What's the Deal with the Sun?

Perry: [00:00:00] Emily, the sun is really big. Did you know that the sun is bigger than all the planets in the solar system?

Emily: [00:00:12] I did know that. Perry yes, but say more about how big the sun is.

Perry: [00:00:17] 99% of the mass in the solar system is in the sun. It's that big. It's almost everything. Everything else is a rounding error. And okay, this doesn't have to do with wellness, but I wanted to give some fun sun facts before we got into our episode about the sun. And one thing that I kept coming across was that, you know, you could fit 1.3 million Earths inside the sun. That's how big it is. That's a lot of Earths. Um, and that's all over the place. But I was like, wait, is that really true? Because it's not like the Earths would just sit there, do you know what I mean?

Emily: [00:00:52] I always sort of imagine it was like if the sun were like a jar and you put and the earth was a gumball. That means it's like 1.3 [00:01:00] million gumballs. Is that right?

Perry: [00:01:01] But do you know what happens if you put a million Earths together? It's like they all have gravity and they start crushing in on each other. And. And it turns out again.

Emily: [00:01:11] Okay.

Perry: [00:01:12] Right now, we're physics, actually. It turns out that as you add Earths into a big ball, these really interesting things happen. So after 333 Earths, adding additional Earths actually makes the volume of the Earths smaller. 333 Earths, because the earth is made primarily of iron, is when gravity can pull the atoms together, or the nuclei of the atoms together, even though the electrons are trying to fight against it. Right. So it is actually getting denser and denser and.

Emily: [00:01:45] Denser, sucking it in. Okay.

Perry: [00:01:47] By the time you're at 334 Earths, the thing is just getting smaller. When you get to 333,000 Earths, that exceeds gravity exceeds the electron degeneracy pressure, and all [00:02:00] those Earths form a white dwarf star. So it just sits there, being a white dwarf star about the size of the earth. So 333,000 Earths end up.

Emily: [00:02:13] Being earth.

Perry: [00:02:15] About the.

Emily: [00:02:15] Size of one earth, but very hot.

Perry: [00:02:18] If you took the 1.3 million Earths that the internet says, you can stick inside the sun.

Emily: [00:02:23] And.

Perry: [00:02:24] Actually put them in the sun, you would get a black hole, and the size of that black hole would be 11,500m across about the size of New Haven, Connecticut city limits.

Emily: [00:02:39] That is totally fascinating. And I think it's a good open because a lot of people might be wondering like, hey, this episode's about the sun. What is the sun? You know, and we'd like to provide some information at the top. And I also thought about a way to provide people information. And you went with science and I went with They Might Be Giants. And so let me just give you a little [00:03:00] clip in song from the best song ever written about the sun by They Might Be Giants. Sun is a mass of incandescent gas, a gigantic nuclear furnace. Where hydrogen is fused into helium at temperatures of millions of degrees. It goes on from there. And if you have any children who are interested in the sun, I highly recommend that you have that. Listen them. Listen to that song instead of listening to Perry's description, even though I did think it was very interesting. I'm Emily Oster, I'm an economist and a data expert.

Perry: [00:03:35] And I'm Perry Wilson, I'm a medical doctor.

Emily: [00:03:38] It's Thursday, July 30th, 2026. And this is Wellness, Actually.

Perry: [00:03:42] Because you're getting a staggering amount of health and wellness information nowadays from every source imaginable. And some of it is awesome.

Emily: [00:03:50] And some of it is, well, actually Bullshit. Fortunately, we're both people who know how to read studies, how to parse the data, [00:04:00] and can tell you what's worth thinking about and what you can safely ignore.

Perry: [00:04:04] But before we dig in, a note that this podcast is for educational purposes and should not be construed as medical advice. We don't know your unique situation, so talk to your doctor for personal health decisions.

Emily: [00:04:15] Here comes the sun. This week we're asking, what's the deal with the sun? Perry and I will give the official smash or pass. Do we even need the sun anyway? And then we'll get to your questions of the week. Too hot. But first, let's do the health news roundup after the break. And now let's do the health news of the week. My first question for you, Perry. I noticed that the cardiologists have finally come out in support of one of my more central personal habits, which is consumption of coffee. And the cardiologists [00:05:00] of America have said, coffee's great. Why did they say that now?

Perry: [00:05:06] I guess people were kind of down on cardiology and they were like, you guys are such wet blankets, always telling us not to drink alcohol or eat fatty foods or whatever, and they needed to get some street cred. So the American Heart Association has released a formal document on caffeine and the cardiovascular risks and benefits, and it goes through decades of research into the substance. But I'll summarize in saying they basically gave a thumbs up to coffee, to ingesting caffeine in the form of coffee, noting across several studies that there's stuff in coffee that might be healthy even beyond caffeine and sort of are equivocal on caffeine supplemented beverages and gels and energy drinks and things like that. But overall, some of the sort of myths that got dispelled in this document, number one, that was surprising to me even was they talk about generally [00:06:00] coffee being less likely to promote atrial fibrillation, the most common cardiac arrhythmia. We always sort of counsel people with AFib or we used to counsel people with AFib like, oh, don't avoid coffee if you're trying to stay out of AFib. Aha says not true. In fact, the current guidelines advise specifically against telling people not to drink coffee if they have atrial fibrillation. Um, some other interesting stuff. They note a randomized controlled trial which showed that coffee increases LDL cholesterol. That's the bad cholesterol, but not if you pass it through a paper filter. There's a substance in coffee that raises cholesterol but gets adsorbed into paper filters. So maybe that's an argument against French presses, although that is a nice form of coffee that I like. I love finding things though. Emily. Like I have a list of three things. I wonder if you can guess these. There are three things in life where that are pleasurable, and science also tells you that they're good for you. Like most things, it's like a, you know, [00:07:00] it's not that pleasurable, but you got to do it. Eat your broccoli. Right? So coffee is one of them. I have two more.

Emily: [00:07:07] What are your other two?

Perry: [00:07:08] I'm curious what your. So so the only the only other two I've been able to think of are sleep and sex. Coffee, sleep and sex. That's it. Everything else. If it feels good, it's bad for you.

Emily: [00:07:19] Yeah. That sounds that sounds right.

Perry: [00:07:21] I mean, people would be like, oh, exercise. Like I, I love exercise. No you don't. Come on.

Emily: [00:07:26] I do, I do. No, I will tell you, I do actually love exercise.

Perry: [00:07:30] It's the endorphins love. But if you could just lie around eating Doritos.

Emily: [00:07:34] No, I would, I totally would not do that. Um, but, uh, I will go with. Yeah, yeah. Coffee, sleep, sex and exercise on my end. Here is what I will say about this coffee thing. Very nice. I broadly think that there's a lot of good stuff in this report. I will say I am always very frustrated that these reports seem to rely on both observational and randomized data and not distinguish [00:08:00] them. I mean, Coffee Makes You Live Forever is like a standard headline that shows up in a lot of coverage of garbage. Observational studies, these guys, like some of what they're saying is based on randomized trials, some is based on observational data. I just wish they would talk about the randomized trials. Like here are the things we actually know. And here are some, you know, associations which you should take with a grain of salt. And I think they don't do that because they don't have the same skepticism that I do for observational data. But anyway, that's my, my problem.

Perry: [00:08:30] I, I hear you. Um, and that skepticism comes through loud and clear. Let's move on to, um, a rather bleak, uh, record that we have, um, there have been more measles cases reported in the United States in the last two years than in all the years from 2000 through 2024 combined. Emily, what's going on with measles?

Emily: [00:08:58] Yeah, there's some actually other [00:09:00] ways to look at that data, which I think are even more disturbing. Like there was a single week in January when there were more measles cases than all like, than the yearly count for all but a few years in the past 20 years. So we're having a very unusual outbreak, set of measles. What is happening is pretty clear. We are in a period of increased vaccine hesitancy. Vaccine rates have been going down for a long period of time, and that means we have a lot of kids who are unvaccinated. Measles is super, super, super contagious. The are not is something like 12 to 15, which means any individual person with measles can spread it to is expected to spread it to 12 to 15 other people. If everyone was unvaccinated, that's way, way, way higher than almost any other viral illness that we talk about. And so it's just really.

Perry: [00:09:49] The flu is like 1.5.

Emily: [00:09:51] Yeah, it's just super, super contagious. And if you have a school where 50% of the kids are vaccinated, which we do have some of, then one kids get measles, [00:10:00] a lot of people get measles. And so, you know, look, I mean, there is an obvious solution for this. It is for more people to get vaccinated. It's not rocket science. We have a great, great way to fix this problem. Vaccine hesitancy continues to rise. The CDC currently features a website that says that autism has something like vaccines have not been shown not to cause autism or something incredibly misleading. That is totally wrong. And the whole thing is very frustrating.

Perry: [00:10:31] Yeah, yeah. It is. Um, if you look at vaccination rates, uh, nationwide for measles, they look okay, you know, 93% of kindergartners or something like that. But one of the problems in infectious disease epidemiology is that infectious diseases spread locally. And so the problem is it's not 93% everywhere. It's 100% in some places, and it's 80%, 75% even lower in other places. And, um, [00:11:00] and those tend to cluster together, which is why you see all these outbreaks. And yes, the CDC despite, I will say, officially, the HHS says the Health and Human Services Department says, quote, vaccination is the best defense against measles. Okay, folks. So there you go. That's their official word. But of course, they also put up this website. And yeah. Emily, it says basically it's like while there's no evidence that vaccines cause autism, there's no good evidence that they don't cause autism, which a even that's not true. Like we have plenty of studies showing no link.

Emily: [00:11:31] So.

Perry: [00:11:31] Much and so.

Emily: [00:11:32] Much.

Perry: [00:11:33] Proving a negative. Like you can always kind of say that it's like, it's like, you know, I can't prove to you that there's not a whale orbiting the earth right now. Like there could be like, it's possible we just didn't detect it yet, right? Like, which is just such wishy washy stuff. No medical science is ever going to be 100% on anything, but we're actually pretty darn close when it comes to vaccination.

Emily: [00:11:57] Totally. All right. Well, uh, you know, perhaps [00:12:00] people will respond to the existence of measles by vaccinating at higher rates, which we do see happen. So I guess that's a self-limiting aspect here, potentially. Last thing we want to talk about was peptides. The FDA is back for your peptides. If you are a listener to this show, please go back and listen to our episode on peptides. And one of the things we said there was, you can't get peptides in America. You have to get them from overseas manufacturers. The FDA heard us and they were like, oh, we should make those here.

Perry: [00:12:32] Why? Why are we outsourcing all?

Emily: [00:12:33] Why are we outsourcing.

Perry: [00:12:34] Unproven injectables to China? Uh, an FDA panel has voted to authorize several peptides, which people may have heard of, including on our prior episode, such as BPC 157.

Emily: [00:12:48] That's part of the Wolverine stack.

Perry: [00:12:50] Fabled Wolverine Stack Kpv and TP 500 for bulk compounding that gives compounding pharmacies here in the US the ability to mix that into [00:13:00] stuff that you can then inject into yourself. A bit of controversy here, because the staff at the FDA recommended against this. They cited lack of safety and efficacy data, which which we of course, highlighted in our prior episode. There are some interesting rat data on some of these things, but in general, we expect there to be human safety and efficacy data before the FDA approves something. The panel that voted to approve it had. It won't surprise you to hear. Been recently reconstituted by RFK Jr. The new members include six people who run businesses selling peptides.

Emily: [00:13:36] Okay.

Perry: [00:13:37] Which is like, I don't know. It's okay. I understand that you want expertise, and a lot of times experts do have relationships with industry. That's true. But you know, the people that run HHS, including RFK, really criticized the FDA for having people with industry ties on these panels. And now they have people who run clinics in Florida that make money injecting overseas peptides on these panels. [00:14:00]

Emily: [00:14:00] Okay. So to play to play devil's advocate on this question of whether we should approve these, I think they do. There is an argument which the panel made, which is that people are already using these, and they're getting them from these unsafe overseas sources. And if we provide them in the US, they will get them here. And that will be safer for me, that trades off against the fact that if you provide them here in the US, many more people will use them.

Perry: [00:14:26] Yeah. And it's also it's like, that's like cool mom energy, right? It's like, I know you guys are going to be drinking. I'd rather you drank here. Like, and I got you a bunch of vodka. Like I just that's the FDA.

Emily: [00:14:37] White Claw and some social tonics so you can try things out.

Perry: [00:14:40] Yeah, I don't know. The FDA is supposed to not.

Emily: [00:14:43] It's not a regular mom, the FDA, it's a cool mom.

Perry: [00:14:45] It's cool. It's cool. Fda just like do safety and efficacy. That's like your whole thing, like prove that a drug works, prove that it's safe. That's what we have to do. And maybe these things do work, but you got to run the trials. It feels like the bare minimum. And like, this is what they complain about [00:15:00] with vaccines. They're like, ah, they haven't gone through adequate trials, which again is untrue. But in this case it is true. But all of a sudden it doesn't matter because we can make a lot of money, like with these things that aren't going to be covered by insurance being sold in wellness clinics without any evidence except for social media clout.

Emily: [00:15:17] All right. Well, so before you buy your Wolverine stack, please listen to our last episode about the data. Thank you. All right. That's it for the health news of the week. And now let's dive into the sun. Not literally. Let's dive into information about the sun.

Perry: [00:15:33] Do you know what would happen to the sun if you were to put a human body into it.

Emily: [00:15:39] I don't think you could get that close to the sun without.

Perry: [00:15:41] Like, magically, like if you magically transported a human body into the sun, you know what happened to the sun? Nothing, nothing, nothing, nothing at all.

Emily: [00:15:49] Nothing would happen. Do you know what happened to the human? Not anything good. Nothing good.

Perry: [00:15:53] It's not good for the human.

Emily: [00:15:54] Not good for you. Uh. All right, so I think it's worth asking the [00:16:00] question. Why are we talking about the sun? What does it mean to ask? What's the deal with the sun? And obviously, we should say the sun is crucial for life on earth.

Perry: [00:16:08] Um, not controversial.

Emily: [00:16:10] That's not controversial. But on Instagram, there are some more controversy about the sun. Uh, not about whether we should have it, but about your relationship to exposure to it. And so in particular, I read an increasing sense that maybe we should be more exposed to the sun, right? Like we just like to back up. I was born in the 1980s, and in the 1980s, we had a lot of sun exposure. You know, one time I got a sunburn so bad that my face blistered because we weren't just, like, wearing that much sunscreen. And now it's like my kids are in like, a hat and full on sunscreen and like a long sleeve bathing suit. Like there were no long sleeve bathing suits when we were children. Now everyone's in like a parka. Like a beach parka. And so then the Instagram has pushed back a little and be like, hey, we're not, you know, you're wearing too much sunscreen. Instead, [00:17:00] you should eat a lot of watermelon because that's just as good as sunscreen.

Influencer: [00:17:04] Okay, here's an idea for you. Instead of lathering on chemically filled, unnatural sunscreens, what if instead you drank some watermelon juice? It's true. Watermelon juice acts as a natural sunscreen. Watermelon has something known as lycopene in it, which contains antioxidant and anti-inflammatory properties that help hydrate and nourish the skin to protect it from the sun. It's well known that hydrated and nourished skin is far less likely to be damaged from the sun.

Emily: [00:17:31] So I think that's what we're going to kind of talk about here, like exposure to the sun health, vitamin D, sunscreen, mood disorders.

Perry: [00:17:39] I love.

Emily: [00:17:39] It. What questions do you have about the sun?

Perry: [00:17:41] It's the summer. So the sun is the sun is on my mind and it's very hot. Um, no, I think there's a lot of good stuff to talk about here. When you mentioned sun when we were kids. Totally. I once got a sunburn on my forehead and, like, my skin was gonna peel off but hadn't yet. So, like, there was a layer of skin that was kind of loose and I was like [00:18:00] 11. And I remember looking in the mirror and raising my eyebrows and like, all these wrinkles appeared on my forehead and I, I thought, oh my gosh, I have become old. Like the sun has given me wrinkles. That's what everyone says the sun does. And then three days or so passed and that dead skin all kind of fell off. And I had a nice smooth far head again. But that image burned into my memory. And then about ten years ago, I was looking in the mirror and I raised my eyebrows. And there they were again.

Emily: [00:18:27] For reals, for reals of real time.

Perry: [00:18:29] And, um, the prophecy has been fulfilled.

Emily: [00:18:33] All right. So let's start, I think, talking about sunscreen because sunscreen is weirdly controversial, actually.

Perry: [00:18:44] Yeah.

Emily: [00:18:45] I don't know what happened there.

Perry: [00:18:46] I mean, I think we can unpack why it's controversial. Well, okay. Overall, there's money to be made in controversy, right? If you're an influencer and you kind of are going to be a contrarian and say like, well, all the nerds at [00:19:00] the ivory tower are telling you to wear sunscreen, I'm going to tell you not to. And by the way, you know, buy my product or whatever. Like there's, there's always the grift and we should just say that. But I think we can find some other reasons that people are skeptical of sunscreen. The reason we wear. Well, there's two reasons we wear sunscreen really. One is to prevent skin cancer and one is to prevent the solar aging. The fact that it's true, although it didn't happen to me when I was ten. The sun does age your skin And, you know, I think just I'll briefly touch on, on mechanism here. I think the only thing that we need to take home is that the sun, the bad stuff that comes from sunlight. Not bad. The potentially damaging stuff are UVA and UVB wavelengths of light. If you go all the way back to our Red light therapy episode, you'll remember that the shorter wavelengths have more energy. They can kind of do more damage, but they don't penetrate as deeply. Uvb has that shorter, high energy stuff that can [00:20:00] damage DNA. Um, and that's one of the mechanisms by which this causes cancer. Whereas the UVA, which can get a little deeper, actually might be more responsible for aging, you know, sunspots, wrinkling, uh, and stuff like that. And of course, sunscreen. We'll dig into a little bit of how sunscreen works. But sunscreen, if you're wearing a good one, will block both of these things.

Emily: [00:20:25] Both the sun and tanning beds provide the same thing. So sometimes people will talk about tanning beds being worse or or better. I think that that for the most part, what we are going to say here applies to using a tanning bed or being outside. Maybe there's some small differences here.

Perry: [00:20:44] Yeah, I would just think of tanning beds as the same as sun. There are there's a little weird stuff. There's an interesting article in Science Advances in 2025 about this that showed that the Melanocyte mutation burden was higher [00:21:00] and distributed more broadly in people who use tanning beds, people use tanning beds are also more likely to get multiple primary melanomas. So a primary cancer is like a cancer in a spot as opposed to metastatic, which has spread from somewhere else. And so multiple primaries is like getting cancer twice. But these are all really kind of marginal on the edge stuff. I wouldn't like consider one being safer than the other.

Emily: [00:21:23] I will say, I don't think people should use tanning. Like if you are looking to be tan. There's a spray for that. You know, like if your goal is physical tanning experience, like to look tan. You should just go spray tan yourself.

Perry: [00:21:36] Hey, there's also a peptide for that.

Emily: [00:21:38] There's also a peptide for that. Now you can probably get it. Uh, and so I would sort of put that aside because for many people, the question is more, you know, I'm going to be outside and then therefore, you know, should or should not, should I not protect myself? And I will say the debate on both sides is basically [00:22:00] about cancer. So the reason that people that we think you should wear sunscreen is because of cancer. And a lot of the reason people think you shouldn't wear sunscreen is also about cancer, maybe some about endocrine disruption, but like cancer comes up on both sides of this and sometimes the same kinds of cancers. And the conversation is confused.

Perry: [00:22:20] Yeah. Um, let me play you a clip from a typical influencer that people see online talking about the dangers of sunscreen.

Influencer: [00:22:31] I am the single biggest hater of sunscreen on the planet. I stopped using sunscreen two years ago when I found out all the problems with it, and I'm never going back. For starters, the lie that we've heard is that sunscreen helps protect you from melanoma and skin cancer. Sunscreen wasn't invented until the 1930s, and I believe it wasn't brought to the United States until the mid 1940s, but it didn't get FDA approved until about 1980. Since 1980, we've seen an increase of over 700% of melanoma cases. Mm. What? I thought it was supposed to protect us from the sun. That's what all the dermatologists say. Who curated [00:23:00] their education.

Emily: [00:23:01] Right? This guy's confused.

Perry: [00:23:04] This guy is shirtless, too. Emily. Is this. Do we need to do this? Do we need to be recording our podcast without our shirts on? Because apparently, this is how you get engagement nowadays?

Emily: [00:23:13] Yeah. Are you going to. I think you should. I see how it goes. And then if we have to ramp up to me, we'll try that anyway. Okay. So the claim here is that sunscreen somehow causes skin cancer. That's confused.

Perry: [00:23:31] Yeah. I mean, so so this influencer is like, oh, we started using sunscreen, you know, in the 60s and skin cancer rates have also gone up. A classic ecological fallacy. For the epidemiologists out there, but also a lot of reverse causality, like sunning and getting tan, was not as much of a thing in the 1930s and 40s that like, was in fact. And until people could travel to exotic places [00:24:00] and get tan and display that they were wealthy by being tan, they used to display their wealth, telegraph their wealth to others by being pale, to show that they didn't have to like, work in the fields and stuff. And so it was sort of the ideal of beauty to be very fair and pale and like, I've never seen the sun. And then that started to change as society changed and travel became easier. People wore more sunscreen to avoid sunburns. People got more cancers because they were in the sun more often. That's really all it is.

Emily: [00:24:26] Yeah. I will also say detection rates for these things have gone up over time. And so it is, you know, in 1850, if you got a melanoma, you just died. Nobody was like, hey, you know, let me screen you every six months for a weird mole and take it off and diagnose you, but then you're fine. You just died. And so it's a bit weird to say, you know, and probably you died from something else first anyway. So yeah.

Perry: [00:24:50] Anyway, none of the chemicals in sunscreen have been associated with cancer. None of them damaged DNA. None of them have a mechanism by which they could cause cancer. If I'm really, [00:25:00] like, waving my hands and I want to play devil's advocate, I could say, well, maybe wearing sunscreen gives you a false sense of security when you're out in the sun. And so you sort of spend more time in the sun, and you don't reapply as often as you should. And maybe that's a risk factor, but you can't really blame the sunscreen for that, right? Like it doesn't cause cancer.

Emily: [00:25:22] And we have a fair amount of data that wearing sunscreen reliably reduces cancer. So I think the best data comes from Australia. So there's a trial published in the late 1990s. 1600 Australians, they were randomized to either daily SPF 15 or discretionary use, which just meant use it whenever you want. Since people don't do things they used less. Uh, over a period of about five years, there was a 38% lower rate of I never know how to say.

Perry: [00:25:52] Squamous cell carcinoma.

Emily: [00:25:54] Squamous cell carcinoma, over eight years of follow up. And there is a non-significant [00:26:00] but sizable reduction in the number of invasive melanomas. Melanomas is fairly uncommon. So there were only three invasive melanomas in the sunscreen group and 11 in the other group. And so that's that's not really enough to be statistically confident, but it is. It is meaningful. I think that's our best. Yeah, I think that's our best randomized data.

Perry: [00:26:23] It's a randomized trial. It wasn't even that much SPF. I mean, 15 is kind of on the low end of what we would probably use today. And and it's good the observational data, like influencers will pull out studies that you can find studies that show people who use sunscreen have lower rates of cancer. Studies that show that people use sunscreen have higher rates of cancer, um, of skin cancers. So much of this is what we call confounding by indication, right? Which is that people who are at higher risk use more sunscreen, right? Because it's not randomized, it's, you see a similar thing. I'm almost like hesitant [00:27:00] to say it. People who take statins have a higher risk of heart attack overall than the general population of people who don't take statins, because people who take statins take them for a reason, because they're at higher risk of heart disease. They're older, they have diabetes, they have high cholesterol. Whereas an 18 year old who's perfectly healthy, doesn't take a statin and is unlikely to have a heart attack. So this is all over the observational literature, which is why you need randomized trials. We have one sunscreen reduces the risk of skin cancer.

Emily: [00:27:28] We call that reverse causality not count, but like in economics. Okay. This thing medicine. I mean, this is just like an interesting like there's different words for this. We call it reverse causality, which I like better because I think it's easier to say than confounding by indication. And it makes more sense.

Perry: [00:27:43] Uh, well cheerfully withdrawn.

Emily: [00:27:46] Uh, all right. There are multiple kinds of sunscreen that one could use. There is mineral sunscreen. This is the sunscreen that makes your face white. It blocks with zinc or titanium dioxide.

Perry: [00:28:00] And [00:28:00] you, too, can look like an 18th century consumptive queen.

Emily: [00:28:05] Elizabeth covered her face in lead, and you can cover your face in zinc oxide and achieve the same activity without the facial pitting.

Perry: [00:28:13] Yeah. Um, I was surprised actually, to find I didn't actually know this, uh, zinc oxide has broader spectrum coverage. So the way these work, by the way, is just it's a physical barrier. Like the UV reflects off the tiny particles of zinc or titanium and just reflects into away towards some someone else. Zinc does that both for UVA and UVB, whereas titanium is really UVB focused. And so, um, some dermatologists will recommend to make sure that if you're using titanium alone, like you want to be using something else for UVA, particularly because you don't want that skin aging effects. For those of you who don't want to look like 18th century consumptives, these nanoparticle formulations that they have now are a little less white. I don't know if you've tried them, [00:29:00] Emily. They look okay. Um, and they seem to. And medically speaking, they're just as good as the, the other kinds.

Emily: [00:29:07] They're also chemical sunscreens. And that is anything you're using in a spray. There are other chemical sunscreens which are using chemicals to block the UVA and UVB light. They do not turn your face white. Some people are afraid of these due to concerns about endocrine disruption from some of the chemicals that are used in this, and will say that if you feed a rat very, very high doses of some of the chemicals in these sunscreens over their whole lifetime, it is not good for them and their reproductive system. But the kinds of level of exposure that you have as a person using this sunscreen is very different than if you are a rat who's primarily eating it. And in fact, people have looked carefully at how much would you have to use sunscreen over your whole life cycle to get to this exposure? And [00:30:00] it's like not feasible. So I would say if chemical sunscreen is the thing that is easier for you or more acceptable, you should use that. And if you like the white stuff, that's also great. And if you want to just wear a lot of clothing instead, that is also okay, but less feasible for most people, and especially for kids.

Perry: [00:30:19] Totally agree. Whatever will make it easier for you to use for the chemical sunscreens. Those chemicals also have different levels of UVA and UVB protection. The FDA has an official labeling for stuff that covers both and it's broad spectrum. So you do want a sunscreen that has that broad spectrum coverage on it that's legally regulated.

Emily: [00:30:42] Also, you don't need SPF 3 billion, so they will sell very expensive spfs like SPF 100. Or does it even really make any sense, given what I understand to be what this means? But SPF 30 is the American Dermatological Society says SPF [00:31:00] 30 or higher, so 3050. You do not have to have 99, which is expensive.

Perry: [00:31:06] There is one part of sun hitting your skin that I debated putting in this episode, Emily, but I think we just have to talk about it. And that is, should we be sunning our peritoneums? Let me play you a clip from Mr. Health Nut. Oh, this is a good one.

Influencer: [00:31:30] Okay, here we are, guys. You guys ask about the Butthole Sunning all the time. And this is another one of my practices. I don't always talk about it, but it's well known that your sphincter or your butthole is one of the most sensitive or thin mucous membranes in the body. 30s of sun on the butthole is like eight hours of sun outside with your clothes on. And so let's face it, the sun is the source of all energy. And so [00:32:00] you're getting that sunlight up into the channels of the body. You're giving yourself a nice energetic electrical butt plug for men. Son on your testicles or naked son is good for testosterone boosting. This is just energy for the soul.

Emily: [00:32:19] My favorite part of that clip, Perry, is when he says he doesn't. People don't talk about it all the time. It's like, that's true. That's true. Don't talk about this all the time.

Perry: [00:32:27] Can you describe what you're watching for people who are listening to this in audio format?

Emily: [00:32:31] There's a man, he's both shirtless and pantsless, although you can't see too much and his legs are over his head, and it is obvious that he is exposing his butthole to the sun. Uh, while explaining the benefits of doing so.

Perry: [00:32:48] This I this is in the zeitgeist, in no small part because Tucker Carlson himself tried this. He he had some documentary on, you know, being a man or manliness in [00:33:00] America. And somehow somehow this incredibly unmanly thing, like I just, I look at this video and I'm like, this just does not scream macho to me. Uh, apparently boost your testosterone or something like that.

Emily: [00:33:14] Yeah, I should say your butthole and your perineum are actually not the same thing. So, uh, first of all, that's not the scientific word for your anus, but, uh, there's the perineum is the area between your vagina or your scrotum and your and your butthole. Uh, so I guess all of that area could be sunde. Uh, but don't do it. Yeah, you'll get sunburned. That's a terrible way to get a terrible, painful sunburn in a very uncomfortable area.

Perry: [00:33:42] Absolutely. First of all, this doesn't work. There is some data that human testosterone levels peak in late summer, early autumn. But that has nothing to do with your perineum, and it probably doesn't even have anything to do with sun exposure. There's multiple factors that change testosterone levels, so that's nothing. And there is some risk here [00:34:00] just digging in so people with psoriasis can get UV therapy. So ultraviolet lights to treat the psoriasis. Uv light is immunosuppressive to some extent. That's one of the reasons that cancers can develop with excessive UV exposure. But for psoriasis, you want to suppress the immune system. And when they first started doing this, they found that people getting UV, A and B therapy for psoriasis had a four fold increase in genital tumors. And that was because the skin around the genitals is very thin. So that high energy UVB can penetrate to more important stuff than it can in the other parts of your body. And so now the guideline recommendations for people getting that therapy, even whole body UVA, UVB for psoriasis is to specifically cover the genital area, the perineum. Um, so don't do this.

Emily: [00:34:53] Okay. Should we take a break?

Perry: [00:34:56] I feel like.

Emily: [00:34:56] We're gonna take a break. If you need to go sun your butthole, this is a great time. [00:35:00] And then come back and we'll talk about vitamin D. Welcome back. We are going to turn to vitamin D and whether the need for more vitamin D is part of why you should be exposed to the sun. Let me set the stage here by saying there are many vitamins A, C, E, a bunch of different B vitamins. Most of these you get through your food. Vitamin D is one that you get some through your food, but also through exposure to the sun. Like other vitamins, if you do not have enough of this, it's very bad. So vitamins are in general substances that our body cannot produce on its own. So we must be getting from some outside source like extensive vitamin D deficiency is associated with [00:36:00] with rickets in kids with kind of bone decay. You need vitamin D to support to support your bone, but you basically can't get enough of it through food. So most foods don't have very much at all. Your milk is fortified with that, but most people in the US are not getting anything close to the appropriate amount of vitamin D in food, and so they have to get it through the sun. Okay. How does it happen? Science. Science. Perry. How do you get vitamin D through the sun? Um, it involves the kidneys. So I'm going to give this to you.

Perry: [00:36:31] Yeah. It does. Uh, so you have in your skin a substance called seven dehydrocholesterol, which is a cholesterol derivative, and UVB converts that to vitamin D3. So you've probably seen D3 supplements in the GNC or CVS or whatever. That's what it is. Um, vitamin D3 is not active. It has no physiologic effects, but it is a substrate that gets converted by the liver [00:37:00] to 25 hydroxy vitamin D that is also not active. You can get a prescription for that. This is called ergocalciferol, but it's generally not sold in stores. That 25 vitamin D goes to the kidneys and becomes 125 hydroxy vitamin D, and that and only that is the biologically active form of vitamin D. There's a prescription form of that as well called calcitriol, which is very expensive and has a lot of side effects. But basically, there's a lot of processes in your body that are designed to get you to vitamin D, and it all starts with UVB exposure. But I think what will surprise people is how much vitamin D you get from a little bit of sunlight. So the recommended daily intake for vitamin D is varies 200 to 400 international units is sort of typical. And you'll see supplements ranging from like 1000 to 2000 [00:38:00] international units per day. Vitamin D supplements if you had UVB exposure for 20 minutes to your whole body. So imagine 20 minutes on the beach. If you're a light skinned individual, and this is an important consideration that produces approximately 10,000 international units of D3. So about ten times the dose you'd get from from taking a vitamin that's 20 minutes.

Emily: [00:38:25] It is also, I think, important to say at this point that you cannot overdose on vitamin D through the sun. So you could, if you were outside for a very long time, like putting aside the sunburn risk and you say you were outside for five hours. And so it's going to be, you know, many bajillion units of vitamin D that will just that does not that does not cause you to overdose. Whereas taking that amount in a supplement would actually be quite dangerous.

Perry: [00:38:54] Thank you for saying that. Yes, the sun Degrades vitamin D three in [00:39:00] the skin. So as it's making it, if if there's a ton there, it'll degrade and sort of nothing. It puts the brakes on automatically. But ingested vitamin D3 is its own thing. People can absolutely overdose on this stuff. Um, you can get something called milk alkali syndrome. Fascinating. You can get very high calcium levels which can cause a lot of things kidney damage, coma, arrhythmias, that stuff. I think though, the reason vitamin D like comes up a lot is that we have a slew of studies linking low vitamin D level measured vitamin D, and I'll just say, typically when people are measuring vitamin D in the blood, they're often measuring 25 vitamin D, that liver one before it gets the kidney. It's just an easier test to run than the real vitamin D. It's fine. But we have a slew of studies linking low vitamin D levels to a variety of diseases and I. I listed a few. So low vitamin [00:40:00] D level increases the risk of cancer. Low vitamin D level increases the risk of cardiovascular disease. Low vitamin D level increases the risk of diabetes. Low vitamin D increases the risk of falls. Covid all cause mortality. Like looking at all that observational data, you'd be like, oh my God, vitamin D is the most important thing in the world. But Emily, we don't like observational data. What are the randomized trials of vitamin D supplementation?

Emily: [00:40:28] Show us the randomized trials of vitamin D supplementation. Show us that there's nothing. So there are actually a large number of randomized trials on all of the outcomes that you have listed. Some of it is the same trial looking at. And these trials are big. You know, 25, 26,000 people, true placebo control trials. And they just don't show anything. They just show no differences. When you supplement people with vitamin D, it doesn't look any [00:41:00] different. They don't. Nothing different happens than if they weren't supplemented with vitamin D. And this is because the observational data is driven by bias, by the fact that the people who are taking the vitamin D are different from the people who don't take the vitamin D, and in fact, like before I get off my high horse about this, we have for many years been telling people to take vitamin D like vitamin D is good for you, take vitamin D to prevent cancer. And so not only is there this baseline, just like people who take more vitamins tend to be positively selected in various ways. But over time, we've made that worse with our advice. So we tell people, take vitamin D, and the people who take the vitamin D are also the people who are doing all of the other things. And so the problem has gotten worse and worse and worse over time. About half of Americans take a vitamin D supplement now, and if you look at what half it is, it's also the half that's exercising and eating vegetables and doing other things that not [00:42:00] smoking. And so it just it's just a classic case where like the observational data is super is super misleading.

Perry: [00:42:08] Even people, even if you exclude people who are supplementing at all, you do find observationally that lower level, like blood level of vitamin D associates with all these bad outcomes. But the way I often describe it is that vitamin D, your vitamin D level, if you're getting your vitamin D measured, it's very much a lifestyle biomarker. Like if you are the type of person who goes outside and gets sun and exercises and touches grass like you're going to have and eats a very diet, right? With multiple sources of vitamin D in it, you're going to have a higher vitamin D level. Conversely, if you're a person who is sick from other things, who is, you know, has nutritional deficiencies, who isn't getting outside and getting exercise, you're going to have a low vitamin D level. It is a very nice marker of kind of overall health, but that doesn't necessarily mean that [00:43:00] making the marker look better makes your health look better. It's it's the canary in the coal mine and, you know, bringing in a better canary or whatever doesn't fix the coal mine. That's a bit of a tortured analogy. Sorry, Canaries. You're all.

Emily: [00:43:12] Dying. I see where you were going with that. Yeah. So from the perspective of the sun, I will say like, you know, you are probably getting enough vitamin D from your exposure to the sun already, and you don't need to either stand outside more in the sun for more vitamin D, nor do you need to take a vitamin D supplement.

Perry: [00:43:32] Yeah, it is a bit harder, of course, in the winter and in certain climates where the sun doesn't shine as much, and it is certainly harder for darker skinned individuals that melanin that protects the DNA in your cells from UV causing mutations also decreases the ability of UVB to help synthesize vitamin D, and so if you are darker skinned, there's more rationale for focusing on dietary intake of vitamin D. I'm still not very [00:44:00] pro supplement of vitamin D just because even in the randomized trials, we don't see a signal across any skin tone for for benefit, by and large.

Emily: [00:44:09] Totally right. I'm a negative on on vitamin D supplements, even though my many people are always telling me to to take them, but I don't know them.

Perry: [00:44:19] Don't do it.

Emily: [00:44:21] All right. So, uh, the sun necessary for vitamin D, but you don't need more of it. Sunscreen. Very important. Uh, there are other ways in which we have evolved to like the sun in particular. Uh, it makes us happy.

Perry: [00:44:36] Yeah.

Emily: [00:44:37] People like to go outside and be in the sun.

Perry: [00:44:40] That's nice.

Emily: [00:44:41] Yeah. I mean, and we see this. Well, we see it in observational data where people who spend more time outside have a lower risk of depression. Is that causal? I don't I don't know. But we do have evidence on seasonal affective disorder which responds to light [00:45:00] therapy. So I think there's a sort of clear randomized trial that supports a mechanism that light exposure makes us happier. Seasonal affective disorder is actually a big problem in a lot of these countries where it's really dark all the time.

Perry: [00:45:15] Yeah. And it's interesting. It does not appear to be vitamin D mediated. So it's not that your vitamin D gets low. And that's what causes sadness. Because vitamin D supplementation does not improve seasonal affective disorder. But the blue light therapy does. That's clear, as you say, from randomized trials. A lot of the mechanism apparently is circadian sleep disruption. And the blue light therapy is done early in the morning to sort of reset your circadian clock. And if there's any theme of the Wellness Actually podcast, it is that sleep is the most important thing and is tied to everything else. And so I think this is yet another example of that.

Emily: [00:45:51] Yeah, sleep is very important.

Perry: [00:45:53] Yes. I found a couple of other weird like sun benefits that I'm curious what you think about [00:46:00] Emily. Um, one is some fairly consistent links between low childhood sun exposure and subsequent multiple sclerosis. So multiple sclerosis is clearly diagnosed more in the northern latitudes. And this is not just a rich country, poor country thing because even across, for example, the United States, like the further north you are, the higher the risk of multiple sclerosis is. I don't have a great mechanism for why this would be. But like, it's not just 1 or 2 studies that have found this link. Uh, and I don't know, what do you think? Do you think that there's an Ms.. Sunlight thing.

Speaker 6: [00:46:43] You could.

Emily: [00:46:44] A little hard to tell from the studies that are on this. Most of these are what's called a case control study. And so they identify you because most of us multiple sclerosis is not common. I mean, it's not vanishingly [00:47:00] rare, but it's not like it's not a common thing. So you don't see it that much in these large population studies. The way these studies often work is they will take a set of people who have the diagnosis and then find some other people without the diagnosis and compare them on like questions. They ask them survey questions, other, other characteristics. That kind of study has all of the problems of basic observational data that these groups may differ for in in many other ways. It also has the problem that they differ in how you select them. And you're asking about stuff often that happen in the past. It's just, it's not a it's not a very strong empirical approach. It's sometimes the only approach that we have. And so I don't want to like say we should never look at this, but it feels as an approach, like something that would generate a hypothesis rather than prove one. And so this sort of this feels like there's probably something more clever someone could do to try to get more of an answer here. We don't understand that much about [00:48:00] miss and what drives people. It seems clear that there's genetic risks, but also epigenetic issues and other things that happen. So it's an interesting research area. My guess is that sun exposure will not turn out to be the most important feature here.

Perry: [00:48:16] Fair enough. If it gives people motivation to get their kids outside in the sun. All for the good, but make sure they're wearing their sunscreen.

Emily: [00:48:24] There is actually some better evidence that outdoor time reduces myopia. That's probably not just about the sun, but about being outside. Oh, sure. And some of that is from randomized data.

Perry: [00:48:34] Yeah, yeah, yeah. Um, yeah, I guess it turns out that, I mean, I guess our moms were right, which is like sitting too close to the TV is going to ruin your eyesight, right? Like you, when you're outside, you're forced to, um, what is it? Accommodate your pupils to distance, which flexes those muscles a little bit.

Emily: [00:48:55] Right. Something like that. Yes. Anyway, it's good to go outside. Yeah. Be outside. That's another theme of the [00:49:00] wellness. Go outside and then also go to sleep, but not outside. Right? Right.

Perry: [00:49:06] All right. Emily, um, I think it's time to to decide whether this sun thing is all it's cracked up to be. Smash or pass the sun.

Emily: [00:49:17] I'm. I'm a smash. I mean, you know, it has its limitations. But I would say on the whole, I'm pleased that we have the sun, uh, around and I'm, I'm going to keep. I like to keep it.

Perry: [00:49:28] I agree, uh, the sun is one of my top five stars. Um, in the, what.

Emily: [00:49:37] Is your second favorite star? Is it Alpha Centauri?

Perry: [00:49:39] Yeah. It's it's it's Rigel actually. Um, because that's where the pleasure planet is in Star Trek. That's for Tamar's husband.

Emily: [00:49:51] I will say I'm going to pass vitamin D supplements, uh, because we also talked about that and I'm going to smash sunscreen. What [00:50:00] about you?

Perry: [00:50:01] I will pass on vitamin D supplementation and smash sunscreen. Yes.

Emily: [00:50:07] Amazing. All right, that's it for the sun. Your mailbag. Question of the week. After the break. All right, let's move to our question of the week. And if you have a question, you can go to wellness.fm and leave us a recording and we will try to answer it. All right. This week here's the question.

Mailbag: [00:50:29] Hi. Emily and Perry settle a bet between my husband and me. Which organs can you live without? Thanks.

Perry: [00:50:38] This is such a fun question.

Emily: [00:50:39] It's the kidney, right? You only need one of those. I know they're your favorite, but it's not important.

Perry: [00:50:44] Oh well, if we're saying we can only take out one, then you can definitely take out one lung. That's fine. You can take out really half a liver, basically. Oh, sure. Yeah. Yeah, yeah. Okay.

Emily: [00:50:54] So I could take I only need one of my. Come on.

Perry: [00:50:57] I was yeah, I mean, okay, I'm not saying it's going [00:51:00] to be great, but you're, you're fine. You can take out people's whole lung all the time for cancer and stuff like that. I thought this question was the whole organ system, in which case I was going to say kidney because of dialysis. Um, because we don't really have a dialysis. So dialysis, kidneys clean the blood and dialysis can kind of take over that for people who have end stage kidney disease, which you would have if both your kidneys were removed. Um, it's, it's not the greatest thing in the world. You're getting four hours of dialysis three times a week, but you'd stay alive and we don't really have that. I'm trying to think we don't really have that for anything else. I mean.

Emily: [00:51:38] What about your reproductive organs? We could take out your your uterus, your your ovaries. Yeah. Who needs them? No problem. Not not using them all the time.

Perry: [00:51:49] Uh, yeah. Our producer Tamar says gallbladder. Sure you can remove that. Is that an organ?

Emily: [00:51:53] Appendix.

Perry: [00:51:54] Um.

Emily: [00:51:55] Is that an organ?

Perry: [00:51:55] Yeah. I don't think.

Emily: [00:51:56] More. Just like a useless end end organ.

Perry: [00:51:59] Um. [00:52:00] Let's see. Brain, you probably need.

Emily: [00:52:03] You need that.

Perry: [00:52:04] You know. Uh, well.

Emily: [00:52:05] Colon, would you remove your whole colon?

Perry: [00:52:07] Yeah, we can get we can take out your whole colon. That's that's done. Um.

Emily: [00:52:13] Mm.

Perry: [00:52:15] Spleen. Absolutely can do without a spleen. Wow. We can remove a lot.

Emily: [00:52:20] A lot of that. Why did.

Perry: [00:52:21] Minimal.

Emily: [00:52:21] Viable product.

Perry: [00:52:22] For.

Emily: [00:52:22] Humanity. Let me ask you, Perry, why did you choose to be a doctor specializing in one of the organs we don't need? Why didn't you pick an organ that is necessary?

Perry: [00:52:31] Oh, that that does hurt a little bit. Um, but it's it's it's it's a good point. Do you know why? It's because the kidneys are one of the few organs where you can very easily measure the input, which is blood, and the output, which is urine, and infer the miracle that is going on inside. Try that with anything, any other organ. It's very difficult.

Emily: [00:52:53] Spoken like a true lover of kidneys in the human. All [00:53:00] right, so it turns out we don't need many of our organs, but yet somehow, uh, let's just say there aren't. There's very few organs other than maybe your reproductive organs where removing them even then, probably those we're removing them like would not result in some change to how you would have to behave.

Perry: [00:53:19] Yeah, yeah, yeah, they're there for a reason.

Emily: [00:53:21] They're there for a reason. Evolution didn't except for the appendix, which is a waste of time. Uh, most of our stuff is is useful. Okay. That's it. Join us next week when we will ask, what's the deal with gluten? Wellness Actually is produced in association with iHeartMedia. Our senior producer is Tamar Avishai. Our executive producer at iHeart is Jennifer Bassett. Our theme music is by Eric Deutsch and our content is for educational purposes only.

Perry: [00:53:52] If you like the show, help other people find us. Leave a rating and review on Apple Podcasts or your podcatcher of choice and help us spread the word [00:54:00] about the show. You can follow us on Instagram at pod. And don't forget, we want to hear from you. Head over to wellness.fm and leave us a question for our mailbag or suggest a topic for a future show.

Emily: [00:54:13] We'll let the influencers have the last word. The sun is a mass of incandescent gas, a gigantic nuclear furnace. Where hydrogen is fused into helium at temperatures of millions of degrees.