Sunlight Matters

Surviving Winter. You don't need to be SAD with Dr Roger Seheult

• Dave Wallace • Season 1 • Episode 14

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As winter approaches in the North, the days get shorter, the skies darker, and for many of us, our energy, mood, and health start to dip. In Part 1 of a 2-part special of Sunlight Matters, Dr Roger Seheult joins Dave and Georg to share science-backed tips to help you stay healthy, energized, and resilient through the long winter nights.

From understanding the hidden power of infrared light to simple daily routines that boost your immune system and mood, this episode is packed with practical advice for winter wellness—even when it’s cold, cloudy, and grey.

🌟 What You’ll Learn:

  • Why spending just 15–20 minutes outdoors (even in cloud cover) can boost your mitochondria and mood
  • How to make your indoor environment healthier using incandescent bulbs or even a simple fireplace
  • What types of clothing still let infrared light through—and why that matters in winter
  • The truth about vitamin D, UV exposure, and whether supplements or food sources are enough
  • City dwellers: how to find hidden patches of winter sun between buildings and trees
  • The surprising benefits of saunas, cold plunges, and honoring your body’s slower winter rhythm
  • Why old wisdom—like afternoon walks and letting in sunlight—might be good for us

☀️ This episode is all about resetting your relationship with winter—with strategies that cost little or nothing but make a big difference. Whether you're fighting the winter blues, looking to boost your energy, or just want to stay well, these are the seasonal habits your body has been craving.

📲 Listen now and build your personal toolkit for surviving (and even enjoying) the darker months ahead.

Roger Seheult:

The sun is not just touching the outside of your body and the skin. It's actually having a direct effect on the inside at the mitochondrial level. Here's the good news is that even if you go outside with a couple of layers, even three or four layers of clothing, you are still going to get more infrared light in that scenario because it's able to penetrate through clothes. With cloud cover, you would think that that would drop off tremendously. It actually doesn't seem to when you're looking through the film at infrared light. There is a little bit of a drop-off, but it's still many, many times more than you would get if you stayed inside. There was a very strong link between sunlight exposure and influenza diagnosis. In fact, they said that sunlight was strongly protective against getting influenza. As soon as they looked at the amount of time that people spent outside, as time went up, the mortality rates dropped significantly. Looking at cancer and skin cancer, and they realized that what they've been saying before were, you know, avoid the sun at all costs is not correct, that they have to rethink it, and that they do acknowledge that there are benefits to sunlight. This is how strong this evidence is.

Speaker 1:

Welcome to Sunlight Matters, the podcast that reconnects us with the sun. Join us as we explore the power and influence of our star, the force at the heart of everything. Each episode, we speak with leading experts to uncover the ways sunlight shapes our world.

Dave:

Welcome to this episode, this very special episode of Sunlight Matters. And we are joined by the incredible Roger Schweld.

Roger Seheult:

Apologies. We're joined by I've had to deal with it my whole life.

Dave:

Oh my goodness. We're joined by the incredible Roger Schweldt. Welcome, Roger. Thank you so much for joining us. And today we're gonna be digging into some practical advice for people to help them survive winter. Uh the days are getting shorter, um, the temperature's going down, and I can already feel my energy levels sort of starting to drop off. And I, for one, dread winter because I get uh sad, and uh yeah, I so any helps help you can give in terms of tips, ideas, thoughts, anything backed up by the research that you've been looking out for would be fantastic. I'm also joined by Georg as well, he's uh come to provide his wisdom and ask questions as well.

Georg:

Yes. Thank you.

Roger Seheult:

Yeah, I mean, I think uh for those that, you know, there's people in the audience that that already know that sunlight is very beneficial and and infrared light particularly. There's others that may be joining us that um don't understand why we're talking about this subject. And I think it's good just to maybe take two minutes just to sort of review the science in the last literally five years of where we've come from. We used to think that getting outside in the sun was was just for the benefit of vitamin D. And certainly vitamin D has benefit. It comes from ultraviolet light. But what we're finding out now is that there is a portion, actually a very large portion of sunlight in the infrared spectrum. The majority of the photons from the sun are in this section, and they are able to penetrate deeply into the body and even have been found to have this light on the other side of the body. So Glenn Jeffrey's work recently published this year was able to detect infrared light coming through the body. So what that means is that when you go out into the sun, that the sun is not just touching the outside of your body and the skin, it's actually having a direct effect on the inside, and specifically, we believe, at the mitochondrial level, which is the powerhouse of the cell. And what he showed in that study was that it improves the very aspect of the cell that we know gets worse as we age. So this is really important. Um, a number of research uh articles that have come out, these are, I mean, yes, epidemiological studies that are out there, but we're talking randomized, placebo-controlled in a case of a paper that we're going to talk about shortly here, um uh a triple blinded study that shows that infrared light, the very type of light that we're not getting inside the homes, the very type of light that we don't get from LED bulbs, the very type of light that is plentiful in the sun, but we try to avoid it because of technology. This is the very type of light that in randomized placebo controlled trials in a number of patients have actually not only reduced COVID-19 hospitalization by four days out of 12, but has just recently been shown in a in an intensive care unit in 60 patients in a randomized fashion, was able to cut about 30% off of their length of stay just by giving them about 10 to 15 minutes of this during the day. So the point of all of this is that we now know very clearly, scientifically, that there are benefits of the sun. Um, there are a number of um uh societies, even in Australia, uh, that are uh that are looking at cancer and skin cancer, and they realize that what they've been saying before, where you know, avoid the sun at all costs, is not correct, that they have to rethink it, and that they do acknowledge that there are benefits to sunlight. This is how strong this evidence is. So here we are in October, the days are getting shorter, and we know from the data that this is the time of year where hospitalizations go up, deaths from cardiac disease, lung disease, kidney disease, all sorts of diseases all go up all at the same time, a peak about one to three weeks after the shortest day of the year. And the question really comes down to what can we do right now to avoid being part of that statistic? Is that basically what the question is?

Dave:

Yeah, I know. And I mean, I think it's like digging straight into all-cause mortality. It goes up in in winter time and it goes up in wintertime in the northern hemisphere and up in wintertime in the southern hemisphere. Now, I think the prevailing wisdom has been that that's because everybody's inside and they're sharing germs more rather than being outside more. But I think what the evidence is starting to point to is there's something else which is going on, which is indoor lifestyle means that as you as you were just saying, Roger, we're more and more starved of infrared light, which means that our the way we function is is suboptimal in winter time.

Roger Seheult:

Isn't that absolutely and and to really put a nail in the coffin of that idea that it's when we're inside because it's cold and viruses are floating around. Uh, Kennedy School at Harvard, Harvard Kennedy School did a study and published this in 2020 where they looked at influenza particularly, which is very seasonal as we know. And there was something very interesting that happened in 2009. It's when we had the H1N1 pandemic. What was interesting about that year with the flu season is that it came very early. It actually came in June and July. And so they were able to decouple that whole issue of temperature of being inside, because obviously this came in June and July. That's not when people are generally inside uh trying to keep out from the cold. They're inside for other reasons, but they're also outside a lot more. And even in that study, they were able to look at solar radiation data and they were able to look at the CDC data on where the hot spots were in the United States and also in New York specifically. And they came to the conclusion that there was a very strong link between sunlight exposure and influenza diagnosis. In fact, they said that the that sunlight was strongly protective against getting influenza. So I I'm convinced. Well.

Dave:

And and so, I mean, it it then makes me sort of think that as we're getting into winter time, um you know, we all need to do more to kind of optimize exposure to infrared and potentially UV. So, I mean, the obvious thing to say is, you know, everybody needs to get outside more. Now uh we had a look at some data, I think, last week, which showed that sort of people measure people using Apple Watch is measuring sort of daylight exposure. That in winter people people in America are getting something like 20 to 30 minutes of outside time a day, which you know, I think is is very short, isn't it?

Roger Seheult:

It is very short. And um there there was a graph that I recently uploaded that showed the the amount of sunlight exposure versus the amount of deaths, and it correlated it was perfect. I mean, it literally, as one went up, so did the uh so the other one went down. It was an inverse relationship. So you know, if you look at Glenn Jeffrey's work, Bob Fosbury's work, he'll he'll look at the mitochondria and he'll say that it takes about 15 to 20 minutes of sun exposure to get the mitochondria into a state that it's in. That's that's full on uh uninterrupted. And so if people are spending a total of 20 minutes out in the sun, you can be sure that that's mostly not you know uninterrupted. There's there's probably a threshold there where it starts to kick in. So I would say, you know, if you're getting a maximum of just 20 minutes total per day, that's probab that's obviously not enough. Now, there's another study that looked at it uh epidemiologically, and this was uh part of the Adventist Health study too, where they looked at longevity and how much time they spent out in the sun. And what they found was that there was a J-curve type of relationship that as soon as they looked at the amount of time that people spent outside, that as you at the beginning, as time went up, the mortality rates dropped significantly. And then it went down to as a low, the lowest mortality was associated with about two hours a day. And then after that, increasing time in the sun, it the the uh effects stopped and started to actually come back up a little bit. Uh obviously, we can't prove causation by the way that study was conducted. But if you look at the people in that study, in that cohort that had the longest survival benefits, it was people who were outside for two hours a day.

Georg:

Roger, when you when you talk about the um like being outside even in winter, are you talking about direct sun exposure? Do you need to see the sun? Um, or is it like okay, if it's behind clouds, or even like if you're, let's say, in in the shade of a building, is that still enough of indirect sunlight to nurture your cells? Yeah, that's a great question.

Roger Seheult:

And you know, I uh people always accuse me, well, that's easy for you to say. You live in Southern California, um, and we do get quite a lot of sundays, but um, we also get some cloud cover. I live up about a mile up, we get snow, we get precipitation. And uh one of the things I was able to do in the last month is get a film that you can actually put over uh your smartphone camera. And um, yeah, you can use a spectrometer and actually measure infrared with numbers. I just think it's such more, it's so more cool, so much more cool to actually take photographs and and upload them so people can actually see, see for themselves that green leaves and things of that nature reflect light. So, you know, I know we're going into the wintertime, and I'm going to be taking some photographs to see how that actually looks. But in the summertime, we actually had some rain and some cloud cover, and I was fortunate enough to be able to take some photographs when that happened, when the sun was going in and out. You would be very surprised how how much difference there is between being inside, being outside with cloud cover, and then being outside without cloud cover. And what I'm trying to say is, if I could put it into sort of a uh a way of describing it, outside without cloud cover, obviously the very brightest sun, 100,000 lux, uh very bright. Um, with cloud cover, you would think that that would drop off tremendously. It actually doesn't seem to when you're looking through the filter or through the film at infrared light. There is a little bit of a drop-off, but it's still many, many times more than you would get if you stayed inside. There's there's another photograph that I took where I'm inside my home. I've got a window with one of the panes open. So there's really three things that you're looking at. You're looking about at the amount of infrared light that's in the home during the day, and you think you're getting plenty of light when you're doing that, and you're actually not. Uh we're and then there's uh part of the photograph where you're looking through the window. And so these windows that we are now supposed to be putting into our homes, especially here in California, are what we call low e-glass. They they specifically reflect back outside the infrared light so it doesn't come inside, heat up your home, and you have to pay a lot of money to run the air conditioner. And so you could see that it was very, there was very diminished. Outside, it didn't look very bright. And then when I opened the window on the on the right hand side, you could see a tremendous amount of of red light, which is basically a surrogate with this film of infrared light, coming through the window and bathing. And you can clearly see that picture was worth a thousand words. You could clearly see that even on a cloudy day, you were much better to go outside to get that type of light. Now, I I think you alluded to this question, Georg, when you talk about going outside and having your skin exposed. So in the wintertime, it's cold. Who wants to go outside and be exposed? You're going to get hypothermic, it's going to be very uncomfortable, even for 15 or 20 minutes, unless you're, you know, crazy enough to be in the polar bear club or something like that. Here's the good news is that even if you go outside with a couple of layers, even three or four layers of clothing, um, you are still going to get more infrared light in that scenario because it's able to penetrate through clothes than you would if you were inside your home, because it cannot penetrate through walls, can't penetrate through your roof. So that's that is the that is the the the calculus there in terms of the benefits, even in the wintertime, of getting outside into the sunshine, even if in the shade, there's plenty of infrared light there.

Georg:

So that's that's what like thank you very much for for elaborating it. And I think that's a really crucial information for people that the infrared penetrates through through clothes. But what I what I what I still want to get your your professional confirmation, like if I'm in the city, which I do, and if I go outside in the winter months, the sun is pretty flat on the sky, there's a lot of shade by buildings. Is the indirect illumination, like the scattering from the infrared through through the atmosphere, through buildings, like facades, for example, also still enough to to charge up my cells, or is it should I really try to get at least towards the sun, even if it's behind clouds?

Roger Seheult:

Yes, you should. Even if it's behind clouds, you you definitely want to get outside and into the sunlight. Um couple of things there. Uh you need to uh people need to understand that uh when you're living in the city, it's it's difficult to get enough sunlight for a number of reasons. Number one, the buildings can create a huge shadow. And uh you really need to seek out where you are. I mean, I I remember uh visiting uh large cities. Uh one in particular I remember is Toronto, which has a lot of tall skyscrapers downtown. We were actually staying at a hotel downtown, walking those streets, and it's only certain times of the day when the sun is aligned with those parallel streets that you will get the street illuminated in that type of sunlight. And obviously, when you're in the wintertime, the sun is going to be very low. And this is where you have issues with, you know, after precipitation and rain, you can get ice that may melt and you can get uh black ice. So when you are in living in a city with tall buildings, the issue is going to be uh getting that sunlight and figuring out where that sunlight is going to be because of the tall shadows. The other issue that many people have with the cities, depending on how the city is built, is the issue with um uh trees. So we've just described that that this infrared light, which is very beneficial, is highly reflected from green trees and grass. And so if you're lucky enough to have a city like New York where you have Central Park, that might be a good thing, especially in the wintertime where you have may have some evergreen trees and things of that nature. Obviously, in the wintertime a lot of the leaves fall, you don't get the benefits of that. But if you're in living in an area where even in the wintertime there is a lot of alpine trees and and uh evergreen trees, these type of trees also are highly reflective of infrared light. The other benefit with Central Park.

Georg:

Go ahead. They they basically act like an amplifier. So if you're uh below them or close to them, they act like an infrared amplifier and and it's it's even better than being just without the tree. Okay.

Roger Seheult:

Absolutely. The other the other aspect that I would uh bring up real quickly as well is uh many people believe that when the sun is low in the sky, it's impossible to get infrared light. That's uh that's well enough. And and I would just again reiterate that infrared light, the property of infrared light is that it's able to penetrate very easily. Um and so, yes, for for ultraviolet radiation and vitamin D, when the sun is low at that uh level at the sky, it's very difficult for ultraviolet light to penetrate because it's a short wavelength, not able to penetrate very easily through the oblique atmosphere. Infrared light does not have that issue, and I can prove it to you as when when in the wintertime you have snow on the ground and the sun comes up, it does melt the snow. That specifically is infrared light that is melting that snow. It's causing a heat transfer that is even at low temperatures can melt that snow. I once saw this very easily. When the sun was going down, uh my roof was dripping because the sun was on it. And as soon as the sun went down, even though the temperature didn't change, the dripping immediately stopped as soon as the sun went down. This is actually a problem uh for people who have black ice, right? So, what happens during the day? The snow falls, the sun melts, and then it refreezes at night. The next morning you have accidents because there's black ice on the road. That black ice comes from melted snow. The melted snow comes from the sun.

Dave:

Very, it's very interesting. So I I think, you know, in terms of sort of wrapping this bit up, like getting outside sounds like something that we have to do and we have to do more of. Um, you know, I I think a long time ago we had a small exchange. You may or may not remember it, but we had a small exchange on X about getting a dog. I mean, I I think everybody, if they could, could should get a dog, to be honest. My dogs have just heard me and now barking in the garden.

Roger Seheult:

I hear it, I hear it.

Dave:

They agree. But you know, I I certainly found that having a dog means that you know I've got much more motivation for getting outside. And you know, it's um they've become my sort of sun buddies, to be honest with you, over the the summer. And now when I'm thinking about the winter, I'm thinking about walks we can do, which are gonna be great in terms of optimizing like a lovely day. We've had a lovely day here, like optimizing the sun that you get. So um, yeah.

Roger Seheult:

And and if if you do live in the city, I was just gonna say it's it's it's good to plan out your walk where you're gonna have the ability to actually be in the sun. And Georg, I know that you've got a an app that you're looking at too that you're that you've developed where you're able to actually figure out where that sun is going to be so you can be more efficient. Uh, I think that's a great idea.

Georg:

Exactly. I mean, uh also what we talked before, like the the issue in the cities. This was the original reason I came up with this, because I had these two weeks in Vienna some 14 years ago where I just couldn't see the sun in the sky for two weeks. And and then I was like, okay, at least in the lunch break when the sun is at the highest position, you have the best chance to catch some. But then you need an application that shows you among the three-dimensional buildings where you can even find these spots. So exactly right.

Roger Seheult:

Yeah. Um, and of course, on you know, on satellite maps, you can also see where the um where the trees are, and uh and you can also put that into it as well. So you can actually map out the best trip to maximize the the time that you're gonna put into this and actually get the most amount of benefit in terms of infrared light.

Dave:

Very it's very interesting. I th I think it the the other side of this is you and you mentioned about LED lighting as well, is if you're inside and all your lighting is LED, then you're not getting anything in terms of infrared. So, you know, there is a simple thing which I talked to to Glenn and Bob about about just swapping out LED light for uh incandescent bulbs, old incandescent bulbs. And y incandescent bulbs actually give you quite a good dose of infrared.

Roger Seheult:

Yeah, I mean there there's uh there has been a debate I saw going back and forth on X about whether or not the amount of infrared light coming from an incandescent light bulb would be enough to have any sort of clinical outcomes. And um and and of course the the topic that you just described, which is switching out a LED bulb, a commercial LED bulb which has no infrared light in it at all. Uh just as a note to those watching, it is possible to make LED bulbs that have infrared in it. And we're actually, we could talk about that clinically in a clinical setting. But I know you're you're talking about commercial LEDs that are sold that are required to be in homes so that they don't use up excess energy, creating, quote, wasted light in the infrared spectrum. Um but you know, Glenn Jeffrey has a paper right now in review where he actually ran in a randomized fashion put 60 watt incandescent bulbs, not not replacing LEDs, but just adding them to that environment. So if people are concerned about that and they've got, you know, LED bulbs in their ceiling that are not screw-in, that they can't replace with an incandescent without having a huge contract uh cost to go in there and replace those out, and they want to know what they can do. First of all, I would say the best thing to do is to get outside. Okay. But if they're working in that environment and they want to make that environment healthier, um paper in review right now, Glenn Jeffrey being looked at where they randomly put 60 watt incandescent light bulbs into those work environments. And he was able to show that the mitochondria, specifically in the retina, uh, revved up enough to improve, uh, to produce enough energy that the colorblindness in the proton and the tritan, those are colorblindness thresholds, were actually dropped statistically significantly. So what's interesting about that is that it was very robust. Uh it worked very well in both uh types of colorblindness. Glenn Jeffrey is a professor of ophthalmology at UCL. He uh this is how he assesses mitochondrial function in the tissue of the body that has the highest mitochondria. And this was a regular work environment, unstructured, uncontrolled in a sense uh that it was it's in an everyday working environment. He very showed very clearly in this office building at UCL that the windows on the structure were very uh efficient at blocking infrared light. He took a photograph inside the building. It was pitch black, except for the light that was coming through the open door. Um he took another photograph with all the LED lights on in the infrared spectrum, and it was pitch black. There was no light. So uh I I think I think that basically that study has answered the question, at least as far as I'm concerned, can incandescent light bulbs inside the home, just one added to an LED environment, cause enough of a change in the human body to actually cause an end organ uh difference? And the answer is yes.

Dave:

It's incredible how finely tuned our bodies are to, it turns out, to things like infrared. And I think, you know, it's uh the more I've kind of listened to people like Glenn and you and some of the others talk about it, the more miraculous I think that you sort of realize that the human body is. And it's I I think one area that I'm just like confused by is how this was overlooked for so long, you know, that uh you you know, we are we're in the UK, I guess in Europe, in the US, we're heading for this sort of low-energy future, but nobody at any stage has gone. Maybe incandescent bulbs were doing something else. And by the way, you know, I mean, I was talking to an architect friend who, you know, he he was delighted when I told him this news because he's like, Well, the light from an incandescent bulb is so much nicer, and I know that because I've sort of replaced all my bulbs, and I'm like, I just I feel so much more relaxed just sort of looking at them compared to I've got two LEDs sort of facing off to me, and I I can sort of feel so but he was saying, you know what they give off warmth as well, you know, that infrared is warmth, and actually ambient warmth in homes is no bad thing in winter as well, you know. So um anyway, it's a it's a it's a really interesting topic, and um so people starting to think about putting uh incandescent bulbs in, and I know Bob Fosbury said like and and Glenn said the cheapest thing to do is just get an angle poise lamp and get you know an incandescent bulb, put it in your room, and that will probably be enough to kind of keep you keep you going. So then the we again we touched on it, which is ultraviolet and vitamin D. You know, I think one of the things that we do see is vit people's vitamin D levels dropping off over winter because we're not getting like even if you're outside you're not gonna get that the levels of UV that you do in the summer. Is there things that people can do to kind of food they can eat or supplementation or you know, just sunbeds, or you know, is there stuff people can do to kind of really or or I wanna I wanna add maybe is it maybe just the way it is?

Georg:

Like if you live in the like further northern hemisphere and you you just need to shift your your lifestyle, like not winter hibernation, but maybe just um be also in in acceptance that winter is just a different time of the year where you maybe have a different life.

Roger Seheult:

Yeah, it's it's possible. So we've talked about ultraviolet sorry, infrared light. Um what let me just finish that topic off. There's uh for those of you that can do hydrocarbon fires in your fireplace, right? That's a source of infrared light as well. Um and obviously that's very common in the wintertime. So that may be helped mitigating that. So something that we used to do culturally. Uh society used to have fires. That's how we would warm ourselves, even through uh a glass, that infrared light's going to penetrate uh through there. So um, but ultraviolet, yeah. So that's, you know, interestingly, Bob Fosbury uh has some data that uh even though the sun itself may be too low in the sky during the wintertime to give off enough uh ultraviolet, there is some evidence that the scattering of ultraviolet light into the sky may be enough to give some ultraviolet. But nevertheless, the the point is that if you look at human beings in an epidemiological way, we have less vitamin D in the wintertime than we do in the summertime. And so the the only, well, one of the ways of supplementing that is through diet, uh taking supplements. Another way of doing it is to get into tanning beds. So the problem I see with tanning beds is that you're getting just ultraviolet light generally. I mean, there are tanning beds that can do both, but generally the purpose of tanning beds is to give ultraviolet radiation, which stimulates melanocytes, which gives you a tan. And uh it's also the ultraviolet light that makes vitamin D. The issue with that is that there's been a lot of associations of skin cancer with that type of behavior. So I'm not sure I can really uh wholeheartedly, full-throatedly uh uh recommend doing tanning beds to get your vitamin D. It may be safer to supplement with uh vitamin D. So, talking about vitamin D supplementation, there's two types, two forms of vitamin D. There's vitamin D3 and there's vitamin D2. The other name for vitamin D3 is co-calciferol. And uh that co in there is the same co that we see in cholesterol. And cholesterol is only seen in animals, it's not seen in plants. And obviously, since we are an animal, uh, the skin takes cholesterol, a cholesterol derivative, and using the high-energy photons of ultraviolet B radiation is able to actually break uh double bonds and convert it into vitamin D in our skin. So that's vitamin D3 in our skin that we can make. You can also supplement with vitamin D3. It has to come from an animal, generally speaking. And I would say 90% of the vitamin D3 on the market is coming from lanolin, which is a wax that is uh produced with sheep's wool that they uh that they process when they harvest the sheep's wool. And then they uh through some chemical reactions and ultraviolet light, they can make uh a vitamin D3 that you can buy in a capsule. Vitamin D2, on the other hand, is not cocalciferol, but ergocalciferol, which is a plant-based uh steroid or hormone. That is uh a lot of that you can get that in the in shiitake mushrooms, for instance. Uh you put you grow shiitake mushrooms and put them out into the sun. They will make vitamin D2 in in various amounts depending on how long you leave it out in the sun. And uh you can grind that up, put it into a capsule, and take that. That's uh vegan, it doesn't require any animal products. Uh there's also some Nutritional benefits in the mushroom itself that you can get from that as well. Interestingly, the question is vitamin D2, vitamin D3, what are the differences between those two? So they are structurally different. They have a lot of overlap in terms of their effects, vitamin D pathways. It takes usually more vitamin D2 to get vitamin D levels up. And what's interesting though, as they do have some overlap, there are some things that vitamin D3 will do to the human body that vitamin D2 cannot do, and vice versa. One of the things, for instance, specifically is vitamin D3 does seem to have some effect on interferon, which is a powerful substance in the innate immune system. Vitamin D2 doesn't, but there are some genes that vitamin D2 can affect if vitamin D3 doesn't. And I'm wondering, since typically one is created in the skin and the other one is a dietary, I'm my hypothesis, I don't have much proof to this, is I wonder whether or not we need both.

Georg:

Well, this is the first time I'm hearing this. That's really, really interesting. So you would you would supplement both, or would you share what you're doing?

Roger Seheult:

I haven't seen a lot of data. They're usually treated pretty much the same in the literature. They'll say vitamin D2 slash vitamin D3 when they're looking at studies and meta-analysis. But there are some very detailed studies where they've actually looked at the vitamin D2 and vitamin D3 pathways, and there are some genes that one will hit and the other will not, vice versa. I would say the vast majority of the genes and things that they activate, there is a large overlap, and that's why they're sort of treated the same. But there are some very fine, distinct differences. And uh it's they're interesting. They they do behave a little bit differently.

Georg:

And again, like the body um is synthesizing which variant um uh with sun exposure?

Roger Seheult:

Vitamin D3 is the one that is exposed, uh sorry, is the one that is produced in the skin from sun exposure. Vitamin D2 is what is produced in the mushrooms when they get vitamin D. Sorry, when they get ultraviolet B exposure.

Georg:

Aaron Powell So D2 is not in the human body from sun exposure. It's not created through any sun exposure in the human body per se.

Roger Seheult:

Correct. It's only uh taken in by um oral ingestion. Now, there is a D3 that is produced by algae. Uh algae is not is not an animal. Uh I guess it's a plant in a sense. So that's kind of a little bit of an exception there. You can you can get vitamin D3 produced in algae. Um and most of that, I believe, is sourced from the ocean uh when you do that. Um you have to I'd have to look more into that about microplastics and things of that nature. There's also the potential of microplastics in mushrooms, although I haven't seen the data on that. So those are some of the things you have to think about with supplementing.

unknown:

Okay.

Dave:

Well, it's good. I mean, I think like I mean, it's interesting what you said about like um what Bob Fosbury had said about like even with when you don't have direct sun, you you you know, if you've got a blue sky day, get outside because you you know you will be getting some UV from that through through scattering.

Roger Seheult:

But as he has some data, yes.

Dave:

Yeah, yeah, yeah. So I think that's like the the the sort of most basic thing that you can do. But I I've always been slightly confused about supplementation around vitamin D. And it I think you know it's great to kind of hear your your thoughts. And I mean, as you're talking, it kind of almost seems obvious that they you probably would need both, and they're doing slightly different things. But you know, I once again we're sort of in in a realm where we're kind of flying against not perceived wisdom, but the way that things have been kind of set up, aren't we?

Roger Seheult:

You know, uh you you had asked the question before about uh about sunlight and why didn't we realize this before? Um the actual the answer to that, uh if I could try to make an attempt at a stab of that, is we we actually did know about this before. We about knew about a hundred years ago, and you know that too. Uh it's just it it's not it's not in our consciousness anymore because it's so many generations back. But if you look at the old photographs and you look at the sanitariums and you you read people like um, you know, Florence Nightingale and many other health reformers that were in the late 1800s, early 1900s, uh they knew clearly that there was no question in their mind. It was almost uh a foregone conclusion that sunlight, fresh air were very good for people. And what happened, I believe, is you know, it wasn't a bad thing in and of itself. We discovered penicillin, we discovered medications, we discovered uh uh things through randomized controlled trials. And I I believe that that we sort of took for granted some of the things that we knew worked, and and it's what we did was something that I think is very pervasive in society at all times, and that is instead of going into a understanding with an and, we tried to do medical reductionism and go to the or. So in other words, it wasn't the argument wasn't sunlight and fresh air and hey, let's implement some of this new technology in the form of medications and randomized controlled trials and penicillin. It was, hey, we have a new way of treating things. We're gonna do this instead of sunlight and fresh air, and we'll be able to build bigger hospitals and put more patient rooms in there so we can treat more patients and they won't have to have all this space and sunlight, and we can architecturally actually be able to treat more people. And I think there was sort of a bottom line there. Uh, but what they did, uh, they may not have realized this. What they did when they did that was they be they made healthcare dependent on a supply chain. And when you when you do that, when you make instead of going to an and type of situation, so sunlight, fresh air, all of those things that we were doing, you know, 100 years ago, and you add to it all of these other things, you can still say, you can still fall back on a backstop of if the supply chain crumbles, you still have fresh air, sunlight, and all these things that we know how to do how to implement. What I believe, unfortunately, what happened, maybe unconsciously, maybe over decades, is we abandoned the knowledge of what we used to be doing in hospitals, sanitariums, and things of that nature because we had to. And we said, hey, we've got this new technology, we have this new way of doing this. And we didn't think about pandemics, we didn't think about supply chains, we didn't think about all of the things right now that are plaguing our world in terms of how do we get enough medications to enough people and get past international disruptions and supply tra uh supply chains and natural disasters. Uh, because if that were to happen, because we've we have made this decision of an or instead of an and, we've completely put all of our eggs in that basket of pharmacological uh uh distribution. Now what happens is if we have a supply chain disruption and we have need, we have no, we have nothing. And then we could we how hard is it now to go back and say, well, this is something that we used to do, but nobody's trained on that. Nobody even understands that that's even an option. And I think that's where we are right now.

Dave:

It's really interesting because I as this sort of review going back to old you're totally right. I mean, I hadn't thought of it. Like we've got to retrain ourselves. And I guess one of the ironies of COVID, for you know, because I mean as an ICU doctor, you'll know this better than anybody. But you know, if people were outside in the sun, their chances of survival went up dramatically. But one of the ironies is is it pushed people inside. So we have whole cohorts of of children and teenagers who they they they forgot how to go outside and play, basically, and do all of these things. And you know, it's it's how it's almost imperative that we start unlearning all of this stuff. So, you know, when I was growing up, I mean I grew up in the tropics, but you know, I'd go to church on a Sunday, would have Sunday lunch, and then my parents would always say, Right, time for a walk, and I would sort of amble off behind them and you know, sort of like, why are they doing this? But then, you know, that was the way things were done. People that was you know, traditional, wasn't it? But it was good, wasn't it? Because that leads to that one day you were kind of outside uh for a few hours, you know. But you know, going back a few years, we all spent a lot more time outside anyway. But anyway, I was just sort of wondered about your thoughts around like the what happened with COVID in terms of pushing people inside.

Roger Seheult:

Oh, absolutely. Well, we know we've got data. Uh there's actually data that shows that the time spent outside the home had been decreasing on a on a on a on a scale, uh a gradual scale. And then when the pandemic hit, that thing just fell off the face of the planet, just dropped dramatically. And then after the pandemic ended, it did not rebound. In fact, it came up just slightly and is now continuing to fall down even further. And what happened? This is something that we see all the time in in psychology, is we learned new pathways. We knew learned new behaviors to to prevent us or to allow us to stay inside the home. Things that used to get us outside the home, that uh like shopping, like uh meeting people, all of these things, we learn new ways of getting around that. And now we've learned those pathways. We we we're not gonna unlearn them, and now we have even less need to go outside.

Georg:

And the side effect is that those new pathways involve like screen-based dopamine addiction and people are just sticking to the screens more. I mean, I think this is something we can really observe on ourselves as well. It's it's really wild, so yeah.

Dave:

Yeah, I mean um it's really because I think what's happened is convenience. We the pathway is convenience. Like, you know, because Amazon can deliver, and you know, every day we have a queue of people delivering stuff to us. Because Amazon can deliver, we're not going to the shops, you know. And because we can get like groceries delivered, we're not going to the soup. So all of these things that we used to do mean that we're kind of spending more and more time in inside, as you say, from a kind of convenience point of view. So then what you've got to do, and I guess this is part of this podcast, is if people want to feel better in winter, they have to retrain their pathways. And one of the simple pathway things to do is to get outside more, you know. So, like if even if it's raining and cloudy and miserable, you're gonna get, like, as you were describing, those that dose of infrared that your body kind of craves, aren't you? So, you know, and I think it's fascinating that that that that's a conclusion, you know, that's a no-cost solution to this whole thing. Um so the there's something else that I was I've been pondering quite a lot, which is saunas. So, you know, I'm a huge fan of sauna, Georg and I, you know, we we we've We do business in the sauna. We do business, you know, we think the sauna is the new golf course, to be honest with you.

Roger Seheult:

So I I I think there's an old story of of uh some some dispute between uh the Russians and the Finns, and they settled it naked in a Finnish sauna.

Dave:

Well, there you go.

Roger Seheult:

Something about when the general takes off the uniform, he doesn't have all the badges and stuff, and you just have a one-on-one conversation and settled settle the issue. I think that's what what we need for that.

Dave:

If you see where saunas are kind of distributed, they tend to be like, you know, northern hemisphere. Something's gone on, but that sort of heat treatment in sort of extreme heat treatment in winter seems to have remedied something. So have you got any clues as to what's on the what's happening to the body in the sauna?

Roger Seheult:

Well, it's interesting because when you look at the Swedes, very famous study, 2016, uh sunlight exposure in women, 20, 20,000, 30,000 women, was associated with an all-cause reduction, not only in all-cause mortality, but cardiovascular, non-cardiovascular cancer, non-cancer mortality. In fact, the magnitude was so high that that women who went outside avidly got sunlight and smoked had the same mortality as those women that avoided the sun and didn't smoke. So huge mortality difference. Yeah, the lingquist study. And of course, by the way, that study was repeated by Richard Weller just last year, UK Biobank, ten times the number of subjects, both men and women, exactly the same findings, no increased statistical significant increase in melanoma incidence or mortality. So there's that data, but then there's also the data that we get right next door in Finland. So multiple studies where everybody saunas, you know, your control group is the one that is the one guy that does it once a week. Uh, everybody else does it twice, three, four times, seven times a week. And so you can see a dose response curve. Uh Rhonda Patrick's talked about this quite a bit on her channel and gone over the data. So, you know, it's an association, so you can't really say causation. However, Bradford Hill criteria clearly states that if you see a dose response curve, then it does imply that there is some causation there, right? So someone who does it three, four, five times a week is going to get a a better reduction in all-cause mortality than the guy who just does it once a week, who's probably still getting a benefit, but you've got to compare it to somebody. I mean, let's face it, if they were to at one point in Finland tell everybody to go into their sauna at the same time, there would be enough room in Finland for everybody to go into a sauna. That's how many saunas there are in Finland. It's it's crazy.

Georg:

The Swiss built bancas and the Finns built saunas and each injury on the on their own. Yeah, no, it's what about cold exposure? Going to the sauna usually also involves to really cool down directly afterwards than uh more people like doing ice baths. And we we had like the solar athlete on our podcast quite recently. He was talking about the the massive benefits of cold exposure, especially in winter when you get less sunlight. Do you have any insights on that? I don't.

Roger Seheult:

I've been looking into that because I do believe my hypothesis is that this is what anthropologically, those cultures and societies, let's face it, right? Let's back up here. Um, if we were to go back in time far enough to see where you know human civilizations began, they b they began near the equator. And they probably had very dark skin. And as those cultures and societies moved away from the equator, sunlight was such an important uh factor in human in human life that they adapted by reducing the amount of melanin so that sunlight could come in even better uh at higher latitudes. And this is the reason why people, generally speaking, in higher latitudes have lighter skin than people at uh at the equator. So, but did that did that completely fully um uh you know t uh compensate for that lack of sunlight? It it may have, it may not have. They may have, through society, figured out because they were susceptible to infections, that when people went into hot saunas and did these things, that they actually uh did better. And I agree with you. I think the the very thing that you're showing here is that it's the high-latitude societies that have adapted in their culture the use of sauna. And so I have to believe that there's got to be something there. We know from epidemiological studies that that's the case. We know from physiological studies that it's an exercise equivalent, and that reduces all-cause mortality and things of that nature. So I agree. Uh the studies, by the way, for those of you who are listening to this and say, I want to do that, um, the studies show that really you need to be above, I'll put it in terms of Fahrenheit. I don't know what it is in Celsius, but in Fahrenheit, it's got to be 174 degrees for at least 20 minutes to really show a benefit. And then, as you said, Garrett, cool cooling down afterwards. And and this is another thing. This is amazing. I know that uh that it's it's finished culture and society to take birch trees and sort of uh you know flagellate themselves to try to hit themselves. I don't I don't know if they knew why they did that, but I think what it what it shows is that it's causing better vasoconstriction, it's causing demargination of the white blood cells when you go into a cool environment or a cold environment. And but not only does it do that, but when it also vasoconstricts, it's preventing the heat that you have just spent the last 20 minutes building up from coming off of your body as well. And so you lock in that heat, it keeps it up higher longer, you get a better benefit from it.

Dave:

So, I mean the other thing is sort of sauna hats as well, which again, like I I I I mean, I don't know what the science is behind them, but it was in Austria. I was in a in a sauna and there was a lady wearing a hat, and I was like, Whoa, that looks ridiculous. Um but then I sort of read more about it that it's quite and you know, I guess the science is it locks in the heat as you're describing in because your head is a is where a lot of heat is lost from your body, isn't it?

Roger Seheult:

So um it's it's interesting, you know, when uh going back to that time a hundred years ago in the United States, the the largest hospital in the world was the Battle Creek Sanitarium run by John Harvey Kellogg, who was a big believer in all of these things that he went around the world learning about sunlight, hydrotherapy. I remember seeing a photograph where there was a long hallway with little holes out of these individual rooms, and there were heads popping out of these holes, and you could see them all the way down the line, and their bodies were in the treatment rooms and they were being heated up to I don't know what temperature, but exactly.

Georg:

I was once in such a sauna, like where you're just locked until your until your neck, and you can stay in the in them forever. Because I think also the sauna heads they they kind of protect your head from heating up so much because that's where it gets uncomfortable, and then you need to get out of the sauna. And also like these saunas where your head is um still in the regular temperature, you can stay in them forever and your body is like sweating and everything, but it's super comfortable because your head is not overheating, so yeah. Yeah. Yeah.

Dave:

So the uh so the other thing, I mean, we're we're sort of uh look, we could talk all day, but I I know that you've got um a busy day ahead of you. Gail said something which I think is really interesting, which is actually sometimes you just need to be kind to yourself and say, you know, in winter things will change. Like your body is designed to slow down a bit in winter. So rather than kind of getting upset about it, maybe just sort of listen to what your body's telling you a bit more and go to bed earlier or slump in front of a fire, or you know, just just be a bit more kind of relaxed about the whole thing. And you you know, it was listening to your stuff around New Start when you went on the Huberman show, and I that got me thinking about so many things. So thank you so much because it's made such a difference to me. But one of the things I felt was uh actually you were telling me things that if I was honest with myself, I I knew I just had not listened to myself enough. You know, so I just wondered if you've got any thoughts around being kind to yourself as well, around yeah, you know, as we go into winter time, not being too worried if you do feel a bit down.

Roger Seheult:

Yeah, I think that's a really important point. It's one point that is not lost on me as a sleep physician. Many times in uh patients that come to see me for insomnia, they are very the the term that we use is psychophysiological insomnia, and it's simply this is that the anxiety of not being able to sleep is a self-fulfilling prophecy. And so if you are anxious about the fact that uh something is happening, that's not good for your body either. And it's adding an undue burden. Um and so there comes a point in time where you say, I've done everything that I can do, and I just need to be happy with what the results are and just be satisfied because any further uh worrying about something that you can't change is not really going to help the situation.

Dave:

That's really interesting. Well, listen, thank you so much. I mean, as as it happens, I'm heading off to uh the Middle East tomorrow, where you you know, it's basically permanent winter for them because they're all inside the whole time because of the heat and things. So, you know, and I think they've got an epidemic of vitamin D deficiencies and uh, you know, so one of the things I'll be talking to to people in the Middle East about is actually you need to readdress the balance that you've got with the sun, you know, and I think that's very difficult where you know the temperature in Dubai tomorrow is 40 degrees, it's almost impossible to go out at 40 degrees. But you know So it's kind of interesting that all of these things around physiology, you know, winter is is something that we've got to kind of face, but I think is very durable. You know, the Middle East they have to do they've got to face it as well, but they've got to come up with different solutions.

Roger Seheult:

So Yeah, in the Middle East, I would say that that is very they're very susceptible to technological advances because it's so much more comfortable going into an air-conditioned building for the whole day, every day, when it's 40 degrees outside for months on end. Yeah.

Dave:

Yeah, well I'll be I'll be taking a few incandescent bombs to give to people as presents. So um, you know, I don't know whether you can get them in Dubai or not, but it's it's it's very interesting.

Georg:

But listen, I'll wrap this up, Dave. Um, can I just ask two final questions? Because it's really hard to get Roger on a call, and I think it's really quite the honor, so thank you, Roger. But um, like maybe quickly recapping what what we what we talked about vitamin D, so I have two questions. The first one is I have I have heard a few times already that vitamin D it's only one artifact of UV sun exposure. So if people just think they can replace sun exposure solely by vitamin D, do you have any information on what else UV creates in the body? Are there any hints already, or is it um still in research? Yes.

Roger Seheult:

Uh so if I didn't know, I would say it would be a bad assumption to just say that it only does one thing. Again, this is our medical reductionism that says since I know something, then that must be the only thing because things must be simple. No, things are very complex. There are there there are likely many things. I I think in the hypothalamus and the pituitary and uh the the um the way that the light interacts with our pituitary gland and the pineal gland and all of those, that there's more to life than just vitamin D from the sun. Absolutely.

Georg:

Thank you. And the other question which also comes up all the time I myself had skin cancer like 13 years ago, melanoma, and and I'm not using sunscreen anymore. I'm out in the sun as much as I can, and I'm not afraid anymore. But still, like that's the common belief that the sun is dangerous, you get skin cancer if you're exposing yourself. But then what I've heard in the past a few times already is that all the studies concerning skin cancer have been uh have been done with artificial UV lamps without any infrared aspect, and I think you've mentioned it before. So I think the the infrared aspect is crucial when you have UV exposure. Um and can you confirm like because it would be really, really interesting to finally like really clarify that there have not been real skin cancer studies happening with actual sunlight.

Roger Seheult:

Yes. So my understanding, so let me point to some of the data. Richard Weller, who I would who's a dermatologist, University of Edinburgh in Scotland, uh, and actually will be coming up very shortly in uh giving a lecture in England. Um uh you may want to give away.

Dave:

Tomorrow. I think on Wednesday.

Roger Seheult:

Yes, yeah. So by the time this podcast comes out, he probably will already be out. Um and and and he did a study, UK Biobank, uh, I think it was 300,000, 400,000 subjects looking at um solar radiation data, solariums, and over, I think, 12 and a half years, if I'm not mistaken. And what he showed was that uh even in people who got the highest sun exposure, the very same people that had the lowest mortality in that study, that there was no statistical significant increase in melanoma. And there was certainly uh the confidence intervals were very wide on the mortality, meaning that there was no absolutely no trend at all in terms of what was going on with mortality from melanoma. What I have heard from dermatologists is this is that the deadly type of melanoma usually appears on the skin that is not exposed to the sun. That's the first thing I've heard. The second thing I've heard is that when you look at what determines mortality, what are the risk factors for mortality or for in you know uh improvement or survival in melanoma, it's very counterintuitive. So, you know, uh solar elastosis, which is basically skin damage, uh sun damage, that is actually predictive of a better outcome with melanoma than if you don't have that. So, in other words, it seems as though melanoma may be being caused by other factors, that sunburn may be one of those factors. So we want to avoid sunburning, of course, but that sun exposure is actually a mitigating factor, a reducing factor on uh on melanoma and its properties based on some of the risk factors we're seeing. Look, I I'm not I'm not here to say anything definitive. I am not a dermatologist, but I think the one that would be able to answer that question precisely and probably with much more data is Richard Weller. And there is actually a review that he did that was published in a dermatological uh journal, actually a very prestigious one, the Journal of Investigative Dermatology. And uh it's titled Sunlight, Time for a Rethink, where he actually goes over the data of sunlight, sunlight exposure, and it's its risk-benefit ratio between the fact that we see such clear benefits from all-cause mortality, cardiovascular mortality, non-skin cancer, cancer mortality. And on the other hand, we see maybe a uh uh I mean, maybe we see it, maybe we don't, about melanoma and non-skin or skin cancer, non-melanoma skin cancers on the other side. So all that to say is that he believes, and and and I believe societies, and he shows this, are coming around to this thinking that we really shouldn't be having blanket statements for everybody about whether they should be in the sun or not in the sun. It should be individualized based on skin type, skin color, history of melanoma, history of skin cancer, and and uh a number of various things to really optimizing because if we tell people to avoid the sun at all costs, it is coming with a cost. It really is coming at a cost. And so um the answer to that I think is going to be more nuanced.

Dave:

Fascinating. We will um, as you say, I think Richard Weller's talk is in a couple of days' time. By the time this podcast comes out, it should be we should have the published um version because I think the Guide Foundation very kindly are publishing all of the videos on YouTube, so we'll put a link into that. But I think it's a it's a fascinating topic. Well, listen, Roger, thank you so much. I sort of walk away from this, you know, with like my plan for winter, which is actually to spend a lot more time outside. Um actually look forward to uh cloudy days rather than you know worrying about uh whether it's gonna be sunny or not. Um think about supplementation, definitely get into the sauna because I love a sauna so I don't need an excuse. I gotta try a bit of cold. Um you know, so I actually did a plunge on on Saturday and you know found that quite good and then went for a swim in the lake, and the lake was like 13 degrees, so that was that was pretty cold.

Georg:

How many kilometers, Dave?

Roger Seheult:

I was only one and a half kilometers, and then you know, but but but I I'm feeling a lot better about winter already, so thank you so much for for Yeah, and and for I would say for those people that uh go to work and they don't get to see the sun before they go to work or after they go to work, try taking that break outside, uh at the very least.

Dave:

No, I think that's very, very good advice. So thank you so much for joining us.

Roger Seheult:

Thank you so much.