#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 Stats
Words per Minute
170.19308
Summary
In this episode, we cover two topics that we ve not covered before, but that we have seen a lot of questions about over the years: 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, photoaging, and its role in skin cancer. 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, and what SPF levels to look for. Finally, we discuss the differences between organic and mineral sunscreens.
Transcript
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
00:00:42.700
and benefits above and beyond what is available for free. If you want to take your knowledge of
00:00:47.940
this space to the next level, it's our goal to ensure members get back much more than the price
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.
00:02:45.320
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
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
00:13:05.220
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,
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,
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,
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
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,
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?
00:18:38.100
Thank you for listening to this week's episode of The Drive. It's extremely important to me to
00:18:42.420
provide all of this content without relying on paid ads. To do this, our work is made entirely
00:18:47.540
possible by our members. And in return, we offer exclusive member only content and benefits above
00:18:53.860
and beyond what is available for free. So if you want to take your knowledge of this space to the
00:18:58.180
next level, it's our goal to ensure members get back much more than the price of the subscription.
00:19:03.460
Premium membership includes several benefits. First, comprehensive podcast show notes that detail
00:19:09.940
every topic, paper, person, and thing that we discuss in each episode. And the word on the street is
00:19:15.860
nobody's show notes rival ours. Second, monthly Ask Me Anything or AMA episodes. These episodes are
00:19:23.380
comprised of detailed responses to subscriber questions typically focused on a single topic
00:19:28.660
and are designed to offer a great deal of clarity and detail on topics of special interest to our
00:19:33.620
members. You'll also get access to the show notes for these episodes, of course.
00:19:38.180
Third, delivery of our premium newsletter, which is put together by our dedicated team of research
00:19:43.300
analysts. This newsletter covers a wide range of topics related to longevity and provides much more
00:19:49.220
detail than our free weekly newsletter. Fourth, access to our private podcast feed that provides
00:19:56.340
you with access to every episode, including AMA's sans the spiel you're listening to now and in your
00:20:02.420
regular podcast feed. Fifth, the Qualies, an additional member only podcast we put together that serves as a
00:20:09.780
highlight reel featuring the best excerpts from previous episodes of the drive. This is a great
00:20:15.060
way to catch up on previous episodes without having to go back and listen to each one of them. And
00:20:19.940
finally, other benefits that are added along the way. If you want to learn more and access these member
00:20:25.460
only benefits, you can head over to peteratiamd.com forward slash subscribe. You can also find me on
00:20:32.420
YouTube, Instagram, and Twitter, all with the handle peteratiamd. You can also leave us review on Apple
00:20:38.900
podcasts or whatever podcast player you use. This podcast is for general informational purposes only
00:20:45.140
and does not constitute the practice of medicine, nursing, or other professional healthcare services,
00:20:49.860
including the giving of medical advice. No doctor patient relationship is formed. The use of this
00:20:55.940
information and the materials linked to this podcast is at the user's own risk. The content
00:21:01.700
on this podcast is not intended to be a substitute for professional medical advice, diagnosis, or
00:21:06.580
treatment. Users should not disregard or delay in obtaining medical advice from any medical condition
00:21:12.020
they have, and they should seek the assistance of their healthcare professionals for any such conditions.
00:21:17.540
Finally, I take all conflicts of interest very seriously. For all of my disclosures and the
00:21:22.580
companies I invest in or advise, please visit peteratiamd.com forward slash about where I keep an