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

00:00:00.000 Hey, everyone. Welcome to the Drive podcast. I'm your host, Peter Atiyah. This podcast,

00:00:16.540 my website, and my weekly newsletter all focus on the goal of translating the science of longevity

00:00:21.520 into something accessible for everyone. Our goal is to provide the best content in health and

00:00:26.720 wellness, and we've established a great team of analysts to make this happen. It is extremely

00:00:31.660 important to me to provide all of this content without relying on paid ads. To do this, our work

00:00:36.960 is made entirely possible by our members, and in return, we offer exclusive member-only content

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00:00:53.200 of the subscription. If you want to learn more about the benefits of our premium membership,

00:00:58.020 head over to peteratiyahmd.com forward slash subscribe. Welcome to Ask Me Anything, episode

00:01:06.460 61. I'm once again joined by my co-host, Nick Stenson. In today's episode, we cover two topics

00:01:12.660 that we have not covered before, but that we've seen a lot of questions over the years. They are

00:01:17.380 skin cancer and sunscreen. We begin the conversation by laying the foundation on what UV is and the

00:01:24.440 impacts that UV has on vitamin D conversion, photoaging, and its role in skin cancer. We

00:01:29.800 look at various skin types and what the implications are of these skin types on sun exposure, vitamin

00:01:35.540 D levels, as well as how to understand where you may fall on the scale and what the implications

00:01:39.560 are. We talk about photoaging and the factors that contribute to it, and then we dive into the

00:01:43.920 different types of skin cancers. We talk about UV and its role specifically in melanoma, which is of

00:01:49.800 course the skin cancer that matters most, as well as other risk factors besides the sun that pertain

00:01:55.560 to melanoma. We speak about tanning beds, skin checks, and why it's probably important to catch skin

00:02:01.840 cancer earlier rather than later. From there, we move into the topic of sunscreen, which seems to be

00:02:06.400 clouded with some confusion. We discuss all things related to sunscreen, its impact on UV radiation,

00:02:12.480 its impact on skin cancer, what SPF levels to look for, and finally, we talk about the differences

00:02:19.720 between organic sunscreens and mineral sunscreens. If you're a subscriber and want to watch the full

00:02:25.920 video of this podcast, you can find it on the show notes page. If you're not a subscriber, you can watch

00:02:30.840 a sneak peek of the video on our YouTube page. So without further delay, I hope you enjoy AMA number 61.

00:02:36.440 Peter, welcome to an AMA. How are you doing?

00:02:44.320 Good. Thanks for having me.

00:02:45.320 Always welcome here. You are always welcome on your own show. So I'm happy to have you be a little

00:02:52.840 awkward without you to tell the truth. But for today's AMA, we're going to cover two topics,

00:02:58.040 a little bit related that we see a lot of questions come through. Also appears to be a lot of confusion

00:03:02.760 around, which I think is why we see so many questions. And that is skin cancer and sunscreen.

00:03:08.200 And so what we did is we gathered all the questions on this, organized them. We're going

00:03:13.160 to start with skin cancer, move to sunscreen. We have a lot to cover through this. So I think we'll

00:03:19.080 hit it right away. But anything that you want to add before we get rolling?

00:03:24.280 No, I mean, look, I think this is a topic that I know we internally took very seriously,

00:03:30.520 because it is, I think, easy to just assume the standard chant. And we came at this from

00:03:37.080 first principles is basically what I can say. So months and months of work by the part of our team,

00:03:43.480 in particular, one of our analysts, who I think now literally probably knows more about this

00:03:48.280 subject than anyone else, including me. And so I'm excited to kind of dive into it.

00:03:52.440 As we get going on the first skin cancer section, I think it'd be important to just quickly cover

00:03:58.280 what is the impact of UV radiation on the skin.

00:04:02.920 I think we should spend a minute talking about what UV is. But given that we're going to talk

00:04:06.840 about that in a second, there are really three things that you want to be thinking about,

00:04:10.840 right? You want to understand the impact that UV has on vitamin D conversion. You want to understand

00:04:16.840 the impact that ultraviolet light has on photo aging. And then ultimately, you want to understand

00:04:20.840 the role it plays on skin cancers. And we're going to break those out into two buckets.

00:04:24.520 Right. And you hinted at it there, but I think it'd be good to cover a little bit more here,

00:04:29.160 which is when we say solar UV, what are we referring to?

00:04:33.720 This is a great example of where I think a figure is very helpful. And I realize not everybody's

00:04:38.120 watching this on video, but I'll do my best to articulate it. I do think this is one of those

00:04:42.440 times when it helps to look at the show notes or watch us on video so you can sort of see what

00:04:46.040 we're doing here. So there are a couple of figures on this slide here. And the first one is a great figure

00:04:51.720 that just sort of tries to explain what is happening when wavelengths across an electromagnetic spectrum

00:04:59.640 change in size. Let's take a step back. So many of the waves that are out there are of different

00:05:06.440 wavelengths, right? So you have sound waves, you have waves of light. I remember this learning this in

00:05:11.560 sort of my physics class in high school and having a big aha moment. So sound waves are invisible.

00:05:16.920 light waves are invisible. Why can you hear around a corner, but you can't see around a corner?

00:05:24.040 Well, it has to do with the length of the waves and sound waves are literally meters long. And so

00:05:31.000 the way they bounce and move is such that they're basically going around corners, whereas light waves

00:05:36.680 are tiny. And to give you a sense of how tiny they are, they're measured in nanometers. So not even

00:05:43.480 millimeters, but actually nanometers. And what you see on this slide here is the entire visible

00:05:48.280 spectrum of light. So that which we can see with our eyes, right? We can't see radio waves. We can't

00:05:54.280 see microwaves. We can't even see infrared. And as you see in a moment, we can't see ultra wave or x-rays.

00:05:59.560 We can see light provided that the length, the wavelength is between about 400 and 700 nanometers.

00:06:06.280 That's a really, really tiny sliver of the entire electromagnetic spectrum, but that encompasses

00:06:13.080 everything from red light all the way down to blue light. Now, when you get right, right, right beneath

00:06:20.200 the lowest level of visibility, you get into ultraviolet light. Now, one other point I should make is,

00:06:29.320 the shorter the wavelength, the more energy that is contained within it. And this is, by the way,

00:06:35.240 just as an aside, when people say, oh my God, I can't believe you stand next to your microwave when

00:06:39.400 it's cooking. Aren't you worried about anything? The answer is no, because microwaves are actually

00:06:43.880 longer than visible light. So if I'm worried that my microwave is hurting me, I should be really worried

00:06:49.960 that just living is hurting me, right? Because I'm getting visible light that's more powerful than

00:06:54.040 microwave. But nevertheless, when you go just below what we see with visible light, you get into ultraviolet

00:07:01.000 light. And ultraviolet light exists from about a hundred nanometers to that upper limit of 400

00:07:08.200 nanometers, where we just start to be able to see it at blue light. And it's really broken down into

00:07:12.520 three types. And people have heard these terms, but I think it's helpful to understand what they mean.

00:07:16.440 So you've got UVA, UVB, and UVC, or ultraviolet A, B, and C. Now, as you go from A to B to C,

00:07:26.200 the wavelength is getting smaller. And if you recall what I said a moment ago, that implies

00:07:31.800 that the strength is getting higher. Now, that means that ultraviolet C is the strongest, i.e.,

00:07:40.920 the most ionizing of radiation. But ultraviolet C does not really reach Earth. So UVC doesn't make

00:07:48.600 it through the atmosphere, and therefore we don't really deal with it. So instead, what we're dealing

00:07:52.280 with is UVA and UVB, both of which reach our surface and therefore our skin. So for the purpose

00:08:00.040 of this discussion, when we talk about UV radiation, we're talking about UVA and we're talking about UVB.

00:08:06.360 UVB, although UVA occupies a much broader band. As you can see on this figure, it's about 315 to 400,

00:08:14.360 whereas UVB is about 280 to 315. Now, why is this relevant? It's relevant because of what these things

00:08:22.840 do. So UVB is much smaller, right? It's about 5% of the UV radiation that we're exposed to from the sun

00:08:32.900 versus UVA, which is about 95%. UVB is shorter, doesn't penetrate as much, but it's higher energy.

00:08:43.300 So it's the UVB that is really responsible for the sunburn and the vitamin D conversion,

00:08:49.380 whereas UVA goes deeper, but it's not as ionizing in energy. So maybe spent a few more minutes on that

00:08:56.420 than I wanted to, but I think it's important for people to understand the difference between

00:08:59.300 UVA, ultraviolet light, visible light, and other forms of energy. And then the difference between

00:09:04.100 UVA and B. Yeah, no, I think it is helpful just to kind of set the stage for the discussion here.

00:09:09.860 And you hinted at it earlier, but a lot of time when people talk about sunlight, they naturally

00:09:14.500 think of vitamin D. And so what do we know about how UV can help in the production of vitamin D?

00:09:21.620 Well, vitamin D is produced when UVB light converts D2 or pre-vitamin 3 into D3. And it's a little bit

00:09:36.740 more complicated than that in that it doesn't just require the ionizing radiation, it also requires heat.

00:09:44.340 And it turns out just the heat of our body is sufficient. So when you take sunlight coupled

00:09:49.460 with body heat, you make vitamin D3. And maybe people are aware that when they're buying, you go

00:09:55.380 to Amazon to buy vitamin D supplements. If you look at it, it doesn't just say vitamin D, it says D3.

00:10:01.060 Now, look, you can get D3 in food as well. And obviously you can get D3 in a supplement.

00:10:08.100 At the end of the day, it doesn't really matter where the vitamin D comes from. It is the same molecule.

00:10:14.340 It's a fat soluble vitamin. And therefore you have to basically be able to get it in fat soluble

00:10:19.460 manners. So you're going to see it in foods that are fatty foods, such as fish oil and eggs and

00:10:26.420 fortified dairy products and things of that nature. What do we know about too little UV exposure and how

00:10:32.980 that can relate to vitamin D deficiency? And is it something that people can overcome by taking vitamin D

00:10:40.260 supplements? Obviously, vitamin D supplements are often talked about. So how does that interact here?

00:10:46.660 Well, this is where it starts to get a little bit confusing. And it is the case that vitamin D

00:10:53.860 deficiency, first off, there's not even a really clear definition of what that is. I believe

00:11:01.460 medically it's defined as a vitamin D level less than 15, although some labs would consider it a

00:11:07.220 deficiency if you're less than 30. I will say this in our practice, we consider below 30 to be

00:11:13.460 deficient, not 15. And there's a clear association between vitamin D deficiency and less time in the

00:11:19.940 sun. But it's not that straightforward because you have other things to consider. So again, because I

00:11:26.500 said vitamin D is a fat soluble vitamin, the more adipose tissue a person has, the greater the sequestration

00:11:34.020 of vitamin D into the fat cells. In other words, you take two individuals that have the same amount

00:11:39.380 of sun exposure and other factors, even skin tone and things we'll talk about in a second.

00:11:43.860 One of them has much more adipose tissue than the other. They're going to have lower vitamin D,

00:11:47.700 all things equal, because they are sequestering more of the vitamin D in their fat cells. So obesity

00:11:52.180 right off the bat is a potential risk factor that drives low vitamin D. The other thing we talk about,

00:11:59.060 of course, is skin tone. So we'll, I guess, talk about this more shortly.

00:12:02.340 But those who have more naturally occurring melanin have more built in protection from

00:12:07.380 UV radiation, which means less UV conversion for vitamin D. So darker skin people are going to have 0.99

00:12:15.540 lower vitamin D levels. And then I think one other thing to mention here, because we've talked about

00:12:20.260 it so much in the past is the impact of magnesium. And people may recall from the previous AMA on this

00:12:25.700 topic that, you know, I take a kind of hard line view on this. And I actually think most people

00:12:29.860 do not have adequate levels of magnesium are certainly not optimal. So maybe they're

00:12:34.500 biochemically adequate, but they certainly wouldn't be optimal. And so suboptimal levels of magnesium

00:12:40.820 will also impede metabolism of vitamin D. And therefore we will see low magnesium associated

00:12:48.500 with low vitamin D because magnesium is a cofactor in the enzymatic conversion of vitamin D.

00:12:54.820 Do we know anything about how much time someone would need with UV radiation to not be deficient

00:13:04.500 in vitamin D?

00:13:05.220 It's not a very straightforward formula because it depends on obviously your skin type. And we'll

00:13:12.980 talk about the five or six skin types in a second. It's going to depend on your location. It's going to

00:13:17.940 depend on the time of day. And it's obviously going to depend on the amount of skin surface area that is

00:13:23.540 exposed. So let's just start with skin types. There are six skin types that are described on

00:13:29.940 something called the Fitzpatrick scale. So it's a kind of semi-quantitative scale that describes skin

00:13:36.020 color by its basal complexion, melanin level in response to UV. So you have types one through six,

00:13:43.060 and they go from most pale to least, right? So type one is very pale white skin, burns very easily, 0.99

00:13:50.180 does not tan. Type two, white skin, burns easily, doesn't tan with much easily, but isn't a guaranteed

00:13:57.860 under the right circumstances can develop a little bit of a tan. Type three, white skin, might burn, 0.99

00:14:03.060 but also tans kind of easily. Type four, light brown or olive skin, hardly burns, tans easily. So that's me,

00:14:10.420 I'm a type four. Type five, brown skin, usually doesn't burn, tans very easily. And then type six is black skin, 0.95

00:14:17.620 unlikely to burn, and becomes significantly darker with significant UV radiation exposure. So

00:14:24.500 Caucasians, which are usually defined as type one to type three, believe it or not, don't need that much

00:14:30.820 sun exposure to reach adequate levels. And so one study noted that people who were type one to type

00:14:37.380 three, so again, Caucasian, with as little as nine minutes per day of sun exposure in midday during the

00:14:44.820 summer months in the Northern hemisphere, so March to September, assuming at least a third of their

00:14:50.020 body was exposed, were getting sufficient vitamin D. Now, again, it's important to understand a third

00:14:56.340 of your body exposed means you're in shorts and a t-shirt, but everything else is exposed. So again,

00:15:02.580 if you're walking around in pants and you're in a long sleeve shirt, you're obviously not going to get

00:15:06.180 that. Now, if you talk about people that are type five skin, so South Asian populations, for example,

00:15:13.300 they're going to need to spend three, four times that amount of time in the sun under the exact same

00:15:18.820 conditions just to reach the same vitamin D levels. One caveat I should point out that this study

00:15:25.540 defined deficiency as below 25 nanomole per liter or 10 milligrams per milliliter. So we think that that is

00:15:35.380 really deficient. We think that that's like three X below what we consider deficient. So I would say

00:15:42.660 that these numbers don't really apply to how we think about it. But for the purpose of comparing

00:15:49.220 different skin types, I think it's a pretty reasonable assessment. The other thing obviously 1.00

00:15:53.940 that goes without saying is where you are from a latitude perspective. So the bottom line is you don't

00:15:59.860 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

00:16:06.340 to get all of your vitamin D from the sun and not to supplement it. On the other end of deficiency,

00:16:14.180 what happens if we get too much UV? Well, I'm not aware of too much UV ever resulting in too much

00:16:21.940 vitamin D. And so we can put that aside as a concern. So rather what we want to talk about is what are the

00:16:29.460 other effects. So obviously you can develop a sunburn and that can be a very acute thing and that can be

00:16:34.980 painful. And we'll obviously talk in a moment about the impact of that on subsequent skin cancers. I think

00:16:40.580 it's always worth talking about photo aging. And even though this is not exactly a podcast that focuses

00:16:45.620 on the aesthetic side of living longer, I don't think it's a bad idea to imagine what our skin is going to

00:16:52.020 look like as we age. And so photo aging, which I think we all recognize as sort of the wrinkles and sagging skin

00:16:58.660 that occur with aging are indeed the result of sun exposure. So recall that when you are exposed to

00:17:05.060 UVA and especially UVB, the epidermis has to thicken. It's a defense mechanism. And there's a decrease in

00:17:13.460 the amount of extracellular matrix proteins, so collagen as a result of this. And it's probably due to UV

00:17:20.660 related increases in the expression and activity of the proteins and enzymes responsible for the degradation of

00:17:27.060 the ECM. So I think we all understand what this looks like, but we found an interesting picture

00:17:31.940 in the New England Journal of Medicine as part of the Images and Clinical Medicine series that I think

00:17:35.860 does an interesting job of showing you something. So this is a picture here, Nick, if you pull it up,

00:17:39.940 it's a gentleman who I believe spent like 32 years as a truck driver. And obviously this was here in

00:17:46.180 North America. So that meant the left side of his face was out the window. And this is a very interesting

00:17:52.420 and stark example of what just a little bit more sun is doing. It's also worth pointing out that

00:17:57.700 probably most of the time he's driving, the window is closed. So a lot of the UV was actually being

00:18:02.980 deflected by the glass, but I'm sure that there were times when the window was open and you can

00:18:07.140 see an obvious and clear difference between the left side of his face and the right side of his face.

00:18:12.100 That is a rare example of how in one person with their own skin being the perfect control, 0.99

00:18:18.100 you can see the significant difference. Finally, as I alluded to, obviously skin cancer becomes

00:18:23.940 perhaps the most important concern as we think about excessive UV exposure.

00:18:28.660 On skin cancer, the next question is which skin cancers have known associations with UV directly?

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00:21:52.580 paul x

The Peter Attia Drive - July 01, 2024

#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

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