Unexplainable - An argument for the sun

Episode Date: July 27, 2026

It can be hard to know how to interact with the sun. Some people have swung to opposite ends of the spectrum — either over-tanning or avoiding the sun entirely. But what would a middle ground look like? Guest: Rowan Jacobsen, author of In Defense of Sunlight For show transcripts, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unxtranscripts⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠For more, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unexplainable⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠And please email us! ⁠⁠⁠[e-mail]⁠⁠⁠We read every email.Support Unexplainable (and get ad-free episodes) by becoming a Vox Member today: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/members⁠⁠⁠⁠⁠⁠⁠⁠Thank you! Learn more about your ad choices. Visit podcastchoices.com/adchoices

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and access better data across the business. The result? Less time spent on operations, more time connecting brands with the moments and fandoms that matter most. Learn more at Accenture.com slash Spotify. All right. Sally, Helm. No, I'm. A host of Unexplanable. What do you got today?

What are you working on? Okay, well, first I want to ask you a question. When you think of the sun, what do you feel? I immediately go to Telitubbies. Is that weird? That's not what I expected. You know, the baby's son that wakes up at the sun. the morning, it's like really creepy.

Okay, so I feel good. Warm, right? Totally, classic effect of the sun, yeah. Makes me happy. Yeah. Yeah, the sun is good. This feels like a simple question. Well, okay, I'm going to just let you know that I read a whole book about sun and it's facts on our bodies.

And I learned from reading this book that the sun has just like all of these mysterious effects on our body. And there's a lot that we still don't understand. I mean, if you think about it, it's more bizarre than we give it credit for it. It's like photons of light hitting us and ricocheting around. Photons of light from 93 million miles away. Yeah. That somehow make us happy when we go outside.

Among many other things. So I really, I wanted to get into all this with the author of that book in defense of sunlight. His name is Rowan Jacobson. And I have that interview for us today. Amazing. Are you going to explain the sun? I'm going to explain the sun totally and completely. and you'll never have any questions about it again.

Okay. I want to... Can I hear it? You can. No? Now. Now? Rowan Jacobson, welcome to the show.

Thanks, Sally. Good to be here. All right. We're going to go deep down the rabbit hole together here. I want to first, though, can you just give me a little bit of a hint of the ending here? Tell me, after doing all this research, how have you changed the way that you relate to the sun? I think totally differently about sunlight and about light in general. People don't realize all the light that surrounds us is actually being absorbed by our molecules.

So I started seeing light as this physical force that's interacting with my body in a lot of different ways. And like, what does that mean? Is it good? Is it bad? Is it both? But then if you want to get really cosmic for a moment here. I do. Please. Well, so all of the energy in our bodies, was once light. All of that energy was sunlight. Came from the sun, came to Earth,

usually got absorbed by a plant, and then made its way to us. So it's just sunlight taking different forms. And our entire consciousness is basically this flow of light transformed into different types of energy that is just moving through our bodies all the time. Over the past few decades,

we've all been kind of trained to feel a little guilty when sunlight hits us. And that went away for me once I'd done this research. And it fixed my relationship with the sun in a sense, you know. Yeah, let's talk about the history of that a little bit because you're right. I think a lot of us feel guilty about the sun because of skin damage, which we will get into. But you do in your book, you take us back to a time when heliotherapy was actually all the rage.

So tell us about that, like starting in the 1800s, peaking in the 1920s, what did that look like? We are in a bit of a historical anomaly with this idea that sunlight is bad for us. That would have been a strange notion to most peoples throughout history, but especially this era, the heliotherapy era, which started in the early 1900s in both Europe and the U.S., and was really a reaction to two diseases that were rampant, tuberculosis and rickets. And both those diseases can be treated with sunlight. Ricketts is a lack of vitamin D, and vitamin D is producing the skin. with the help of sunlight.

And one of the things that vitamin D does is it helps to get calcium into your bones, so your bones get hard. Kids in the Industrial Revolution, who were never seeing the sun, had almost no vitamin D in their bodies, and they were all getting rickets. So they had soft bones. It's really bad disease. Even bigger was tuberculosis, which, you know, back in the 1800s was responsible for, like, one out of every four deaths in Europe and parts of the U.S.,

And it can be a pulmonary kind that infects your lungs, and that's kind of like the classic consumption that we think of as, you know, like John Keats dying of consumption. But it can also infect the skin. It's like this flesh-eating bacteria, basically. Oh, God. But that one can be fixed by sunlight. Wow. Once scientists figured out that both rickets and tuberculosis could be solved by light, they didn't quite understand why at the time. But they're kind of like, maybe light's good for other stuff, too.

And it actually got a little out of hand where they started believing that light was probably good for everything. So, you know, we're familiar with this whole sanitarium era where people would go up to the sanitariums in the Alps to take the fresh air. Totally. I've heard of people going to the Southwest. I do feel like I have a sense that back in the olden days, they were just getting sent off to take the outdoor cure kind of thing. Exactly, the outdoor cure. First was the Alps. And then California was advertising itself as early as like 1870 as the sanitarium. to the world, right? Like, come to California. Yeah. Cure all your ills. Totally, I believe it. Well, that's the question. Like, did it help? Maybe it did help in some ways. Like, they were definitely cooks at a certain level. What did that look like? What were some of the kooky things they did? The kooky thing was

they went too far. So they would purposefully get sunburns. Company like General Electric made these UV lamps. You could get sunburned in the comfort of your own home. And everyone bought these lights, they would hang them over their kids' cribs, right, for health. Oh, no. Irradiating children as they slept. So it was truly, truly cookie. I mean, were they onto something in that early era? It sounds like there is some truth to the idea that it helped with rickets, certainly,

and possibly tuberculosis too? Like, were they right? Were they wrong? A mix? The doctors who were running these heliotherapy clinics up in the Alps, they were noticing that all these patients, not only did their tuberculosis go, way, but they just got healthier in general. They seemed more robust. They had more energy. And we now know the reasons behind a lot of those factors. Like a moderate dose of sunlight will reduce inflammation

throughout the body. It'll lower your blood pressure. It'll generally improve your metabolism. So there's these sort of like low level general effects on the body that are positive in almost every way. But that only requires a moderate amount of light. So they were going too far. When doctors started realizing, wait a minute, we actually think that ultraviolet light might be a cause of skin cancer. The pendulum swung hard in the other direction. The messaging sort of got stronger and stronger and stronger after World War II. Like stop frying yourself, you know? Right. Fair enough. Yeah. It does sound though like part of what was going on might be that they didn't know that UV light would cause skin cancer, which of course is something that we now think about, you know,

it's very top of mind when we think about the sun. Tell me, how did that discovery unfold and how did it change the way that people relate to the sun? The researchers just started to realize it in the 1930s, kind of in the same era, and that was, I think, part of the issue. It was the exact same era that people were like, let's lie out in the sun for 10 hours for our health. They were doing tests with UV and mice and realizing that ultraviolet light was looking like one of the major, if not the major cause of skin cancer, and suddenly worrying that all these people were getting way too much exposure in their lives. I mean, doctors start to realize that Sun is affecting people's risk of skin cancer. Then they see the rates go up.

I assume this must be the time when the public messaging that I'm really familiar with is born, when dermatologists do start to get the word out that we should protect ourselves from the sun. But tell me about that. How does that message get shaped and how does it take hold? Really, like 1980 is the sort of pivot point. And before that, the sunscreens that were out on the market were really not there to project you from skin cancer. They were there to help you get a great tan, right? They weren't even called sunscreens. They were called, you know, sun tan lotions. That was the focus in the 60s and 70s is sunscreen that blocked UVB, the rays that caused burning, so that you could stay out in the sun longer to get more tan, right? It did not block UVA, which at the time they didn't think was the cause of skin cancer,

but it would make you nice and tan. So then skin cancer rates are still going through the roof, especially in Australia, which is one of the sunniest places on Earth. So 1980, Australia starts its slip, slop, slap, camp. pain, which with Sid the Segal doing the fellow messaging. Slip Slip Slip Slop slap. Slop, slap. Slap on a shirt, slop on sunscreen, a slap on a hat. Okay, I love it. I love Sid the Seagull. I'm obsessed with him.

I mean, does this work? Do people slip, slap, slap and problem solved? It was super successful. So then that pretty much got copied around the world, variations on that. And sunscreen has also changed. So the broad spectrum sunscreens hit. in the 1990s mostly that blocked both UVB and UVA and those are much more successful. And it does feel like somewhere along that trajectory,

the tide really did change and we did land in a place where the message that sun can be dangerous got out there. I think it's really, really out there. Oh, yeah. But as that was happening, there was some other stuff happening to,

some other corners of science where the benefits of sunlight were becoming clearer and clearer. So let's dive into that a bit And I want to start with a scientist that you talk about in your book, Pelle Linkfist. He is an obstetrician in Sweden, and it's back in the 2000s. He's investigating a strange pattern that he had noticed among his patients. So tell me about that.

What did he find? Yeah, Pelle Linkfist is an obstetrician in Sweden. And one of his specialties is blood clots. And blood clots tend to be more common in women when they're pregnant and right after they've given birth. he had noticed that less inflammation meant less blood clots, and he had a hunch that that was because of vitamin D. And he found this great data set called the melanoma in southern Sweden study, which had tracked like 40,000 Swedish women for like 20 years. It tracked all their health metrics, including how much sunlight they got, because the focus was melanoma. So they were trying to figure out what raised your risk of melanoma.

So they tracked all of their sun-seeking behaviors, I think is what they called it. Okay, that sounds perfect. What did they find? So we look at the data, and it turned out it was true. Like the women who spent the most time in the sunlight had higher vitamin D, lower risk of inflammation, and fewer blood clots. Wow. More sunlight, fewer blood clots. More stunlight, fewer blood clots.

So then he started looking at other factors. And it turned out it wasn't vitamin D. Like the connection with actual sun exposure was stronger than the connection with the vitamin D levels. Okay. So there's something going on that's not just vitamin D, something mysterious in the sunlight. Right. And he had no idea what it was. But he noticed it for blood clots, then he noticed it for diabetes. And so then he looked at the same data set just for all-cause mortality. And the sun-seekers had significantly less mortality than the sun-ovoiders. The sun-of-voiders were twice as likely to die from any cause as the sun-seekers.

So he published this study, and there's sort of like a notorious line in there. where he says, son avoidance seems to be a risk factor for mortality apart with smoking, which upset everybody. But he wasn't even looking to make a statement. He was just laying out the data. Why did it upset people? Well, the implication that avoiding the sun was, like, as bad as smoking for your health, was not the message that, you know, the powers that be had been, like, pushing for several decades.

At that time, and to this day, the official advice is do not ever expose yourself to sunlight without protection. So sunscreen or clothing, the proper amount of sun exposure of UV in particular to get is zero, right? So this was one of the first papers that really sort of flew in the face of that recommendation. Yeah, so it sounds like we're kind of tracing some swings. here. We had the heliotherapy era where everyone started to feel like as much sun as possible is good. Then we swung in another direction where the public health message became largely the sun's dangerous. Stay out of it. Make sure you protect yourself from it. And now there's like some cracks in that. And some people beginning to suggest that maybe there's a middle ground, something sort of more in a

gray area in terms of whether the sun is good or bad for us. What hints do we have? that there are benefits of the sun that we didn't really understand, that science hadn't explained. So that was sort of the next stage in this story. There had been a guy named Robert Furchott. He was working with rabbit aorta's because, you know, why wouldn't you?

He just had some? He happened to have some in his lab. He was trying to figure out what, yeah, like what made blood vessels contract and dilate. Okay, fair enough. Had a jar of rabbit aorta's on the window sill in his lab. And it had been a cloudy day. And then suddenly the clouds cleared and the sunlight hit the jar with the rapid aorta's in it and the blood vessels dilated. And he thought,

what the heck? And then some clouds came and they contracted. And he called the effect photo relaxation. There were a lot of nitric oxide researchers out there trying to figure out how it worked because it seems like if you could master that, you could really improve cardiovascular health. Nitric oxide. Okay, what is that? What does that mean? Nitric oxide is a very simple compound. It's just a nitrogen and an oxygen put together, but it dilates blood vessels. It tells the muscle and the blood vessel to relax. Which, I mean, that's good, right? That lowers blood pressure. It lowers blood pressure, which is in cardiovascular disease, number one cause of death in the world by

far. It's the biggie. So anything that lowers cardiovascular disease is a huge win for public health. Like what hints do we have that there are benefits of the sun that we didn't really understand, that science hadn't explained? So that was sort of the next stage in this story. It's after Pelle Linkfus papers, a dermatologist in Scotland named Richard Weller and some other colleagues of his discovered was that the skin actually produces a bunch of nitric oxide when hit by sunlight. The more sunlight that hits your skin, the more nitric oxide will be released into your bloodstream, the more blood pressure goes down. Wow.

So he's discovered a way that standing in the sun can improve your heart health, which again, it's kind of a surprising finding to me the idea that light is doing all that. And I mean, this has huge implications, right? What are the implications of that for our health? Huge. Because as we're talking about cardiovascular disease is the number one killer. So if you could reduce blood pressure, even modestly, you could save millions of lives. And skin cancer, and this is surprising to a lot of people, it doesn't kill very many people.

It's not a big killer. It's not one of like the top 40 causes of death. Cardiovascular is number one. If you took that research seriously, then you had to sort of ask the question of tradeoffs. Like, yes, sunlight raises your risk of skin cancer, but if it lowers your risk of heart disease, then how do we pick, right? So we've now talked about ways that sunlight can affect your heart health. We've seen some evidence that it might affect all cause mortality, so it might just make you healthier in general. But we still haven't really talked about the theory that I would have had coming into this conversation.

about what sunlight is doing for you, that's good, which is vitamin D, which I've heard so much about vitamin D, the sunshine vitamin, being in the sun gives you vitamin D. I've seen and taken vitamin D supplements, which I did learn is not actually a vitamin. What is it? It's not a vitamin. It got misnamed back when they discovered it in the 20s. It's a hormone. And it's used in tons of different ways by the body. We used to 20 years ago think it was like, the magic bullet that was like the wonder drug that could cure everything or could at least prevent disease across the board. And that was because when we looked at levels of vitamin D in people's blood, the ones who were deficient in vitamin D had higher levels of every disease

you can think of. Cancer's, heart disease, autoimmune diseases, depression, diabetes, dementia, you name it. Raise vitamin D and you should have lower levels of all those things. The easiest way to do that would be to tell people to go out in the sun, but we didn't want to do that because we didn't want to raise people's risk of skin cancer. So instead, the advice was stay out of the sun, but take vitamin D supplements. But there's been huge clinical trials to prove that worked, and they have across the board failed to show that these vitamin D supplements fix any condition whatsoever. Wow. What did science feel when those results came out? It sounds like a real upending of the conventional wisdom.

It was, except it turns out conventional wisdom is really hard to upend. You can upend it in practice, or in theory, but in practice it is really hard. But that was another big mystery. Like, how could that be? If people with naturally high levels of D have lower rates of all these diseases, then how come raising that D artificially with pills makes no difference? And how come? What do you think?

Any guesses? I mean, my guess is. is that it has to do with sunlight. Oh, you knew. So D was just a marker for sun exposure, and D is a really, really accurate marker for sun exposure. You get more sun, you're going to have higher levels of D. So that D readout in people was really just saying

these people with lower diseases are getting more sunlight. So probably D is part of the reason for the beneficial properties of sunlight. but it seems like it's got to happen through your skin for some reason. There's something different when you're taking it orally. We tend to do this where we learn a little bit about something and we boil it down to one very simple formula. Like, oh, D-good, take D-pill, you'll be good. And then we get surprised when it turns out the body works

in incredibly more complicated ways than that. So this seems to be one of those cases. What do we still not know about how sun is affecting our bodies? What are the big mysteries that remain? I think we are probably just scratching the surface. After the break, Rowan and I go further down the rabbit hole here and deeper into the science of light itself. Running a business shouldn't feel like surviving a software group project.

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slash your rich BFF. Light, you may recall, comes in different wavelengths, carrying different amounts of energy. As we talked about at the beginning, different wavelengths of light penetrate different depths into the body. But some of those wavelengths in sunlight, those photons of light, are bouncing around your body like, you know, pinball. until they finally meet a molecule and get absorbed. And we know that those interactions are really important, but certainly if you change your light diet, what I like to think of was a light diet,

it's going to change that. Like if you're indoors, you are getting a completely different dose of photons, kinds of photons and amount of photons, than if you're outdoors. So what the heck is all that doing to our bodies and to our minds? Yeah, you have some kind of cool charts in the book that show the different wavelengths of different kinds of light. And the compact fluorescent light is weird. It's like this spiky, strange graph. And something like fire has this sort of beautiful, gradual going up and including lots of red light in it. But I do want to ask you about that red light because this is something I've like seen out there in the world is people with those red light masks on their face or different red light.

light devices who seem to feel like they're trying to correct this imbalance that you're talking about, right? They're trying to get a different new kind of photon that comes specifically from red light. What do we know about that? What do we know about red light therapy or infrared light and how it affects us? Yeah, red light therapy, huge now. You see it in every clinic, even dentists are using it. It seems like it improves mitochondrial function, mitochondria, big word, tiny little things that are in each of our cells. There's hundreds to thousands of them in each of our cells, and they're what create energy for the cell. And it looks like red and especially infrared light, when it hits mitochondria, it's kind of like scrubbing them clean. They make energy more efficiently

after those red and infrared photons hit them and actually knock off the rust in a sense. But the interesting thing is that, you know, everyone's doing the red light therapy. They're putting the crazy hockey masks on their faces. But red and especially infrared is a big part of the solar spectrum. So more than 50% of sunlight is in the infrared. I mean, I do feel like I'm hearing people actually in the Maha movement talk about getting more and more sunlight and how important that is. I know that Health and Human Services Secretary Robert Kennedy, he tweeted about, like ending the war on sunshine.

Hi, I'm Robert F. Kennedy, Jr., your agent secretary, and I try to hike every day because the sunlight is medicine, give you vitamin D in your body. Where do you think we are right now in the back-and-forth swing of our relationship with Sun? Like, what's happening in this moment? Some of the Maha crowd seems to be, some of the first ones to really discover, you know,

Discover the sun as a rallying cry. But one concern that I have is that rather than doing the 300-page book that explores the nuances, you get the quick tweet, you know, sunscreen causes skin cancer, the sun heals everything. You should go out in the sun again. It's kind of like, here we go again with heliotherapy. I mean, you did mention sunscreen there, and I'm curious, where did you land on the question of whether sunscreen's important and how to think about it in your own life? I think sunscreen actually can be a great tool for helping people get outside more.

The safe thing to say from all this research that's been done is that it looks like indoor life is really unhealthy for us. I think probably like the push for wear sunscreen every day, you know, 24-7, 365, doesn't matter if it's summer or winter, doesn't matter what your skin tone is, doesn't matter what you're going to be doing that day, even if you're going to be just at your desk all day. you got to wear a sunscreen and reapply all day long. That was never really supported by any science. It was more of just a public messaging thing. And most of the researchers I've spoken with, their message was, you really don't want to burn, never burn, burns bad.

But I think those little garden variety, quick hits of sun exposure that we tend to get, if we're just going about our day, those are going to come to be seen as a good thing. You know, you were saying at the beginning, Rowan, that stepping out in the sun now, you can almost feel it on a different level now that you know that the energy is bouncing around inside you. And you have actually a beautiful line in the book, you say,

we are lumps of mud animated by light and having a conscious experience of the universe. Tell me a little bit more about how all of this has changed your conscious experience of the universe. I like the way you put that because it really is. It's about the universe. And once you start thinking about light and how it enters you or how it affects you, then you're thinking about energy because light is just pure energy, no mass at all. And, you know, one of the rules about energy is that it's never created or destroyed. Right. It's just transformed. So since the Big Bang, no one knows how it arrived with the Big Bang, but since then, it's just been knocking around, transforming into this and that.

And so everything that we are is some of that energy. that goes back through the sun all the way to the Big Bang. And we are just like this iteration of it on its journey to wherever. So I do think about that whenever I'm walking around and aware of the way that light is flowing through me. And it sort of helps connect you to the rest of everything. I think that's a really nice place to end. Rowan, thank you so much for joining us on Unexplainable. Thanks for such a great conversation.

If you would like to watch this episode, you can find our show Unexplainable on Netflix. This episode was produced by Valerie Shankman and me, Sally Helm. It was edited by Alex Coles and story edited by Joanna Solitaraff. Fact-checking by Colleen Barrett. Mixing in sound design by Christian Ayala. Meredith Hodnott runs the show. Noam Hassanfeld and Kareem Karea are rays of sunshine. And Bert Pinkerton shouted, the guitar.

I completely forgot about it. Also, this beak beeper is really driving me nuts. Anything you can do about that? Flapton took the batteries out of the beeper, and he got to work on Plattie's guitar. Thanks as always to Brian Resnick for co-creating the show, along with Bird and Noem. If you have thoughts about the show, send us an email.

We are at Unexplanable at Vox.com. You are also welcome to leave us a rating or a review wherever you listen. That would be so nice and helpful of you. And if you are into supporting the show and all of Vox in general, join our membership program. You can go to Vox.com slash members to sign up. Unexplainable is part of the Vox Media Podcast Network, and we'll be back soon with another episode

about everything we do not yet know. Running a business shouldn't feel like surviving a software group project. One app for accounting, another for inventory, another for sales, and somehow none of them talk to each other. That's where Odo comes in, an all-in-one business management software that brings every part of your business together. From sales and accounting to inventory and marketing, all in one powerful platform.

No messy integrations, no bouncing between tabs, and best of all, no spreadsheets. Stop managing software and start managing your business with one unified system. Try for free today at odu.com slash Vox. That's ODOO.com slash Vox.