The Peter Attia Drive - #308 - AMA #61: Sun exposure, sunscreen, and skin health: relationship between sun exposure and skin cancer, vitamin D production, and photoaging, how to choose a sunscreen, and more

Episode Date: July 1, 2024

View the Show Notes Page for This Episode Become a Member to Receive Exclusive Content Sign Up to Receive Peter’s Weekly Newsletter In this “Ask Me Anything” (AMA) episode, Peter delves into two topics that have generated a lot of questions over the years: skin cancer and sunscreen. He begins by exploring the basics of UV radiation, discussing its effects on vitamin D conversion, photoaging, and its role in skin cancer. He examines various skin types, discussing their implications for sun exposure and vitamin D levels, as well as how to determine where you fall on the skin type scale. He then delves into the various types of skin cancer, with a particular emphasis on melanoma, exploring its complex relationship with UV exposure and other contributing risk factors. Additionally, he covers tanning beds, the importance of early skin cancer detection through regular skin checks, and the often confusing topic of sunscreen. He explains how sunscreen affects UV radiation and skin cancer risk, what SPF levels to choose, the differences between organic and mineral sunscreens, and what to consider when selecting the best sunscreen for your needs. If you’re not a subscriber and are listening on a podcast player, you’ll only be able to hear a preview of the AMA. If you’re a subscriber, you can now listen to this full episode on your private RSS feed or our website at the AMA #61 show notes page. If you are not a subscriber, you can learn more about the subscriber benefits here. We discuss: The impact of UV radiation on the skin [2:00]; Understanding solar UV: from the electromagnetic spectrum to skin health [3:45]; The role of sunlight in vitamin D production [8:30]; Factors contributing to vitamin D deficiency: insufficient UV exposure, magnesium levels, and more [9:45]; Sun exposure needs for different skin types, and the limitations of current studies in defining vitamin D deficiency [12:45]; The acute and long-term effects of excessive UV exposure: sunburn, photoaging, and the increased risk of skin cancer [15:30]; Types of skin cancer and associations with UV exposure [17:45]; The complex relationship between melanoma and UV exposure [22:15]; Why UV exposure alone doesn’t necessarily explain the risk for melanoma [25:15]; Other risk factors for melanoma [29:15]; Tanning beds and skin cancer risk [34:45]; Balancing sun exposure: benefits and risks [38:15]; Tattoos and sun exposure [40:30]; The importance of regular skin checks, dermatologists, and emerging technologies showing promise for early detection of cancer [41:45]; Self-skin checks: what to look for [46:30]; Prevalence of skin cancer and the importance of early detection [49:30]; Summary of the major risk factors for melanoma [54:15]; The role of sunscreen in reducing skin cancer risk [55:45]; How sunscreen works, the differences between chemical and mineral sunscreens, an explanation of SPF, and more [58:30]; How to determine the appropriate sunscreen SPF to use based on the UV index [1:04:45]; Choosing the right sunscreen for your individual needs [1:07:00]; The impact of water and perspiration on sunscreen effectiveness [1:12:00]; Chemical vs. mineral sunscreens: safety concerns and recommendations [1:14:00]; Concerns about hormone effects from chemical sunscreens [1:19:15]; Sunscreen summary: skin types, key considerations, recommended brands, and more [1:23:15]; and More. Connect With Peter on Twitter, Instagram, Facebook and YouTube

Hey everyone, welcome to the Drive Podcast. I'm your host, Peter Attia. This podcast, my website, and my weekly newsletter all focus on the goal of translating the science of longevity into something accessible for everyone. Our goal is to provide the best content in health and wellness, and we've established a great team of analysts to make this happen. It is 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.

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 a subscription. If you want to learn more about the benefits of our premium membership, head over to PeterAtiyaMD.com forward slash subscribe. Welcome to Ask Me Anything, episode 61. I'm once again joined by my co-host, Nick Stenson. In today's episode, we cover two topics that we have not covered before, but that we've seen a lot of questions over the years.

They are skin cancer and sunscreen. We begin the conversation by laying the foundation on what UV is and the impacts that UV has on vitamin D conversion, photo aging, and its role in skin cancer. We look at various skin types and what the implications are of these skin types on sun exposure, vitamin D levels, as well as how to understand where you may fall on the scale and what the implications are. We talk about photo aging and the factors that contribute to it, and then we dive into the different types of skin cancers.

We talk about UV and its role specifically in melanoma, which is of course the skin cancer that matters most, as well as other risk factors besides the sun that pertain to melanoma. We speak about tanning beds, skin checks, and why it's probably important to catch skin cancer earlier rather than later. From there, we move into the topic of sunscreen, which seems to be clouded with some confusion. We discuss all things related to sunscreen, its impact on UV radiation, its impact on skin cancer, what SPF levels to look for. And finally, we talk about the differences between organic sunscreens and mineral sunscreens.

If you're a subscriber and wanna watch the full video of this podcast, you can find it on the show notes page. If you're not a subscriber, you can watch a sneak peek of the video on our YouTube page. So without further delay, I hope you enjoy AMA number 61. Hey! ["Amazing Grace"] Peter, welcome to an AMA, how you doing?

Good, thanks for having me. Always welcome here. You are always welcome on your own show, so I'm happy to have you. It would be a little awkward without you, to tell the truth. But for today's AMA, we're going to cover two topics, a little bit related, that we see a lot of questions come through. 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? No, I mean, look, I think this is a topic that I know we internally took very seriously because it is, I think, easy to just assume the standard chant.

And we came at this from first principles is basically what I can say. So months and months of work by the part of our team, in particular, one of our analysts who I think now literally probably knows more about this subject than anyone else, including me. And so I'm excited to kind of dive into it. As we get going on the first skin cancer section, I think it'd be important to just quickly cover what is the impact of UV radiation on the skin?

I think we should spend a minute talking about what UV is, but given that we're going to talk about that in a second, there are really three things that you want to be thinking about, right? You want to understand the impact that UV has on vitamin D conversion. You want to understand the impact that ultraviolet light has on photo aging. And then ultimately, you want to understand the role it plays on skin cancers. And we're going to break those out into two buckets. 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?

This is a great example of where I think a figure is very helpful and I realize not everybody's watching this on video, but I'll do my best to articulate it. I do think this is one of those times when it helps to look at the show notes or watch us on video so you can see what we're doing here. There are a couple of figures on this slide here. The first one is a great figure that just tries to explain what is happening when wavelengths across an electromagnetic spectrum change in size. Let's take a step back. Many of the waves that are out there are of different wavelengths. You have sound waves, you have waves of light. I remember this learning this in my physics class in high school and having a big aha moment. Sound waves are invisible, 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. Sound waves are literally meters long. The way they bounce and move is such that they're basically going around corners, whereas light waves are tiny. To give you a sense of how tiny they are, they're measured in nanometers. Not even millimeters, but actually nanometers. Not even millimeters, but actually nanometers. What you see on this slide here is the entire visible spectrum of light. That which we can see with our eyes, 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 ultra wave or x-rays.

We can see light provided that the wavelength is between about 400 and 700 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. And this is, by the way, just as an aside, 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?

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, because I'm getting visible light that's more powerful than microwave. But nevertheless, when you go just below what we see with visible light, you get into ultraviolet light.

And ultraviolet light exists from about 100 nanometers to that upper limit of 400 nanometers where we just start to be able to see it at blue light. It's really broken down into three types. People have heard these terms, but I think it's helpful to understand what they mean. You've got UVA, UVB, and UVC or ultraviolet, A, B, and C. Now, as you go from A to B to C, the wavelength is getting smaller. If you recall what I said a moment ago, that implies that the strength is getting higher. Now, that means that ultraviolet C is the strongest, i.e., the most ionizing of radiation, but ultraviolet C does not really reach Earth. So 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 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, 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%. UVB is 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 few more minutes on that than I wanted to, but I think it's important for people to understand the difference between ultraviolet light, visible light, and other forms of energy, and then the difference between UVA and B. 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? Well, vitamin D is produced when UVB light converts D2 or pre-vitamin 3 into 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 and it turns out just the heat of our body is sufficient. When you take sunlight coupled with body heat, you make vitamin D3. Maybe people are aware that

when they're buying, you go to Amazon to buy vitamin D supplements, if you look at it, it doesn't just say vitamin D, it says D3. Now, look, you can get D3 in food as well and obviously you can get D3 in a supplement. At the end of the day, it doesn't really matter where the vitamin D comes from. It is the same molecule. It's a fat soluble vitamin and therefore you have to basically be able to get it in fat soluble manners. You're going to see it in foods that are fatty foods, such as fish oil and eggs and fortified dairy products and things of that nature. 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? Well, this is where it starts to get a little bit confusing. And it is the case that vitamin D deficiency, first off, there's not even a really clear definition of what that is. 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.

I will say this in our practice, we consider below 30 to be deficient, not 15. 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 again, because I said vitamin D is a fat soluble 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 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 going to have lower vitamin D, all things equal because they are sequestering more of the vitamin D in their fat cell. Obesity right off the bat is a potential risk factor that drives low vitamin D. The other thing we talk about of course is skin tone. We'll 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. Darker skinned people are going to have lower vitamin D levels. 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. People may recall from the previous AMA on this topic that I take a hard line view on this and I actually think most people do not have adequate levels of magnesium or certainly not optimal. Maybe they're biochemically adequate, but they certainly wouldn't be optimal. Suboptimal levels of magnesium will also impede metabolism of vitamin D and therefore we will see low magnesium associated with low vitamin D because magnesium is a co-factor in the enzymatic conversion of vitamin D. Do we know anything about how much time someone would need with UV radiation to not be deficient in vitamin D?

It's not a very straightforward formula because it depends on obviously your skin type and we'll talk about the five or six skin types in a second. It's going to depend on your location, it's going to depend on the time of day, and it's obviously going to depend on the amount of skin surface area that is exposed. Let's just start with skin types. There are six skin types that are described on something called the Fitzpatrick scale. It's a semi quantitative scale that describes skin color by its basal complexion, melanin level in response to UV.

You have types one through six and they go from most pale to UV. So you have types 1 through 6 and they go from most pale to least, right? So type 1 is very pale white skin, burns very easily, does not tan. Type 2, white skin, burns easily, doesn't tan with much easily, but isn't a guaranteed under the right circumstances can develop a little bit of a tan. Type 3, white skin, might burn, but also tans kind of easily. Type four, light brown or olive skin hardly burns, tans easily. So that's me, I'm a type four. Type five, brown skin usually doesn't burn, tans very easily. And then type six is black skin, unlikely to burn and becomes significantly darker with significant UV radiation exposure. Caucasians, which are usually defined as type 1

to type 3, believe it or not, don't need that much sun exposure to reach adequate levels. One study noted that people who were type 1 to type 3, so again Caucasian, 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, were getting sufficient vitamin D. Now again, it's important to understand a third of your body exposed means you're in shorts and a t-shirt, 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 going to get that. Now, if you talk about people that are type 5 skin, so South Asian populations, for example, they're going to need to spend three, four times

that amount of time in the sun under the exact same conditions just to reach the same vitamin D levels. One caveat I should point out that this study defined deficiency as below 25 nanomole per liter or 10 milligrams per milliliter. We think that that is really deficient. We think that that's like 3X below what we consider deficient. 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 pretty reasonable assessment. The other thing obviously that goes without saying is where you are

from a latitude perspective. So 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. On the other end of deficiency, what happens if we get too much UV? Well, I'm not aware of too much UV ever resulting in too much vitamin D. We can put that aside as a concern. Rather, what we want to talk about is what are the other effects. Obviously, you can develop a sunburn and that can be a very acute thing. That can be painful and we'll obviously talk in a moment about the impact of that on subsequent skin cancers. I think it's always worth talking about photo aging.

Even though this is not exactly a podcast that focuses on the aesthetic side of living longer, I don't think it's a bad idea to imagine what our skin is going to look like as we age. And so photo aging, which I think we all recognize as sort of the wrinkles and sagging skin that occur with aging are indeed the result of sun exposure. So recall that when you are exposed to UVA and especially UVB, 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 proteins and enzymes responsible for the activity of the proteins and enzymes responsible for the degradation of the ECM. I think we all understand what this looks like, but we found an interesting picture in the New England Journal of Medicine as part of the Images in Clinical Medicine series that I think does an interesting job of showing you something. This is a picture here, Nick, if you pull it up. It's a gentleman who I believe spent 32 years as a truck driver. And obviously this was here in North America.

So that meant the left side of his face was out the window. And 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. So a lot of the UV was actually being deflected by the glass. But 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 is a rare example of how in one person with their own 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 excessive UV exposure. On skin cancer, the next question is which skin cancers have known associations with UV directly? Thank you for listening to this week's episode of The Drive. 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,

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