#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

This episode delves into the relationship between sun exposure and skin health, discussing aspects like skin cancer, vitamin D production, and photoaging. It also explores the correct use and selection of sunscreen.

1. UV radiation plays a complex role in health, impacting vitamin D synthesis, skin aging, and skin cancer risk.
2. The type of sunscreen (organic vs. mineral), SPF level, and proper application are crucial for effective protection.
3. Photoaging and skin cancer are significantly influenced by the type and amount of UV exposure.
4. Vitamin D can be synthesized efficiently through moderate sun exposure, tailored to skin type and geographic location.
5. Regular skin checks and understanding one's skin type on the Fitzpatrick scale can guide effective sun protection strategies.

1: Introduction to Sun Exposure and UV Radiation

Overview of UV radiation and its effects on skin health and vitamin D production. Key focus on how UV contributes to photoaging and skin cancer.

• Peter Attia: "UV radiation, especially UVB, is crucial for vitamin D conversion but also plays a role in skin aging and cancers."

2: Deep Dive into Skin Cancer Types and Risks

Discussion on various skin cancer types, focusing on melanoma, and the specific risks associated with UV exposure.

• Nick Stenson: "Melanoma is significantly influenced by UV exposure, but other factors like genetics also play a role."

3: Understanding and Choosing Sunscreen

Comprehensive guide on different types of sunscreens and how to select the right SPF.

• Peter Attia: "Choosing the right type of sunscreen and applying it correctly is crucial for effective UV protection."

1. Choose the Right Sunscreen: Opt for broad-spectrum sunscreens with adequate SPF to protect against both UVA and UVB.
2. Understand Your Skin Type: Use the Fitzpatrick scale to tailor your sun exposure and sunscreen use.
3. Regular Skin Checks: Early detection of skin changes or abnormalities can prevent serious outcomes.
4. Moderate Sun Exposure: Balance sun exposure to optimize vitamin D production without increasing skin cancer risk.
5. Educate on Photoaging: Understanding the effects of UV on aging can motivate better sun protection practices.

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.

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Peter Attia, Nick Stenson

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Peter Attia
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, 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 peterattiamd.com 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.

Nick Stenson
They are skin cancer and sunscreen. 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 photoaging 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 want to 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.

Peter Attia
Peter, welcome to an AMA. How are you doing? Good. Thanks for having me always welcome here. You are always welcome on your own show.

So I am happy to have you 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 going to 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 want to 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.

Nick Stenson
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 photoaging. 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 sort of see what we're doing here. So there are a couple of figures on this slide here. And the first one is a great figure that just sort of tries to explain what is happening when wavelengths across an electromagnetic spectrum change in size. Let's take a step back. So many of the waves that are out there are of different wavelengths.

So 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. So 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. 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. So not even millimeters, 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 that the length, the wavelength is between about 400 and 700 nm. 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 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, that upper limit of 400 nm, 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 got UVA, UVB and UV C, or ultraviolet a, B, and C. Now, 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 the strongest, that is the most ionizing of radiation. But ultraviolet C does not really reach Earth.

So UV C 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 UV A and B. Yeah.

Peter Attia
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 D two or pre vitamin three into D three. And it's a little bit more complicated than that in that it doesn't just require the ionizing radiation.

Nick Stenson
It also requires heat. And it turns out just the heat of our body is sufficient. So when you take sunlight coupled with body heat, you make vitamin d three. And 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 d three. Now, look, you can get d three in food as well. And obviously, you can get d three 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. So 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?

Peter Attia
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.

Nick Stenson
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 cells. So 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. So 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 skinned people are going to have lower vitamin D levels. 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 I take a kind of hardline view on this. And I actually think most people do not have adequate levels of magnesium or certainly not optimal.

So maybe they're biochemically adequate, but they certainly wouldn't be optimal. And so 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 cofactor 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. So let's just start with skin types. Are six skin types that are described on something called the Fitzpatrick scale.

So it's a kind of semi quantitative scale that describes skin color by its basal complexion, melanin level in response to uv. So you have types one through six, and they go from most pale to least, right. So type one is very pale, white skin, burns very easily, does not tan. Type two, 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 three, 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. So Caucasians, which are usually defined as type one to type three, believe it or not, don't need that much of sun exposure to reach adequate levels.

And so one study noted that people who were type one to type three. 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, we're 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 five 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 ten milligrams per milliliter. So we think that that is really deficient. We think that that's like three x below 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 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, and so we can put that aside as a concern. So rather, what we want to talk about is 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. I think it's always worth talking about photoaging.

And 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. Photo aging, which I think we all recognize as the wrinkles and sagging skin that occur with aging, are indeed the result of sun exposure. Recall that when you are exposed to uv A, and especially uvB, the epidermis has to thicken. It's a defense mechanism, and theres a decrease in the amount of extracellular matrix proteins. So collagen as a result of this, and its probably due to uv related increases in the expression and activity of the proteins and enzymes responsible for the degradation of the ECM.

So 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. So this is a picture here, Nick, if you pull it up, it's a gentleman who I believe spent like 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?

Peter Attia
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Nick Stenson
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Peter Attia
For all of my disclosures and the companies I invest in or advise, please visit peteratiamd.com about where I keep an up to date and active list of all disclosures.