we need to talk briefly about the circulatory system for blood. Now, everybody knows what the heart is. The heart is this organ that pumps blood. Many of you are probably familiar with the fact that the heart has different chambers, different compartments, but the heart also has two major jobs that are quite different from one another, and two major anatomical distinctions that allow those functions to occur.

Andrew Huberman: And those functions, broadly speaking, are to deliver oxygenated blood to all the tissues of your body, including your brain, your spleen. Every organ and tissue in the body needs oxygenated blood. And also to return the non-oxygenated blood back to the heart and back to the lungs so that it can get re-oxygenated. So I'm just going to briefly describe the blood circulatory system in very broad terms. We probably should do an entire episode about heart health and heart function, and we will.

Andrew Huberman: But for those of you not familiar with how the heart works, basically, the heart is going to pump blood out through what are called "arteries." You've all heard of arteries, which are fairly large-diameter tubes. They have walls of those tubes that can resist a lot of pressure, and that's important because we need to put a lot of pressure to be able to pump blood far out into the body, out to your fingertips, your toes, and everything in between.

Andrew Huberman: Okay, oxygenated blood is going to travel out through those arteries, and then eventually, as those arteries approach the tissues that they need to oxygenate... And by the way, the blood is delivering not just oxygen but also glucose, blood sugar, hormones, different proteins, amino acids, all the stuff that your tissues need, not just oxygen.

Andrew Huberman: But then those arteries are going to transition into smaller diameter tubes that we call the "arterioles," and then eventually, as those arterioles approach the tissues they need to deliver all that stuff, all those goodies within the blood, those arterioles are going to transition and start branching into what are called "capillaries." Most of you have probably heard of capillaries. Capillaries have a very, very thin wall, just one cell thick, which allows things within the blood, like oxygen, amino acids, and other things that the cells and the tissues of your body need to actually get out into those tissues.

Andrew Huberman: Okay. So, most of us think about the blood system as pumping stuff out there, but we probably haven't thought about how the stuff that needs to get to our cells actually gets out of the blood and into those cells, and I just explained how.

Andrew Huberman: By having a very thin-walled set of capillaries carrying that oxygenated, amino acid-containing, glucose-containing blood, those nutrients and that oxygen can actually get out of the vasculature, out of those capillaries, and into the cells that need them. Okay. At a future date, I'll talk about the actual mechanics of how that's done. But for right now, I think that's sufficient.

Andrew Huberman: Now, once that stuff arrives in the tissue, and here, when I say tissue, it could be brain tissue, it could be muscle tissue, it could be liver tissue. Once that stuff gets out into the cells, the cells are going to use it. They're going to use the oxygen. They're going to use the glucose. They're going to use the amino acids. They're going to use the hormones. And as a consequence, they are going to create some waste products. There's going to be carbon dioxide that's created. There's going to be cellular waste in the form of actual physical debris. There are going to be metabolites. There's going to be ammonia.

Andrew Huberman: Basically, a bunch of waste product is going to then get kicked out of those cells into what's called the "extracellular space." Now, a couple of times today, I'll talk about what's referred to as the "interstitial space."

Andrew Huberman: The interstitial space is the area around the cells of the various tissues and organs of your body, and fluid, and these waste products get kicked out into that interstitial space between the cells. So, once it's there, it needs to be cleared out of there. How is it cleared out of there? Some of it will be taken back up into the blood supply, and with it, a lot of water, a lot of fluid.

Andrew Huberman: I didn't mention this yet, but a lot of fluid, a lot of water gets out of the vasculature and into those cells and into the interstitial space around those cells while it's delivering all those nutrients and goodies that we talked about a minute ago. Now, some of the waste product and the water, so carbon dioxide and water, et cetera, will be taken back up by the blood supply. How does that happen? Well, there are capillaries that are referred to as "venous capillaries." Okay. So we talked about the arterial system, which delivers oxygenated blood.

Andrew Huberman: There's also another system called the "venous system," which takes deoxygenated blood back up to be oxygenated by the lungs, and it does that, of course, in concert with the heart. So, we have the arterial system that delivers oxygenated blood. There are rare exceptions of arteries that deliver non-oxygenated blood to tissues such as the lungs, but let's just set that aside for now. We've got this arterial system that delivers oxygenated blood, and then now, we have the venous system.

Andrew Huberman: So, we have these little venous capillaries that are also just one cell wall thick, and the water, the carbon dioxide, the ammonia, the waste products are going to get reabsorbed there.

Andrew Huberman: It's going to then go from small diameter tubes, the venous capillaries, up to larger diameter tubes, and eventually into the veins that are going to deliver that blood, and the waste products, and the carbon dioxide back to the heart and lungs to be re-oxygenated and then sent back out to the body, okay? And you may have heard the word "pulmonary" before. If you haven't, that's okay. The pulmonary system is the aspect of the circulatory system that is directed towards the lungs to oxygenate the blood.

Andrew Huberman: Okay. So we've got this really nice looped system where oxygenated blood can get out to the tissues of the body. The cells in those tissues can use the oxygen, the nutrients, et cetera. And the water, and the carbon dioxide, and ammonia, and other waste products that come from just cells doing their business, from them doing all the things that they need to do as a liver cell, as a brain cell, et cetera, is then going to be passed back into the circulatory system, and then back to the heart and lungs so that the waste products can be expelled. For instance, when you exhale, the carbon dioxide is expelled from your body. And when you inhale, you bring in more oxygen that then gets on hemoglobin, and then back through the arterial system, and so on and so forth.

Andrew Huberman: Okay? So, it's a beautiful system, and even if you only captured 5% to 10% of what I just said, you certainly will have in mind now that your circulatory system for your blood is sending out oxygenated stuff, returning non-oxygenated stuff that also has a lot of waste product in it, and that there's a lot of water in that whole business. This is all liquid, and proteins, and glucose, et cetera, but there's a lot of water in this whole thing.

Andrew Huberman: After all, your blood is liquid. So, the important thing to understand about the lymphatic system is that the lymphatic system is there waiting at the interstitial space and at the interface between this arterial system that delivers oxygenated blood, and the venous system of capillaries that collects the deoxygenated blood and all these waste products.

Andrew Huberman: And it's right there as a series of tubes ready to catch the excess fluid and the waste products, and bring them back to the heart, also, but to do a lot of really important things with them along the way. You might say, "Why would you have this third system," right? "The circulatory system for blood sounds nearly perfect," and the key is that it's not perfect.

Andrew Huberman: Your lymphatic system is responsible for taking the fluid that remains in the extracellular space and all the gunk, all the waste products from cellular metabolism, again, proteins, ammonia, carbon dioxide, and bringing that back into the circulatory system of blood, but along the way, doing a number of very important things, including checking it out to see whether or not there are any contaminants, right? Any infections, bacterial or viral infections.

Andrew Huberman: That occurs in structures called the "lymph nodes," which you've probably heard of, and we will return to a little bit later. But leaving aside the immune surveillance role of the lymphatic system, just the mere role of needing to clear away what really is about three to four liters of excess fluid in the interstitial space is so important. You might say, "Well, how important can it really be," right? "Three or four liters, is it really that important?" It is absolutely crucial. Why?

Andrew Huberman: Because if too much fluid and amino acids, and cellular waste products build up in the tissues that are using the oxygenated blood and need all the nutrients, that is ripe for infection, right? Bacteria love to grow in warm environments with lots of amino acids. It's ripe for inflammation because of the CO2, and because of the ammonia and the waste products, and if that inflammation occurs, you get a buildup of tissue.

Andrew Huberman: In particular, adipose tissue can really thicken, skin can thicken, and it starts becoming chronically inflamed. And this is something that, believe it or not, is fairly common. It's common in people who are obese. It's common in people that don't move enough. We'll talk about why that's so in a moment. The lymphatic system's just basic role for draining that fluid out, out of the interstitial space, is something that all of us should really care about, healthy or unhealthy.

Andrew Huberman: So, even if you're not obese, you need to get your lymphatic system tuned up so that it's clearing that stuff. It's clearing what we call "lymph," which is kind of like a sticky kind of sticky fluid because it's got stuff other than water in there. It's got all those waste products, and it rarely has red blood cells in it, but it often can have a few white blood cells, and it can have some other stuff in it, and we need to clear that out. So it's semi-viscous. It's not superfluid. It's not a gel.

Andrew Huberman: It's kind of somewhere in between, and we need to clear that out. In fact, if we don't clear it out, our body very quickly goes into local or systemic inflammation, and if we don't clear it out within the brain, we get what's called "brain fog." You get cognitive impairment, and the brain fog that occurs from lack of lymphatic clearance from brain tissue comes on very quickly, even after one poor night's sleep, and it is very severe. If any of you have ever experienced brain fog, it is awful. The inability to kind of hold a thought or maintain a thought, and you're kind of somewhere between sleep and awake, and then you're kind of stressed about that, is serious.

Andrew Huberman: So, the mere clearance of the stuff from the extracellular space, the water, CO2, and waste products by the lymphatic system is crucial. So, before I talk about the immune surveillance role of the lymphatic system, I want to talk about what you can do to encourage the collection and drainage of all that extracellular fluid and the waste products with it.

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Andrew Huberman: Okay, so let's talk about the lymphatic system, focusing on the lymphatic vessels, which are basically just tubes.

Andrew Huberman: Okay? Tubes of different sizes depending on where you are in the body and what you need to accomplish, but here's a really key point that everyone should know. We spend so much time and attention thinking about the lymph nodes, which, of course, are super important, right? You go to the doctor, and you say you're not feeling well. They're going to feel your lymph nodes. I'll explain why they do that in a minute. They're going to feel under your jaw. Maybe you've had swollen lymph nodes where your legs meet your groin. You have them under your armpits. You'll occasionally feel some swelling or some kind of dull pain.

Andrew Huberman: By the way, that dull pain or swelling isn't necessarily a sign of a systemic infection. It could be, but it's not necessarily a sign of an infection. We'll talk about what the lymph nodes do, but the lymphatic vessels don't get nearly enough attention, in my opinion. Your entire body is innervated, as we say, by these lymphatic vessels, right?

Andrew Huberman: From your little pinky toe, and all your toes, and your feet, any tissue in your body because it needs blood and oxygen and nutrients, and because the cells there create waste products, and because some of that fluid remains in the interstitial space, doesn't make it back into the vasculature, you need lymphatic vessels everywhere. You need them in your brain, you need them in your skin, you need them in your adipose tissue, your fat, that is. You need them everywhere.

Andrew Huberman: And so, if I were to give you a map of the lymphatic vessels across the body, it would just look like spaghetti everywhere. Lymph nodes are going to be those larger compartments where some of the lymphatic fluid and the stuff within it is sequestered for a bit, monitored for infections, and then passed along. We'll get back to that later. The lymphatic vessels have a very important property, which is that they are one-way vessels, okay?

Andrew Huberman: Fluid can only pass in one direction through them, and that unidirectionality of the vessels is oh-so important when thinking about how to encourage lymphatic drainage and lymphatic flow. And when I say lymphatic flow, what I really mean is the passage of fluid from the interstitial extracellular space into these lymphatic vessels. Sometimes people will call them lymphatic ducts, but that's actually a technical term related to something else.

Andrew Huberman: But into these lymphatic vessels, then through these vessels and back into the venous blood supply, where all sorts of good things happen, and we'll talk about it in a bit. So they're one-way vessels, and if you think about the lymph that accumulates and then goes into the vessels in, say, your feet, if it's a one-way vessel, you know you need... That vessel is going to be directed towards the heart, right? The fluid will be able to go towards the heart, right? Because eventually that's where this stuff needs to go.

Andrew Huberman: It needs to dump back into the venous blood supply, get oxygenated, and so forth, and waste has to be disposed of. And we have this thing called gravity, which is pulling down, right? It's pulling down. It's a force that's literally pulling down, and you've got these one-way vessels trying to pass lymph, which is fluid, but it's kind of a slightly viscous fluid, up toward the heart.

Andrew Huberman: You also have lymphatic vessels in your hands, in your arms, and gravity is, of course, pulling down on the fluid within them as well, and your brain, et cetera. Now, here's a critical feature of the lymphatic system that is different from the cardiovascular system, which is, there's no pump. In the cardiovascular system, you have a pump.

Andrew Huberman: You have a heart that can generate a lot of force to move that liquid out through the arteries and back through the veins, and you've got a lot of mechanical force coming from that heart. The lymphatic system doesn't have that at all. On its own, it's a passive system, no pump, and it's fighting gravity all the time. So how does lymph move through these lymphatic vessels? Nature came up with a brilliant solution.

Andrew Huberman: It's actually the movement of your body that creates the movement of lymph up through these vessels from the lower half of your body, or down from the vessels in your upper part of your body, or in from your arms and fingers toward the center of your body to eventually be returned back to the venous blood supply. This is really important to understand.

Andrew Huberman: The movement of your muscles, not necessarily resistance training, although that would contribute to it, but low-level muscular contractions of the sort that occur when you walk, when you stand up and sit down again, when you make little micro movements, but certainly the movement of the large musculature of your body in particular, like your legs, and your trunk, and your arms, that's what's going to move this lymphatic fluid along because the lymphatic vessels can sit very superficially just underneath the skin, right, very, very close to the surface.

Andrew Huberman: The lymphatic system also has these small-diameter things we call "lymphatic capillaries," but it has bigger-diameter vessels within the deeper tissues, closer to the muscle, and intimately related to what's called the "fascia." I know some of you have heard of the fascia. Some of you perhaps have not. If you've ever prepared a steak and you saw there's kind of, not the fatty stuff, but the... It's like a white fibrous sheet that you can almost peel off the meat.

Andrew Huberman: Your muscles are surrounded by fascia, and those deep lymphatic vessels are closely tied to the fascia and to the muscular system, so that when you move your body walking or running, it could be exercise, but even just everyday activities, that lymphatic fluid is being carried back up toward the heart to return and join the blood supply. So hopefully you're getting a sense of the organizational logic of the lymphatic system.

Andrew Huberman: Nature has co-opted movement as a way to move lymphatic fluid along and encourage lymphatic drainage, and you want lymphatic drainage. You want that fluid pulled out of the extracellular space into those vessels and then returned back to the heart, and as I mentioned before, a bunch of other great things happen along the way in terms of immune surveillance.

Andrew Huberman: So, if we're going to discuss protocols, one of the most important ways to encourage lymphatic drainage, which is a good thing, and to encourage the general health of your lymphatic system, because you don't want lymph sitting stagnant in those vessels, especially if it has contaminants within it, is to make sure that you're moving enough each day. And we hear a lot these days about, you know, you need 10,000 steps a day, or maybe it's just 7,000, or maybe it's 3,000.

Andrew Huberman: No one can really come up with a single answer because it depends on which system you're trying to create support for, the cardiovascular system, the brain system, but I think a good number, a good thing to shoot for, is at least 7,000 steps per day. I happen to have some steps in my home, not a lot of them, but I find that if I'm going up and down those stairs a lot per day, that's good and probably is a little different than if I was just walking on a flat surface.

Andrew Huberman: Sometimes I'll get out and get 12,000 steps in a day, or if I'm visiting a new city and I'm walking a lot, 20,000 steps, but I really strive to get enough steps per day. And you will notice that if you don't get enough steps per day, your system, your body, will feel kind of sluggish. If you're sitting a lot because of travel, you should really strive to get as much movement in the airport as you can. Maybe, ideally, you take the stairs, you don't get on the conveyors, if you can manage to do that.

Andrew Huberman: Getting a lot of steps will help your body feel less sore, less sluggish, and not all, but a fair amount of the sluggishness that we feel when we don't move around a lot, when inactivity leads us to feel less energy, is the slow movement and the buildup of that lymphatic fluid. And keep in mind, that lymphatic fluid isn't, quote-unquote, "bad," but it contains a lot of waste products that you do not want sitting around in the local tissues.

Andrew Huberman: And I'll underscore that later when we talk about lymphedema that occurs under conditions where somebody is being treated for, say, cancer, and their lymph nodes and their lymph vessels are intentionally destroyed as a way to try and eradicate the cancers that have invaded the lymphatic system. When that happens, you get a lot of swelling of tissue. It can be painful. The tissue can become necrotic, infected, and inflamed, and it can lead to all sorts of local and systemic issues, and cosmetically, of course, it's not good either.

Andrew Huberman: Movement, movement, movement is the way you're going to encourage lymphatic flow. Walking is one way to do it. Yes, cardiovascular exercise is excellent for that, and later we'll talk a little bit about the specifics of how cardiovascular exercise benefits your heart. Little hint, it's through the growth of lymphatic vessels. Did you know that? Much of the benefit of aerobic exercise for your heart is because of the way that exercise stimulates the growth and health of lymphatic vessels, not heart cells directly. We'll get back to that.

Andrew Huberman: Walking is terrific. Cardiovascular exercise, you know, these days we are all told we need about 150 to 200 minutes of so-called "Zone 2 cardio." People debate whether or not it's better to do high-intensity interval training.

Andrew Huberman: Look, I think it's all good. It's all excellent, but none of it really is a replacement for just as much movement during the day as possible. I work a desk job, mainly researching podcast episodes or doing research. Back in the days when I was doing experiments in my lab, I was getting up and standing up, and moving around a lot.

Andrew Huberman: I've noticed that with each passing year, I'm 50 now, with each passing year, I tend to move a lot less just spontaneously, and as a requirement of my life, so I do more exercise. But if you move a lot during your day, that's great. Vacuuming, cleaning, this is a great thing for your lymphatic system. Okay? This is also an appropriate time to talk about some of the, quote-unquote, kind of, "goofy practices" that you'll see out there. I'm not calling them goofy, but they can look a little odd, where people are talking about, like, shaking their body, or they're talking about jumping up and down, or rebounding, jumping on a small trampoline.

Andrew Huberman: I confess, I own a small trampoline that I jump on in the morning. I just think it's fun, and it turns out to be really good for your lymphatic system, as is treading water, excellent for your lymphatic system, and swimming, excellent for your lymphatic system. There are great studies showing that. You might say, "How is it that jumping up and down is moving lymphatic fluid up toward my heart, because I'm jumping down? Wouldn't this be like stamping the fluid down toward gravity?"

Andrew Huberman: When I was a kid, we used to go to 7-Eleven and we'd get Slurpees, and we wanted to get as much Slurpee in there as we could, and so we used to just, like, bang the cups there, and we used to get yelled at. "No Slurpee stamping." And we would do it anyway. I don't drink Slurpees anymore. So no Slurpee stamping, but we were pushing that ice and fluid down so we could get more in there. Why would rebounding, jumping on a small trampoline, or even shaking or jumping at all, why would it bring the fluid up? Wouldn't it stamp it down?

Andrew Huberman: Ah, those lymphatic vessels are one-way vessels, so as you shake the fluid, right, it's going up, up, up, up, up. There's another way to really encourage a lot of lymphatic flow, and this will serve people cosmetically and just generally in terms of feeling more energetic, and it's kind of a lightness in your lower limbs. If you've ever felt a lot of heaviness in your lower limbs, there could be a variety of reasons for that. It could be related to something in your vascular system, could be because you train your legs too hard.

Andrew Huberman: Almost always, some of that is due to not moving around enough and the buildup of lymphatic fluid in the interstitial space or within the lymphatic vessels themselves. One of the best documented ways to improve lymphatic flow, to improve the rate and the extent of the lymphatic drainage, is actually through breathing. When I first heard this, I thought, "Oh, boy. Now we're getting into breathwork."

Andrew Huberman: My lab has studied breathwork, aka "respiration physiology," and it's known to be powerful, but the domain of breathwork oftentimes has naming of breathwork practices and stuff that can start seeming a little counterculture, new age, woo biohacking, which is not my flavor.

Andrew Huberman: But get this. Along the network of lymphatic vessels, some of those vessels are somewhat larger, and there's a particularly large compartment that sits within your abdomen called the "cisterna chyli." Okay? Fancy name, but cisterna chyli is an outpouching or a swelling of the vessels that contains a lot of lymph. And we haven't quite gotten to how lymphatic fluid gets back into the venous supply and joins up with the blood, et cetera. But the cisterna chyli is kind of like the sink or the drain for a lot of the lymphatic fluid that's made it back to your body, but has not yet made it back to the blood supply, hasn't cleared the lymphatic system yet.

Andrew Huberman: So it turns out one of the best ways to encourage the movement of lymph fluid that's already been checked out for infections, et cetera, and that's been taken out of the interstitial space to go back into your blood supply, which is what you want, is through what's called "diaphragmatic breathing." And the reason for this is that when you do diaphragmatic breathing, I'll explain how to do that in a moment, it's very simple.

Andrew Huberman: The reason diaphragmatic breathing is so useful for encouraging lymph drainage and lymph flow is because when you do diaphragmatic breathing, which is having your belly extend as you inhale, so you have this thing called the diaphragm, which is a muscle inside your body, and when you inhale, the diaphragm moves down. Of course, the lungs inflate, and ideally, your belly moves out a little bit, right?

Andrew Huberman: We generally tell people that it's not so good to breathe by lifting your chest and using your ribs, although you can use the muscles between your ribs, the intercostals, and your ribs to breathe, but you don't want to be breathing like this.

Andrew Huberman: Ideally, diaphragmatic breathing is what you do most of the time, unless you need to breathe much harder and you're inhaling... and your belly's moving out, okay?

Andrew Huberman: When you inhale and your belly's moving out, you are certain that you're doing diaphragmatic breathing. Diaphragmatic breathing creates a pressure differential between this cisterna chyli, right, this reservoir of lymph, and your blood supply, which has a different pressure within it. And so, if you do a few rounds of diaphragmatic breathing, and when I say rounds, I just mean a few breaths.

Andrew Huberman: So, inhale deeply and have your belly move out, and then exhale, you're greatly encouraging the passage of lymph from the lymph vessels back into the blood supply. Okay? Doing this just two or three times when you wake up in the morning, doing this two or three times in the afternoon, or in the evening, or really any time that you remember, will really encourage lymphatic drainage. It will really encourage the movement of that lymph fluid.

Andrew Huberman: And this is especially important to do if you're stuck on a plane or behind a desk, or you haven't had the opportunity to move quite as much as you would like, because again, the other way to move lymph fluid along is through low-level muscular contractions. But if you're trapped behind a desk or in an airplane seat, you can't do that. So, make it a point to do a few diaphragmatic breaths per day, and you will greatly encourage the movement and drainage of lymphatic fluid.

Andrew Huberman: And it actually can make a cosmetic difference. It can actually make a real difference in terms of less swelling of your lower body tissues, because as you clear the cisterna chyli, you allow the lymph coming up from your legs, and from other locations, to also move up, right? Because you're just creating room for it to move into those now empty tubes. So, while things like rebounding, and turns out treading water in a pool or swimming in a pool is an excellent way to create lymphatic drainage.

Andrew Huberman: I mean, it's one of the best ways, just because of the way that the physics of the water interacts with those superficial vessels of the skin. As you swim, there's kind of a shearing along of the skin. You might not notice it unless you used a slow-motion camera, but there's kind of a rippling of the skin. And those lymphatic vessels that sit just below the skin, those really tiny little capillaries, they're getting kind of squeezed along by the movement, that shearing of the skin along the top. So, swimming is great.

Andrew Huberman: It's sometimes hard to get access to a pool. A really fun way to do this as well is you can kind of go down to the bottom of the pool, and then blast off the bottom, grab a gulp of air, go back down, and blast up and grab a gulp of air. For those of you that have ever seen the great surfer, Laird Hamilton, and Gabby Reece, who's also great, his wife, they've developed tools and protocols for this called XPT.

Andrew Huberman: I don't have any formal affiliation with XPT, but they've developed a whole set of workouts related to this for general health reasons, for athletic performance, and it will also improve lymphatic drainage and lymphatic passage up from the bottom of the body. And you can think about the physics of bouncing off the bottom of the pool, like doing a squat and then grabbing a gulp of air, and going back down and up. That's almost perfect for what we're trying to accomplish when we talk about the movement of lymphatic fluid up and back toward the heart.

Andrew Huberman: But most people don't have access to a pool, so low-level muscular contraction from walking, diaphragmatic breathing. If you want to get a rebounder, a little trampoline, they're kind of fun. I think they're fun anyway. Hard to travel with. If you ever see people doing tai chi-type movements in the park in the morning, oftentimes they'll also include some shaking and things like that. Might look a little goofy, but there's a clear structural functional basis for why that would actually work.

Andrew Huberman: And along those lines, if you ever were to look up lymphatic massage, either lymphatic massage or it's sometimes called manual lymphatic relief. It comes by different names. Keep in mind, there are a lot of quality peer-reviewed studies exploring this, mostly in the context of treating lymphedema, the clearance of lymphatic buildup under conditions of cancer. Lots and lots of peer-reviewed studies. I've linked to some of those in the show note captions, which show over and over again, this can be a very useful practice.

Andrew Huberman: There are also drugs that are being developed for clearing out of lymph fluid, so-called lymphedema. Actually, a lab at Stanford School of Medicine is working hard. They've identified some of the molecular players that can help move lymph fluid out under conditions of lymphedema. I'll provide a link to an interesting discussion about that if you're curious about it, if you know someone who's undergoing cancer treatment and suffering from lymphedema. But lymphatic massage is a very common medical practice.

Andrew Huberman: A couple things about lymphatic massage that you should know. I've had a lymphatic massage before, and I was struck by how light the touch is. This is not a deep tissue massage. Lymphatic massage is intentionally rather light, and sometimes will transition from kind of a pushing along of the skin. For those of you that do this professionally, forgive my lack of specificity here. I am going to make the point in a moment that the people who are skilled at doing this really need to be the ones doing this.

Andrew Huberman: You could do it too for yourself. If you wanted to do self-lymphatic massage, there are ways to do this. There are instructions online. And it generally goes from people rubbing their skin fairly gently. People are always encouraged to do this more gently than they think they have to, to then usually there's some slapping or tapping, which seems kind of odd to those of us that aren't familiar with this. But it all makes perfect sense given that those lymphatic capillaries are so small in diameter.

Andrew Huberman: You don't want to be pushing hard on the surface of the skin because those lymphatic capillaries will collapse, or in some cases, rupture. And so, deep-tissue massage is kind of the opposite of what we're talking about when we talk about lymphatic massage, which is also why when people talk about gua sha, or a jade roller, it seems kind of woo, but the whole point is that you're applying gentle pressure.

Andrew Huberman: And I think it's really important to point out that there's a lot of discrepancy out there in terms of the direction and places to start and finish when doing lymphatic massage, and we'll talk about that in a little bit. This is actually crucial, because you really don't want to be squeezing or pushing on the lymphatic nodes, especially because they often contain infections that are being battled there, right?

Andrew Huberman: So, massaging your lymph nodes directly should be left to professionals. And in many cases, those professionals told me it's not generally a good idea, right? Because within those lymph nodes is where you've got the battle between infections, and bacteria, and things that just need to be cleared by your immune system. We're talking about massaging the lymphatic vessels.

Andrew Huberman: So, we've talked about a couple practices for improving lymphatic drainage. We've talked about some of the practices that might seem odd when you first encounter them, but they make perfect sense when you understand the structure function of the lymphatic system. I want to talk a little bit more about how the lymphatic system is organized, so that you can leverage any practices, including the ones I talked about, and some that I'm going to talk about more in a few minutes, in order to get drainage of lymphatic buildup in the areas of your body and/or face that you want and need.

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Andrew Huberman: Okay, so now you have a picture of your lymphatic system, right? It's a bunch of vessels, tubes that are collecting this fluid and all the waste products within them, headed back toward the heart to get that stuff back in with the venous blood supply, so it can be reoxygenated.

Andrew Huberman: There are a couple of really important features to how it gets back to the blood, that if you understand, you will be able to facilitate your own lymphatic health, and as a consequence, general health. If you've ever seen anything about the lymphatic system, or lymphatic drainage, or massage, or anything related to lymphatics, as they're called, this region...

Andrew Huberman: In fact, I've been pointing to this region throughout today's episode. For those of you just listening, I'm pointing to my clavicle region, to my upper chest, and where the neck meets the chest, in particular. This area is extremely important, because it's the area where lymph fluid is returned to join up with the blood supply. Remember, that fluid started off in the blood supply, it got out into the interstitial space. It could have, but didn't, rejoin the blood supply out in the tissues.

Andrew Huberman: The lymphatic vessels grabbed it, maybe way down in your feet, maybe in your liver, maybe in your spleen, maybe in your brain, and now it's got to get back in with the blood. How does that happen? Well, you have two ducts, okay? Two tubes, right? In biology, we've got so many names for tubes. You have two ducts. You have the right lymphatic duct, which is on the right, and you have the left lymphatic duct, which is the thoracic lymphatic duct on the left. Okay?

Andrew Huberman: Here's the deal. If you were to draw a line right down the middle of your face, or so, and out towards your shoulder and below it on the right, maybe a little bit of torso and your right arm, that right side of your face, your right arm, your right shoulder, kind of upper part of your torso on the right-hand side, that's all going to drain to the right side, that right thoracic duct.

Andrew Huberman: And that right thoracic duct is going to take all the lymph fluid, and it's going to dump it back into the venous blood supply. It's literally going to join up with there. There's a not-so-little, actually, vascular tube delivering that deoxygenated blood back to the heart, and the lymph is going to dump into there, okay?

Andrew Huberman: The rest of your body, both your left and right feet, left and right legs, the torso, that's everything I didn't describe for the right thoracic duct, left arm, shoulder, all of that, that's all going to drain to the left thoracic duct. It's actually just called the thoracic duct, and it's going to join up with the venous supply there. The veins that the lymphatic system feed into, before all of that gets back to the heart, are called the subclavian veins. Okay?

Andrew Huberman: You have one on your right, and you have one on your left. And as the name suggests, they sort of sit below, sub, your clavicles. Okay? So, you have your clavicles, which are your collarbone, sometimes people call them, and below those are these vessels that feed back to the heart with deoxygenated blood, and a bunch of other stuff that needs dealing with by your cardiovascular system. The lymphatic drainage into these subclavian veins is a major drainage site.

Andrew Huberman: So, these are big tubes dropping lymphatic fluid into big tubes. So, this is the end point of the lymphatic system. Remember, it's a one-way system, up from your legs, out and in from your arms, up through the cisterna chyli, and then dumping all that lymphatic fluid back into your blood supply.

Andrew Huberman: This is why in most practices that encourage lymphatic flow, or what's often talked about, lymphatic massage, whether or not it's for lymphedema, or whether or not it's for cosmetic purposes, very often you hear about people encouraging some light rubbing first, followed by some gentle tapping, and maybe even eventually some harder slapping of the region around the clavicles. Very important that you start with light touch and move up towards a more forceful touch, although never particularly forceful, because you don't want to collapse those lymphatic vessels.

Andrew Huberman: They're very small. You don't want to crush them, you don't want to pinch them, because then the lymphatic fluid won't move through them. So, there's kind of this progression from lighter touch and kind of gentle rubbing, or shearing of the skin, very, very light, to maybe some light tapping to encourage movement of the fluid along, and then maybe some slightly more vigorous, it's not really slapping, but kind of like a patting of the skin. That's it, a patting of the skin.

Andrew Huberman: Almost always, that's somewhere in a lymphatic massage protocol, whether the protocol is for lymphedema, under conditions of cancer treatment, or it's for purely cosmetic purposes. Almost always, there's an encouragement of movement of lymphatic fluid from that cisterna chyli, as well, because again, that's a major reservoir just below where the lymphatic system is going to drain back into the blood supply.

Andrew Huberman: People debate where to start these lymphatic massages. This is a whole field and, frankly, I've found differing opinions on this. Some people say, "Well, you have to start at the distal limbs," meaning out towards the hands and fingers, move things in. Other people say, "Well, no, you actually want to push down to the legs, then up through the legs." There's a lot of debate here. I think if you look at the mechanics of the lymphatic system, a couple of things become clear. You don't want to use firm pressure. This is not deep tissue massage.

Andrew Huberman: At some point in the protocol, you're going to want to include some encouragement of drainage from the clavicle regions, for all the reasons that we discussed, and from the cisterna chyli. And then, in terms of the lower legs, and the legs, and the arms, the out-to-in progression makes perfect sense. How you order those differs depending on the practitioner, and indeed, even in different research papers they use different approaches. I'm not so sure that it matters.

Andrew Huberman: What does seem to be very important is that you're not impinging or pushing hard on the lymph nodes, because you want lymph fluid in the lymph nodes for a certain period of time so that your immune system can surveil that lymph fluid and decide whether or not there are indeed any bacterial or viral infections, or other contaminants, that need to be dealt with by the immune system.

Andrew Huberman: Let's take a couple of minutes and talk about the immune functions of the lymphatic system. Now, for most people, when they think about the lymphatic system, they think about the immune system, and that's because most anyone who's ever had a cold, or some other virus, has had the experience of having their lymph nodes feel kind of swollen and maybe even a little bit painful. Typically, that occurs in the throat or the area right below the jaw.

Andrew Huberman: If you go to the doctor, you say you're not feeling well, one of the first things they're going to do is they're going to kind of palpate gently and touch gently behind your ears, along your jawline, along your throat. They're going to do this. They might ask you if you have any swollen lymph nodes in your armpits or in your groin. You may even be able to sense that swelling yourself. And what that swelling reflects is the accumulation of lymph fluid in so-called lymph nodes.

Andrew Huberman: Lymph nodes are these out-pouchings or swellings along the lymph vessels, where lymph fluid and the stuff within lymph fluid is sequestered, so it's kept there for a while, as opposed to just passing along through those one-way tubes, and it is surveilled by the immune system. Why and how is it surveilled by the immune system?

Andrew Huberman: Well, first of all, remember, when your cells are active, your liver cells, your brain cells, your muscle cells, by doing the things they do, they use nutrients and energy, glucose, they use oxygen, they use amino acids, they rely on hormones and all that stuff, and they generate waste. They generate waste products in the form of little bits of cellular debris. They generate ammonia. There's carbon dioxide. We listed off some of these earlier.

Andrew Huberman: But keep in mind that those cells are fed by the blood supply, and stuff gets into the blood supply by way of what you breathe, okay? So, you can inhale a virus, for instance, bacteria that could be in food, bacteria from things that you touch that somehow gets beneath the skin and into your blood supply through a scratch or a cut, maybe a bite, these sorts of things. Or maybe you cut yourself with a knife that had some bacteria, it gets into your blood supply.

Andrew Huberman: And so, you have foreign bodies, contaminants within your blood supply. Some of that is going to get out into the interstitial space. Some of that will be taken up by the lymphatic system. You also have things, again, waste products that are being generated by the cells of your body, and the lymph nodes are the place where all that stuff can be surveilled by the immune system. What do I mean surveilled by the immune system?

Andrew Huberman: Well, within the lymph node, you have immune cells. You have things like T cells and B cells, so named because the T cells mature in the thymus, which is a structure that is very prominent when you're young, as a baby and as a kid, and then over time, you actually lose your thymic tissue as you become an adult. And by the time you reach kind of 40s, and 50s, and 60s, 70s, you may not even have any thymic tissue whatsoever. You have T cells. You have B cells, which come from the bone marrow. These are different types of lymphocytes, different types of white blood cells.

Andrew Huberman: Again, these are all different categories. So, I'm talking about lymphocytes, white blood cells, T cells and B cells, different subcategories that go into the lymph nodes, and then check out and see whether or not there are bacteria, and viruses, and other kinds of foreign invaders that might need to be dealt with by the immune system. In addition to that, you have cells that go out into your body, things like macrophages, things like dendritic cells, okay, the names don't matter so much, that are looking for foreign invaders.

Andrew Huberman: Again, it could be viruses, bacteria, funguses. It could be even just physical bodies that somehow made it into your system one way or the other. And they will literally present things to the T cells and B cells, and other immune cells within the lymph nodes, so that the T cells and B cells can generate, through a process, this takes some time, to generate antibodies to fight those things off. Okay? I've talked about the immune system in previous episodes.

Andrew Huberman: You have an innate immune system, which is a kind of generic response to all forms of foreign invaders that cause some local inflammation, some swelling, sometimes some symptomatology in response to a virus that's just very generic, like feeling stuffy, lethargic, a little bit of a headache, or a stomachache, this kind of thing.

Andrew Huberman: And then you have your adaptive immune system, which recognizes the specific surface of foreign invaders, and generates antibodies to essentially bind that specific surface and its properties, and neutralize that foreign invader. So, innate immune system and adaptive immune system.

Andrew Huberman: Within your lymph nodes, you basically have a confluence of a lot of different immune cell types evaluating what's coming through in the lymph fluid, which reflects, of course, what's in the blood, because remember, the blood supply is giving oxygen, and nutrients, and other things to your cells.

Andrew Huberman: A lot of the fluid that's put out into the interstitial space, remember, about 16 or 17 of the 20 liters per day will be drawn back up into the blood supply. But then some significant portion, that three to four liters of fluid that ends up in the lymphatic system, is going to reflect what's in the global circulation system. And these lymph nodes are a place where what's in the lymphatic system can be evaluated to determine whether or not you've got something in your body that you shouldn't, or that you would like to eradicate.

Andrew Huberman: So, the lymphatic system, which we've mostly been talking about up until this point as a drainage system, has a second purpose, right? It's a multitasker. It also serves an immune system role to evaluate what's in the lymph, and therefore in the blood, and therefore in the entire body. Now, while we have lymph nodes in our jaw, behind our ears, in the back of our head, in the occipital area, lower-back part of our head, we also have them behind our knees, in our groin, inner elbow region.

Andrew Huberman: We have collections of lymph nodes distributed essentially across the entire body, okay? You're not going to see them continuously across the body, but every area needs to be surveilled, right? And so, you have these checkpoints everywhere along the lymph system, where viruses, bacteria, other foreign invaders can be evaluated and combated by your immune system.

Andrew Huberman: Now, does that mean that if you have, for instance, sore lymph nodes in your left armpit that you necessarily have something wrong with your left arm? No, not necessarily, because of the way the lymphatic drainage occurs. However, many people who have a sore lymph node in their armpit will kind of rub it, and that makes perfect sense, the way the pain system works. We have a natural reflex to rub, to provide sort of broadly distributed medium pressure to an area that's in pain.

Andrew Huberman: It actually deactivates some of the pain response within that area, so like the rubbing of a wound. We don't just rub our boo-boos because we learned to do that when we were kids. It actually shuts down some of the nerves that transmit pain. So, that's why we have that reflex. But you want to make sure that you don't squeeze your lymph nodes, or put too much pressure on them, because, again, your immune system is fighting things within those lymph nodes, or is evaluating whether or not something needs to be destroyed by your immune system within those lymph nodes.

Andrew Huberman: Now, some soreness can exist in the lymph nodes simply as a matter of swelling of the lymph nodes, and that doesn't necessarily reflect infection, okay? It can, but it doesn't necessarily reflect infection. If it's, of course, coupled with symptoms, stuffy nose, lethargy, things of that sort, chances are you're battling something.

Andrew Huberman: And if you do notice that your lymph nodes are particularly swollen and you haven't done, for instance, a really hard workout recently, or not slept as much as usual recently, then you may be at the threshold of potentially getting sick, and you want to take some measures to get some extra rest, extra hydration, probably don't want to exercise too hard those days. We've talked about this in previous episodes. You're feeling a little run down, not sick. Exercise can probably help you. You're a little sleep deprived one night, exercise definitely can help you. Two nights' sleep deprivation and you certainly don't want to be exercising with a ton of intensity, because you will get sick.

Andrew Huberman: So, those sore lymph nodes are a flag that your system is combating something. They're a flag that your immune cells are being recruited to that area. The lymph is staying in those areas longer because your immune system is trying to fight something back, so you should pay attention to that.

Andrew Huberman: But you don't want to be squeezing those lymph nodes. And as a general theme, I should've mentioned this earlier, if you've ever had deep tissue massage, right, you may notice afterwards, even if you weren't lying face down in that halo-like thing where your face is there, constricting your breathing a little bit. Those things aren't that bad. They're actually kind of pleasant, lie on your stomach, get a massage. But if you've ever had a deep tissue massage, you may notice afterwards that your face is kind of puffy, and you feel a little bit inflamed.

Andrew Huberman: And they'll often say, "Oh, make sure to drink a lot of water." Turns out that deep tissue massage can encourage enough movement along those deeper lymphatic vessels and can push things through the lymph nodes earlier than it would have been pushed through, and in some sense, generate an inflammation response. Not a major one, but a minor one. And usually this resolves within a couple of hours if you're up and walking around a bit, again, gently pushing through the lymphatic flow as it's supposed to be pushed through.

Andrew Huberman: The point here is that your lymph nodes are a site for combating infection. You don't want to push things through them any faster than it normally would occur, but you also don't want accumulation of lymph to occur in the nodes too long. And the way you ensure that it doesn't happen for too long is to keep the general lymphatic circulation going, and we've talked about ways to do that earlier.

Andrew Huberman: Earlier in our discussion about lymphedema, which is the swelling of typically the lower limbs, that can occur, for instance, in people who are being treated for breast cancer or for other cancers, where the lymph nodes are intentionally destroyed by chemo or radiation therapy, and that's because cancer cells can actually get into the lymph nodes and they can proliferate there.

Andrew Huberman: We often hear that "the cancer has spread to the lymph nodes," and that's one of the reasons why often the lymph nodes are removed prior to the spreading, or early in the spreading of a cancer, to try and prevent the broader migration, or so-called metastasis of that cancer to other tissues. The lymphatic system is targeted in this way, because if you think about it, the lymphatic system is in a position to distribute all sorts of things, including bad things, like cancer cells, that could proliferate further in other tissues.

Andrew Huberman: So, that's why lymph nodes and vessels are often intentionally destroyed as part of cancer treatment. And as a consequence, there's less drainage, leading to so-called lymphedema. Now, lymphedema can occur for other reasons, and it has various stages. It's actually been mapped out. I'll provide a link to this. But there's Stage 1, 2, 3, and 4. And to briefly summarize, Stage 1 is asymptomatic, so the lymphatic system has some abnormal flow, but no real fluid buildup in the tissue that you necessarily see. Might be just slight swelling.

Andrew Huberman: In Stage 2, you see swelling due to accumulation of the lymph fluid, and that may subside if you elevate that limb. So, if you're getting some swelling of the ankles, for instance, you put your legs up and it disappears after putting your legs up for 20 or 30 minutes, then it's so-called Stage 2 lymphedema.

Andrew Huberman: Stage 3 and 4 are where you get a more permanent swelling, so an accumulation of fluid and waste products in that interstitial space, that extracellular space, and that's when things start to become problematic, because that buildup of fluid and waste products leads to a local immune response, which then causes thickening of the tissue above it, which then makes it even harder to clear out waste products, and the whole thing starts to cascade.

Andrew Huberman: And this is a particular problem, again, for people being treated for cancers where the lymphatic vessels or the lymph nodes are intentionally destroyed, and that's why these people often need a fair amount of lymphatic manual drainage, or massage, it's sometimes called, in order to encourage the movement of the lymph fluid out. And as I mentioned earlier, there are drugs being developed to try and treat lymphedema through non-manual massage techniques, but that's still very much in development.

Andrew Huberman: But there's great hope for that, because as you can imagine, not everyone has access to proper lymphatic massage for lymphedema. But it's a very important aspect of cancer treatment and management of cancer treatment. Lymphedema is something that we should all be mindful of, even minor lymphedema, and this means even if you're not dealing with cancer treatment, you should be cognizant of whether or not you're getting some limb swelling due to lymphedema.

Andrew Huberman: A little bit? Fine. You put your feet up. We'll talk about ways to clear it from your brain in a few minutes. But lymphedema and that buildup causes a number of problems. First of all, the waste products in the interstitial fluid that's accumulating there, because you're not getting enough lymph drainage, can cause local inflammation, which can give way to more global inflammation.

Andrew Huberman: It also so happens that you get a thickening of the tissue in that area in response to that inflammation, and that thickening of the tissue causes a kind of hypoxia, or a low oxygen availability, for the cells in that area, so that now you've got more cells that get less oxygen that they need, and the whole thing starts to cascade. So, while I'm not trying to alarm anybody, you do want to do things to encourage that clearance of fluid and waste products from the interstitial space into the lymphatic system.

Andrew Huberman: And we talked about some of the things you can do for that earlier. There are other tools, by the way, that are more sophisticated, like for instance, they have compression boots. If you've ever been on a plane, or you've been running a lot, or basically using the tissues of your lower body, or upper body, a lot. If you've ever run a 10K or a half-marathon or a marathon, the heaviness of your legs, the soreness of your legs the next day, I highly recommend you get into a pool and tread some water, do some light swimming.

Andrew Huberman: Again, not an intense workout. But compression boots can be very helpful, because they basically fill up with air and compress your lower limbs, and then pulse your lower limbs to move that lymphatic fluid up toward the drainage system, back into your venous blood supply. These lymphatic boots can be very, very useful. There is some cost to them, but if you have access to them, those can be great. If not, just try and walk around a lot, put your legs up, do anything you can to get that lymphatic flow going.

Andrew Huberman: You do not want too much buildup of fluid and waste products in the interstitial space to occur for too long. And if you've been using a tissue a lot, there's going to be a lot of buildup of cellular waste products, which brings us to the glymphatic system, which is basically just the lymphatic system for the brain.

Andrew Huberman: In fact, as beautiful as this system is, and as delighted I am and everybody else is that in 2012 it was finally verified that the brain also has a lymphatic system, I don't like the branding. I don't like the naming. Yes, glia are involved. But by calling it the glymphatic system, people think that it's entirely different, and in fact, it's just somewhat different from the rest of the lymphatic system. And I think this so-called glymphatic system, which is the lymphatic drainage system of the brain, is so important to all of us.

Andrew Huberman: If you understand a little bit about how it's designed, its architecture, there are some very straightforward protocols that we'll discuss in a moment that will allow you to experience less brain fog, less swelling of your face in the morning, less bags underneath your eyes, and in general, improved wakefulness and cognition, and that just cascades into everything we know about how to support health.

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Andrew Huberman: Okay. The glymphatic system, which is the proper name for the lymphatic system of the brain. I was sort of joking earlier. I just want to make the point that our brain does have a lymphatic system.

Andrew Huberman: Up until 2012, no scientist, no physician believed that there was a lymphatic system for the brain, that lymphatic clearance, or flow, or any of that occurred in the brain. It was assumed that it was not, because it had not been discovered, except there was one scientist who had discovered it earlier and was told that she was wrong about it. We'll return to that a little bit later.

Andrew Huberman: But the point is that in 2012, a neuroscientist by the name of Maiken Nedergaard, who studies glia, a form of support cell that also plays an active role in brain function and plasticity, et cetera, she discovered that the brain has a system for clearing out waste that, by all accounts, looks a lot like the lymphatic clearance system in the rest of the body, and that it involves these cells we call glia.

Andrew Huberman: I'll just briefly describe this system, because it's incredible. It's beautiful in its organization. And if you understand that organization just a little bit, you'll be in a position to resolve some things that, chances are, you and many other people you know suffer from. Things like brain fog, things like puffiness of the face and under the eyes when you wake up in the morning, things like changes in your cosmetic appearance that occur throughout the day, and when you don't sleep as well as you might have wished you had slept the night before.

Andrew Huberman: In fact, let's just do a little mental experiment for a moment. Have you ever had a poor night's sleep and compared the way that you look after a poor night's sleep versus after a great night's sleep? Just next time that happens, take a picture of yourself, right? You don't have to show it to anybody. Just take a picture of yourself after a great night's sleep, and take a picture, ideally in the same location, under the same lighting, but even if it's under different lighting, of yourself after a poor night's sleep, where you either didn't sleep at all, or you got maybe two hours less than usual sleep, and you will see that you look very different.

Andrew Huberman: Your eyes will be sagging. You get those bags under your eyes. The eyebrows generally drop. There's a kind of a change in the tone of the eyes. You'll notice that's very typical. And any creases or wrinkles that you have will become more apparent. If you think about it, that's wild. You sleep two hours less, or three hours less than usual, or you get one poor night's sleep, and you look very, very different. And equally impressive is if you then get a great night's sleep the next night, you kind of bounce back, and you look yourself again, as we say.

Andrew Huberman: And your mind also parallels these changes, right? If you get three hours less than your usual allocation of sleep, your brain just does not work as well. We know that. And you don't feel as well. You're more reactive. You're more likely to have kind of attention deficit-like symptoms, right? You might not have full-blown ADHD, but you tend to be a bit more moody. You're certainly more susceptible to infections. But at the level of the brain, your brain is not the same as when you get a great night's sleep. Get a great night's sleep and you're just right back where you normally are.

Andrew Huberman: And if you don't sleep well for a few nights, or many nights, you'll notice that your appearance will very rapidly change. I'm not trying to scare people, right? We have lots of episodes on how to get great sleep. We have a zero-cost toolkit on how to get great sleep. All that's available at hubermanlab.com. Just put "sleep," "sleep toolkit," "perfect your sleep," all that, and you'll find all those tools in whatever format you want. But what is it about sleep that is so markedly changing our appearance and the way that our brain works?

Andrew Huberman: And the answer is, the clearance of waste products from your brain, which occurs through essentially what is the lymphatic system of your brain during sleep, doesn't get the opportunity to do that when you don't get enough sleep. It is that straightforward. So let me explain this brain lymphatic system and how you can get it to operate at its best. And I'm not just going to tell you to do that by getting enough sleep.

Andrew Huberman: You certainly should try to do that, but there are some things that you can do to encourage better lymphatic clearance within the brain while you sleep, and maybe even get by with a little less sleep than you think you need, but making that sleep better suited for lymphatic clearance within the brain. Okay, so it wasn't even two decades ago that this system was discovered, of clearing out a waste product from the brain. And what Dr. Nedergaard so beautifully hypothesized was that there has to be a system for this, right?

Andrew Huberman: There has to be a system. Why? Because your brain cells are some of the most metabolically active cells in your entire body, right? Your brain is just a small portion of your total body weight and volume, but it has a super high metabolism. The cells there need things. They need oxygen, they need glucose, even if you're on a keto diet, they need nutrients, and they're kicking out waste products like crazy, and that stuff has to get cleared from the brain.

Andrew Huberman: Now, you have a fluid within your brain called cerebrospinal fluid that moves within the so-called ventricles of the brain, so the spaces within the brain. And really, your whole brain is bathed in cerebrospinal fluid. Your brain is floating in this stuff, and it essentially has access to all the cells in your brain. So, as your cells make waste, it's picked up by the cerebrospinal fluid. Now, the cerebrospinal fluid is circulated, right? You create the cerebrospinal fluid.

Andrew Huberman: It's actually manufactured in a very interesting tissue, a kind of collection of tissues, broadly referred to as the choroid plexus, but there's stuff like meninges. If you go to medical school or you become a neuroscientist, you'll learn all about the details of these things, but for today's discussion, understand that the cerebrospinal fluid is made, it bathes your brain, and it can collect the waste products from the brain.

Andrew Huberman: Beautiful observations by Dr. Nedergaard and others found that in animal models, and now we know this is also true in humans, when you go to sleep at night, the vasculature that goes into your brain, because of course your brain does get artery inflow, okay? You have to give a blood supply, oxygenated blood to the brain, and it actually comes up from the bottom of the brain. There's a structure down there called the Circle of Willis, so your brain is actually resting on kind of a little trampoline of vasculature down at the bottom.

Andrew Huberman: If you ever flip over a brain and the vasculature is intact, there's a little circle down there called the Circle of Willis. And those arteries, remember, they're thick, they generate a lot of pressure, so your brain is kind of bouncing on those like a little, you know, kind of rebounding itself. Seriously. And then the vasculature climbs up along the top of the brain, and it makes basically a right angle, and then dives into the brain, and then it branches out to basically make sure that all the cells and areas of the brain get blood supply for oxygen and nutrients and so forth.

Andrew Huberman: Now, that's the case during the daytime, and it's also the case at night. However, during sleep, what happens is the areas around the vasculature that goes into the brain literally spreads out. They call it the perivascular space. Literally, it's as if every bit of vasculature has a little area around it where there aren't neurons, and that space gets 60% larger in sleep.

Andrew Huberman: It literally clears away so that there's big tubes or big areas along the blood vessels where cerebrospinal fluid, this fluid that's bathing the brain, can then run up to the surface of the brain and out to the areas of the brain away from the cells and then literally get cleared out of the brain and into the venous blood supply. Okay, that's a very general description of how this works, but I want to put a slightly more detailed picture into your mind because this is amazing, right?

Andrew Huberman: You have these cells, these glial cells called astrocytes. They're a bunch of different glial cells, but astrocytes are one of them, and the astrocytes have what are called little end feet, and the end feet can touch the synapses, the connection points between neurons, and they can also touch the vasculature. And at night, when you go to sleep, what these astrocytes do is they literally push out and create more perivascular space. "Peri" just means near, near the vasculature.

Andrew Huberman: They create more perivascular space, and they express a protein, a channel, which is really cool, called aquaporin-4. Someone won the Nobel Prize for discovering aquaporin-4. And aquaporin-4 is under circadian regulation, so it tends to be more active at night, and when you go to sleep, you basically create these spaces around the vasculature so that all the waste that's built up in the cerebrospinal fluid can flow out along the vasculature and get cleared from the brain.

Andrew Huberman: Now, there's a whole process by which it goes out, and then from the brain, and then it travels in different ducts and different pathways. It even can travel along your cranial nerves out of your brain stem and out, but it eventually all joins up in the blood supply just like the rest of the lymphatic flow. So this is incredible. While you sleep, you clear out the garbage from your brain.

Andrew Huberman: Although I don't really like calling it garbage because it's the natural byproduct of healthy cellular function, but I find it so interesting that people didn't think that there was a lymphatic system in the brain, or at least they couldn't find it, but Dr. Nedergaard found it. And I'll just briefly tell you, she wasn't the first one to find it. The first person to find it... This is just a kind of brief science anecdote here, but it's pretty important to hear. The first person to find it was a woman by the name of Patricia Grady.

Andrew Huberman: She was at the University of Maryland, and she was doing some experiments, and she discovered that the brain has something kind of like a lymphatic system, okay?

Andrew Huberman: She was doing some injections of this dye, which gets circulated, and she noticed some of this dye was making it along the perivascular areas and now into the surface of the brain, and so on, basically the same observation that was made in 2012, but much earlier. And she talked to her colleagues about it, and she talked about it at meetings. And other groups, in particular, I won't mention names, two very large, famous scientific groups, tried to replicate her work but in a different experimental model, and they tried to image the movement of dye out of the brain at night, and they did not observe it.

Andrew Huberman: But the reason they didn't observe it was not because they were bad scientists, but they made a mistake they weren't aware of, which is they created a little hole in the skull in order to image the movement of the dye in the brain, and they didn't close that hole in the skull with a lens or something else to keep the pressure in. So all the pressure was gone, so the lymph couldn't move along at all. They didn't observe it.

Andrew Huberman: They concluded it wasn't there, and everyone believed them, not her, because they were the more famous, larger groups. She moved off to a different field. Fortunately, she ended up at the National Institutes of Health and funded a lot of great work, including the later work that Dr. Nedergaard used to discover that there is, in fact, a lymphatic system in the brain. So, give credit where credit's due, and also remember, just because somebody observes something and somebody else doesn't, does not mean that it doesn't exist.

Andrew Huberman: Going back to the glymphatic system, how can you encourage better clearance of waste products from your brain at night, which is something you absolutely want to do if you want to have less brain fog and wake up from sleep, perhaps even less sleep than you think you need, feeling fresh and cognitively focused, et cetera?

Andrew Huberman: Well, it turns out, there have been a number of studies looking at sleeping position. Every animal, or at least every mammal, puts its head down to sleep, okay?

Andrew Huberman: My bulldog, Costello, because he had a big, thick skull, used to put his chin down, and he'd sleep basically with his chin along the floor. I saw a picture of giraffes; I don't know if they all sleep like this, where they actually put their head down and sleep, perhaps because lying on their side is tough.

Andrew Huberman: Some animals sleep on their side. Some animals sleep on their back. Humans, of course, can sleep in any of those different configurations. But all mammals make some attempt to put their head down in sleep. Okay, so what sleeping position is best for humans to encourage glymphatic drainage?

Andrew Huberman: And it turns out, the answer is to sleep on your side. Okay? There haven't been a ton of systematic studies of this, but if you were to compare sleeping on your back, sleeping on your stomach, or sleeping on your side as it relates to the efficiency of glymphatic drainage, you would say that sleeping on your side is best, so much so that there are even people, believe it or not, in sleep studies that are putting on what equates to like, a fanny pack and putting the fanny in the fanny position. I know everyone carries the fanny pack up front, so it's not really a fanny pack.

Andrew Huberman: Use your imagination for what it should be called. But in any case, there are studies where people are taking the fanny pack, putting it behind them so that they can't roll onto their back, at least not easily, and sleep at night, forcing them to sleep on their side; either the right or left side does not seem to matter. So, if you want to experiment with this, you can.

Andrew Huberman: I'm a back sleeper, sometimes a side sleeper, what they call, I think it's like, crawling soldier stance, where I find myself, if I wake up with one arm bent and one extended, kind of like, reaching out for the wall or something like that, one knee bent. But I actually have been making some effort to sleep on my side as a reflection of what I learned in the preparation for this episode and the papers that I read about glymphatic clearance. And I'm going to make more of an effort to do that, because I personally would like to get by with a little less sleep. I love getting eight hours.

Andrew Huberman: I generally get somewhere between six and seven. I feel pretty good. But I've noticed with each successive year that I wake up a little bit foggier from that six or seven hours of sleep than I did previously, and I haven't changed anything else dramatically. What is changing? My age. What changes with age? The amount of inflammatory molecules that you release in the brain as a consequence of its normal levels of activity, and this has a detrimental feedback loop, right?

Andrew Huberman: Same level of mental attention, same level of mental demand, more inflammatory response because of more waste product created. More clearance of that waste product, therefore, is a good thing for brain health. So much so that there are really nice studies showing that, A, if you impair glymphatic clearance by disrupting sleep or use some other method to impair glymphatic clearance, like disrupt the aquaporin-4 channel, that you get more buildup of things like amyloid plaques, things associated with dementia-like diseases, like Alzheimer's, but also more buildup of inflammatory molecules, like interleukins and TNF-alpha, generally, which make the brain more susceptible to microstrokes, and at a very low level, are probably what's relating to this thing that we call brain fog.

Andrew Huberman: So, I really would encourage everyone to try and emphasize side sleeping if you can, if you are sleeping your normal ration, or even if you're not getting your normal ration of sleep, to really try and optimize your sleep environment a bit in order to improve glymphatic clearance.

Andrew Huberman: A couple of things that we know reduce glymphatic clearance are alcohol intake in the day and night before, which reduces REM sleep, which reduces glymphatic clearance. We know that exercise actually can have a beneficial effect on glymphatic clearance, provided it's not too late in the day, not too much caffeine, or anything with that exercise to impair your sleep.

Andrew Huberman: But cardiovascular exercise, in particular, can improve glymphatic clearance later that night. We know that keeping your sleep environment cool, which optimizes sleep, all the things that promote sleep will promote glymphatic clearance.

Andrew Huberman: But there are a couple of things, in particular, sleeping on your side, as well as perhaps elevating your feet a bit, maybe 5 to 10 degrees, just putting a pillow underneath your feet to get a little bit of elevation on the feet for more lymphatic clearance in the legs. And some people have even hypothesized that sleeping on your side with a pillow that isn't super flat, so your head at least isn't tilted down.

Andrew Huberman: Remember, the lymphatic system fights gravity all the time, so you don't want your head falling back, at the very least. And maybe instead of sleeping flat or having your head falling back, you have your head slightly tilted up.

Andrew Huberman: Usually, a pillow will accomplish that. So all of these things are very simple to implement. They're essentially zero cost to implement. But all the studies of disrupting sleep and looking at glymphatic clearance and waste products and the downstream effects on cognition and brain longevity all point in the same direction. You need the waste cleared out of your brain at night, which means getting great sleep, and you also need the lymphatic system to be positioned literally, pun intended, for you to get the maximal amount of glymphatic clearance while you sleep.

Andrew Huberman: And as it relates to the cosmetic effects that I think most people want, I don't think anyone wants to wake up with puffy eyes and a puffy face. Sleeping with your head a little bit elevated will also assist there. Okay?

Andrew Huberman: I talked to two dermatologists who confirmed that a lot of the puffiness that people are concerned about with their eyes in the morning, and they feel like they need to ice underneath their eyes; some people even sell these patches that go on the eyes. It's kind of interesting, those patches, by the way.

Andrew Huberman: The dermatologist I spoke to said that the reason those patches probably work is that they just provide some gentle pressure to encourage the lymph out of that area, right? It may be as simple as that, something you probably could accomplish with your fingers just as easily, but it makes sense why those stickers would probably help. A lot of them are lined with other things these days, peptides and collagen and things to make them more attractive as a commercial product, but you don't necessarily need those.

Andrew Huberman: And there is this business of lymphatic massage and fascial massage for the face, and there, I have to say, there are some very, very striking examples of before and afters of people who do just a little bit of pressure-based and very specific, meaning in the proper, right order and in the proper locations, for the neck.

Andrew Huberman: We already talked about why the neck and clavicle region is so important. Under the jaw, the face, for the lymphatic system, and for the fascia, as we talked about earlier, is intimately related to those lymphatic vessels. And especially in the face, the lymphatic vessels, that is the lymphatic capillaries that innervate the eyelids around the eyes, those are going to be tiny, tiny, tiny and very easy to impinge, to pinch shut.

Andrew Huberman: So, the degree of pressure that one requires at different locations in the face and the proper order to do all that is indeed very important. And the before and afters of people's, let's just call it what it is, youthfulness and, kind of, levels of alertness, appearance, the height of the natural kind of resting place for the eyebrows, as opposed to sunken eyes and sunken eyebrows, open eyes, and even what appears to be like the cheekbones, those can undergo very dramatic shifts with proper fascial and lymphatic massage. And those approaches are out there.

Andrew Huberman: So one person who's considered one of the best experts in this area and who has tutorials about this, of how you can use fascial and lymph drainage and massage for the face in order to make it look more youthful, is somebody... By the way, I have no financial relationship to, is Anastasia Beauty Fascia. It's an account on Instagram. I believe there are also accounts on other social media channels. I'll put a link to it in the show note captions.

Andrew Huberman: The before-and-afters that she shows there of the people who apply these methods, which are nonsurgical, non-drug, non-Botox methods, she makes it very clear that's the case, are absolutely striking. I mean, you see some before and afters after two weeks, 30 days, 60 days that are like, absolutely striking, really.

Andrew Huberman: And you go, "How could that possibly be?" Well, when you learn how the lymphatic system works, when you understand about how lymph can pool, how fluid can accumulate in the interstitial space if it's not getting cleared by the lymphatic system, and when you understand the both superficial vessels and deeper vessels of the lymphatic system are related to light touch at the surface in the proper directions and the drainage out of the head and neck as well as accessing the deeper lymphatic vessels that are associated with the fascia, it all makes perfect sense.

Andrew Huberman: There's absolutely no reason why those sorts of results couldn't be accomplished, but the order of operations for something like that is very important. It's not the case that one can just rub under the eyes and rub a bit on the forehead or hold up the eyebrows. If it were, of course, everyone would be doing it, so it's nice that there are people such as Anastasia Beauty Fascia who are providing the methods for people to do that. So if you're interested in those methods.

Andrew Huberman: Again, I have no financial relationship to them whatsoever, but it makes sense why they could, should, and indeed appear to work.

Andrew Huberman: I'd like to take a quick break and acknowledge one of our sponsors, Function. Last year, I became a Function member after searching for the most comprehensive approach to lab testing. Function provides over 100 advanced lab tests that give you a key snapshot of your entire bodily health.

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Andrew Huberman: The other thing about the lymphatic system and appearance, not just puffiness of the face but swelling, we talk about water retention and edema, and we generally don't want that, right? Most people don't want water retention. You can clear a lot of water retention simply by hydrating well. You know, you're going to urinate more. You're going to balance the amount of fluid and salt appropriately.

Andrew Huberman: I've done an entire episode about this, talking about kidney function, aldosterone, et cetera. But the point is this. A lot of fluid accumulation occurs in the interstitial space because the lymphatic flow is not sufficient, the rate of the lymphatic flow is not sufficient, I should say. Hydration will definitely support lymphatic flow and drainage, okay?

Andrew Huberman: This is one of the major reasons why you need to make sure you're drinking enough water. It's very important to maintain proper blood volume, and your lymphatic flow will be improved. How much is enough water?

Andrew Huberman: We've talked about that in previous episodes. If you're exercising, you're sweating a lot, you can use the Galpin equation. I'll put that in the show note captions if you really want to get technical. For most people, the best thing to do is the following. When you wake up, drink 16 to 32 ounces of water, in addition to whatever other fluids you happen to be drinking. Yerba mate if you're me, coffee perhaps if you're you, or both for me on some days if I really need to get caffeinated.

Andrew Huberman: But also drink enough water. And then just make sure that every hour or two, you drink eight to 16 ounces of water. It might seem like a lot. Yes, you might take a few extra trips to the restroom, but by doing that, you can ensure that your blood volume, your sodium balance, as well as your lymphatic system are operating about as well as they could be, as long as you're doing all the other things that we talked about to encourage your lymphatic system to be flowing along.

Andrew Huberman: So by now you're probably realizing that a lot of the things that you and other people are already doing are probably helping you in part through the lymphatic system. Okay? I think we all know that we should hydrate well. I just gave you another reason why you should hydrate well, because of its effects on the lymphatic system. Most everybody knows that we should be doing cardiovascular exercise and resistance exercise every week. Okay?

Andrew Huberman: For some people, it will be a bit more of one versus the other. Some people are doing an equal amount of both. You do resistance training to strengthen your muscles, your bones, and your tendons, to offset loss of power, speed, and muscle that occurs as you age. Also, for the aesthetic reasons for many people. Cardiovascular exercise, also for aesthetic reasons, but also of course to improve the functioning of your cardiovascular system, your heart, right?

Andrew Huberman: Most people believe that you do cardio to improve your heart function. You increase stroke volume of your heart, for instance, how much blood you can beat out to your body by strengthening and in some cases even enlarging your heart a bit. What most people probably don't realize is that many of the positive effects of exercise, in particular cardiovascular exercise, occur because cardiovascular exercise promotes what's called "lymphangiogenesis," the growth of new lymphatic vessels that innervate the heart, remove waste products from the cells of the heart.

Andrew Huberman: Remember, your heart cells are active all the time, generating tons of waste and also consuming tons of oxygen and nutrients, and that needs to be cleared out, and as we age, our heart gets less efficient at clearing out that waste. Cardiovascular exercise increases literally the number of lymphatic vessels that allow the drainage of those toxins away from the heart, which greatly supports the cells of the heart, but also because this whole thing is a loop.

Andrew Huberman: If you remember, the lymphatic system feeds back to the venous blood supply, then that blood gets oxygenated, and it goes back to the heart. The heart, of course, is supplied by its own blood system, right? The heart also needs oxygen and blood supply, that's why we have so-called coronary arteries, right? The arteries that serve the heart itself. So by increasing the amount of lymphatic vessels, you can increase the amount of lymphatic drainage from the heart, and the whole system functions much better.

Andrew Huberman: In fact, there are several papers, and I'll link to these in the show note captions. I'll just read you the titles of these, and they make it obvious what the conclusions are. One is "Lymphangiogenesis contributes to exercise-induced physiological cardiac growth." The actual growth of the heart is enabled by the development of these new lymph vessels to the heart that are induced by exercise. So that's really cool, and in addition, I hate to break it to you, but for all of us, your heart gets less healthy as you age, even if you stay very healthy as you age.

Andrew Huberman: In part, that's due to inflammation from the buildup of waste products within the heart. There are other reasons for this, too, but it has now been demonstrated, and here I'm quoting the title of this paper, again, I'll put a link to it in the show note captions, "Exercise-induced cardiac lymphatic remodeling mitigates inflammation in the aging heart." So this isn't the addition of new lymphatic vessels. This is remodeling the branching and extension of existing lymphatic vessels into areas that they weren't before, so they can pull waste from the cells in those areas.

Andrew Huberman: So the exact opposite of lymphedema, where there's not enough drainage and there's buildup of waste products and fluid, and you end up with a bunch of issues there of local inflammation that makes that tissue sick, and then eventually can spread to other tissues. It's quite serious. This is the exact opposite of that. You're getting more entry of the lymphatic vessels.

Andrew Huberman: You're getting new lymphatic vessels from cardiovascular exercise, and as a consequence, more clearance of waste products from the heart, and the heart can function better, so much so that, at least, the conclusion of this paper was that it significantly contributes to the offset of inflammation of the aging heart.

Andrew Huberman: So again, this isn't pushing you to necessarily do something you're not doing already. If you're doing your cardio, keep up your cardio. You should also be resistance training. We all should. But if you're not doing cardiovascular exercise and you're just lifting, I know a number of people that do that. They think, "Well, my heart rate gets up and I can hop on the bike every once in a while and I don't get too fatigued. My VO2 max is decent," and this sort of thing.

Andrew Huberman: Yeah, well, resistance training has its own set of benefits, and it probably can positively impact the lymphatic system as well, but there's just now oh-so much data supporting the fact that regular cardiovascular exercise can really improve heart function by improving lymphoneogenesis and the growth and extension of existing lymphatic vessels into areas of the heart that they weren't before or that they were slowly receding from. So I really encourage you to keep up that cardiovascular exercise if you're already doing it, and if you're not, to start.

Andrew Huberman: And if keeping your heart healthy is not incentive enough, it turns out that, here I quote again, "Aerobic exercise improves clearance of amyloid-beta by the lymphatic system," and this is in a mouse model of Alzheimer's disease, but this is just one example of many, many examples.

Andrew Huberman: Whereby, as I've talked about before, exercise improves sleep, which improves glymphatic clearance, which clears away toxins in the brain, which can offset age-related dementia and a bunch of other negative effects like brain fog. But in addition to that, exercise has direct effects on increasing the amount of glymphatic clearance that's occurring in those perivascular spaces of the brain while you sleep.

Andrew Huberman: So, more and more evidence that we should, yes, get enough sleep, but we should also exercise, not just because it improves our sleep, but because it can improve glymphatic clearance from the brain. And this is probably the major reason, in my opinion, why cardiovascular exercise done regularly improves brain function. I know people love to talk about BDNF, brain-derived neurotrophic factor. I've worked on brain-derived neurotrophic factor. I know a lot about brain growth factors.

Andrew Huberman: I think it's super interesting, and indeed, I think that high-intensity interval training, anything where you experience a burn, a lactate accumulation in the muscles. Yes, it can stimulate more BDNF.

Andrew Huberman: And I think there's "oh, so much evidence that that's great," but I think when you look at the literature carefully, most of the positive effects of regular cardiovascular exercise on brain function, working memory, declarative memory, focus ability, and a number of other things occur because you're getting excellent glymphatic clearance during sleep, and you're getting just more clearance of waste products even in wakefulness.

Andrew Huberman: So, here we are again: exercise, exercise, exercise, and sleep, sleep, sleep. And to really hit on this theme of things that you may already be doing, and if you're not, you probably should, I want to just briefly mention one or two other things. First of all, this wouldn't be a Huberman Lab podcast episode if we didn't talk about light. And no, I'm not going to tell you to get morning sunlight in your eyes to set your circadian rhythm and boost your morning cortisol because I've said that many times before, and you should already be doing that. And if you're not, you should do it.

Andrew Huberman: However, there is a place for light, in particular long-wavelength light, in supporting lymphatic health. So, perhaps you know, perhaps you don't, light has many different wavelengths. Short wavelengths tend to be things like UV, blue light, green light. Longer wavelength light is red light, near-infrared, and infrared light. You can't see infrared light. Pit vipers can, you can't. However, long-wavelength light and short-wavelength light, and everything in between, does come from the sun.

Andrew Huberman: When the sun is low in the sky, such as near sunrise and around sunset, you see more of the long-wavelength light in the form of oranges, reds, pinks, and so forth. And any time the sun is out, you can feel the warmth of the sun, especially when there's not too much overcast clouds in the way, and that warmth from the sun, that's infrared light, okay? The light you can't see but feels warm, that's infrared light. The red light, of course, is red light. Near-infrared is somewhere in between.

Andrew Huberman: Turns out that the long-wavelengths of light that come from the sun or that come from so-called red light devices, which most commonly are not just red light but they're red light, near-infrared, and infrared, what we refer to as somewhere between about 620 and maybe 1,000 nanometers, so that's long-wavelengths. By comparison, short wavelengths would be down in the 300s, 400s, and 500s.

Andrew Huberman: But the long-wavelength light of, say, 620 nanometers all the way out to, usually, about 850 nanometers that comes from a red light device, near-infrared light device, or infrared light device, that can penetrate deep into the skin. So it has effects on the skin, it has effects deep in the skin, and there are a lot of different ways that it can affect our health. But one of the main ways is that it improves the mitochondrial function of cells.

Andrew Huberman: Now, there's a lot of data out there now showing that red light exposure from a red light device and even from the sun can improve wound healing in the skin, reduce symptoms of acne, and can reduce inflammation.

Andrew Huberman: There are now also data showing that long-wavelength light exposure can reduce lymphedema in conditions like people who are being treated for breast cancer, or can simply reduce inflammation for people that are not suffering from cancer or full-blown lymphedema but have some puffiness of the face or some other tissue that's experiencing swelling. Long-wavelength light can help.

Andrew Huberman: And that much of that effect is by way of improvements of blood flow to that area as well as improvements in mitochondrial function, and that's because the long-wavelength light can actually have impact on the skin itself and deep to the skin.

Andrew Huberman: And I've talked about the mechanism before, but to make a long story short, the long-wavelength light, those photons, can actually impact the electrons on mitochondria and, for lack of a better way to put it, charge the mitochondria, which leads to more ATP, more cellular energy, and so forth.

Andrew Huberman: What's interesting is that there are now more and more data showing that long-wavelength light exposure to the skin can reduce inflammation, improve skin appearance, reduce acne, et cetera. In part by improving the function of the lymphatic system. And it does that, apparently, through the same mechanism that it does to improve skin cells and the circulatory system for blood, meaning the capillaries and blood vessels and so forth.

Andrew Huberman: So when we hear that red light devices, near-infrared light devices, and infrared saunas and getting some low solar angle sunlight on our skin, either near sunrise and perhaps also in the evening, at sunset, or in the late afternoon, is beneficial for our skin, it appears that that, quote-unquote, "benefit for the skin" is direct to the skin cells, also to the vascular cells that are delivering blood, and also to the lymphatic vessels that are removing waste from the general area.

Andrew Huberman: So the point is that long-wavelength light exposure, either from a device or from low solar angle sunlight, can reduce inflammation in your skin and can improve appearance. And in part, that effect is occurring through the lymphatic system. And in terms of protocols, the typical kind of 10 to 30 minutes of morning sunlight viewing, as well as getting some long-wavelength light on your skin at a time where the UV index isn't too high, so maybe in the late afternoon or evening, can be very beneficial.

Andrew Huberman: If you're trying to decide whether or not to get long-wavelength light exposure for the sake of appearance and lymphatic clearance from a device or from the sun. Just keep in mind that the sun always includes some UV in it, right? UV exposure is going to be highest in the middle of the day, and less when the sun is low in the sky, near sunrise and near sunset.

Andrew Huberman: A long-wavelength light device that delivers red light, near-infrared, and infrared light, of course, has no UV in it, so you're just purely getting the benefits of the long-wavelength light for your lymphatic system and the other systems that are local to the skin.

Andrew Huberman: Okay, so we've taken quite the tour through the lymphatic system, and I'm guessing for most of you, this is the first time that you've explored or heard about the lymphatic system in depth. And I just want to underscore again what an incredible system it is.

Andrew Huberman: It's intimately related to every organ and tissue in our entire body, and it's crucial for the removal of waste from those tissues, and it's crucial for immune surveillance. So if nothing else, I hope that you can now thoroughly appreciate this incredible system that is the lymphatic system. It's not just a passive system, and yet, as you recall, it does not have a pump, so you need to do things to help move that lymphatic fluid along to support all its critical roles.

Andrew Huberman: In researching this episode, I personally was just blown away by how many important roles the lymphatic system plays, and I was surprised that I hadn't heard about a lot of these important roles before. And I think in large part, that's because it's only recently, in the last decade and a half or so, that we've really come to appreciate just how critical the lymphatic system is, for instance, in the brain, and the relationship between brain and body dynamics and the circulatory system that makes it central to everything.

Andrew Huberman: So, I'm amazed by it. I hope you're amazed by it, and I hope you will indeed take action to support your lymphatic system, because it's super important.

Andrew Huberman: If you're learning from and/or enjoying this podcast, please subscribe to our YouTube channel. That's a terrific zero-cost way to support us. In addition, please follow the podcast by clicking the follow button on both Spotify and Apple. And on both Spotify and Apple, you can leave us up to a five-star review, and you can now leave us comments at both Spotify and Apple. Please also check out the sponsors mentioned at the beginning and throughout today's episode.

Andrew Huberman: That's the best way to support this podcast. If you have questions for me or comments about the podcasts or guests, or topics that you'd like me to consider for the Huberman Lab podcast, please put those in the comment section on YouTube. I do read all the comments. For those of you that haven't heard, I have a new book coming out. It's my very first book. It's entitled "Protocols: An Operating Manual for the Human Body."

Andrew Huberman: This is a book that I've been working on for more than five years, and that's based on more than 30 years of research and experience, and it covers protocols for everything from sleep to exercise to stress control, protocols related to focus and motivation, and, of course, I provide the scientific substantiation for the protocols that are included. The book is now available by pre-sale at protocolsbook.com. There, you can find links to various vendors. You can pick the one that you like best.

Andrew Huberman: Again, the book is called "Protocols: An Operating Manual for the Human Body." And if you're not already following me on social media, I am hubermanlab on all social media platforms, so that's Instagram, X, Threads, Facebook, and LinkedIn. And on all those platforms, I discuss science and science-related tools, some of which overlaps with the content of the Huberman Lab podcast, but much of which is distinct from the information on the Huberman Lab podcast. Again, it's hubermanlab on all social media platforms.

Andrew Huberman: And if you haven't already subscribed to our Neural Network Newsletter, the Neural Network Newsletter is a zero-cost monthly newsletter that includes podcast summaries as well as what we call protocols in the form of one- to three-page PDFs that cover everything from how to optimize your sleep, how to optimize dopamine, and deliberate cold exposure. We have a foundational fitness protocol that covers cardiovascular training and resistance training. All of that is available at completely zero cost.

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Andrew Huberman: Thank you for tuning in for today's discussion about the lymphatic system and all the incredible ways that it supports your health and the things that you can do to support your lymphatic system. And last, but certainly not least, thank you for your interest in science.