How to Improve Skin Health & Appearance

Andrew Huberman 0:00 (music plays) Welcome to the Huberman Lab podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today, we are discussing skin health. Our skin is an incredibly important organ, not just for our appearance or because it serves as a barrier to the other organ systems of the body, but because it actually reflects the health status of all the other organs and systems in our body, including our brain. As well, you'll learn today about the direct and reciprocal relationship between the immune system and our skin. And if you think about it, you've seen this relationship in action before. When any of us is feeling fatigued or sick, the color, the tone of our skin tends to be a bit, quote-unquote, "off," at least for us, relative to what it normally is. Conversely, when we are feeling particularly well-rested and vibrant and healthy, our skin reflects that. So today, we will discuss the skin as an organ. We'll talk a little bit about the biology of skin so that everybody's on board the nomenclature of the different cell types in the skin and how they're affected by various things, and then we will discuss those things, such as sunlight and sun exposure as it relates to skin cancers. We'll talk about sunscreens, of course, something that I know garners a lot of interest these days and even some controversy. We will talk about common conditions of skin that concern people such as acne, rosacea, psoriasis, eczema, and of course, we will talk about so-called anti-aging treatments for skin. That is, the things that can be done to help reduce the degradation of the protein components in skin, things like collagen, things that you can do to improve collagen turnover, as well as elastin. These are other proteins within skin that give skin its youthful or, in some cases where it's degenerative, non-youthful appearance, things like wrinkles and sagging skin. So we'll talk about all of that. We'll also talk about the various products that have been developed in order to treat wrinkles, treat sagging skin, reverse acne, et cetera. We'll talk about which ones are safe, which ones are not safe, and which ones for which there still is no clear answer. I want to make very clear here at the outset that while I'll discuss various skin products during today's episode, I nor the podcast has any financial relationship to those products. I will provide examples of certain products and provide a few links in the show note captions, but I want to point out that those serve merely as examples that I found during research in this episode, which, by the way, included speaking to several board-certified dermatologists, including a dermatologist expert in oncology, cancers of the skin. So by the end of today's episode, you will have a much clearer understanding about skin and what it is at the level of biology and function, its relationship to other systems in the body, including the immune system and gut microbiome, and you will be armed with the knowledge to make the best possible decisions for you in terms of skin health and skincare depending on your age, your goals, and any current conditions

Andrew Huberman 2:59 you may have. Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero-cost-to-consumer information about science and science-related tools to the general public. In keeping with that theme, I'd like to thank the sponsors of today's podcast. Our first sponsor is Joovv. Joovv makes medical-grade red light therapy devices. Now, if there's one thing I've consistently emphasized on this podcast, it's the incredible impact that light can have on our biology. Now, in addition to sunlight, red light and near-infrared light have been shown to have positive effects on improving numerous aspects of cellular and organ health, including faster muscle recovery, improved skin health and wound healing, even improvements in acne, reducing pain and inflammation, improving mitochondrial function, and even improving vision itself. 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Initially, I didn't have a choice. It was a condition of being allowed to stay in school. But pretty soon I realized that therapy is critical to overall health. In fact, I consider doing regular therapy just as important as getting regular physical exercise, which of course I also do every week. Research tells us that excellent therapy includes three critical ingredients. The first ingredient is a strong rapport between you and the therapist, somebody that you can really trust and talk to about the issues that are concerning you. Second, great therapy should provide support in the form of emotional support or directed guidance towards the issues you're facing. And third, excellent therapy should provide insights, either directly from the therapist or that you arrive at, that you would have otherwise not been able to arrive at had you not had that emotional support and strong rapport. 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Andrew Huberman 7:18 to get 20% off. Okay, so let's talk about skin health, and by extension, skincare. What should we all be doing to take care of this organ that we call our skin? Our skin is a very interesting organ, as I mentioned earlier, not just because it protects all the other organs of our body. And I should mention it protects them not just by a physical barrier, but there's also chemical things, a chemical composition, a skin microbiome to the skin that also provides additional layers of support, such as neutralizing different bacteria that land on your skin. There's a lot more to skin than you might realize. But to start off, let's just talk about what skin is at the level of its structure, some of the cell types, because in understanding that, you'll be best-equipped to understand some of the recommendations for skin health and skincare. The skin, like many other organs in the body, is a layered structure. So the very outermost layer is called the epidermis. The epidermis has cells in it. Below that, there are other cells that comprise what's called the dermis, or sometimes referred to as the dermal layer. And then beneath that, you have subcutaneous fat. Now, of course, in different areas of the body, the skin, and as a consequence, these different layers of the epidermis and dermis, and the fat layer below it are of different composition and different thicknesses. Think, for instance, about the thickness of the skin on your forearm versus the thickness of the skin on your belly, versus the thickness of your skin on your eyelid, okay? And as soon as you think about your eyelid, you realize, okay, this thing that we call skin varies tremendously in thickness, depending on whether or not we're at the scalp, the eyelid, the face, the chin, even, you know, neck versus chin, body, et cetera. So what we think of as skin, while it may have a designated set of layers that have particular names, can vary tremendously in terms of its overall thickness, and therefore, its vulnerability to things like sunlight, which indeed can mutate the cells within the skin, cause them to, you know, have dysregulation of the expression of DNA and the production of other cells. We'll get into that. So I just want you to think about skin as having these critical components of layers, epidermis and dermis below it. And by the way, within the dermis is where you're going to find the blood supply, the vessels and capillaries that innervate the skin. Innervate simply means that supply or go to the skin. You, of course, have hair follicles and hair growing out of those follicles in many cases. And then, of course, you have skin that does not have hair, the so-called glabrous skin, like on the palms of your hands, the bottoms of your feet, et cetera. So I don't want to give the impression that skin is the same everywhere. It varies in thickness. It varies in terms of the presence of hair or lack of hair. It varies according to a lot of different parameters, including how much oil is produced in one region or another. But if you just know that the skin has an epidermis, an outermost layer, a dermis, or sometimes referred to as the dermal layer, which is below it, and then it has fat below that, and that the vasculature, right? The vessels and capillaries are at the level of the dermis. They come up through the subcutaneous fat and into that dermal layer, but they don't reach into the epidermal layer, that outermost layer. And if you understand also that nerve endings, okay, the little terminals, as we call them, of neurons, nerve cells, also go up into that dermal layer. You've got temperature sensors in the skin. All of this becomes very important for our discussions of skin conditions, things like rosacea, things like acne, which sometimes can be painful or can be exacerbated by things like heat. They can be suppressed in some cases, or even activated by things like cold. Okay, so if you just understand that there are three layers, epidermis on the outside, dermis below it, subcutaneous fat, and that skin varies in thickness, and that nerves, that is nerve endings and blood vessels and capillaries, are within the dermal layers of the skin, well, you're going to be very well-equipped for the rest of today's discussion. I'll throw in some additional information about oil production within the hair follicle and a few other things, like extracellular matrix, which, as the name suggests, is extracellular. It's outside where the cells reside, but gives it its composition as either plump and moist-appearing on the outside, or it can be kind of sagging and wrinkled and dry-appearing. All of that relates to the different components of proteins and other things within those skin layers. But if you understand what I just told you, even at a crude level, if you can just imagine it just a little bit, those three layers,You're going to be very well-equipped for the rest of today's discussion. I should also mention that there are glands within the skin. This won't be surprising to most of you. Those glands will produce oil, either more or less, depending on certain conditions. And there are things that live on the skin, on that epidermal layer and within it, that we call microbiota. You've no doubt heard of the gut microbiome, right? The existence of trillions of little microbacteria that live within your gut, that provided they are varied in their composition and of the right sort, really support your immune system and other aspects of health, including brain function and health. Well, you also have a skin microbiome. That is the existence of microbiota on the outside of your skin that serve as a barrier to infections, but that also provide things that are nourishing to the skin and give it that vibrant look that most people want. And by cleansing your skin in particular ways, that is washing it with certain substances and avoiding other substances, you can support, as opposed to diminish,

Andrew Huberman 12:40 that skin microbiome. Okay, so to start today's discussion, I want to jump right into the deep end, meaning into one of the more controversial issues related to skin health and skincare out there right now, which is sun exposure and sunscreen. Now, it makes sense why this would be such a heated issue, no pun intended, because most everyone is exposed to the sun or has the opportunity to be exposed to the sun to some degree or another every single day, even on cloudy, overcast days. It's also the case that we've learned a lot in the last 10 years or so about how different sunscreens and their components may be good for us, may be less good for us, and today we're going to talk about what is known and what is still unknown. But before we do that, we need to take a step back and look at the context in which all this controversy is happening. My read of the online community as a whole, as it relates to sunscreen and sun exposure in particular, is the following. I think most everybody, I didn't say everybody, but most everybody out there seems to accept the idea that excessive sun exposure can cause certain cancers of the skin. That's the general belief out there, and there is good reason for that belief, because indeed, the sun as full spectrum light includes long wavelengths. It's probably easier to think about those long wavelengths as the reds and oranges and yellows and so forth that are present in... Well, they're always present from sunlight, but they're most obvious to us when the sun is low in the sky, so-called low solar angle sunlight, at sunsets and also at sunrise. But of course, as full spectrum light, sunlight also includes UV, ultraviolet light of different types, we'll talk about those types today, as well as blue light and green light, and in midday sun, when the sun is overhead, we just see the sun as white light, right? Because it's containing all those different wavelengths. So while this is not a discussion about wavelengths and optics, for sake of today's discussion, just understand that long wavelength light tends to be more of the red, orange, yellow variety, okay, loosely speaking. And down at the other end of the spectrum, the short wavelength light is more of the blue and green and so-called ultraviolet light. So it's well accepted light of different wavelengths such as UV, blue light, green light, all the way out to red light, even near infrared light, can penetrate into cells. It can actually pass through surfaces. It turns out that long wavelength light can actually go deeper into the surface of our skin, right? It literally can penetrate. Just by shining a red light on your skin, it can actually penetrate the skin to a deeper layer than can short wavelength light like UV light. And it's well accepted that UV light, when it penetrates mostly that epidermal layer of the skin, that outermost layer, it can cause changes in the way that DNA functions. It can cause mutations such that DNA, which as many of you probably remember from high school biology, DNA is transcribed into RNA, and RNA is translated into proteins. The proteins are the things that the cells produce. They're actually made up of proteins. Well, UV light can disrupt which DNA are expressed and how they are expressed, in some cases leading to overproduction of too many cells or disruptions in the functions of cells, and that's why people link UV light to skin cancer. That's the whole idea there, and that's the whole notion behind using sunscreens, and notice I'm saying sunscreens, so ways to screen out UV light or maybe all sunlight in some cases, in order to prevent that penetration of the UV light into cells, which can cause mutations, which in some cases can lead to skin cancer. Now, I realize as I'm saying this, there's probably a group of you out there saying, "What's the evidence that sunlight can actually cause skin cancer?" Well, there is clear evidence that sunlight can cause skin cancers. Which skin cancers and how deadly those skin cancers are we'll get to in a few moments. That turns out to be a very interesting twist in the whole story. But I want to highlight the fact that there's very little controversy as to whether or not UV light can cause mutations in cells, right? But what you should be asking yourself is, well, why would long wavelength light, like red light, perhaps be good for skin? We'll talk about that later. There are therapies, phototherapies that use, that exploit red light which can penetrate deep into skin that actually can enhance the health of skin if done correctly. Whereas short wavelength light, which only hits that epidermal layer on the outside of the skin, may be bad for our skin. And I say maybe because it's really a function of dose and timing and genetic background, okay? If all this is seeming rather complicated, I'm gonna make it very simple, and before I do that, I do want you to ask yourself a question. I want you to ask yourself where you reside on the continuum of beliefs about sunscreen, UV light, and skin cancers. So here goes. My read of the landscape out there is that there are some people, it's a small minority, but there are some people who feel that sunscreen in any form is bad for them. They think, okay, sun is great for them, and sunscreens of any kind, chemical or physical barrier, is bad for them. Okay? Some people believe this. I'm not saying I believe this. In fact, I don't believe that. I'm a big believer in sunlight and the power of sunlight for health, but I am not what is called a sunscreen truther, okay? I'm not somebody who-... thinks that sunscreen has no value. In fact, quite the opposite under certain conditions and certain sunscreens. I want to say that for the record. Other people out there believe that certain sunscreens can be valuable, but only the sunscreens that lack certain chemicals because they are concerned about chemicals in certain sunscreens being so-called endocrine disruptors or maybe even causing cancer on their own, okay? Other people are so afraid of sunlight and believe that it causes so many issues as it relates to skin cancer that they basically create beekeeper uniforms for themselves so that anytime they're out in sunlight, they wanna have sunglasses on, they wanna have a hat, they wanna cover their neck, every part of their body, okay? They sit at the opposite extreme of the people who don't believe in using any sun protection whatsoever. And now, of course, there's the backdrop of how much natural melanin production we each make, that is how dark our skin happens to be according to our genetics, and of course, there's the issue of where we live on the planet and how much sun we have available to us in order to potentially expose ourselves to. And perhaps also ask yourself if you are in what I believe is the largest category of people out there, which is the category of people who probably don't wear sunscreen every day. Maybe they put it on occasionally, but only if it's very bright out, very hot out, because they don't want to get a so-called sunburn. And I believe most people fit into that general category of, A, not wanting to be burned, B, not wanting to age any faster than they would h- were they to not wear sunscreen, at least that's their belief, and C, they've just been told that sunscreen's good for them, and they'll reach for whatever sunscreen is on the shelf or that was recommended to them either by their dermatologist or that they happen to find in the pharmacy or when they're out skiing and they, you know, they notice it's a bright day and so they buy some sunscreen and slather it on. So before I go any further, just ask yourself those questions. You know, wh- where do you reside? Are you afraid of sunscreen? Do you love sunscreen? Are you in the beekeeper category? Like you think all sun is bad, it's gonna give you skin cancer, it's gonna age you faster. We'll get to the aging component in a few minutes. But just ask yourself that question as we wade into

Andrew Huberman 19:51 the material I'm about to cover. So what's the story with sun exposure, sunburn, sunscreen, skin cancer, and aging? I spoke to several different dermatologists about this, including one expert in skin cancers specifically, and what I was told is the following. First of all, sun exposure will disrupt the collagen and elastin, but mostly the collagen composition of your skin in a way that makes it appear as if you're aging faster, okay? So sun exposure, yes, ages the skin. Now that does not mean, however, that you want to avoid all sun exposure because the same dermatologist said that some sun exposure is healthy for us. Why? Because our skin is also an endocrine organ. It's involved in making various hormones, it's part of the vitamin D production pathway, although a little bit later we'll talk about the fact that most people get their vitamin D from their diet, and in some cases also from supplementation. But it is a good idea to get some sunlight for sake of vitamin D production, but also the production of other hormones like testosterone and estrogen. Okay? So every single dermatologist that I spoke to said that some sun exposure is good for us, but that too much sun exposure will accelerate the appearance of aging in our skin. So let's pin that up on the wall as fact, okay? This, again, is not saying you should avoid sun completely. It's also not saying you should get excessive sunlight exposure. It's saying sunlight exposure by virtue of the UV wavelengths' ability to cause mutations in the epidermal layers of the skin and to impact the collagen composition of the dermal layers below it, as well as some of the other proteins present in the keratinocytes, okay, one of the major skin cell types and other cell types of the skin, does lead to the appearance of aged skin, which is one rationale for wearing sunscreen. Now, when I say sunscreen, everyone, including myself, thinks about lotions or in some cases sprays. But let's pay attention to the one fact that I do think everybody regardless of what category they are in the general population or what background training a dermatologist has believes, which is a physical barrier, a shirt, a hat, a jacket. A physical barrier can provide, in some cases, very good protection from the sun, and I don't think there's any controversy whatsoever as to whether or not the composition of the physical barrier is having negative effects on the skin, okay? You will find those niche communities out there that are saying, okay, certain chemicals present and certain materials that clothing are made with can be problems for the endocrine system, but we're not talking about that here. Okay? What I'm saying is that all dermatologists I spoke to, and I think most every rational human being on Earth would say that a physical barrier can help to a great degree in order to protect our skin from the sun as it relates to sunburn, but also acceleration of the appearance of aging in our skin. Okay, so I don't think there's any dispute about physical barriers for protecting the skin. How much you want to protect your skin from the sun, well, that will depend on what category you decided you were in from the earlier discussion. We'll get back to that. What else did all the dermatologists and skincare experts that I spoke to also agree upon? Well, they all said that indeed excessive sun exposure can increase the propensity for certain skin cancers. I want to go on record by saying I believe that. Why? Well, because of this ability of UV light and some other wavelengths of light potentially to cause mutations in skin cells that can lead to certain skin cancers. Okay? I don't think that's a debated topic out there. There might be a few people out there who are going to hang their hat on a study that I'll go into a little bit later, which is that the relationship between sun exposure and all cause mortality is a tricky one, and it's one that we'll parse, okay? Meaning, I'll just give it a little, you know, hint into what I'm saying. People who avoid the sun entirely don't tend to live as long as people that get some sun exposure, but there are a bunch of confounding variables that have to be understood in order to really interpret that statement in the study that we'll parse a little bit later. For now, let's just accept the reality that the vast, vast majority of dermatologists out there and skincare experts really understand that i-Sun exposure can accelerate aging of the skin, but most will also tell you that some sun exposure is good for you, not just for skin health, but for overall brain and body health. Now, as it relates to skin cancer, the dermatologist oncologist that I spoke to, all right, who did his training at Stanford, and I'll provide a link in the show note captions to his clinic, and you can learn more about some of his work, he's published some really nice papers, said the following, and this was surprising to me. He said, "It turns out that the skin cancers that sun exposure causes, while they can be serious and should be taken seriously, they should be treated, those generally are not the most deadly of the skin cancers." Now, why would he say something like that? Okay. He said it because it turns out that there are lots of different kinds of skin cancer. Some of them arise or can arise through sun exposure. Others, and indeed some of the most deadly of skin cancers, are independent of sun exposure, and this is where things can get a little bit tricky. You'll hear out there, "Oh, you know, sun can cause skin cancer but not the skin cancers that kill you." I don't think that's really a fair statement. You'll also hear, however, that all the skin cancers that are out there are the consequence of sun exposure, and that also is not true. And if anything, this provides motivation, not just on the part of the dermatologist, but it should be motivation from within all of us to make sure that we understand our background genetics, not just how much pigmentation we carry in our skin by virtue of our genetics. But we should know by asking, if you're not gonna get genetically sequenced, which you can do nowadays, of course, but you should know whether or not your family, your genetics tends to carry certain mutations that make you more prone to skin cancers in general, not just the type that can be exacerbated by sun exposure. What I'm basically saying is that if you have particular genetics in your family, even if you avoid all sun exposure, you know, nobody should do that, of course. You need some sunlight. I mean, like all other, uh, or most all other, uh, creatures on Earth, sunlight is important for us. It's important for setting our circadian rhythms. That's why I'm always telling people to get sunlight in their eyes early in the day, which, by the way, when the sun is low in the sky, low solar angle sunlight, the UV index tends to be very low. Okay. So you are at the lowest possible risk of getting burned, of getting any kind of mutations to your skin. That doesn't mean you should overdo it. It doesn't mean you should stare at the sun and damage your eyes. I've talked about this a lot on other podcasts, how to get morning sunlight exposure properly. But when the sun is low in the sky, that's generally a safe time to get sun exposure. It's that midday sun, typically between the hours of, you know, 11:00 AM or even 10:00 AM depending on time of year and where you're at and 2:00 or 3:00 or 4:00 PM that the sun is overhead and at its greatest intensity and where the UV index can be very high. It's very easy to look up the UV index. And when the UV index is very high, right? I was down in Australia earlier this year, and the UV index down there is so high you can almost feel it. You actually can feel it. You step outside, and you immediately feel like, "Wow, my skin is really being bombarded with the sunlight." And I'm somebody who tolerates sunlight pretty well because my dad's fairly, um, you know, dark pigmentation just naturally by virtue of being South American. Normally, I can tolerate the skin pretty well. But you should not rely on just that subjective feel. You should look up the UV index. And we'll provide a few links of good UV index sites that you can look up the UV index and where you might want to be extra cautious about providing a physical barrier or a chemical barrier

Andrew Huberman 27:24 to protect your skin. Now, a lot of people out there also believe that if you avoid sunburn, you're avoiding skin cancer. Perhaps you're very pale or it's the early phase of the summer season or you have a susceptibility to sunlight such that, you know, you step outside and you get too much sunlight on a given day and you get a sunburn. That reflects an immune reaction, an inflammatory reaction within the dermal layers of the skin, so that means the vasculature, right? Those vessels and capillaries. Uh, they're going to dilate. You oftentimes will get infiltration of things like cytokines, which are of the immune system. You get an inflammatory response. That's why it's red. That's why it's tender to the touch. The nerve endings there can be overly activated. So the reason why your skin actually feels warm, right, when you touch your sunburn is because, in fact, you have an activation of some of the nerve endings at that site as well as the activation of the local immune system properties that give rise to, again, vessel and capillary dilation. It's a wound of sorts induced by excessive sun exposure. Now, does sunburn cause skin cancer? There's no direct relationship between sunburn and skin cancer except the fact that sunburn reflects excessive sunlight exposure. And yes, as I mentioned before, it's conclusive that excessive UV sun exposure to the skin can cause certain mutations in skin cells that give rise to certain skin cancers. Why are we parsing things at this level of detail, right? Is this all just semantics? No, it's not just semantics. Many people believe that if they didn't get a sunburn, they are not at additional risk for inducing skin cancer or other issues with skin, right? We're not just talking about skin cancer. We're talking about accelerated aging of the skin according to sun exposure. So let's make this very simple. You don't need a sunburn for the sun to accelerate the aging appearance of your skin. You don't need a sunburn to induce the kind of mutation that may, again, I want to highlight may, give rise to a skin cancer. It's also not the case that if you've got a sunburn or even multiple sunburns that you'll necessarily develop skin cancer, although by virtue of the fact that sunburn reflects UV exposure, multiple sunburns would reflect increased UV exposure and therefore increased risk for certain skin cancers. So all this to say avoid sunburn however you can. And if you're somebody who just loathes sunscreen, that doesn't want to even hear the discussion we're about to have next about which sunscreens are safe and which ones appear to be less safe, if you're just one of these people that does not want to put sunscreen on because you're very concerned about whatever chemical might be in sunscreen, well, then consider that the physical barrier of an article of clothing or a hat or a bandana of sorts can indeed shield you from the sun to some degree, often to a great degree. And again, I don't think there's any controversy

Andrew Huberman 30:09 as to whether or not those are safe.As many of you know, I've been taking AG1 for more than 10 years now. So I'm delighted that they're sponsoring this podcast. To be clear, I don't take AG1 because they're a sponsor, rather they are a sponsor because I take AG1. In fact, I take AG1 once and often twice every single day and I've done that since starting way back in 2012. There is so much conflicting information out there nowadays about what proper nutrition is. But here's where there seems to be a general consensus on, whether you're an omnivore, a carnivore, a vegetarian, or a vegan, I think it's generally agreed that you should get most of your food from unprocessed or minimally processed sources, which allows you to eat enough but not overeat, get plenty of vitamins and minerals, probiotics, and micronutrients that we all need for physical and mental health. Now I personally am an omnivore and I strive to get most of my food from unprocessed or minimally processed sources, but the reason I still take AG1 once and often twice every day is that it ensures I get all of those vitamins, minerals, probiotics, et cetera, but it also has adaptogens to help me cope with stress. It's basically a nutritional insurance policy meant to augment, not replace quality food. So by drinking a serving of AG1 in the morning and again in the afternoon or evening, I cover all of my foundational nutritional needs. And I, like so many other people that take AG1, report feeling much better in a number of important ways, such as energy levels, digestion, sleep, and more. So while many supplements out there are really directed towards obtaining one specific outcome, AG1 is foundational nutrition designed to support all aspects of wellbeing related to mental health and physical health. If you'd like to try AG1, you can go to drinkag1.com/huberman to claim a special offer. They'll give you five free travel packs with your order, plus a year's supply of vitamin D3 K2. Again, that's drinkag1.com/huberman.

Andrew Huberman 32:00 Okay, so before we dive into our discussion about sunscreens and the chemicals in sunscreens, let's just take a moment and talk about vitamin D. Vitamin D is important for a great number of bodily and brain functions. As I mentioned earlier, most people get their vitamin D from the foods they eat. If you eat dairy, in most countries, the dairy is fortified with vitamin D. Many people nowadays supplement with vitamin D anywhere from 1,000 IUs to 5,000 IUs. There are folks out there who perhaps even take 10,000 IUs. It seems a bit high for most people, but it's going to depend on how much sun exposure you get, the pigmentation of your skin, but there are a number of people, especially in countries where they don't get a lot of sun exposure in particular times of year and maybe they're not eating enough dairy fortified with vitamin D who would benefit from vitamin D supplementation. And many people find they feel better when they supplement with vitamin D, but I encourage you that if you're going to supplement with vitamin D to probably start at the lower end of supplementation, like 1,000 to 3,000 IU, maybe 5,000 IU. Best would be to measure your vitamin D levels. Many people are surprised to find that even if they live in a part of the world where they get a fair amount of sun exposure, and they eat some dairy that's fortified with vitamin D, that for whatever reason, their vitamin D levels are still too low and benefit from supplementation with vitamin D. The dermatologist that I spoke to told me that yes, even if you wear sunscreen or a physical barrier, okay this is interesting, even if you wear sunscreen or a physical barrier when you get outside into the sun, it can still have a positive effect on your vitamin D levels. This was surprising to me, but then of course it makes sense. Sunlight is full-spectrum light. It's not just UV and short wavelength light. The ability for longer wavelength light to penetrate the skin is clear, and those longer wavelengths can also impart a positive influence on the vitamin D pathway. Okay? So if you're concerned about wearing sunscreen because you're worried that it's going to impair your vitamin D synthesis or metabolism in any way, probably no reason to be concerned. Now if you're somebody who is in the beekeeper category who's completely avoiding sun exposure for whatever reason, well then you probably want to get your vitamin D levels checked and you may want to rely on supplementation or something of that sort. At the same time, because of variation in genetic background, there will even be some of you out there who are super anti-sunscreen, who are peeling your shirts off all the time, who are getting lots of sun exposure, who may surprisingly have vitamin D levels that are still low. That's rare, okay? For all the obvious reasons, but it could still be the case, and indeed some of the dermatologists that I spoke to said they occasionally have a patient like that. Vitamin D, as you may recall, is involved in a bunch of different things. It acts as a hormone, it's involved in calcium absorption, it's involved in some of the other hormone pathways, and I should mention that there's a study, I'll link to this in the show note captions, that shows that some amount of sunlight exposure to the skin, this is an Israeli study where they had people, you know, get several tens of minutes of sunlight exposure in the afternoon during particular times of year. Uh, they didn't have them going naked outside, okay? This was sort of like context and culturally appropriate. Um, skin exposure to the upper body and to the legs could induce increases in hormones such as testosterone and estrogen which were correlated with, it wasn't causal, but it was correlated with improvements in mood, wellbeing, libido, et cetera. Well, some of that probably relates to testosterone and estrogen synthesis directly. Again, the skin as an endocrine organ, okay? There are certain elements within the keratinocyte skin cells that can literally communicate with some of the organs of the body that produce testosterone and estrogen, even some of the glands, pituitary, et cetera. This is through a number of different stations. It's not necessarily direct, but also through the sun's ability to impact the vitamin D pathway that then impinges on those testosterone, estrogen, and things like luteinizing hormone pathways. We don't have time to go into all this now. I covered this in an episode about testosterone and estrogen. You have hormones such as luteinizing hormone which then stimulate the gonads, the testes and the ovaries, to make testosterone and/or estrogen. The skin is a not-so-obvious player in this whole thing whereby external environmental stimuli such as the availability of sunlight, which in most places in the world varies across the year, can stimulate more or less.Vitamin D production, luteinizing hormone production that can impinge on testosterone and estrogen production. These pathways are one of the reasons why when we get the right amount of sunlight, not too little, not too much, we feel better. We feel better because certain hormones are being produced at certain levels when we're getting that sun exposure. And when we don't get that sun exposure, we have lower levels of those hormones. This is well-established, and the study that I linked to in the show note captions, which I've covered in previous episodes,

Andrew Huberman 36:50 is but one example of that phenomenon. Okay, let's talk about sunscreens. Now, the reason I change my tone of voice with this is that (laughs) if you look on the internet, you will see claims that I don't use or believe in sunscreen. That is just false. I've worn sunscreen my entire life. I don't necessarily wear it every day. I don't tend to burn easily, okay? I have some natural level of pigmentation in my skin based on my genetics, as I mentioned earlier, but as we talked about earlier, just avoiding sunburn is not going to protect me or anyone else against certain sun-induced mutations in skin cells and the aging effects that sun can have. So I do believe in certain sunscreens, meaning I will put sunscreen on on certain days on certain parts of my body. However, I do believe, now having spoken to multiple dermatologists and looked into the literature very deeply, that there are certain chemicals in certain sunscreens that are of concern. I don't mean that if you put these on once or even twice that you are going to suffer negative consequences. I mean they are of concern, meaning we should pay attention to them, and when given the option, we should opt for the healthier choices. And in fact, there are known healthier choices. To make all of this very clear, I'm going to tell you what is very clear to the dermatology community at this point in time, okay? In June of 2024, here's what we know. There are two major types of sunscreens out there. Well, really three. We talked about physical barrier before. No one argues about a physical barrier. No one's worried about the chemical composition of physical barriers, okay? When we talk about sunscreen, so lotions, creams, sprays, et cetera, there are two major types. The first are organic types, which is essentially chemical sunscreens, okay? So when you hear organic sunscreens, that means chemical-type sunscreens. And then there are inorganic types, which are sometimes referred to as mineral-based sunscreens. Here's what most everybody seems to accept, that mineral-based sunscreens, meaning sunscreens that tend to include either zinc oxide or titanium dioxide, or both in some cases, are generally thought to be safe up to concentrations of 25%. 25% is a pretty high concentration. You can find sunscreens out there that have 25% zinc oxide or 25% titanium dioxide. They're rare to find, however. More often, you'll find sunscreens that have 15%, 10%, 18% zinc oxide, sometimes alone or in combination with titanium dioxide. You'll find some pure titanium dioxide sunscreens out there, although those are a bit more rare, all right? A little bit harder to find. Here's the story. Zinc oxide and titanium dioxide reflect back UV light, the short wavelengths of light that would otherwise potentially cause mutations in your skin cells at the level of the epidermis, okay? On the outermost layers of skin. Remember, short wavelength light doesn't pass very deeply into the skin. Sunscreens containing zinc oxide and/or titanium dioxide were engineered for that specific purpose, to reflect back UV light. This is very different than organic or chemical sunscreens, which contain certain compounds. These go by different names, oxybenzone, uh, avobenzone. There are a bunch of these different chemicals that are contained in so-called organic or chemical sunscreens. Those chemicals in general don't serve to reflect back UV light, but rather absorb UV light. Okay, so when they're applied to the skin, they're designed to absorb the UV light so that the UV light can't negatively impact the skin. Those chemical, again, chemical AKA organic components within organic sunscreens, again, sometimes called chemical sunscreens, are designed to absorb UV light. Mineral-based sunscreen, so-called inorganic sunscreens, containing things like zinc oxide or titanium dioxide, are designed to reflect back UV light. Why am I telling you this? Well, I'm telling you this because it's generally believed that the zinc oxide and titanium dioxide-containing sunscreens are safe up to concentrations of 25%, whereas there is some, again, some concern about the chemicals within chemical, AKA organic sunscreens as potential endocrine disruptors, so disrupting things like testosterone synthesis, estrogen synthesis, and other hormones. It's not all just about testosterone and estrogen, folks. Other hormone pathways that many people, including some governing bodies and agencies that assess the safety of different cosmetic and sunscreen products, are concerned about. Now, how concerned they are depends on where you are in the world, okay? So in Europe, they have different stringencies for what is considered safe versus unsafe or just of concern as opposed to in the US. Here's what every dermatologist in the US, 'cause those are the ones I spoke to, told me, which is that it is advised that on children younger than six months of age, you do not use chemical-based sunscreens. Why? Well, young skin, even the skin on the external part of the body, in children six months or younger acts more like mucosal skin in that it can very easily absorb things transdermally through the skin. However, even as we age, so into puberty, our young adult years, and even into our elderly years, there is still a capacity for things to pass transdermally through the skin. Although because of some of the additional barriers formed within the dermal and epidermal layers of the skin, things like extracellular matrix, the changes in collagen, et cetera, there is less tendency for compounds to pass transdermally through the skin. Now...That just simply highlights the fact that if you are a very young person or if you're applying sunscreen to a very young person, maybe six months or younger, but also perhaps older, depending on how careful you want to be, to avoid these chemical-based sunscreens. There is very little, if any, evidence that the mineral-based sunscreens are of concern for transdermal passage into the skin at concentrations of 25% or less, meaning sunscreens containing zinc oxide and titanium dioxide are probably safe or at least have been deemed safe enough that they are freely available in the market, and we are told that they are safe for people of all ages. So if you are somebody who is concerned about the chemicals in sunscreen, most every dermatologist or chemist who works on sunscreens will tell you, "Well, mineral-based, inorganic sunscreens are going to be your safer option if you're concerned." But get this, the chemical-based sunscreens, while some of the chemicals in them indeed can be quite scary when you read the literature, you look at some of these things like oxybenzone, um, avobenzone, and some similar chemicals, even at low concentrations have been shown to be endocrine disruptors. People talk about how the fact w- when they apply these sunscreens they can taste them in their mouth. There's a lot of fear around these, and some of that fear is substantiated. When one goes and looks at the studies that have been done on these chemical-based sunscreens, you may find it interesting to note that the way these studies were done often involves having people apply a ton of these chemical-based sunscreens, like two full bottles of these sunscreens over the course of a very short period of time and then have their blood drawn, and then it's revealed that some of these chemical components are within the blood. So a big issue that's not often discussed because it's very difficult to control for in a natural setting but is straightforward to control for in a laboratory setting is how much sunscreen one is applying and how often and across how many years of time. So there's no real prescriptive that can tell you, "Hey, if you put chemical sunscreens on once, that's problematic," although certainly pay attention to that six months and younger, what is essentially a rule, uh, that I mentioned earlier. And do not put chemical-based sunscreens on really young kids. You might want to avoid them entirely depending on how stringent you are about this stuff. But when it comes to chemical-based sunscreens, personally I avoid them, but then it becomes a question of if you could only use a chemical-based sunscreen, you simply look at the label. Some of these have, by the way, zinc oxide, titanium oxide, and chemical-based components, okay? Keep that in mind. Some are purely mineral-based. Some are purely chemical-based. But if you look at a sunscreen label, you know, okay, well, this is the only thing available on this very hot day with a very high UV index and otherwise I'm gonna get a burn, well, if you're really concerned, then I would resort to a physical barrier. If you are less concerned, then you could perhaps tell yourself, "Okay, you get to put it on that day," but you might not want to use it every day, and you might want to use a small volume of it, right? Or maybe just on parts of your face or your ears or your neck that are particularly sensitive to sun. Okay? These are the things that need to be taken into consideration. But when we step back from all of this, all of the literature, including, by the way, some of the literature that assessed, and I'll put a link to this review, a review on the potential neurotoxicity of titanium dioxide nanoparticles. I'll get into this in a moment. It has been explored whether or not titanium dioxide is more risky than zinc oxide. We'll talk about that in a moment. But when you step back from all of this, here's what you get. Physical barrier, no one argues about that. No one believes that clothing is dangerous per se when it comes to avoiding excessive sun exposure. Again, excessive relates to your skin tone, your background genetics, your activities, and where you are in the world and what time of year, okay? Very specific to your needs. Very few folks are concerned about mineral-based inorganic sunscreen. So if you want to use sunscreen, as many people do, and you want to make sure that it's not an endocrine disruptor and it's not a neurotoxin or something else that's been raised for some of these chemical-based sunscreens, well, then find a sunscreen that has 25% less zinc oxide and/or titanium dioxide. If you were a bit more concerned about, say, titanium dioxide and some of the suggestive evidence, only suggestive evidence that maybe titanium dioxide is more risky than zinc oxide, especially when it's in its nano form, the very small form that may indeed allow it for more easy passage through the layers of the skin, that transdermal passage, well, then find a sunscreen that is purely zinc oxide sunscreen. And again, they always have other things in them, but what I mean is the only active ingredient in a zinc oxide only containing sunscreen is zinc oxide, and then there are a bunch of other things that allow it to be a lotion, for instance, again, up to 25% concentration. Why would somebody not want to use zinc oxide containing sunscreen up to 25% and opt for anything else, you might ask, right? If that's considered safe. The reason is the consistency of the zinc oxide is it's pretty sticky and thick and kind of pasty, right? Back in the '80s and '90s, some of you may recall they had, um, zinc oxide, um, sunscreens that would actually, you know, color the nose white so you could really see it. It was really prominent on the face. They tried to turn that into a fashion statement and didn't go over so well over time. But in any case, the addition of titanium dioxide to those zinc oxide containing sunscreens allow it to be a bit silkier so that it would spread on more evenly, and then you may say, "Well, why even put chemicals in sunscreen at all if there's risk?" The reason why chemical-based organic sunscreens even exist is that they can come up with compositions of those sunscreens that are very silky and that could spread on clear over makeup and things of that sort. But there are these concerns about some of those chemical components as endocrine disruptors and potentially as mutagens that could cause other issues or, you know, any number of different things you, you know, you can find all sorts of concerns out there on the internet. Most of those concerns are not substantiated, but these chemicals can be problematic at high concentrations, and that takes us back to the point made earlier, which is in the studies of those chemicals and the reasons in some cases being banned in certain countries and other countries carrying, uh, warning recommendations, the amount of those chemical-based sunscreens that were applied was exceedingly high. So if you're wearing sunscreen very often, you're wearing a lot of it.Probably best if you're towards a mineral-based sunscreen. If you are concerned at all about the chemicals in chemical-based sunscreen, wear a mineral-based sunscreen and/or use physical barrier. And if you're somebody who just doesn't believe that sunscreens are safe whatsoever, well, you know, as far as I know, it's a free world. You don't have to wear sunscreen, but then I would say you need to be very aware of the fact that sun can induce the appearance of accelerated aging in the skin, right? That's an actual process that takes place. There's really no debating that, frankly. And sun exposure can potentially accelerate

Andrew Huberman 49:20 or even give rise to certain skin cancers, and nobody wants that. Okay, before we move on to a discussion about what can be done to increase the youthfulness of our skin or the appearance of youthfulness in our skin, we need to have a bit more discussion about skin cancers. Notice I said skin cancers, plural, because there are many different forms of skin cancer. Some of them relate to sun exposure, as we discussed earlier. Others do not. And in fact, some of the more deadly skin cancers are independent of sun exposure. They can relate to genetics and to other factors. So the most straightforward story about all of this is that approximately 80 to 90% of melanomas, which are skin cancers, and they are very serious skin cancers that can indeed be very deadly, arise in what's called de novo skin. De novo skin is non-mole skin. Now, does that mean that you should not pay attention to the shape and any changes in your moles? No, you absolutely should. But for people who have naturally darker pigmentation everywhere or who have very few moles, then you aren't going to be able to use the monitoring of your moles as the only readout of potential development of skin cancer, and frankly, everybody should be thinking about these more serious skin cancers independent of moles or changes in moles. Here are a couple things that everyone should pay attention to. If you have a pimple-like lesion or you have any kind of spot on your skin that seems like it's an acne that's lasted more than a month, or you have an area that's seeping something that might look like plasma or pus or blood and it persists over a long period of time, like a month or more, absolutely get that checked out by a dermatologist, okay? Don't wait any longer than a month. Get it checked out. In addition, it's highly recommended that you go in and you get your moles checked by a dermatologist and, frankly, that you get all of your skin checked by a dermatologist at least once per year. This is going to really protect you against both the sun-induced skin cancers and other forms of skin cancer. The most common form of sun exposure-induced cancers are basal cell carcinomas, and indeed those are less deadly than many of the melanomas, but they still can be exceedingly problematic and they can be deadly. So it's very important to get these checked out. Now, there are websites, and I'll provide a link to one of them in the show note captions, for which you can look at a bunch of different examples of different moles and how they change over time, and if you happen to have a mole that resembles the appearance of any of the moles in that image gallery, then you would be wise to go to a dermatologist right away because it could be, again, could be cancer of some sort. You do not want to let these things linger for too long. At the same time, many people get concerned about one mole that didn't have an irregular border and then suddenly has an irregular border. There are a lot of different features that you'll learn from the website or if you talk to your dermatologist that relate to whether or not something is predicting skin cancer or has become skin cancer. It's not just irregular border. It's changes in size, certainly changes in pigmentation, vascularization, bleeding, any kind of seeping. There are a lot of different things there. So don't be alarmed at first appearance of one of these things, but do take it seriously and keep in mind that there are things that your dermatologist can do to help prevent certain skin cancers. So for instance, there's a growing trend now among dermatologists to suggest laser resurfacing of skin. That is a laser used to essentially disrupt that epidermal outermost layer, turn it over so that it regenerates, 'cause it can indeed regenerate, to create new cells there. Keep in mind that UV light and other factors in the environment can cause mutations within that skin layer. Sometimes they're caused by genetic factors, but often environmental factors like sun and chemicals and other things. And by encouraging turnover of that skin layer through laser resurfacing, which by the way may also increase the sort of youthfulness appearance of your skin, so many people are motivated to do it for that reason, can dramatically reduce the incidence of certain kinds of skin cancer. In fact, the dermatologist I spoke to who's an expert in derma oncology, okay, cancers of the skin, said that laser resurfacing can cause a 30% reduction in skin cancers because of this ability to rejuvenate that epidermal layer. And that's especially true for areas of the body like the face, ears, neck, tops of the hands, et cetera, for which the sun often induces the most damage because those are the most exposed parts of the body on a regular basis. And by the way, this whole thing about skin cancer is not a trivially small number. It's a big number. In the US alone, there are up to four million cases per year of what's called squamous cell carcinoma, one of these forms of skin cancer. So getting checked out by a highly qualified dermatologist on a yearly basis, maybe even more if you're really concerned about this 'cause you have a lot of familial, genetically inherited skin cancers,

Andrew Huberman 53:59 things of that sort, is really highly advised. I'd like to take a brief break and acknowledge one of our sponsors, LMNT. LMNT is an electrolyte drink that has everything you need. That means the electrolytes sodium, magnesium, and potassium in the correct amounts and ratios and nothing you don't, which means no sugar. Now, I and others on this podcast have talked about the critical importance of hydration for proper brain and body functioning. Even a slight degree of dehydration can diminish cognitive and physical performance. It's also important that you get adequate electrolytes. The electrolytes sodium, magnesium, and potassium are critical for the functioning of all the cells in your body, especially your neurons, your nerve cells. Drinking LMNT dissolved in water makes it very easy to ensure that you're getting adequate hydration and adequate electrolytes. To make sure I'm getting proper amounts of hydration and electrolytes, I dissolve one packet of LMNT in about 16 to 32 ounces of water when I wake up in the morning and I drink that basically first thing in the morning. I'll also drink LMNT dissolved in water.... during any kind of physical exercise I'm doing, especially on hot days when I'm sweating a lot, losing water and electrolytes. They have a bunch of different great-tasting flavors of LMNT. My favorite is the watermelon, although I confess I also like the raspberry and the citrus. Basically, I like all the flavors. And LMNT has also just released a new line of canned sparkling LMNT, so these aren't the packets you dissolve in water. These are cans of LMNT that you crack open like any other canned drink, like a soda, but you're getting your hydration and your electrolytes with no sugar. If you'd like to try LMNT, you can go to DrinkLMNT, spelled L-M-N-T, .com/huberman to claim a free LMNT sample pack with the purchase of any LMNT drink mix. Again, that's

Andrew Huberman 55:34 DrinkLMNT.com/huberman to claim a free sample pack. Now, with respect to everything we've talked about, about sun exposure, sunscreen, and skin cancer, I'd be remiss if I didn't discuss a study that's often used kind of as a wedge or a weapon in the online debates about sun exposure, skin cancer, and mortality, and the title of this study is, quote, "Avoidance of Sun Exposure as a Risk Factor," that's right, "Sun Exposure as a Risk Factor for Major Causes of Death: A Competing Risk Analysis of the Melanoma in Southern Sweden Cohort." So the basic design of this study was to evaluate people's self-reported amount of sun exposure across many years and then to correlate that with all-cause mortality and then to relate it to different causes of disease, in particular cardiovascular death, compare this to smokers, keep in mind that some of the people who were reporting their sun exposure were smokers, some weren't. And the conclusion of this study that drew a lot of attention and continues to draw a lot of attention is the following. Quote, and here I quote from the abstract, "Non-smokers who avoided sun exposure had a life expectancy similar to smokers in the highest sun exposure group." Okay, I'm gonna repeat that. "Non-smokers who avoided sun exposure had a life expectancy similar to smokers in the highest sun exposure group." So what many people take this to conclude is that avoiding sun exposure is as dangerous as smoking, okay? (laughs) That's not the conclusion that I'd like you to take away, because what this study basically shows is, and here I continue, quote, "Compared to the highest sun exposure group, life expectancy of avoiders of sun exposure was reduced by 0.6 to 2.1 years." So you go, "Wait a second. Can this really be true, that people that are avoiding sun exposure have a lower life expectancy than people who get sun exposure?" And indeed, in this particular study, that does seem to be the case, but the interpretation of this is not completely straightforward. Here's what we know. Getting some degree of sun exposure appears to be good for life expectancy. That is true. But is it directly related to sun exposure? That's a critical question. And is the increased sun exposure that one gets, if you do get sun exposure, linked to other issues, in particular the development of melanoma? As you recall, melanoma was even in the title of the study. So here's how I think we should think about this study. It does appear that getting sun exposure is correlated with longer life expectancy, but there could be any number of different reasons for that. For instance, people that are getting regular sun exposure presumably are also enhancing activation of the vitamin D pathways, which is related to any number of different things. They no doubt are experiencing increased feelings of well-being. I talked about papers that have substantiated that earlier, and frankly, we didn't even need a scientific study to substantiate that, although it's always great to have it. We know that being out in sunshine for some period of time each day, as long as we don't get burned in the sun, feels good. Why does it feel good? It leads to the production of testosterone, estrogen, some of the endorphins that generally make us feel good. It is directly related to the pathways associated with dopamine release. There's a whole story there about seasonality, both in humans and other animals, about dopamine synthesis. When we get sunlight, there's elevated dopamine and serotonin and testosterone and estrogen and feelings of well-being and libido. This is all well substantiated in animal models and humans. So getting sun exposure makes people feel good. When people feel good, they tend to be lower stress. When people are feeling good and they have energy, because there indeed is a direct relationship between sun exposure, especially to the eyes early in the day, and our feelings of elevated mood and alertness, and energy, they tend to exercise more, walk more, and of course, if you're outside exercising more, walking more, cycling, swimming, you're also going to get more sun exposure, and we know that exercise is strongly related to improved or extended life expectancy. Okay? So the study basically says getting sunlight, as opposed to very little sunlight, is good for life expectancy, but it doesn't say get too much sunlight, right? Because, and this is interesting, it is very clear that the people who lived longer because they were getting more sunlight also tended to have more cancers, including melanoma. But, and this is a very important point, it's also the case that the longer one lives, the more likely you are to develop a cancer, okay? So as you can see, these studies that many people just draw one straightforward conclusion from, such as people who get less sun exposure don't live as long as people who get more sun exposure, well that's true, but when you get more sun exposure, very likely you're doing other things like exercise and feeling better that relate to living longer. So it's very difficult, if not impossible, to isolate one single variable, in this case sun exposure, as the key variable. However, I'm happy to go on record saying that we know from so many studies of animal models and humans that sun exposure, especially early-day sun exposure, when the sun is low in the sky to set your circadian rhythm, and late-day sun exposure, okay, I'm not talking about middle of the day, getting baked in the sun and, you know, sunburned or things of that sort, but around the time of sunset, especially sun exposure to the eyes.... is powerfully modulating your circadian rhythm to elevate daytime mood, focus, and alertness and improve sleep, both of which are strongly correlated with improvements in mental health, immune system function, feelings of wellbeing, enhanced cognition. I mean, there's this whole story about people with Alzheimer's and disruptions in circadian rhythms and sleep. So sun exposure to the eyes in terms of setting circadian rhythm, powerful. Powerful improvement of life expectancy and immediate health. Sun exposure to the skin, no doubt very powerful positive modulators of certain hormone and neuromodulator pathways such as dopamine, testosterone, estrogen, and so forth that make people feel good and do things generally that are good for them. Okay, generally, not all the things people do with elevated dopamine, testosterone, and estrogen are good for them. We know that for sure. But getting some sunlight, that is some appropriate dosage of sunlight, especially to the eyes early in the day. Don't stare at the sun. Don't damage your eyes, but getting some of that sun exposure to your eyes early in the day and some to the skin, especially in the early and later part of the day clearly is positively correlated with various health metrics in terms of mental health and physical health, and not surprisingly, with lifespan. So I mention this study 'cause I do think it's very interesting, right? I think it's really interesting that people who completely avoid sunlight are not living as long as people who get some sun exposure, and some of this actually is on par with what's experienced with cigarette smoking, I think something that everyone agrees is negative in terms of life expectancy and certainly is not good for a great number of different systems within the brain and body. But I think the study sometimes is used to highlight the wrong conclusion, which is that sunlight itself is extending lifespan. I think that that very simple conclusion can be taken too far and can start to negate some of the equally important messages about excessive sunlight exposure causing certain problems as it relates to skin cancers, which we talked about earlier, as it relates to things that you can do in order to offset some of that risk with, if I were to suggest, a physical barrier if you need it, a chemical-based sunscreen if you choose to use sunscreen, and

Andrew Huberman 1:03:13 of course, that's an independent choice that each of us have to make for ourselves. Okay, let's talk about youthfulness of skin or the appearance of youthfulness in skin. Before I did this episode, I put the call out on social media for questions about skin and skin health, and I must say that the vast majority of questions related to this topic, and it's a very interesting one because it relates to a lot of decisions that people are making about what to do, what to buy or not buy as the case may be, and it is an enormous, probably hundreds of billions of dollars industry, if not trillion-dollar industry over time, this business of devices, products, and procedures to try and reverse aging or the appearance of aging in skin or even create de novo, new synthesis of collagen in skin and other things to make skin look more youthful. Okay, so if we step back from this whole area, we have to ask ourselves, what do we know for sure about what makes skin look youthful and what can be done to make skin look more youthful? And to understand the answers to those questions, we simply have to go back to the beginning of today's discussion for just a moment. Remember that we have the epidermal layer of skin, we have the dermal layer of skin, we have the vasculature, the blood vessels and capillaries, you have the nerve inputs there, and you have a bunch of different cell types in there. The keratinocytes. You have different proteins within those cells, like collagen, elastin, that over time can, yes, be mutated by things like UV rays from the sun, but that over time tend to lose their elasticity, which leads to wrinkles and sagging skin. You also have this issue of hydration of the skin, right? The skin has a lot of watery components within it, actual water within it, and those watery components are what give it its kind of plump, moist look, smooth look, as opposed to desiccated, you know, sagging, wrinkled look, to speak in extremes. And there are hundreds if not thousands of different chemicals out there that dermatologists as well as cosmetic surgeons as well as just, you know, frankly, manufacturers of products assert are going to be good for skin. So let's talk about where there is a lot of evidence for certain things that you can do if your goal is to increase the youthfulness or the appearance of youthfulness in your skin, and one of the main ones is collagen itself. Okay, now I have to admit, I was very surprised when I looked at this literature, but I was positively surprised. Here's why. As you know, there are various macronutrients present in foods. You can have proteins, fats, and carbohydrates. When we ingest proteins such as beef, chicken, fish, eggs, as well as some vegan sources of proteins like beans or lentils or tofu, things of that sort, they contain different amounts of different essential amino acids, and those essential amino acids and other amino acids are used as the building blocks for proteins in our muscles, in our tendons, in essentially all the organ systems of our body. The lipids are also used for cell membranes, et cetera, okay? This has been discussed various times on this podcast before, people like Dr. Layne Norton, Dr. Gabrielle Lyon, and others. It's well-established that when these proteins are broken down in the gut, some of those amino acids go and serve for the purpose of tissue repair. Others are for the purpose of other things. What most people in the field of nutrition agree upon and what certainly I believe is that if you were to, say, eat a little bit of liver, right? You might have a little bit of cooked liver, or a little bit of skeletal muscle in the form of, like, a steak, that there's no selective trafficking of the amino acids that are broken down from the liver, that you eat, to your liver, right? So when you hear that eating liver supports your liver, it may do that by the broad p-... process of certain amino acids and vitamins and lipids, et cetera, serving your liver and other organ and tissue systems of the body, but not selectively your liver. However, when we talk about collagen, this protein that forms one of the most essential aspects of what makes our skin what it is, which is elastic and, you know, and, and to have some tensile strength where you can push on it and it returns to, uh, its, uh, original position, especially if it's well hydrated, and makes our skin very youthful in appearance when we're young and then as it degrades when we get old makes it look less youthful, wrinkles and sagging and so forth, well then why would eating collagen protein, which can come from any number of different sources, it can come from fish sources, it can come from, believe it or not, animal hoof sources, it can come from any number of different sources, tendon, et cetera, why would ingesting collagen be selectively trafficked to the collagen in our skin? Right? That doesn't square with everything we know, and yet when you look at studies, including the meta-analyses of studies where people supplement with collagen powders, and these powders typically come from fish or tendon, any number of different sources, when people do this and then measures are taken as to skin appearance, skin elasticity, there are a bunch of measures that can be done in humans in the laboratory to do this, you often will find studies that show statistically significant improvements in collagen composition and skin appearance and even the appearance of reduction in wrinkles and so forth. So this is an interesting exception where the ingestion of a particular protein that naturally exists in abundance in certain tissues, such as skin but also other tissues like tendon, ligaments, et cetera, seems to be assisting in either the repair and rejuvenation of collagen or perhaps some other aspect of collagen synthesis that leads to improvements in collagen composition and the appearance of skin in humans. That's very interesting. And the study that I find particularly interesting is one that I'll link to in the show note captions. It's entitled, quote, "Exploring the impact of hydrolyzed collagen oral supplementation on skin rejuvenation: A systematic review and meta-analysis." And the basic takeaway of this and other meta-analyses and the studies within this meta-analysis is that when people supplement with anywhere from five to 15 grams, okay, grams, of hydrolyzed collagen per day, in particular in combination with vitamin C, it doesn't have to be a lot of vitamin C, that one can observe, okay, not always, but can observe some visible improvements in skin composition, meaning less wrinkles, even some reversal of wrinkles, less skin sagging, more youthful appearance, more kind of, um, let's just call it, uh, rebound elasticity of the skin, I realize that's not the appropriate technical term, but, uh, the ability of the skin to bounce back from an indentation when you push down on it as opposed to saying down or, or sagging. So some pretty impressive results when one considers that what people are basically doing here is just mixing up some hydrolyzed collagen protein and then, uh, drinking that down once per day or so. Now, that is not to say that you have to supplement with hydrolyzed collagen. Why? Well, collagen is also present in various foods. So for instance, drinking bone broth, beef bone broth, chicken bone broth is a rich source of collagen. You can go online and simply look up just by web search, you can just say, you know, what foods contain high levels of collagen? And you'll get a list of things back there. Hopefully a few of those are not just palatable to you but you actually like and you can start to include those in your daily diet, or you could supplement with hydrolyzed collagen protein. There are any number of different sources for these. It's interesting that while indeed I don't believe, and there is frankly zero evidence for selective trafficking of amino acids arising from a particular organ source to that particular organ when you ingest it, it is interesting that consuming hydrolyzed collagen in the form of a supplement or deriving it from foods like bone broth, et cetera, does seem to be able to improve collagen synthesis or the appearance of skin, making it more youthful. For those of you that are interested in ingesting collagen peptides as a way to improve the youthfulness of your skin, should mention that the dosages there, uh, come in a range depending on the studies that you've looked at, and the dermatologist that I spoke to said if one decides to go down this route of supplementing or getting collagen from food sources, you want to aim for anywhere from 15 grams to 30 grams of collagen peptides per day, okay? That's a bit higher than, uh, what was used in a number of, uh, studies, but you'll find studies that use 30 grams, and that that whole process can be augmented, can be improved through ingestion of 500 to 1,000 milligrams of vitamin C as well. But check the label on those collagen peptides that you might be supplementing with 'cause oftentimes they already include that 500 to 1,000 milligrams of vitamin C. I should also mention that the dermatologist I spoke to said that they like collagen protein supplementation not just for the reasons discussed up until now, but that they liked them for a number of other reasons such as the potential anti-inflammatory effects of collagen proteins. To be honest, I don't know what the exact mechanism of that is. Maybe if you get a certain protein threshold, inflammation is down. But anyway, that's still cryptic to me. But in any case, they did describe some of the potential mechanisms by which collagen ingestion can do its thing in terms of improving youthfulness. It's broken down in the blood into dipeptides and tripeptides, which then are used within the collagen itself or the skin, this is the hypothesis, and that it can increase the chemotaxis, the mobility of fibroblasts which make up some of the skin tissue and give rise to the appearance of more youthful skin. There's also evidence that ingestion of hydrolyzed collagen peptides can improve the elasticity of the skin barrier on the outside, right, make it look nice and taut if, I guess we say nice, we're sort of passing subjective readout on this, uh, make it appear taut, um,

Andrew Huberman 1:12:55 through the increase of certain proteins unrelated to collagen such as filagrons, elastins, et cetera.What about other peptides? Okay, so this is a big topic nowadays, especially in the online communities. I did an entire episode of this podcast about peptides. Keep in mind that insulin is a peptide. Ozempic, what, is essentially an agonist for glucagon-like peptide 1. This is a very popular prescription drug now for the treatment of obesity and for the treatment of diabetes. There are lots of things that qualify as peptides. A peptide is simply a small chain of amino acids. A polypeptide is a bit longer chain of amino acids, and then proteins are made up of amino acids. Okay, so when we say peptides, that means many, many things, but these days, when you hear about quote-unquote peptides, especially in online communities, generally people are referring to exogenously given, okay, so pills, ointments, or more typically injections of peptides that are designed to achieve some specific biological or physiological outcome. And one of the more common of these peptides being used nowadays is one that I've talked about before called BPC-157, Body Protection Compound 157, which is essentially a synthetic version of something found in gastric juice in all of us. It's known that certain peptides within the gut that BPC-157 is known to mimic, or it actually is a synthetic version of that exact sequence or a portion of that sequence, can assist in tissue and wound repair of different kinds, tendon, anything involving fibroblasts. All of that has been well-demonstrated in vitro in a dish, okay, so not in vivo, as well as in vivo in certain cases, but only in animal models. To my knowledge, there's only one study, and frankly, it's not a very good study at all on BPC-157 in humans, and yet, a lot of people are taking BPC-157 either orally in the form of a capsule or pill or more typically injecting it. What does it do or what does it likely do in humans? We know from animal models that BPC-157 increases angiogenesis, the growth of capillaries and blood vessels. We know this. It can accelerate wound healing by virtue of increasing fibroblast motility. For this reason, it's used post-injury in sports. It's used by people who want to build more muscle. It's used by endurance athletes. It's used for cosmetic purposes. Any time people are using BPC-157 for any of those purposes, it's likely that they're using it in part to increase the blood flow that's available to a given tissue and the repair of that tissue. Now, again, I do want to caution people that there is very little, basically no evidence in humans besides the anecdotal evidence that people say they healed faster. What I do know is that any time you get vascularization of tissue, you're going to get improved blood flow, so it all makes sense mechanistically. I also know that vascularization due to BPC-157, even if it's injected locally into a given tissue, is likely to occur globally throughout the body. This is why some people taking oral BPC-157 or injecting it, you know, just subcutaneously at the level of, you know, their stomach, a little bit, you know, under the skin at the level of their stomach, report faster wound healing even in a distal limb or, like, a hand or a nerve injury in their foot or something like that. That also tells us that there's going to be increased vascularization of other tissues, such as skin, such as tumors, if tumors exist. So you need to be very careful. I need to say that up front as a cautionary note because it is very clear that many people are starting to either inject BPC-157 or apply it in the form of a topical cream in effort to get more vascularization of skin in order to make that skin appear more youthful, and more and more products are out there that contain BPC-157. I can't in good conscience recommend those products. I can only offer to you the likely mechanism by which they work, if they work, and also offer you the caveat that it is unclear that BPC-157 can go transdermally if it's applied topically. So if you put it on a, say, wrinkly portion of your face, so like I've got crow's feet. Crow's feet come from either aging, smiling, or both. Um, you know, the crow's feet are the kind of wrinkles that extend out the corners of your eyes when you smile, or for me, 'cause I'm, you know, 48, you know, I probably do that even when I don't smile. The, the logic would be that if you take a cream containing BPC-157 and you put it on there, that you'll get increased vascularization of that area, delivery of more growth factors and nutrients, and those wrinkles will either be halted in their aging progression or that they will reverse. That's the logic. To my knowledge, there are no clinical studies, and I'd love to know from you if you've tried these products. Please put your experience of those in the comments on YouTube so we can get a sense of whether or not people are having good, um, results with this. That, of course, is not a controlled study, but I'm very curious as to know. Many of the products that contain BPC-157, by the way, also contain copper. Copper is a trace mineral. It's found in your diet. There is some evidence that copper is important for some of the collagen and other elements of skin synthesis pathways, and so the mechanistic logic and the biochemical logic is there on paper. However, it's also clear that ingesting too much copper can induce an inflammatory response and would lead to the exact opposite desired effect that people who are using copper and usually copper BPC-containing products are taking them for, which is to halt or reverse the appearance of aging in their skin. Why am I going through this whole gymnastics of, you know, BPC-157 and copper? Well, because nowadays, many, many products are starting to include quote-unquote peptides for skin rejuvenation, and most often, those peptides are of the copper variety, of the BPC-157 variety, and oftentimes also with things related to collagen synthesis, sometimes collagen directly. So you'll find oral products that one takes by pill form that are BPC-157, copper, and collagen or things that promote synthesis of collagen. You'll find ointments that are pure BPC-157, still unclear if those go transdermal, okay? So this is still a very, very young science, and most of this is not being explored in randomized control trials. However, I know some of you out there are pretty experimental. You like...... experimenting with this kind of stuff, you like hearing what's working for other people, here's what I suggest. If a sunscreen or a lotion or a pill or an injection is asserted to