Sun exposure, sunscreen, and skin health: skin cancer, vitamin D, & more (AMA 61 sneak peek)

1. 0:00 – 0:11

   Intro

   1. PAPeter Attia0:00

      [upbeat music] Hey, everyone. Welcome to "The Drive" podcast. I'm your host, Peter Attia.

2. 0:11 – 2:38

   The impact of UV radiation on the skin

   1. SPSpeaker0:11

      Peter, welcome to an AMA. How you doing?

   2. PAPeter Attia0:13

      Good. Thanks for having me.

   3. SPSpeaker0:14

      [laughs] Always welcome here. You are always welcome on your own show, so I'm happy to have you. It'd be a little awkward without you, to, to tell the truth. But, um, for today's AMA, we're gonna cover two topics, a little bit related, that we see a lot of questions come through. Um, also appears to be a lot of confusion around, which I think is why we see so many questions, and that is skin cancer and sunscreen. And so what we did is we gathered all the questions on this, organized them. We're gonna start with skin cancer, move to sunscreen. We have a lot to cover through this, so I think we'll hit it right away. But anything that you wanna add before we get rolling?

   4. PAPeter Attia0:55

      No. I mean, look, I think this is a topic that, um, I know we, uh, internally took very seriously because it is, I think, easy to just, um, you know, kind of assume the, the standard chant. Um, and, and I... You know, we, we came at this from first principles is basically what I can say. Um, so m- months and months of, of work, um, by the part of our team, um, in particular one of our analysts who I think now literally probably knows more about this subject than anyone else, including me. Um, and so I'm excited to, to kinda dive into it.

   5. SPSpeaker1:32

      And as we get going on the first skin cancer section, um, I think it'd be important to just quickly cover what is the impact of UV radiation on the skin?

   6. PAPeter Attia1:44

      Yeah. So again, I think we should spend a minute talking about what UV is, but given that we're gonna talk about that in a second, there are really kind of three things that you wanna be thinking about, right? You wanna understand the impact that UV has on vitamin D conversion. Um, you wanna understand the impact that ultraviolet light has on photoaging, and then ultimately you wanna understand the role it plays on skin cancers, and we're gonna break those out into two buckets.

   7. SPSpeaker2:08

      And you hinted at it there, but I think it'd be good to cover a little bit more here, which is when we say solar UV, what are we referring to?

   8. PAPeter Attia2:16

      Yeah. So I-- This is a, a great example of where I think a figure is very helpful, and I realize not everybody's watching this on video, but, um, I'll do my best to kind of articulate it. But I, I do think this is one of those times when it, it helps to look at the show notes or, or, you know, again, watch us on video so you can sort of see what we're doing here. So, um, there are a couple of figures on this slide here, and the first one

3. 2:38 – 7:12

   Understanding solar UV: from the electromagnetic spectrum to skin health

   1. PAPeter Attia2:38

      is, is a great figure that just sort of tries to explain what is happening when, uh, wavelengths, uh, across an electro- electromagnetic spectrum change in size. So y- let's take a step back, right? So many of the waves that are, are out there are of different wavelengths, right? So you have sound waves, you have waves of light, and, and just this-- I remember this, learning this in sort of my physics class in high school and having a big aha moment, right? So sound waves are invisible. Um, light waves are invisible. Why can you hear around a corner but you can't see around a corner? Well, it has to do with the length of the waves, and sound waves are literally meters long, and so the way they bounce and move is such that they're basically going around corners, whereas light waves are tiny. And to give you a sense of how tiny they are, they're measured in nanometers, right? So not even millimeters, but, but actually nanometers. And what you see on this slide here is the entire visible spectrum of light. So that which we can see with our eyes, right? We can't see radio waves. We can't see microwaves. We can't even see infrared, and as you see in a moment, we can't see ultrawave or X-rays. We can see light, provided, uh, that the, that the length, the wavelength is between about four hundred and seven hundred nanometers. That's a really, really tiny sliver of the entire electromagnetic spectrum, but that encompasses everything from red light all the way down to blue light. Now, when you get right, right, right beneath the lowest level of visibility, you get into ultraviolet light. Now, one other point I should make is the shorter the wavelength, the more energy that is contained within it. So, um, as you go from, um... And this is by the way, just as an aside, right? Why when people say, "Oh my God, I can't believe you stand next to your microwave when it's cooking. Aren't you worried about anything?" Uh, the answer is no, because microwaves are actually longer than visible light. So if I'm worried that my microwave is hurting me, I should be really worried that just living is hurting me, right? 'Cause I'm getting visible light that's more powerful than microwave. But nevertheless, when you go just below, uh, what we see with visible light, you get into ultraviolet light. And ultraviolet light, um, exists from about a hundred nanometers to that upper limit of four hundred nanometers, where we just start to be able to see it at blue light. And it's really broken down into three types, and people have heard these terms, but I think it's helpful to understand what they mean. So you've, you've got UVA, UVB, and UVC, or ultraviolet A, B, and C. Now, um, as you go from A to B to C, the wavelength is getting smaller, and if you recall what I said a moment ago, that implies that the strength is getting higher. Now, that means that ultraviolet C is, um, the strongest, i.e. the most ionizing of radiation. Um, but ultraviolet C does not really reach Earth. So, uh, UVC doesn't make it through the atmosphere, and therefore we don't really deal with it. So instead, what we're dealing with is UVA and UVB, both of which reach, uh, our, you know, our surface and therefore our skin. So for the purpose of this discussion, when we talk about UV radiation, we're talking about UVA, and we're talking about UVB, although UVA occupies a much broader band. As you can see on this figure, it's about 315 to 400, whereas UVB is about 280 to 315. Now, um, why is this relevant? It's relevant because of what these things do. So UVB is much smaller, right? It's about 5% of the UV radiation that we're exposed to from the sun versus UVA, which is about 95%. Um, UVB is, um, shorter, doesn't penetrate as much, but it's higher energy. So it's the UVB that is really responsible for the sunburn and the vitamin D conversion, whereas UVA goes deeper, but it's not as ionizing in energy. So maybe spent a, a few more minutes on that than I wanted to, but I think it's important for people to understand the difference between, you know, ultraviolet light, visible light, and other forms of, of energy, and then the difference between UVA and B.

4. 7:12 – 8:45

   The role of sunlight in vitamin D production

   1. SPSpeaker7:12

      Yeah, no, I think it is helpful just to kind of set the stage for the discussion here. And you hinted at it earlier, but a lot of time when people talk about sunlight, they naturally think of vitamin D. And so what do we know about how UV can help in the production of vitamin D?

   2. PAPeter Attia7:28

      Well, vitamin D is produced, um, when UVB light, uh, converts D2 or pre-vitamin D3 into, uh, D3. And it's a little bit more complicated than that in that it doesn't just require the ionizing radiation, it also requires heat. Um, and it turns out just the heat of our body is sufficient. So, um, when you take sunlight coupled with body heat, you make vitamin D3. And m- maybe people are aware that when they're buying... You know, if you go to Amazon to buy vitamin D supplements, if you look at it, it doesn't just say vitamin D, it says D3. Um, now, look, you can get D3 in food as well, and obviously you can get D3 in a supplement. Um, and at the, um, at, at the end of the day, you know, it doesn't really matter where the vitamin D comes from. It is the same molecule. Uh, it's a fat-soluble vitamin, um, and therefore you do get it... You have to, you know, basically be able to get it in, in fat-soluble manners. So you're gonna, you're gonna see it in, in foods that are, um, fatty foods such as, you know, fish oil and eggs and fortified dairy products and things of that nature.

   3. SPSpeaker8:44

      And

5. 8:45 – 11:22

   Factors contributing to vitamin D deficiency: insufficient UV exposure, magnesium levels, & more

   1. SPSpeaker8:45

      what do we know about too little UV exposure and how that can relate to vitamin D deficiency? And is it something that people can overcome by taking vitamin D supplements? Obviously, vitamin D supplements are often talked about, so how does that interact here?

   2. PAPeter Attia9:02

      Well, this is where it starts to get a little bit confusing, and it is the case that, um, vitamin D deficiency... You know, first off, there's not even a really clear definition of what that is. Um, I believe medically it's defined as a vitamin D level less than 15, although some labs would consider it a deficiency if you're less than 30. Um, I will say this, in our practice, we consider below 30 to be deficient, not 15. Um, and there's a clear association between vitamin D deficiency and less time in the sun, but it's not that straightforward because you have other things to consider. So, um, again, because I said vitamin D is a fat-soluble, uh, vitamin, the more adipose tissue a person has, the greater the sequestration of vitamin D into the fat cells. In other words, you take two individuals that have the same amount of, you know, sun exposure and other factors, even skin tone and things we'll talk about in a second, one of them has much more adipose tissue than the other, they're gonna have lower vitamin D all things equal because they are sequestering more of the vitamin D in their fat cells. So obesity right off the bat is a potential, uh, risk factor that drives, um, low vitamin D. The other thing we talk about, of course, is skin tone. So we'll, we'll, I guess, talk about this more shortly, but those who have more naturally occurring melanin have more built-in protection from UV radiation, which means less UV conversion for vitamin D. So darker skin people are gonna have, um, lower vitamin D levels. Uh, and then I think one other thing to mention here, because we've talked about it so much in the past, is the impact of magnesium. And people may recall from the previous AMA on this topic that, um... You know, I take a kind of hard line view on this, and I actually think most people, um, do not have adequate levels of magnesium or certainly not optimal. So maybe they're, you know, biochemically, uh, uh, you know, adequate, but they, they certainly wouldn't be optimal. And so suboptimal levels of magnesium, um, will also, uh, impede m- um, metabolism of vitamin D and, and therefore, um, we, we will see low magnesium associated with low vitamin D because magnesium is a cofactor in the enzymatic conversion of vitamin D.

6. 11:22 – 15:10

   Sun exposure needs for different skin types, & the limitations of current studies in defining vitamin D deficiency

   1. SPSpeaker11:22

      And do we know anything about how much time someone would need with UV radiation to not be deficient in vitamin D?

   2. PAPeter Attia11:33

      I think it's, um... You know, it's not, it's, it's, it's not a very straightforward, uh, formula because it depends on obviously your skin type, and we'll talk about the five or six skin types in a second. Um, it's gonna depend on your location, it's gonna depend on the time of day, and it's obviously gonna depend on the amount of skin surface area that is exposed. So, um, let's, let's just start with skin types. There are t- six skin site, uh, s- six skin types um, that are described on something called the Fitzpatrick scale. So it's a kind of semi-quantitative scale, um, that describes skin color by its basal complexion, um, melanin level in response to UV. So you have types one through six, and they go from most pale to least, right? So, you know, type one is very pale white skin, burns very easily, does not tan. Uh, type two, white skin, burns easily, doesn't tan with much easily, but isn't a guaranteed, uh, you know, under the right circumstances can develop a little bit of a tan. Type three, white skin, uh, might burn, but also tans kind of easily. Type four, light brown or olive skin, uh, hardly burns, uh, tans easily. So that's me, I'm a type four. Uh, type five, brown skin, usually doesn't burn, tans very easily. Uh, and then type six is black skin, unlikely to burn, uh, and becomes significantly darker, uh, with significant UV radiation exposure. So, um, Caucasians, which are usually defined as type one to type three, um, believe it or not, don't need that much, uh, sun exposure to reach adequate levels. Uh, and so one study noted that, um, people who were type one to type three, so again Caucasian, uh, with as little as nine minutes per day of sun exposure in midday during the summer months in the northern hemisphere, so March to September, assuming at least a third of their body was exposed, uh, were getting sufficient vitamin D. Um, now again, it's important to understand, like a third of your body exposed means you're in shorts and a T-shirt, um, but everything else is exposed. So again, if you're walking around in pants and you're in a long-sleeve shirt, you're obviously not gonna get that. Um, now, if you talk about people that are type five skin, so South Asian populations, for example, um, they're gonna need to spend three, four times that amount of, of, uh, of time in the sun under the exact same conditions just, just to reach the same, uh, vitamin D levels. One caveat I should point out that this study defined deficiency as below twenty-five nanomole per liter or ten milligrams per milliliter. So, um, I... You know, we think that that is really deficient. We think that that's like three X below the-- what, what we consider deficient. So I would say that these numbers don't really apply to how we think about it, but for the purpose of comparing different skin types, I think it's a, it's a, it's a pretty reasonable assessment. Um, the other thing obviously that goes without saying is where you are from a latitude perspective. So, um, you know, the bottom line is you don't need to be out in the sun for hours a day, but you do need to be out in the sun if your aspiration is to get all of your vitamin D from the sun and not to supplement it.

   3. SPSpeaker15:07

      And on the other end of deficiency, what

7. 15:10 – 17:40

   The effects of excessive UV exposure: sunburn, photoaging, & risk of skin cancer

   1. SPSpeaker15:10

      happens if we get too much UV?

   2. PAPeter Attia15:14

      Well, I'm not aware of too much UV ever resulting in too much vitamin D. And so we can, we can put that aside as, as a, as a concern. Um, so, so rather what we want to talk about is what are, what are the other effects? So obviously you can develop a sunburn and that can be a very acute thing and that can be painful and we'll obviously talk in a moment about the impact of that on subsequent skin cancers. Um, but, you know, I think it's always worth talking about photoaging. And even though, uh, this is not exactly a, a podcast that focuses on the aesthetic side of living longer, I, I don't think it's a bad idea to imagine, uh, what our skin is going to look like as we age. And so, you know, photoaging, which I think we all recognize as sort of the, you know, the wrinkles and sagging skin that, that occur with a- with aging are indeed the result of sun exposure. So recall that, you know, when you are exposed to UVA and especial- especially UVB, um, the epidermis has to thicken. It's a defense mechanism. And there's a decrease in the amount of extracellular matrix protein, so collagen, as a result of this, and it's probably due to UV-related increases in the expression and activity of the, um, the proteins and enzymes responsible for the degradation of the ECM. So I, I think we all understand what this looks like, but, but I... You know, we found an interesting picture in the New England Journal of Medicine as part of the Images in Clinical Medicine series that I think, you know, kind of does a, an interesting job of showing you something. So this is a, a, a picture here, Nick, if you pull it up. It's a, it's a gentleman who, um, I believe spent like thirty-two years, um, as a truck driver. Uh, and obviously this was, you know, here in North America, so that meant the left side of his face was out the window. And, you know, this is a very interesting and stark example of what just a little bit more sun is doing. It's also worth pointing out that probably most of the time he's driving, the window is closed. Um, so a lot of the UV was actually being, um, deflected by the glass, but, you know, I'm sure that there were times when the window was open. And you can see an obvious and clear difference between the left side of his face and the right side of his face that, you know, is a rare example of how in one person with their own, you know, skin being the perfect control, you can see the significant difference. Finally, as I alluded to, obviously skin cancer becomes perhaps the most important concern as we think about, uh, excessive UV exposure.

8. 17:40 – 20:56

   Types of skin cancer & associations with UV exposure

   1. SPSpeaker17:40

      And on skin cancer, the next question is, which skin cancers have known associations with UV directly?

   2. PAPeter Attia17:51

      Thank you for listening to today's sneak peek AMA episode of The Drive. If you're interested in hearing the complete version of this AMA, you'll want to become a premium member. It's extremely important to me to provide all of this content without relying on paid ads. To do this, our work is made entirely possible by our members, and in return, we offer exclusive member-only content and benefits above and beyond what is available for free. So if you want to take your knowledge of this space to the next level, it's our goal to ensure members get back much more than the price of the subscription. Premium membership includes several benefits. First, comprehensive podcast show notes that detail every topic, paper, person, and thing that we discuss in each episode. And the word on the street is nobody's show notes rival ours. Second, monthly Ask Me Anything or AMA episodes. These episodes are comprised of detailed responses to subscriber questions, typically focused on a single topic, and are designed to offer a great deal of clarity and detail on topics of special interest to our members. You'll also get access to the show notes for these episodes, of course. Third, delivery of our premium newsletter, which is put together by our dedicated team of research analysts. This newsletter covers a wide range of topics related to longevity and provides much more detail than our free weekly newsletter. Fourth, access to our private podcast feed that provides you with access to every episode, including AMAs, sans the spiel you're listening to now and in your regular podcast feed. Fifth, The Qualies, an additional member only podcast we put together that serves as a highlight reel featuring the best excerpts from previous episodes of The Drive. This is a great way to catch up on previous episodes without having to go back and listen to each one of them. And finally, other benefits that are added along the way. If you want to learn more and access these member only benefits, you can head over to peterattiamd.com/subscribe. You can also find me on YouTube, Instagram, and Twitter, all with the handle PeterAttiaMD. You can also leave us a review on Apple Podcast or whatever podcast player you use. This podcast is for general informational purposes only and does not constitute the practice of medicine, nursing, or other professional healthcare services, including the giving of medical advice. No doctor-patient relationship is formed. The use of this information and the materials linked to this podcast is at the user's own risk. The content on this podcast is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Users should not disregard or delay in obtaining medical advice from any medical condition they have, and they should seek the assistance of their healthcare professionals for any such conditions. Finally, I take all conflicts of interest very seriously. For all of my disclosures and the companies I invest in or advise, please visit peterattiamd.com/about, where I keep an up to date and active list of all disclosures. [outro music]

Episode duration: 20:57