The Case for Sunshine with Rowan Jacobsen

- Today is May 18th, 2026, and my guest is author Rowan Jacobson. He was last here in October of 2021, talking about his book, truffle Hound. That episode tied for first place in our annual poll of favorite episodes of the year. His latest book is in Defense of Sunlight, the Surprising Science of Sun Exposure Run. Welcome back to EconTalk. Thanks Rose. It's great to be back. I hope I get another first place this year. Well, we'll see, you know, we'll see. You might have to rig the voting like you did the last time, We last time, multiple Times. Yeah. We're gonna be talking about a number of issues related to health. I wanna remind listeners, we do not dispense medical advice on this show. Even though I am a doctor, I'm not the kind that helps people. As we all know, I'm a doctor of, of philosophy and economics. You should take everything you hear with the greener or more of salt. But this is a very interesting, provocative and contrarian take on what for a long time was received wisdom. So let's get started. What's the central idea of this book, Ron? The basic idea is that we are now at a point where enough science is filled in that we need to reconsider what has been, as you say, the the sort of the perceived wisdom on sun exposure. That the, the recommendations we've received for the past few decades no longer accurately reflect what we know about the science. And I think most people are taught, you know, depending on what age you are, obviously, but particularly young people are taught that, you know, sun is a killer. It, it leads to skin cancer, which I think is scientifically undeniable. We'll talk about what kind of nuance we wanna bring to that statement when we talk about it more thoughtfully. But the sun's a killer, so stay outta the sun and if you have to go into the sun, you should cover your body with clothing or sunscreen and protect yourself. That's the received wisdom I think, for many people. Despite the research you're talking about it, is that a, do you think that's correct? Yeah, for sure. And it's actually become more strident that those recommendations over the years. The sun is a killer. We, we all agree that sun exposure will raise your risk of skin cancer. And so based on that fact, the authorities have recommended that people first reduce their level of sun exposure and more recently, pretty much eliminate any sun exposure where your skin is unprotected from, by either clothing or sunscreen. And that was part of the reason I decided it was time to write the book. Because when I started to see in the past few years that the typical advice you'd see in media was you, you know, stay outta the sun, summer, winter, no matter who you are, no matter what your situation is, use sunscreen even if you are gonna be indoors all day. And it's, and it's winter. And that didn't reflect what the researchers had been discovering for a few decades. And I think I would sum up the lesson of this book. And for, you know, like your previous book, this is a very readable book. There, there is a lot of science, but it's, it's written very, very clearly. I I would sum up one summary sentence would be The sun is not bad for you. In fact, it's good for you. It does have costs potentially, and thoughtful people should be aware of those trade-offs. Is that a fair summary? Yeah. You know, when, when you said the sun is a killer, I I, you know, I almost had to wanted to like jump in and say, well it is, but it's also a, you know, a giver of health and vitality. And that part has been left out of the equation for a while. The sun, and we will get into this, but the, the sun improves. We now have pretty solid evidence that, you know, moderate sun exposure improves health in lots of both direct and indirect ways. And that was what was left outta the equation when we were told the sun is a killer, it raises your risk of skin cancer. That's true, but that's obviously a very small portion of overall health and and longevity. And so I, there's a metaphor that some of the researchers use, which is that it's kind of like if orthopedists started telling people, stop exercising, because when you exercise, your risk of knee injuries goes way up, right? We're seeing a lot of knee injuries from exercise, therefore never run. In fact, don't even walk around if you can help it just sit down because that way that's gonna take the pressure off your knees. And they weren't taking into consideration these other pieces of the picture. That's kind of what's happened with, with, with sunlight. And before I read your book, I would've said, you know, maybe I could imagine that there's some evidence that sunlight's good for your, your disposition, your mood, Right? You know, People say, you know, get, get out early in the morning, get some sunlight, it'll make you feel better. You know, and we, we all know, and you write about it at the very beginning of your book, that if you live in a climate where the sun doesn't shine very often, it can be winter can be very dark, literally, but Also Emotionally yet what I'd say the most powerful parts, you talk about that and it's very interesting. But the most powerful parts of this book is the possible role that scientists are discovering for sunlight with the, the health of our skin, possibly the health of our heart, our autoimmune system. And I have to confess, being a skeptical person, when I hear it stated that way, it sounds a little bit rah rah as a contrarian take on this issue, which has gone so far in one direction. You're going so far in the other, and yet the science is quite quite serious. This is not, this is not qury or a study found a small sample. It's really quite, there's a huge amount of research on this, it sounds like. And that's part of partly what drew me into it and, and made me want to, you know, really devote myself to a book length work on it. Yeah, there's, there's actually decades of science in multiple different fields that have been discovering these, these benefits of sunlight. And they really haven't come into the public discussion, you know, and it's just how science works. There's a lot of specialization in science. You know, these researchers would publish their study and they'd say, you know, well it, it looks kind of like, like sun exposure might be good for you in this case. And, but it wasn't their job to, to take it any farther than that. So, you know, the, the papers get published and they kind of just disappear. So I, once I started seeing so many of them out there and realized there was kind of nobody whose job it was to bring it all together and try, try to synthesize that into, you know, a a some sort of overall understanding of what was going on, it seems like that would be, that was a pretty good like, you know, weighted to focus my time and energy. And it is like you, like you're right to be skeptical. I was skeptical at first too. You know, anytime you, you hear something that really d you know, diverges from the recommendations of the experts in the field, you, you immediately wonder about quacks and, and where the information is coming from. And so it's, it's great to be skeptical and one of the things I'm hoping this book does is just bring that conversation, you know, into the, the general discussion rather than try to make a slam dunk case for it. And I would just add, of course, we should be skeptical sometimes of the advice of the so-called experts. 'cause as you point out, the sunscreen industry is a very large one. There's a lot of money to be made. Dermatologists make a lot of money removing things on the skin that may or may not be harmful to us. So you have to be balanced. You have to be thoughtful. And it's, of course the world's complicated as we know as ERs on this program now. But I wanna start, one of the things that's fun about this book is the narrative arc of how people think about and have thought about sunlight. So there was this period, which is really fascinating in, in the early 20th century, I think is the time period, but it goes back, I think into the 19th as well, when people had this incredible romance about the healing powers of the sun. And the phrase you that's, that was used as helio therapy. Helio is related to the sun. So being out in the sun is good for you. And this was part of a movement. So talk about how that movement started in fighting, say tuberculosis and other really serious things where sunlight did help and but then the sort of obsession with it in, especially in California and elsewhere. Yeah, it's a fascinating history that I wasn't really familiar with until I, I dived into the book and I think we've mostly forgotten about it. But yeah, we had this amazing era of helio therapy in both Europe and the United States and really peaking in the early 19 hundreds. And as you mentioned, it really all came out of tuberculosis. Yeah. In to a large degree. Now, tuberculosis is a, is still a big, like if you look at mortality figures worldwide, tuberculosis is still a big player. But back in the 19 hundreds it was a, a massive, oh sorry, the 19th century. It, it was a huge problem. I think one out of every four deaths in Europe was due to tuberculosis in the later 18 hundreds. And a scientists from the Pharaoh islands of all places was the first to realize that cutaneous tuberculosis, tuberculosis can kind of like go in two different way directions. It, it can either infect the lungs, which is sort of the, the classic consumption of, of like, you know, romantic poetry or it can be cutaneous, it can affect the skin and just like eat flesh. And they're both really bad or they were before antibiotics anyway, this Pharaoh Islands doctor named Finon discovered that concentrated sunlight could kill the cutaneous tuberculosis and could cure cutaneous tuberculosis. And that became a big deal. At the same time, doctors were discovering that another disease that it had sort of popped up in the industrial revolution, rickets was caused by lack of sunlight. All the kids in, in tenement in the UK and elsewhere who were never exposed to the amount of sunlight they would have back in the farming days, were coming down with rickets, which is a terrible disease. Your bones never get hard as a kid, so you get bowed legs and deformed skulls. It was, it was also a, a big problem in this era that also turned out to be cured by vitamin D. And they discovered that it was sunlight hitting skin that produced vitamin D. So suddenly two of the major diseases of that late 18 hundreds period, rickets and tuberculosis were being fixed by sunlight. And there were clinics popping up everywhere to, to do so. And it became to, it came to be known as Helio therapy. And you know, people would go up to the Swiss Alps where the light was really good to the sanitariums up there to take the light. Like we, you know, we, we know that era of like the magic mountain where people would go up to the Alps, to the sanitariums for the fresh air, but fresh air was only part of it. The light, the quality of the light was the other part of it. And, and so once people started thinking about light as a thing that could cure these diseases, they really, they did go a little too far and they began asking like, well, you know, what else might light cure? And doctors kind of started noticing that people who got a lot of light and fresh air tended to be healthier than, than people who didn't. So then you can see through the twenties, thirties, the top medical experts of the time all really like getting on board the light train and saying like, the, one of the keys to public health is that everybody gets light and schools were redesigned to make sure that kids got more light, the kids would be sent out to play in their underwear. It it was really this crazy, crazy era. There's spectacular photos from this time, like in Switzerland of, of kids just in their boxer shorts sitting in the snow at their desks, taking their lessons and instructors also in their boxer shorts in instructing the kids. It was pretty incredible and everybody was on board with it until, you know, until the thirties and forties the first inklings that all that light might also be causing skin cancer began to like appear at which point things started to flip in the other direction. Let's talk about the prevalence of skin cancer and then we will come back to vitamin D in a little bit 'cause it fascinates me, but let's talk about skin cancer. So skin cancer surges probably were a y but certainly in the United States and you'll have a better, give us a better idea of exactly the timing of that. But it's, it's a little complicated by some the kind of usual factors people often ignore when they worry about an increase in, in a disease. So, or in terms of diagnosis of a disease. So talk about the actual, what we know about the history and why it's a little more complicated maybe than it first appears. And the two different kinds of skin cancer, two different kinds of cancers that that, that, that are, that are relevant here. Yeah, it's very skin cancer. You can kind of, there's three major types of skin cancer. One is squamous cell carcinoma and one is basal cell carcinoma. And those often get referred to as SCCs and, and BCCs. And those are responsible for about 98% of all skin cancer cases. Then the third important type of skin cancer is melanoma. And that's more like 2% of, of skin cancer cases. And I, I'm sure we'll dive into this later. Melanoma is the one you really wanna worry about that has, you know, there's significant mortality associated with it. The secs and the BCCs are the ones ev you know, everybody, you know, tends to get after they hit age 70 or 80 and they, you know, you, you have to cut them off 'cause they'll keep getting bigger, but they very rarely become invasive. So they're not associated with significant mortality in any way. Weirdly, none of those diseases were, were very prevalent before about World War ii. Like back in the day in the, you know, in the early 19 hundreds, skin cancer was something that sailors got, sailors get a ton of sun exposure. They also get terrible diets and your diet does affect your risk for skin cancer. So sailors maybe, you know, the occasional farmer would get a skin cancer, but it was not on doctor's radar at all. And then somewhere around World War II numbers go way up. And partly as you're referring to it was partly just a demographics issue. As public health gets better and people don't die of cardiovascular disease or infectious disease at earlier ages, they live long enough to get skin cancer and not just skin cancer. You, you see this funny confounding trend in like lots of different areas where as public health improves rates of cancer go up per a hundred thousand people because people are living long enough to get cancer that you gotta die of something, right? So cancer rates tend to go up when other things improve, but then you look at the age adjusted numbers and maybe they're not going up as much as, as you thought they were. But so what, yeah, what happened in the second half of the 20th century in the US and western Europe is that pe people were living longer, but skin cancer cases were exploding, like even more so than could be accounted for by longer life. So that was when this sort of panic started to set in that we were some sort of epidemic was underway and it had to be sunlight because we we'd, you know, shown in lab tests that if you zap a mouse with enough uv, you can create skin cancers on it. So ba basically doctors assumed that the entire rise of skin cancer was because people were being irresponsible and were exposing themselves to a ton more solar radiation than they used to back in the day. And so that's when the messaging started and then eventually got more strident that you need to stay outta the sun. That's not a very plausible explanation because over the course of the 20th century, people spent more time inside than they had before. You know, we have the rise of offices that farming goes from 40% of, of the workforce in 1900 to 3% by the end of the century. So people aren't in the sun. There aren't many sailors left in the world as a profession. It's not a common profession, it's, there are other forms of transportation. So they, they had to have, there has to be another explanation. And of course the other usual challenge in these kind of trends, and I I won't name particular diseases, but a lot of times people worry about some epidemic in a disease and they assume that epidemic is real when sometimes it's merely an increase in diagnosis. So I don't know when dermatologists were invented seriously as a, as a subspecialty, as a specialty, but that had some, I would guess something to do with this. So talk about the diagnosis issue. I mean, just to give an example, I had an issue, I forgot, I don't need to share with with listeners, but I had a skin issue. I had to be on my face and I went into, my doctor was concerned about it. I went to a dermatologist, dermatologist did a full body check, make sure right, my entire skin was free of things. Of course it's not. It's got spots, skin tags, other, you know, exciting irregularities. Most of us do, I suspect. I don't think it's just me. But once you have that process in place, you are gonna discover more things. The question is whether human health has deteriorated and in theory discovering more things early could be good because then you can treat them. So you'd wanna see if the treatment of it was leading to longer to longevity and lower rates of mortality. So talk about what we know about that. Okay, I'm gonna, I'm gonna lead in with a, a fun, a fun fact. What's the number one best predictor of whether you'll be diagnosed with skin cancer in the us? It's not sun exposure. I'll, I'll, I'll, I'll give you that one for free. It's, Go ahead. How many dermatologists there are in your county and, and the overall age bracket for people in your county. And that, that is to your point about diagnosis. The, the more you look for something, the more you're gonna find it. And a huge amount of the rise in skin cancer cases is because we are looking a lot more carefully. Now that's not a bad thing, right? If you're, you're finding skin cancers that might maybe got missed before and never diagnosed, never even made it into the records, that's a good thing. And that's definitely been one thing that's happened. You're finding 'em earlier, ideally that can be treated more effectively when it's early, Right? That's all, all to the good as, as long as you don't start to panic because you're, now that you're looking, you're finding a lot more and, and think that some something has changed that needs to be dealt with. And yeah, as you said earlier, you, you look back at some of the, like some of these early papers that about the rise in skin cancer and it is almost laughable how bad some of the reasoning was. Like the earliest in the US the earliest like solid data on, on skin cancer was like this Connecticut registry in the forties. For whatever reason, Connecticut started doing it a little bit before any other state. So to, to compare rates of skin cancer today and connect to Connecticut in the forties. The researchers literally assumed that back then in the thirties and forties, nobody ever exposed their skin to the sun. Like you can actually read like these lines in the papers and, and go, what do they talk about? Did they have, they looked at photos of people on the beach in the thirties and forties. But the idea was that back then people were much more conservative. They never spent any time in the sun. So the entire rise in skin cancers is because now we are spending so much more time in the sun. And, and We should add there, there there is a cultural interest in tanning and, and bronzing and, and having a tan that you could argue was when we were talking about what changed. That, that it's true. I, I overstated the case. I said people don't work as much outside in the last half of the 20th century did in the first half. On the other hand, they didn't have much leisure in the earliest parts of the 20th century. They didn't have time to go to the beach and lay in the sun and bake for X hours. And it could be that that's the cause, Right? And I've actually looked for good numbers on time spent outdoors and it doesn't, unfortunately it doesn't really exist. The best numbers you see are for kids. Like they, there, there's some studies that have tracked kids outdoor time over, over the decades and you see unsurprisingly a a a gradual decline per decade from, you know, a few hours per day back in the forties or fifties. You know, when I was, I was a kid in the seventies and eighties after school it would, we would be outdoors playing all the time. Now there's a lot more indoor time and, and kids get like less than an hour per day. So we know with kids that there's been a gradual, significant decline in amount of time spent outdoors. I think we generally assume that it's true for adults as well. Like people spend a lot more time indoors on screens than they used to. But there isn't any real solid data about how much time we're getting outside. But is it fair to say that this explosion in skin cancer rates, which are often not distinguished between current Sonoma and melanoma one not as dangerous one very not good. The melanoma. Yeah. Is It fair to say that that rise is mostly due to increased attention from dermatologists who categorize blemishes nec unnecessarily, perhaps, or what do we know about and and was it good was as you said, it could have been good to, to diag to find more of these? What, what, what do we know about the all, you know, the mortality rate from deaths from skin cancer, which is what we really care about, Right? And this has been looked at most closely with, with melanoma and there's been a lot of discussion in the research community about over-diagnosis with melanoma. Every, everyone agrees that overdiagnosis is going on, but again, maybe it's not that much of a problem because you wanna make sure you catch 'em all right. You wanna err on the side of taking off anything that might be problematic down the line. Actually, one thing that we should mention is that until a melanoma becomes invasive, we don't actually have any solid way of predicting whether it's going to be a problem or not. Like so all the ones that are caught very early on the skin and are called melanomas, they might be fine, but obviously, you know, if a doctor says to a patient like, it might be fine or it might not, do you want me to leave it? Like, no, you're gonna get it cut off. So all these things get called melanomas and get cut off and everyone agrees that some of them would not have been called melanomas back in the day. And there was actually a really interesting study a few years ago where they took slides of, of, you know, lesions that had been called melanomas 20 years ago or, or lesions that might or might not be called melanomas. And they took the exact same slides that have been done 20 years ago and showed them to a group of dermatologists 20 years later, including actually some of the same dermatologists who saw the slides 20 years earlier and asked them to make the call melanoma or not melanoma. And 20 years ago, 11 were called, were judged to be melanomas. And today the exact same slides, 18 of them were judged to be melanomas. So we're getting more lenient on what we call melanomas. And like we said, that's not necessarily a bad thing, but that is definitely a big factor in the rise of melanoma incidents because when you look at mortality in melanoma, there's been no change decade after decade after decade. Mortality is totally flat while incidents is rising steeply. And as some scientists have pointed out, that's kind of like, like the classic sign of overdiagnosis, But it could just be that we're better at treating it and it's good that we're catching it early. It would've been worse otherwise. And I think the, the real, the puzzle here and, and you go into it in some complexity in the book and in a thoughtful way, is that somewhere along the line, and you will tell me when sunscreen gets invented and sunscreen, it's, it's a pretty modern creation. You know, the, the in ancient times sunscreen was called going inside or sitting under a tree, right? Or putting your shirt on, right? There are many ways to screen out the sun that don't require a pasty coconut flavored chemical. But at some point that industry was born as a way to allow people to expose them parts of their body and be outside and even possibly get darker and more in theory, more attractive by, by getting a tan. And it, that's really complicated and we're, we're gonna talk a little bit about it 'cause I think it's really interesting. But this rise in skin cancer is coincident with the enormous expansion of the sunscreen industry, which is surprising, right? All of a sudden we have this special way to keep the harmful ray of the sun from hurting us. And yet at the same time when people are using a whole lot more of it than they did either 'cause it hadn't been invented yet or it just wasn't that available or people didn't know much about it, all of a sudden everybody knows about it. It's, it's everywhere in all kinds of different levels. And we'll talk about SPF in a little bit. Yeah, but I, I hope but why wouldn't that have ended this, this epidemic? Why didn't the creation of sunscreen, which I think used to be called in my days suntan lotion, but sunscreen, which sounds more scientific, why didn't that end this problem? So this is an inconvenient truth that has been sort of lurking in the background and and dogging the industry for a long time. Yeah. Rates of skin cancer and rates of sunscreen use track each other spectacularly well, like decade after decade. Sunscreen sales through the roof compared to what they used to be. And yet rates of skin cancer also go up and all the epidemiological studies tend to show that more sunscreen use is correlated with more skin cancer. Which was also an inconvenient truth. Except you look at it and you're like, well that's fine because who's using sunscreen? People who, who have paler skin who might need more. Yeah. People who are out in the sun. So that's, you know, that's also it. It can be a little awkward classic Reverse, right, Classic reverse causation. Exactly. But it sure as heck hasn't been helping as much as we might have been led to believe that it would. That's clear that, you know, SPF rates have gone up, adoption has gone up, people are using more, people are avoiding the sun more. It's not turning skin cancer cases around at all. So clearly there's more to the story than pure exposure to sunlight. Let's talk a little bit about, I mean it's complicated, but talk a little bit about, so first SPF is that sun protection factor. It is, it is. So This is a startling thing I learned from this from your book, which is an SPF of 15 and 30. I just thought they were numbers that meant more protection. They actually have a technical meaning, which is good 'cause SPF sounds like science, it should be, you know, sigma pi, whatever F is, is there a Greek letter for F pi? It, it should sound more scientific even that way. But when you say S pf dash 15, it looks scientific. Explain where those numbers come from and why it's not as comforting as you might think and why SPF 60, which would be like, oh well that's better. Why it's a little complicated, Right? It's almost like extra strength, you know, Tylenol like we, we, the bigger numbers seems like we're helping ourselves more. So SPF, that factor is how many more times you can stay out in the sun when, when you're using it without burning until you burn than you could if you had nothing on. So if you could stay in the sun for 10 minutes before you started to burn with nothing and you put SPF 20 on your body, you could stay in the sun for 200 minutes before you ha got the same amount of burn going on. And then so S SPF 50, you could stay in the sun 50 times as long before you start to burn. So that's originally the FDA wasn't even gonna let the industry use anything like SBF 50 because nobody should be staying in the sun that long. But basically it, that's a measure of how, what percentage of the ultraviolet light it's blocking. And it's important to understand that sunburns are caused by UVB. We, we divide the ultraviolet light spectrum into UVA and UVB and they actually have very different effects on the body. And UVB was the first one we worried about and it was also the only one that the original sunscreens were able to block. So those first sunscreens focused purely on UVB, which turned out to be a big problem. And SPF only applies to UVB. So you could have a sunscreen that's SPF 50, which means it will block UVB 50 times as well as nothing meaning basically it's blocking 2090 8% of the rays, only two 2% of the UVB rays are getting through to the skin. That doesn't mean it's blocking UVA at all necessarily. And that was a problem in the old sunscreens that we all were using in the seventies and eighties before the, the, what they call the broad spectrum or full spectrum sunscreens came on the market later. So in theory, one explanation for why sunscreen didn't have much impact is that it wasn't really doing what we'd hoped it would do, blocking the harmful part of the Sunrun sunlight. But in theory the improvements in those formulations should have made a difference. And it looks like they, yes, and it looks like they did. And the new sunscreens are, are way better now than those sunscreens were a generation ago. And actually starting next year, we're gonna get even better ones on the market. It looks like the, the sunscreens are used in in Europe and Asia and like Israel are much better than the ones that are allowed in the US when we can, we can get into why, but the US ones are, are a generation behind basically. And yeah, they used to only block UVB because originally we thought UVB was what caused skin cancer. UVB is what caused the sunburns. And yeah, those early sun, they weren't sunscreens, they were sun tanning aids. The whole point was to keep you from burning so you could stay in the skin in the sun longer so you could get even more bronze, right? And then they sort of pivoted to a health, a health aid later on, but they were only blocking UVB because at the time the doctors thought that UVA was not a problem, like UVB, we knew it could, it had enough energy in those, in those light photons that if it hit a DNA molecule in your skin, it could actually mess up the DNA and give you skin cancer. So we thought we had to block those uvs and the original ingredients that were used in sunscreen, those chemical filters were able to do that. So it seemed serendipitous, right? Block the sunburn, block the UVB, so you're not gonna get skin cancer, let the UVA through and you're gonna get tan from that. Perfect. By the eighties and definitely by the nineties, everyone was realizing that UVA was actually indirectly causing skin cancer as well and was probably a bigger problem than UVB all along, which suddenly made those sunscreens look terrible. Like possibly worse than nothing because by blocking sunburn and making you think you were safe from skin cancer, they were allowing you to stay in the sun depending on the SPF 10, 15, 20, 30 times longer at all of that time, gobs of UVA was pouring into your body and probably contributing to melanoma. We now know. So That's, that's part of the problem. It's, it, it's, I think it's actually a huge problem and it's kind of been swept under the rug a little bit like now that now mostly broad spectrum sunscreens are on the market and frankly no, no, no sunscreen that doesn't block UVB and U should even be allowed on the market, I don't think. And they've gotten much better. And you see that like in all the, in all the observational studies that track sunscreen use and skin cancer, the early ones from like the seventies show no effect. And, and often, you know, reverse effect like it was worse to use the sunscreens by the eighties and nineties. It's, it's looking like, you know, an even wash and now more the more modern ones, it's starting to look better for sunscreen now. So I think the new ones are pretty good. I think they can be a very useful part of, of any sun, sun program that you, that you wanna develop and they're gonna get better still in the US and they've been better for a while in most of the rest of the world. So let's talk about vitamin D. I think we've talked about my vitamin D issues on the program in the past. I'm always ready to Sacrifice my body for science for my listeners. You know, I, you go to the doctor for a physical, and this has probably been true for I'm 71, but I I say I suspect it's been true for 30, at least 30 years. You go in my life, I go to the doctor, I get a bunch, I take, blood is drawn, I get a bunch of other tests and when they draw my blood they tell me I'm vitamin D deficient. And then they say most Americans are because we work indoors and we don't get much sun. And I said at the beginning of this program of our conversation that if you'd asked me what's good about the sun, I would've said, well it's, you know, it's good for your, your mental health. It's good. Makes put you in a better mood. You don't get blue in the winter. But of course there is this other thing I forgot to mention, which is vitamin D and vitamin D is not a small thing. It, it's kind of important And my position don't take this as medical advice folks, let's, you know, Rowan will, will chime in with his view. But my position's always been, it's not obvious that taking an enormous supplement A, a vitamin D in the form of a pill, which raises your vitamin D score actually achieves the things you would get from an organic increase in vitamin D from being out in the sun more, which are stronger bones. Other things I think reduced risk of shingles and, and it really, it's not a small thing, it's kind of really important. So you shouldn't vitamin D deficiency. But when my doctor would say take this pill, I would say, well I look at the side effects which include things I'm not gonna mention 'cause maybe they're not true, so I don't wanna mention them. But I would say, well I look at the side effects, it's not obvious to me that this is a good trade off, especially since I'm not convinced that raising my score is the same as reducing my risk of say, shingles or bad bones. What do we know about this? Yeah, it is starting to look a little bit like, it's, it's like cheating on the test basically to take the pill like it, it's not doing the thing that was the goal all along. But it took us a while to get to that point back, like in the 1980s it started to look like vitamin D was really important to health because again, of all this observational data where you look at populations and the, the group that has low vitamin D levels has higher rates of every disease you can think of across the board, cancer, cardiovascular diseases, autoimmune diseases, Alzheimer's, other types of dementia, diabetes, you name it, low vitamin D looked, it was associated at least with correlated all of these different things. Yeah, yeah. So it seemed like, and, and then, you know, the mechanistic studies in the lab would also show that, you know, you, you add more vitamin D to the, the these cells and it prevents cells from going cancerous and improves membranes. It it what we do originally that it helps mineralization in the bones so you get strong bones from vitamin D like going back to the rickets days. Anyway, it looked like there were reasons to think that it really was like kind of a wonder drug that could help all these conditions. But you know, by then, by the 1980s we were also like really worried about skin cancer. So doctors weren't about to say, go out and expose your skin to sunlight, which is the natural way to make vitamin D. So everyone you know, started recommending supplementation and people did it like it's the most prescribed supplement in the world, I believe. And there have been huge really rigorous high powered clinical trials where half the people get vitamin D pills and half the people get placebos that, you know, and they're tracked for years because it seemed like, you know, it was worth putting all that money into these trials 'cause this really did look like a wonder drug. They have completely failed across the board where we know that unless you are extremely vitamin D deficient, raising your, the amount in your blood through a pill doesn't help with any of these conditions. And there's even been, you know, like the editors of the New England Journal of Medicine have published editorials saying stop prescribing vitamin D pills. It's not, not helping, but it has that, that hasn't happened. It's still the most prescribed supplement. I think doctors, some doctors know that it doesn't do much, but you know, it doesn't hurt like it makes their patients feel better and placebos are not nothing. Yeah. Some doctors that probably don't, haven't looked at some of the research, but yeah. So there's the conundrum. Like people who naturally have high levels of D in their, in their body have lower rates of all these diseases. People who artificially raise the level in their blood through a pill, it doesn't help at all. So how can that be? So the real question of course that we all care about is, if I spend more time in the sun and raise my measured vitamin D, will that help? And right, in other words, all the cha many times the challenge of these studies, these observational studies in epidemiology, which are in my view, a cesspool intellectual cesspool to use a a a phrase, the question is what, what happens if you an individual then becomes one of the people who looks like those other healthy people because you now have more vitamin D on your score, but you don't have the other factors that we haven't controlled for, whether it's where you live, your latitude, your diet, your income, your genetics, et cetera, et cetera. So there's always a question whether this is, is is real in response. My doctor wanted me to supplement. I said no, I said gimme a shot, I'm gonna spend more time in the sun. I asked Claude, I told Claude I live in Israel, Israel's very sunny, a huge Portion of the Year. Nice. And it's at a particular latitude, which is not as sunny as some, the, the intensity of it is not as intense as some but more intense than other places. And I gave it my age and you know, where you catch the sun, if you roll up your shirt sleeves or go without a hat or whatever, you know, which is not ideally for other reasons, you know, how much, how much is it gonna help? The answer is not a lot. It's really hard when you're 70 something years old, your body doesn't make vitamin D as well as it used to from sunlight. The, the machinery the factory is, is, is sluggish by the time. If you do it at nine in the morning when I like to have eight 30 or eight 15 when I wanna have my coffee with my wife on our porch, that gets sunlight. Eh, it's not so intense at eight 15, you really need to do it between one and three. But I don't really need, I can't really afford to be out in the sun. I'm working and so on. So however, I got my score very into a, into a range that made my doctor happy. But of course I risk, I raised my risk of skin cancer. So these are the trade-offs that mature adults need to face. And I want you to talk about some of the factors that might also weigh in on that. Like where you live, like your skin complexion, like how often you're out in the sun, et cetera, et cetera. It's complicated, but, but there's some things we can probably think about thoughtfully rather than just never go in the sun or go out in the sun all the time and get your vitamin D up to a million. Yeah, exactly. And you know, moderation once again is gonna end up being the, the best policy here. You mentioned like once you're 70 is harder to make vitamin D and yeah, that's important. I was just looking at some numbers on this basically. Yeah, by the time we're 70, we're on, we're only producing half as much vitamin D for the same amount of sunlight as when we're, you know, in our thirties. So yeah, and there's no, there's no good good but on that it's just, it just kind of sucks the way It is. It's like, so a lot of things that decline after 70, trust me, that is this not the only thing that gets more challenging when you're, your vitamin D production. Not the most thing, the biggest thing to worry about Wisdom, however, way up way. Right? So up, Way up. But so part of the, like one of the questions with the whole vitamin D story is whether vitamin D was actually responsible for all those health benefits in the people that were getting more sunlight or, or whether it was just sort of along for the ride. You know, it was, it was an indicator of sun exposure, but it wasn't the agent that was bringing the good health necessarily that it could be other things about sunlight. So even if you're 70, you're not making vitamin D like you used to, you probably are still getting some of these benefits of sunlight from other things. What, which we can, we can talk about if, if you want we Will in a minute, I wanna come to that next, but continue your thought about that trade off of whatever the benefits are of sunlight, vitamin D and, and the other things we'll share in a minute. Is it, is it worth it? Right? That's the question a person has to always ask. And in the world we live in today, the answer is never. That's, that's why I like your book, I I I'm not gonna say your book is that everything in it is true and listeners should, should ignore the risks of skin cancer. That would be stupid. You don't say it either, but overwhelmingly the i the sun is poison in in our minds. This this, this narrative has become extremely well entrenched. It's death, it's death, it's skin cancer, it's death vitamin D. Okay, fine. Maybe it's, it's a little, it's good for somethings you should supplement. Okay, well turn does doesn't work so well. So what do you do now? Should you, yeah, and should you go out in the sun if you're forget 71 if you're 51, 21 11. Yeah. So the trade off question is the right question to ask. And the first person I ever saw asked that question was a dermatologist in Scotland named Richard Weller, who he, who had done some research that showed that when sunlight hits skin, it produces nitric oxide in the skin. And nitric oxide is a well-known vasodilator. It allows blood vessels to expand and lowers blood pressure because of it. It's used a lot of of heart medications. Even Viagra is, is based on nitric oxide. It it gets, it lets more blood flow. So his studies had shown that, you know, like shining like the equivalent of like 20, 25 minutes of summer sunlight on volunteers, his grad students just shining it on their arm would lower their blood pressure. It raised nitric oxide in their blood, it produced nitric oxide in the skin. That nitric oxide went into the circulatory system and lowered blood pressure by like five or six points, which would be enough like worldwide to, to reduce deaths from heart disease by like a million people or something. So he was the first person to ask that trade off question. He, he ended up doing a TED talk, which you could, you can still find out there. We'll link to it. And the, the reason he wanted to ask the trade off question was because skin cancer, we hear a lot about it, but it doesn't actually kill very many people. It's, it's not a significant cause of mortality in the US It causes, you know, about 10,000 people a year die from skin cancer. And so that's not nothing. If we could get 10,000 to go to zero, that'd be great, but cardiovascular disease is, you know, closer to a million people and cancer is like maybe 600,000 people. So those are the biggies. And diabetes is another big one and infectious disease. So skin cancer is like worldwide is, you know, it's not even on, on the charts in terms of mortality. It's, it's not one of the top 40 causes of death in the world. So if sunlight would slightly raise the risk of skin cancer but would slightly lower the risk of cardiovascular disease alone, that would be a, a massive win in terms of the trade off. And he unfor, I didn't get this new study in the book, but Weller and his group just came out with a new Preprint of a few months ago that looked more specifically at the trade off question. And to do so they used the UK Biobank, which is this fantastic set of the fantastic data set that more and more researchers are using. And what happened is back in the early two thousands there was this push to create a, an incredible health data set in the uk. So they got 500,000 volunteers in the mix, you know, took every health metric they could, questionnaires got every, every possible granular detail about these people's health and they were all like ages 40 to 69. So they were all sort of like middle age and then they've been tracking that group of 500,000 people ever since. So we now have about 20 years of data on them and it's such a rich source of data that, you know, even though observational data can be an intellectual successful, this is a pretty good one, right? So you can get away from some of the, the problems if you're using small data sets. And so, so Weller took a look at that group and you know, you have location data for all of them and some of them have even had their sun exposure tracked. But even if you haven't, you know, attached a light sensing wrist wash to the volunteers, you can check the, the satellite data for their location and get a pretty good sense of how much light they've been exposed to on average. So he just published a preprint that tracked this group. Like I think they had 420,000 people ultimately in their study mortality and incidents of disease against sun, sun exposure. And, and they didn't just use sun exposure, they also asked the people about sun habits, like did they seek sun? Did they, you know, actively try to get some sunlight? So they scored everyone for on, for like a sun, sun seeking, you know, habit and tracked that against disease. And what they found was that, you know, of the four 20,000 people, about 45,000 had died, period. Almost all you know, cardiovascular disease and cancer were responsible for most of those diseases. Only 440 had died of melanoma. Only 60 had died of other skin cancers out of 420,000 people. So skin cancer doesn't kill very many people. And what they found was that yes, if you, the people who got a lot of sun versus a little sun were about 20% more likely to die of melanoma. The people who got a whole lot of sun were actually no more likely to die of melanoma. But so there, there was a, you know, a slight rise in melanoma deaths for the high sun people, but that amounted to, you know, like less than a hundred people overall over 20 years in this set of 420,000 people. Meanwhile they were far less likely to die from cardiovascular disease or cancer and some other, you know, diseases that contributed minor numbers. So I think the ratio was 75 to one that more, more light for every one extra death from melanoma that it created was saving about 75 deaths from other bigger, more problematic diseases. And to have a lot of confidence in that, you'd wanna know more about the connection between sunlight and those, those diseases. The nitric oxide is at least a mechanism, is it plausible of that magnitude? You'd have to look into that. You have to make sure you control for income and other factors. I'm sure they tried, I dunno how well they did it. It could be that rich people have lots of, tend to have better health than poor people and they can go on vacation more so they get more sun. So it's a false correlation. But putting all that to the side, It's provocative and it's a, it's a, an encouragement for people to, cons, I would just say to consider the trade-offs where you come down on that trade off, you know, as a personal decision that everybody has to make on their own. But it, it is thought provoking. I, I confess there's a moment in your book, some really wonderful personal, it's not a large part of the book, but there's some nice stories in the book of your own experiences and doing the research and where you went and your attempts to get sunlight to help you sleep better. We're not gonna get into that, but it's, it's really, there's some lovely writing there, but there's one moment and it's such a small thing, but I just wanna mention it. It's not scientific, this is not a scientific point I'm about to make, but I can put a gloss of science over it. I'm gonna do that and let you comment when it's been a long cold winter and there comes a moment in springtime when you're in the sunshine and you can feel the heat of the sun the way you can, a fire in your fireplace. All of a sudden the sun, which has merely been a palate light in the sky through December, January and February, so march, all of a sudden you feel it's warmth. And I think that you talk about in the, in your book that you feel like it's getting into your bones and you suggest actually there's now some evidence that it does get into your bones. And the idea that we evolved on a planet with a big ball, 93 million miles away that sends photons our way constantly. It, it would be weird if it was a killer now to, you have to temper that 'cause it is a killer up to a point. But that, that it would, that it would, that, that it wouldn't have health benefits would be weird that, that you would have to constantly, especially when we were hunter gatherers, you'd have to be constantly being in the shade of the trees to make sure while you're in the Savannah where the not much shade of the trees anyway, the whole idea of it is, it's comforting. I'll just say it that way. It's not science, it's comforting to think that the sun is, is something of a friend and through most of human civilization, I mean we've worshiped it. I think that was a mistake. It's not a god, but, but it is a pretty extraordinary thing. And so I like the idea is all I'm gonna say that that sunlight, especially on those that first April or whatever month it is, when you actually feel the sun on your face and it lifts your spirits. It's a very human thing. Yeah. I'm so glad you brought that up because learning more about the, the science behind this and becoming more comfortable with the sun, it, it really, it improves your life on a daily basis. You realize that you had that fear in the back of your mind that was probably unnecessary. And so just like with anything else where you, you thought you had to fear something and, and you suddenly realized that maybe your fears were a little overblown, like that improves your life. And the evolutionary part of this I think is actually really important because as you correctly point out a lot of the information we have about what look like to be these benefits of sunlight are coming from observational studies. And yes, the scientists do try to control for all the usual confounders, but that's, that's, you know, that is a, you know, a dark art. Yeah, A Dark Art. Well said. But so all we can do is go well that's interesting, you know, and, and we're not gonna get great randomized clinical trials where half the people expose themselves to a lot of sunshine and half don't because it's, it would be unethical since we think they might be raising their risk of skin cancer. No funding agency is ever gonna approve those studies. So it's just, you know, it's, it's food for thought. But what's interesting here is we don't, we also like the reasons that we believe that skin cancer, that that sunlight it causes skin cancer are also from observational studies. We're, we're not doing long term clinical trials where we tell half the people to go out and and fry themselves and, and you know, we see if they get skin cancer. So it's all kind of guesswork. And anytime you're in that kind of situation, you kind of then wanna default to evolutionary norms and ask, well, you know, what's what, what do we have a pretty good track record of doing? And what's the weird intervention that's new? And so in this case, human beings spent their first hundreds of thousands of years getting 12 hours of sunlight a day. No other species that's out there seems to be suffering from, you know, too much sunlight. Like it seems to be just us that are having this, this issue. So what changed? Well we sort of switched to indoor life mostly in the past hundred years. And that's the weird thing that we need to start, you know, being skeptical about like, did something happen in that switch to indoor life that messed things up. Yeah, I don't, we are, as you point out, you, you do discuss evolution in our, in our origins in the first part of the book. We are relatively hairless. We're hairy, but we're not furry. And that's an interesting thing in and of itself that would seem to be a bad strategy if sun was bad for you. Of course, there may have been some counterbalancing benefits for leaving survivors in the gene pool and so on. So it, it's all complicated. But you, you close your book with some simple advice for adults and children. You wanna share that, and listeners take this with a grain of salt. And I encourage you to read Rowan's book. And if I were younger, and maybe if I were a parent worried about my children's exposure to son, I might go investigate some of the observational and nons observational studies to try to get a feel for how reliable they might be. Maybe you've exaggerated them. Maybe you've, you've, you've failed to, to add enough caveats, but what you got. Yeah, and I would, I would, I totally agree. Like take it all with grain of salt. I'm not, certainly not a doctor either, and people shouldn't be forming their, their medical opinions just from my book. But I do hope people start looking into it because of my book. And we're now in this kind of amazing era where we have these incredibly powerful research assistants on hand all the time. You know, the LLMs that have read everything, and it is pretty amazing. If you ask them, you know, show me the studies on, on X or Y, they'll pull them up and, and you, you don't wanna trust the, you know, the ai because it can sort of get the conclusions wrong sometimes, but it'll point you toward the sources and then go to the direct sources and they can't be hidden. It finds them all. So it's actually be better than it's ever been it to, to like look around and find what the foundational research is on these topics. So that's really worth doing. But in terms of what I think can be, you know, actionable advice for people, it's go, you know, err on the side of moderation all the way, but don't get zero sun exposure. It's very clear from, you know, no matter how we look at it, that zero sun exposure is not healthy for people. It's also clear, and every scientist I've spoken with agrees that burning is bad. If you're actually getting a sunburn, it means you have fried those cells beyond the point that they can recover. So they're basically all just committing suicide and taking themselves out of the game so they won't turn into cancer. But they don't even do that always successfully. So, so burns are truly, you know, a sign that you've gone too far. And I know from my personal experience that even when I'm trying not to burn, it can sneak up on you. So my own rule is to air well on, you know, the safe side of burning to never get close to a burn. That said, I don't sweat the small stuff. It's kind of like, I'm kind of going back to what doctors told us to do in the fifties and sixties, like, you know, don't get sunburned at the beach, don't get overexposed. But a little incidental sun exposure during your day is probably a very healthy thing. And that's, but it really, that's really gonna be influenced by who you are, where you are, and especially your skin tone. People with darker skin tones can take a whole lot more sun exposure than people with light skin tones. And people with the lightest skin tones who tend to have often have red hair and, and reddish freckles are the ones who are super susceptible to melanoma. So they're the ones who do truly need to really be careful. The recommendations are kind of written for them with the assumption that everybody else can just do the same thing and they won't be harmed by that. But now we're realizing that people with darker skin tones really shouldn't be doing the same thing as the people with very fair skin. My guest today has Ben Ronan Jacobson. His book is In Defense of Sunlight. Ron, thanks for being part of EconTalk. Thanks Rus. It was a pleasure.