Using Red Light to Improve Metabolism & the Harmful Effects of LEDs | Dr. Glen Jeffery

Andrew Huberman: Let's talk about indoor lighting, because I am very concerned about the amount of short-wavelength light that people are exposed to nowadays, especially kids.

Glen Jeffery: Mm-hmm. This is an issue on the same level as asbestos. This is a public health issue, and it's big. And I think it's one of the reasons why I'm really happy to come here and talk, because it's time to talk. When we use LEDs, the light found in LEDs, when we use them, certainly, when we use them on the retina looking at mice, we can watch the mitochondria gently go downhill. They're far less responsive. Their membrane potentials are coming down. The mitochondria are not breathing very well. Can watch that in real-time.

Andrew Huberman: Welcome to the Huberman Lab podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. My guest today is Dr. Glen Jeffery, a professor of neuroscience at University College London. In today's episode, we discuss how you can use light, in particular red, near-infrared, and infrared light, to improve your health, and no, not just by getting sunlight, although we do talk about sunlight. Dr. Jeffery's lab has discovered that certain wavelengths or colors of light can be used to improve your skin, your eyesight, even your blood sugar regulation and metabolism. Dr. Jeffery explains how light is absorbed by the water in your mitochondria, the energy-producing organelles within your cells, to allow them to function better by producing more ATP. He also explains how long-wavelength light, things like red light, can be protective against mitochondrial damage caused by excessive exposure to things like LED bulbs and screens, which of course we are all exposed to pretty much all day long nowadays, and simple, inexpensive, and even zero-cost ways that you can get long-wavelength light exposure, and again, not just by getting more sunlight. He explains that long-wavelength light can actually pass into and through your entire body, and that it scatters when inside you. Now, that might sound scary, but it's actually a great thing for your health, because that's how long-wavelength light can improve the health of all your organs, by entering your body and supporting your mitochondria. Believe it or not, certain wavelengths of light can actually pass through your skull into your brain and help promote brain health. During today's episode, we also discuss new findings that correlate the amount of sunlight you're exposed to with longevity. Those are very surprising findings, but they're important. Also, why everyone needs some UV light exposure. And we discuss whether it's important to close your eyes when using red light devices or in red light saunas, and how best to apply red light and things like infrared light in order to derive maximum health benefits. Today, you're going to learn from one of the greats in neuroscience as to how to use light to improve the health and longevity of any and every tissue in your body, and the mechanisms for how that works. Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero cost to consumer information about science and science-related tools to the general public. In keeping with that theme, today's episode does include sponsors. And now for my discussion with Dr. Glen Jeffery. Dr. Glen Jeffery, welcome.

Glen Jeffery: Thank you. Thank you very much.

Andrew Huberman: We go way back. Later, I'll tell a little bit of the story and why it is truly unforeseen that we'd be sitting here talking about what we're talking about. But it's great to see you again. And I'm super excited about the work you've been doing over the last few years, because it's completely transformed the way that I think about light and health, light and mitochondria. And frankly, every environment I go into now, indoor or outdoor, I think about how that lighting environment is impacting my cellular health, maybe even my longevity. So, if you would be willing, could you explain for people a little bit about light as, let's say, the visible spectrum, the stuff that we can see, and the stuff that's kind of outside what we can see, as a framework for how that stuff impacts our cells? Because I think without that understanding, it's going to be a little bit mysterious how it is that lights of particular colors, wavelengths, as we call them, could impact our mitochondria the way they do. But with just a little bit of understanding about light, I think people will get a lot more out of our conversation.

Glen Jeffery: Yeah, sure. We think about light purely in terms of the light we see, and that's perfectly natural. And the light we see runs from deep blue, violet, out to pretty deep red, deep bicycle light. And that's what we see. That's what we're aware of. The trouble is that actually there's a lot more of it than that. The sun kicks out a vast amount of light that we don't see. So, let's say the visual range is, just grab the numbers, which is, say, 400 to 700. That's our spectrum.

Andrew Huberman: Nanometers.

Glen Jeffery: Yeah, nanometers.

Andrew Huberman: And there we're talking about the wavelength, how bumpy those wavelengths of light are.

Glen Jeffery: Yeah. Yeah. Sunlight extends out almost to 3,000 nanometers. Just think about it. Which is a big, big range, and then that's in the infrared. And on the other end, the bits that we don't see, the deep, deep blues and the violets, that goes down deeply to about 300 nanometers. Now, this is a continuum. We parcel it up because there's bits we see and there's bits we don't see. But you can think about it as a continuous wavelength, and the wavelength gets longer and longer and longer as we go out into the deep red. So, short-wavelength lights, the ones just below blue, they're very, very high frequency. They carry quite a kick, and that's why when you're sitting in the sun and you get sunburned, it's mainly because of those ultraviolet short-wavelengths that are present, and then you go beyond our visual range, beyond 700, and the wavelengths become very, very long, and they carry a certain kind of energy, but they don't carry the kick. So, the important point to think of is when you go out in sunlight, you see all these colors, blues, greens, reds, but there's so much out there that you don't see. And we thought probably you didn't need to be aware of. But nearly all animals basically see this visual range that we have.

Andrew Huberman: Red, orange, yellow, green, blue, indigo, violet, right?

Glen Jeffery: Blue. Yeah.

Andrew Huberman: We can separate those out by shining light through a prism.

Glen Jeffery: Yeah.

Andrew Huberman: Think the cover of the Pink Floyd "Dark Side of the Moon" album.

Glen Jeffery: Pink Floyd album. Yeah.

Andrew Huberman: And that's separating out the different wavelengths. You say that the short wavelengths have a kick. I want to talk a little bit about what that kick is. We distinguish between ionizing and non-ionizing radiation. And I think for a lot of people, they hear the word radiation, and they think radioactive, and they think that all radiation is bad or dangerous. But in fact, light energy is radiating, right?

Glen Jeffery: Mm.

Andrew Huberman: So, it's radiation energy, but at the short wavelengths, below UV, they are ionizing radiation, and maybe we could just explain what that means, how that actually changes our cells. Because if we get too much of that, it indeed can alter our DNA.

Glen Jeffery: I think the important point to think about is not only what the wavelengths are, but also how a body responds to those wavelengths. So, let's bounce back a little bit to, for instance, the sunburn. We're getting sunburnt because the body is blocking those wavelengths. Those wavelengths cannot penetrate very far. So, when you're out on a hot sunny day, and part of your body goes pink, it's going pink because it's blocking those wavelengths. So, the energy is not being distributed throughout the body. The energy is hitting the skin, and you're getting an inflammatory response to it. Now interestingly, we block those from our eye because our lens and our cornea also blocks those short wavelengths. So, that's part of the reason why we don't see them, but it's also the reason why, for instance, people get snow blindness because it's just sunburn on the cornea and the lens. It's recoverable from, but it's very painful.

Andrew Huberman: And with age, some people who get a lot of sun exposure will get cataract.

Glen Jeffery: Yes. Yeah.

Andrew Huberman: Which is kind of the lens becomes more opaque.

Glen Jeffery: It does. And I've heard that described as being the lens being cooked.

Andrew Huberman: Mm-hmm.

Glen Jeffery: But in actual fact, I used to run the eye bank at Moorfields Eye Hospital, Eyes for Research, and you can actually open a patient's eyes up when they're dead, and you can look at the color of the lens, and you can get a rough idea of how old that person was.

Andrew Huberman: Mm-hmm.

Glen Jeffery: So, one of the surgical procedures that medics love is to replace a cataract. Take an older person, they've got this thick brownish lens, and pop it out and put a clear lens in, and the instant response in 90% of them is, "Wow!"

Andrew Huberman: In the patients?

Glen Jeffery: Yeah.

Andrew Huberman: These are live patients? Yeah.

Glen Jeffery: Yeah, live patients. It's done under a local anesthetic in older patients, and they just go, "Wow! Isn't that amazing?" Suddenly, they're getting a lot more light in their eye.

Andrew Huberman: Mm-hmm.

Glen Jeffery: Because the lens was brown, it blocked a lot of the bluer wavelengths, and so they go, "Everything is very bright. Everything's very sparkly." And it was quite a dramatic response. But the interesting thing is, two days later they said, "Yeah, it's gone."

Andrew Huberman: Hmm.

Glen Jeffery: And the brain kind of readapts that visual input from the retina. But going back over the literature of replacing cataracts, it's quite interesting. It tells you actually quite a lot. Now, when we put those plastic lenses in, we have UV blockers in them, so you don't actually get a lot of short wavelengths coming through. But it was certainly the response in the earlier days when we didn't have UV blockers of people saying, "God, that's sparkly."

Andrew Huberman: I see.

Glen Jeffery: "That's really sparkly."

Andrew Huberman: Yeah, the sparkliness being those short wavelengths.

Glen Jeffery: Yeah.

Andrew Huberman: Like, think of off the top of water on a really sunny day. So, I think the takeaway for me is that we should all be protecting our skin against too much UV and other short wavelengths, and we should probably protect our eyes against too much ultraviolet exposure over time. We know that you don't want the mutations of the skin, or the clouding of the lens.

Glen Jeffery: Yeah.

Andrew Huberman: I mean, you pointed out you can replace the lens, but I think at the same time we need UV, right? I mean, vitamin D production requires UV exposure.

Glen Jeffery: Mm.

Andrew Huberman: Do we know how that works, what that pathway is?

Glen Jeffery: Yeah, we've got a fairly good idea, but I want to just take you back a step, if I may. There's some really fantastic work coming out at the moment where a few dermatologists are reevaluating the issue of sunlight on the human body, and the leader of that is a character called Richard Weller from Edinburgh, and he's going back over all the data. And Richard's coming out and saying, "All-cause mortality is lower in people that get a lot of sunlight." And his argument is that the only thing you've got to avoid is sunburn.

Andrew Huberman: Mm-hmm.

Glen Jeffery: The mutations of DNA are occurring really when you've got very, very high levels, not when you've got relatively low levels. And Richard's work has been terribly interesting because he's dug out all the little corners, all the little things that you think about three days later. He's dug out all those little corners, and things like Aborigines in Australia don't get skin cancer. White people there probably are in the wrong place, given their evolutionary stage.

Andrew Huberman: Yeah, high levels of skin cancer in Australia

Glen Jeffery: In the Caucasian population.

Andrew Huberman: Yeah. But maybe they're getting too much sun exposure too fast. The UV index is very high down there, I will say.

Glen Jeffery: Yes, exactly.

Andrew Huberman: I mean, quote unquote, "you feel it."

Glen Jeffery: You feel it. Yeah. Yeah.

Andrew Huberman: Quote, unquote.

Glen Jeffery: Yeah.

Andrew Huberman: It's interesting, I hosted a derm-oncologist on this podcast.

Glen Jeffery: Mm-hmm.

Andrew Huberman: Dr. Teo Soleymani. So, he's a dermatologist who's also in derm-oncology.

Glen Jeffery: Mm-hmm.

Andrew Huberman: So, skin cancer is one of his specialties.

Glen Jeffery: His business.

Andrew Huberman: And he surprised me when he told us that indeed sunburn can lead to skin cancers. Too many sunburns can lead to skin cancers, but that the most deadly skin cancers, the most deadly melanomas, are not associated with sun exposure.

Glen Jeffery: Yes. Yeah.

Andrew Huberman: Those can occur independent of sun exposure, and they often occur on parts of the body that get very little sun exposure.

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: Like the melanomas will show up... I think Bob Marley died eventually from one that started between his toes or something, or on the bottom of the foot.

Glen Jeffery: Mm. Mm-hmm.

Andrew Huberman: There's a lot to unpack about the relationship between light and skin cancers, and I'm going to chase down the literature trail of this Weller guy.

Glen Jeffery: Well, Richard Weller is very interesting. I think he said he hasn't got any dermatological friends anymore.

Andrew Huberman: Probably not.

Glen Jeffery: But he also pointed out that if skin cancer was directly related with sunlight, then we should find in skin cancer patients very high levels of vitamin D. In actual fact, they've got relatively low levels of vitamin D.

Andrew Huberman: Mm.

Glen Jeffery: So, as you say, that story needs to be unpacked. And what's happened, I think, in the dermatological literature is that we've followed a pattern. Yeah. We've followed an assumption, and it's gone a very long way down the line, and then it's taken a little bit of a rogue to come out and say, "Hang on. We need to take a step back here." And I think Richard Weller's leading that. And we obviously both have an interest in daylight, but his interest in daylight tends to be focused a little bit more on those blue short wavelengths, whereas I'm at the other end of the spectrum.

Andrew Huberman: Mm-hmm. Mm-hmm. Mm-hmm.

Glen Jeffery: But I think he's a mover and a shaker.

Andrew Huberman: Great. Well, I'm excited to see where that literature leads.

Glen Jeffery: Mm.

Andrew Huberman: And I'm glad that somebody's parsing, as you said, all the corners of it, because I think we've been fed a story that excessive sunlight leads to skin cancer. And the data on reduced all-cause mortality in people that get a lot of sunlight, I saw a study out of Sweden. Looks very, very solid.

Glen Jeffery: Mm.

Andrew Huberman: But more data is needed, clearly.

Glen Jeffery: Yeah.

Andrew Huberman: So...

Glen Jeffery: I think that that story... There was a story out of Sweden. There was also a story out of the University of East Anglia. And we're talking big numbers. We're talking very big numbers on that. So, it could have a lot of points that we don't quite understand yet. But I think the solid thrust of it, and the interesting thrust of it, for me, is that all-cause mortality flagships up on that are cardiovascular disease and cancers.

Andrew Huberman: Mm-hmm.

Glen Jeffery: It's not the obvious ones that we'd be thinking about.

Andrew Huberman: Mm-hmm.

Glen Jeffery: So, yeah, let's use the term unpacking.

Andrew Huberman: Mm-hmm.

Glen Jeffery: That one definitely needs unpacking. But from a public health perspective, that's an important area.

Andrew Huberman: Well, I'm certainly a fan of people getting sunlight both in their eyes and on their skin, although not to the point of burning, obviously.

Glen Jeffery: Mm-hmm. Yeah. Yeah.

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Glen Jeffery: Yeah, sure. That area is expanding enormously. And it's expanding enormously in lots of little pockets, and the pockets weren't always talking to one another very well. The first person that came along and said, "Look, longer wavelengths are really positively affecting mitochondrial function," was a lady called Tiina Karu in Russia, and who was very largely ignored. I think she's still alive. I would love to buy her a glass of champagne, if only because she started it off. She kick-started it off. But she was very much of the opinion that mitochondria absorb long waves of light. Parts of the mitochondria absorb it. And one of my studies to try and pin this down was to take a whole load of mitochondria, put them in a test tube, put a spectrometer on them, and a light, and say, "What are these guys absorbing?" Well, I found the point where they were absorbing the damaging blue light, but I could not find the red. I could not find it. There was a lot of stomping around in the lab, who's made a mistake, everyone parceling the blame on. But it changed. It changed because what absorbs long-wavelength light? Well, a most obvious one is water. The sea is blue because the long wavelengths are absorbed. So, someone came along and said, "Is it about water? Is it about water in mitochondria that's doing this?" Mitochondria make energy. They make energy called ATP, and you make your body weight in that every day. It's a vast process, and you make it as a wheel turns round. Mitochondria have these little wheels, these pumps that spin around, but they spin around in water, nanowater. And apparently, I'm not a physicist, nanowater is viscous. So, one idea, I think, which we have to take quite seriously is that the viscosity of water is changing as a consequence of long-wavelength light that penetrates deeply in the body. There is an increase in the spin rate of the motor that produces ATP, and it gains momentum. Now, that is absolutely fine. I can stick with that one. I think that one makes considerable degree of sense, and it gets us over a problem. Mitochondria themselves are not absorbing long-wavelength light.

Andrew Huberman: It's the water that they're surrounded by.

Glen Jeffery: It's their environment.

Andrew Huberman: Mm-hmm.

Glen Jeffery: Okay. So, I think in the end, when you talk about the function of anything, we tend to focus on that thing, and we don't talk too much about where is it.

Andrew Huberman: Mm-hmm.

Glen Jeffery: What's it surrounded by, and how does it influence it? So, the first reaction I think is that the motor starts to go round a little faster. But then something else happens, which is really interesting, which is we start to make more of these chains that make energy. So, let's say mitochondria is a chain, it's a series of things, and electrons are passed along that chain to produce energy. Well, when we give long-wavelength light, we find the proteins in those chains, we find a lot more of them. So, my analogy is that giving red light gets the train to run down the track faster. That's true. But then something detects the speed of that train and says, "Lay down more tracks. We need more tracks."

Andrew Huberman: Hmm.

Glen Jeffery: So, we're finding a lot more protein there that is associated with passing that electron down the pathway to make energy.

Andrew Huberman: Interesting. So, it sounds as if long-wavelength light via water is actually changing the structure of mitochondria and its function as well.

Glen Jeffery: Yeah. I think I would say it's improving the function, and it's influencing more mitochondrial proteins to be synthesized.

Andrew Huberman: Mm-hmm.

Glen Jeffery: So, we've got an immediate effect, and we've got a longer-term effect as well.

Andrew Huberman: Well, one thing we know about mitochondria is that they started off as independent bits of biology and then the eukaryotic cells, which we have, essentially took those in and they became fundamentally part of the cell, and it's passed on through the genome.

Glen Jeffery: Mm-hmm.

Andrew Huberman: So, the idea was that mitochondria were separate from our cells at one point, or from cells, and were essentially co-opted by our cells or hijacked our cells, we don't know which.

Glen Jeffery: Mm.

Andrew Huberman: And then now, because they share a genome, mitochondrial DNA, and genomic DNA, they're passed along.

Glen Jeffery: Yeah.

Andrew Huberman: And it makes perfect sense to me as to why that if they're really of bacterial origin, which we think they are, that they would be absorbing or through the water they would be absorbing long-wavelength light because they evolved in water. I think it's worth us just mentioning this business of absorption versus reflection in terms of colors.

Glen Jeffery: Mm-hmm

Andrew Huberman: I think people might find this interesting, that you said the ocean appears blue because it's absorbing all the red, all the long-wavelength light, and it's reflecting back the short-wavelength blue light.

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: Red stuff does the exact opposite. Like when we see a red apple, it's doing the exact opposite.

Glen Jeffery: Yeah.

Andrew Huberman: It's reflecting the red light back towards us the long-wavelength light.

Glen Jeffery: Yeah.

Andrew Huberman: I think most people probably don't realize that, and then we talk about white containing all the wavelengths, right?

Glen Jeffery: Yes. Yes.

Andrew Huberman: And black absorbing all the wavelengths, right?

Glen Jeffery: Yes. Yeah.

Andrew Huberman: That's the notion.

Glen Jeffery: Yeah.

Andrew Huberman: So, it's interesting to think about light as either being absorbed or reflected back, and makes perfect sense to me why the mitochondria would absorb the red light, but of course I'm saying that already hearing the just so story. So, it makes sense once you hear it, right?

Glen Jeffery: Yes. It makes sense once you hear it. And why the hell did we not think about that five years ago? Scientists make really big mistakes in the pathways that they follow, and they don't talk about their mistakes.

Andrew Huberman: Mm-hmm.

Glen Jeffery: But their mistakes are every bit as important as their great results. Why didn't we think about water? Because our minds were trapped at a certain pathway going down a certain alleyway.

Andrew Huberman: Mm-hmm.

Glen Jeffery: And so, whatever you think about the water hypothesis, the key point is that improvements in function as a consequence of exposure to longer-wavelength light correlate tightly with what water absorbs, right? So, okay, that's a big one. That's a big one. That is there. We know that's true. You can pull it apart and find there are things called water holes, where there are places where water absorbs a bit more than it does in other places. But fundamentally, the absorption of long-wavelength light fits water.

Andrew Huberman: So, much of your work focuses on how long-wavelength light can enhance the function of cells that are not on the surface of the body. They're not on the skin. They're in the eyes, and now we'll get to this data soon, but you published data that long-wavelength light can penetrate very deeply, and even through the body.

Glen Jeffery: Mm-hmm.

Andrew Huberman: Even when people are wearing a T-shirt, like all the way through the body and impact mitochondria all along the way.

Glen Jeffery: Mm. Yeah.

Andrew Huberman: So, maybe we should just talk about long-wavelength light and how it can penetrate through the skin. You mentioned that UV is essentially blocked by the skin.

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: So, if I step outside, for instance, on a nice sunny morning or even a partially overcast morning, but some long-wavelength light is coming through, is it passing all the way through my body and impacting the water and mitochondria of every cell along the way? Is it scattering? I mean, how deep does this stuff go?

Glen Jeffery: Okay. So, let's stand you out. Let's strip you off and stand you out in sunlight 12:00 in July. The vast majority of long-wavelength light is being absorbed in the body, so what we assume is that it has a very, very high scattering ratio. So, the vast majority of that long-wavelength light it's going to get through into your body, and it's going to bounce around.

Andrew Huberman: So, it's going to literally go through the skin.

Glen Jeffery: It goes through the skin, and let's take the simple experiment. The simple experiment was you strip people off, and you stand them in front of sunlight, and you put a radiometer on their back.

Andrew Huberman: Tell us what a radiometer is.

Glen Jeffery: A radiometer measures the amount of energy coming through, okay? And then we put a spectrometer on your back as well, which tells us the wavelength. So, what we get from that, the reading we get from that, is that a few percent, a few percent is coming out the back. Now, we shouldn't concentrate on that. What we should concentrate on is what happens to the rest because it's not bouncing back from the surface of the skin. Very little bounces back. It's being absorbed.

Andrew Huberman: Amazing.

Glen Jeffery: Okay.

Andrew Huberman: Which is amazing.

Glen Jeffery: Well, it's very interesting.

Andrew Huberman: It makes sense, based on the physics of it, but it's amazing, right, that the long wavelength light is actually penetrating our skin, bouncing around in our internal organs, and some's getting out the other side.

Glen Jeffery: Yeah. Yeah. Yeah.

Andrew Huberman: I think that's going to surprise a number of people.

Glen Jeffery: In any conversation like this, we need to talk about silos, people coming from different angles at a problem. And I have the advantage of Bob Fosbury working with me. Bob was lead for analyzing atmospheres on exoplanets with the European Space Agency. He had a lot to do with the European use of Hubble, and a lot of his spectrometers are up on the James Webb telescope. Now, there are super advantages for having someone from another silo to come in, but there are also really annoying issues as well. So, I said, "Bob, I only want to measure whether light goes through the body." And he said, "We all know that. Forget it. It's a waste of time." And I said, "You think you know it based on principles of physics. I don't know it. And actually, I don't think you know something until it's published and everybody knows it and can talk about it."

Andrew Huberman: Mm-hmm.

Glen Jeffery: So, yeah, Bob came along and said, "Yeah, long-wavelength has to go through." But it needed demonstrating. Now, the other thing that Bob did pick up on this and did start to get a lot more interested in it, because then he went through his wardrobe, and he took different layers of clothing from his wardrobe and put long-wavelength lights behind them, and said, "What goes through clothing?" And the amazing thing is long-wavelength light goes through clothing.

Andrew Huberman: It goes through clothing.

Glen Jeffery: It goes through clothing. Okay.

Andrew Huberman: Any clothing?

Glen Jeffery: Well, if you want to wear rubber, I think not. But if you want to wear your standard T-shirt, I think he used six layers, T-shirt.

Andrew Huberman: And does color matter? Like, I'm wearing a black shirt right now.

Glen Jeffery: No. Makes no difference whatsoever. And the other thing we do not know, and this is terribly important, there's lots of we don't knows here, is this long-wavelength light bounces around all over the place.  So, we have got some long-wavelength light sources, and I think I'm shining this long-wavelength light there, right?

Andrew Huberman: Mm-hmm.

Glen Jeffery: And then when I put my instrumentation up, it's all over the place.

Andrew Huberman: Inside the body.

Glen Jeffery: And inside the body, inside the room. It's going every... I can't control it, not unless I start putting materials like aluminum foil to block it.

Andrew Huberman: Mm-hmm.

Glen Jeffery: So, when we think about long-wavelength light, its advantages, we talk about using this device or that device. What we also need to think about is, okay, you've got a small device with a small beam of light going here. It's bouncing all around the room. It's coming in from a different angle and different parts of your body.

Andrew Huberman: But certainly most concentrated in terms of energy at the point source.

Glen Jeffery: Most... Yeah. But you cannot assume that the point source is the only source of that long-wavelength light if you're in a confined space.

Andrew Huberman: Mm-hmm. Well, let's use that as an opportunity to talk about a related study, and then we'll circle back to the let's call it the light passing through the body study.

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: Because the study I'm about to mention, I think, is going to be so interesting to people and a little bit shocking and very, very cool, because it's actionable, which is you did a study showing that even if you illuminate just a small portion of the skin with long-wavelength light, it changes the blood glucose response. Literally, blood sugar response is altered by shining red light on the skin.

Glen Jeffery: Mm-hmm.

Andrew Huberman: And for years, there were these, let's call them corners of the internet that would say things like, "Oh, when you eat out of doors, it has a different effect on your body than when you eat indoors."

Glen Jeffery: Yeah.

Andrew Huberman: But there are too many variables there, right? Because when you eat out of doors, typically it's at a picnic, and then you have greenery, and there's socializing.

Glen Jeffery: Yeah, yeah, yeah.

Andrew Huberman: And no one's going to fund a proper study to parse every variable in a picnic versus an indoor cafeteria.

Glen Jeffery: No.

Andrew Huberman: And it's not worth the taxpayer dollars, frankly. You did the right study, which was to shine light on, what was it, the back?

Glen Jeffery: It was on a small area of the back, yeah. And I must make it very clear, first of all, the person whose idea this was my colleague Mike Powner. And Mike's thought processes were very, very clear. We were on a long drive to do some research well out of London, and that's a great time for... Because the journey starts at 5:00 in the morning, it's a great time for gossip. It's a great time for wild ideas, for streams of consciousness, which sometimes are very important in science. And it was Mike who said to me, "If we make mitochondria work harder, then they need glucose, and they need oxygen." So, pause while Glen, who is driving, kind of has to catch up on this idea. I'm generally about a mile behind him intellectually. And I mean, yeah, yeah. So, he said, "Well, let's not make idiots of ourselves. Let's do it with bumblebees." So, our first experiment was to increase...

Andrew Huberman: Of course, bumblebees. Yeah.

Glen Jeffery: Of course, why not?

Andrew Huberman: Yeah.

Glen Jeffery: First experiment was on bumblebees because it didn't involve people. It was simple to do. And all we did was we starved bumblebees overnight, gave them a standard blood glucose test.

Andrew Huberman: Sounds a lot harder than working on humans.

Glen Jeffery: No, it's not. You just give them a little bit of glucose because they have that and then go, "Dub, dub, dub, dub, dub," and their blood glucose goes up.

Andrew Huberman: Okay.

Glen Jeffery: We gave them red light or blue light. We give them red light, and their blood glucose does not go up as much. We give them blue light, and their blood glucose goes very high.

Andrew Huberman: Mm-hmm. So they're using more of the energy.

Glen Jeffery: Yeah. So...

Andrew Huberman: In the red light condition.

Glen Jeffery: In the red light condition. But in the blue light condition, we're slowing their mitochondria down, and so there is more glucose flowing around. I should say that sampling the blood in a bee is a little bit difficult, but you basically pull off one of the antennae, and you squeeze a bee, and you get a little piece of...

Andrew Huberman: All the bee lovers out there are cringing.

Glen Jeffery: But we went to the chemist, and we bought just the standard blood glucose, the test that you can get for a few dollars.

Andrew Huberman: Mm-hmm.

Glen Jeffery: We got a result. Therefore, it's worth moving forward. Therefore, we got the ethical permission. I can't do the experiment on blue light. I regard that as unethical.

Andrew Huberman: Really?

Glen Jeffery: Yeah. I don't...

Andrew Huberman: We're under blue light all day. I'm absolutely convinced that being under blue light or short-wavelength shifted light all day is altering blood glucose in ways that are detrimental.

Glen Jeffery: I complete...

Andrew Huberman: But in any case, before I rant about that, what happened in human?

Glen Jeffery: So, in the humans, we did a standard blood glucose tolerance test, which is horrible. So you get people to starve overnight, they come in, they drink this big sort of cup of vial glucose. So, we really pump up the glucose in their body. And then we prick their fingers at regular intervals and sample their blood, and see how their blood glucose level changes. And your blood glucose level will peak in about 40 to 60 minutes. It's hard getting subjects for this one. And we also put a tube up their nose so we could detect how much oxygen they were consuming. You're calling on friends. I mean, I even dragged my son in as a subject for that one. The result when we gave people a burst of red light beforehand to stimulate their mitochondria was super clear. It wasn't ambiguous. The blood glucose levels went up, but they didn't peak anywhere near as seriously as they did without the red light. Now, I'm told that the level of your blood glucose is not necessarily a massive issue for concern. What is an issue for concern is it spiking, how much it spikes. And the reduction in the spike was of the order of, it was just over 20%, if I remember correctly.

Andrew Huberman: Where was the light shone on the body?

Glen Jeffery: It was shone on the back, and it covered... I forgot what the percentage of the body area was. I did this calculation four or five times because it was ridiculously small. So, we were stimulating a very limited area of the body, but we got a systemic response. There was no way that the mitochondria in that little patch of skin was having that effect. But it fits into a wider notion that all these mitochondria act as a community, and we now know that. That's coming all from different corners. They do things together. It takes them a little time to have a conversation about it, but they act together. And if we're doing something which was over one to two hours, that's long enough for them to hold that conversation. I'd love to know more about that.

Andrew Huberman: Do you recall whether the subjects could feel heat from the infrared light?

Glen Jeffery: No.

Andrew Huberman: Okay. So they're not feeling heat, so that removes also a potential placebo effect of some sort.

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: Do you recall just roughly what the area of illumination was? Was it...

Glen Jeffery: It's in the publication.

Andrew Huberman: Okay.

Glen Jeffery: But let's go like this.

Andrew Huberman: Okay. So for those just listening, maybe like a four-by-six rectangle.

Glen Jeffery: Four-by-six rectangle makes sense.

Andrew Huberman: Four-by-six inches.

Glen Jeffery: Yeah, yeah.

Andrew Huberman: Yeah, for all those metric system folks out there.

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: We're on common ground here given you're from the UK.

Glen Jeffery: But we're not unique in finding this. It's just that other people are finding things with red light that are sitting behind different walls.

Andrew Huberman: Mm-hmm.

Glen Jeffery: So John Mitrofanis, he did most of his research in Australia. He induces Parkinson's disease in primates, which you can do pretty much overnight with a drug, and then he was giving red light to different parts of the body. Now, Parkinson's disease originates from a very small nucleus deep in the brain stem, but he was reducing the symptoms of Parkinson's disease in these primates very significantly with lights that were being shone on the abdomen. So in any one of these, you take in isolation, and there are many of these studies, and you go, "Yeah, maybe. Yeah."

Andrew Huberman: What does he think it was doing? I mean, clearly it's not rescuing the dopamine neurons that degenerate in Parkinson's, but maybe it's rescuing components of the pathway?

Glen Jeffery: It could be rescuing components of the pathway. I think that we know that red light, and we're using that term very loosely, and perhaps we shouldn't. We know that long-wavelength light reduces the magnitude of cell death in the body.

Andrew Huberman: Mm.

Glen Jeffery: Cell death is very often initiated apoptosis by mitochondria. When mitochondria get fed up and the... I see them as batteries. When the charge on the battery goes down low enough, they put their hand up, and they say, "Time to die."

Andrew Huberman: And I think they actually present a molecular eat me signal which is interesting.

Glen Jeffery: Yes.

Andrew Huberman: When we talk about cells dying, we think about it as sort of they go from a shout to a whimper, and then they get cleaned up. Like, they die. But actually, they solicit for their own death with this eat me signal.

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: Yeah. They'll get opsonized for the people that anything about the immune system, opsonization. They're similar things. So if I understand correctly, he induced an insult to these dopamine neurons, and then he used red light shone on the abdomen to offset some of the degeneration that would have occurred.

Glen Jeffery: Yeah.

Andrew Huberman: Okay.

Glen Jeffery: Now, that again fits into the wider spectrum of other research that's not put together. So that was John, and John has been a big leader in red light dementia and Parkinson's disease, and a lot of it in primate models, which means it's got a lot of validity to it.

Andrew Huberman: Yeah, they're similar to us.

Glen Jeffery: Yeah, they're very...

Andrew Huberman: We're us to them.

Glen Jeffery: Yeah.

Andrew Huberman: Yeah.

Glen Jeffery: Another experiment we did was... Over life, you will lose a third of your rod photoreceptors in your retina.

Andrew Huberman: Maybe just explain for people what the rod system does. Yeah.

Glen Jeffery: Okay. The rod system is the majority of photoreceptors are rods. They're the receptors that you use when you're dark-adapted, which a lot of us aren't very much these days. So we've got our cones, which deal with color and deal with bright light. Then, as we turn the lights down, we start to use our rods. So loads and loads of rods, relatively few cones.

Andrew Huberman: What I usually tell students is this is like in the old days when everyone didn't have a smartphone near their bed, you wake up in the middle of the night, and you need to use the restroom. You can navigate to the restroom. You might flick the light on in the restroom. I don't recommend doing that. It'll quash your melatonin unless it's a red light.

Glen Jeffery: Yeah.

Andrew Huberman: Or you go out on a hike, and you don't bring what we call a flashlight, Glen. You guys call it a torch.

Glen Jeffery: Yes. Yeah.

Andrew Huberman: But as you come back, your eyes start to adapt. It's getting dark. You can still see the outline of the trail. There's not starlight yet. But you're able to, as you say, dark adapt, and you can see enough of what you need to see. You're using your rod system.

Glen Jeffery: Yeah. The key thing here is rods are very numerous. Cones are not so. So what happens then, for instance, if we take aging animals and we just expose them to red light every day? We give them a burst of red light, and then we count the number of rods they've got when they reach old age, and the result is super clear. We have reduced the pace of cell death in the retina, okay? So, red light is affecting mitochondria. Mitochondria have the ability to signal cell death, and we're drawing back the probability of that cell dying. Now, we did that in mice. We did it on a lot of mice. It was a killer of an experiment to keep animals going forever. And then I forced one of my graduate students basically to go one, two, three, four, and count photoreceptor outer segments. She was a hero. So, we can use red light to reduce the pace of cell death. So, I am not too surprised that John Mitrofanis would have reduced the pace of cell death in the substantia nigra, that nucleus that gives rise to Parkinson's disease. I'm seeing that coming out of loads of different labs, things that are all consistent with that kind of story. The other thing that I think you can start to address is, if you've got bad mitochondria, say, very loose term, if you've got bad mitochondria, as you do have in Parkinson's disease, they're bad, they're not functioning very well, on their way to death, are they influencing other parts of your body? Parkinson's patients, you think, well, okay, they're all going to have movement disorders. But in actual fact, a lot of Parkinson's patients have a lot of other things that are going on in them, and we're minded to think that as good information can be passed to mitochondria and can be shared in that community, so can bad information.

Andrew Huberman: Mm-hmm.

Glen Jeffery: If you really upset mitochondria in one place, then other things are changing in different places. So, the big takeaway here, and it's not controversial to say, I've heard lots of people saying it, and I didn't say it originally, is that they're a community. You can't deal with them in isolation.

Andrew Huberman: Even across cells in different areas of the body, they're a community.

Glen Jeffery: They are a community.

Andrew Huberman: Probably by secreting certain things that support each other. Maybe I've heard some evidence that mitochondria can actually be released from cells.

Glen Jeffery: Oh, yeah.

Andrew Huberman: Different, although not entirely different than neurotransmitters are released between cells and communicate between cells.

Glen Jeffery: Mm-hmm.

Andrew Huberman: Very interesting when one thinks about mitochondria of having maybe bacterial origin, again, that our cells co-opted or they co-opted us. We don't know, again, the direction there. I have a question about how far long-wavelength light can penetrate and through what tissues. I realize that in the studies we've been talking about, it's long-wavelength light exposure to the back, lowering the blood glucose response.

Glen Jeffery: Yes.

Andrew Huberman: Or to the abdomen, offsetting some of the degeneration as it relates to this Parkinson's model. If I were to take a long-wavelength light and put it close to my head, would it penetrate the skull?

Glen Jeffery: Oh, definitely. If you look at a long-wave light source, and again, this is published, Bob Fosbury did this, he put his hand on one, comes straight through his hand, but the interesting thing is you can't see the bones. It's passing through the bone. So, that led me to go into grabbing a few skulls, and yeah, it's really not affected that much by bone. I was talking to some audiology guys in Cambridge who wanted to use red light, and they were taking, I think, heads or something, and looking at them. And they were shining red light in the eye, and they say, "We can see it in the ear."

Andrew Huberman: Mm-hmm.

Glen Jeffery: "I can see it," and vice versa. So, there are things that red light does not, will not, doesn't go through. So, it is absorbed by deoxygenated blood. So, you get fantastic pictures of your veins in your hand or in your head.

Andrew Huberman: Mm-hmm.

Glen Jeffery: But the most obvious thing that you think is that long-wavelength light would be blocked by something thick, like a skull. The answer is no.

Andrew Huberman: So, going back to our example of the ocean appearing blue because of blue light getting reflected back and red light getting absorbed.

Glen Jeffery: Mm.

Andrew Huberman: I think this is very important to kind of double-click on in people's minds. Because people will see an image, for instance, and I'll put a link to it from this recent publication of yours, of red light and other, excuse me, long wavelength light, not just red light being shown on a hand. And indeed, you don't see the bones, and you see the vasculature, this deoxygenated blood.

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: When people see a structure under a particular wavelength of light, the kind of reflex is to assume that those structures are the ones that are using the light. But in fact, it's the exact opposite.

Glen Jeffery: Exactly the other way around.

Andrew Huberman: It's the stuff you don't see, right, that it's passing through.

Glen Jeffery: Yeah.

Andrew Huberman: And I think for a lot of people, that's just kind of counterintuitive.

Glen Jeffery: Yeah.

Andrew Huberman: So they'll see an image of the veins carrying that deoxygenated blood, and they'll say, "Oh, red light is impacting the veins," right?

Glen Jeffery: Mm.

Andrew Huberman: But the interesting thing is that it's passing through... that is interesting in itself, but it's passing through all these other structures. And to me, the idea that when I go out on a sunny day, because the sun includes long wavelength light, or were I to be near a long wavelength light-emitting device, that it's actually getting into the deep brain tissue through the skull.

Glen Jeffery: Mm.

Andrew Huberman: I think for most people, it's just not intuitive to think about light passing through things that are solid in that way.

Glen Jeffery: Yes, and I had exactly the same problem. I had exactly the same problem. If you put a radiometer and a spectrometer to measure the energy and the wavelength on one side of someone's head and a light source on the other side of someone's head, you get a clear result. Now, interestingly, it's not a sideline, it's actually a very important issue. A biomedical engineer, Ilias Tachtsidis at UCL, has used this because he works on, some of his work is on neonates that have had stroke. And he takes the neonate and actually does exactly that experiment. He passes red light wavelengths of light through the side of the neonate's head and records them coming out the other side, and he can use that as a metric of how well the mitochondria are functioning in that damaged brain.

Andrew Huberman: Mm.

Glen Jeffery: And the readouts that he gets are readouts that are indicative of the potential survival of that neonate.

Andrew Huberman: Wow.

Glen Jeffery: Now, I think there are lots of wows here. First of all, he's got his work into a major London teaching and research hospital. He's got it into kids, and we've acknowledged that this is not dangerous, right? He's gone through loads of ethics committees.

Andrew Huberman: The long wavelength light, red and out towards infrared and near-infrared, is non-ionizing.

Glen Jeffery: Yeah.

Andrew Huberman: Right? It's not altering the DNA of the cells.

Glen Jeffery: No.

Andrew Huberman: It's contributing to the healthy function of the mitochondria. Forgive me for interrupting.

Glen Jeffery: No, it's a good point.

Andrew Huberman: Because when people hear about light passing through a baby's head in order to make that kid healthier, I mean, it's spectacular.

Glen Jeffery: Yeah.

Andrew Huberman: I love that this is being done at such a fine institution and so carefully. But the reason it's safe is because that's long wavelength light.

Glen Jeffery: Long wavelength.

Andrew Huberman: Were this to be short wavelength light, we have no idea what it would be doing. I mean, babies have very thin skulls. UV would be, who knows? X-rays, certainly you would never, ever, ever want to do this. So yeah, I think it's important that people really remember what we're talking about passing through.

Glen Jeffery: Yeah. Yeah. Yeah. Yeah.

Andrew Huberman: Okay. Yeah.

Glen Jeffery: And I think that it's a very important point because I have gone through so many ethics committees to shine long wavelength light to do various things, including on people that are... They've got problems, or they've got sight problems. They're patients. We've actually also done it with children. And we've got through ethics committees really with very, very little comment.

Andrew Huberman: Mm-hmm.

Glen Jeffery: Because on many of the ethics committees, they're physicists and they understand the issue.

Andrew Huberman: By now, I'm sure that many of you have heard me say that I've been taking AG1 for more than a decade, and indeed, that's true. The reason I started taking AG1 way back in 2012, and the reason why I still continue to take it every single day, is because AG1 is, to my knowledge, the highest quality and most comprehensive of the foundational nutritional supplements on the market. What that means is that it contains not just vitamins and minerals, but also probiotics, prebiotics, and adaptogens to cover any gaps that you might have in your diet while also providing support for a demanding life. Given the probiotics and prebiotics in AG1, it also helps support a healthy gut microbiome. The gut microbiome consists of trillions of little microorganisms that line your digestive tract and impact things such as your immune status, your metabolic health, your hormone health, and much more. Taking AG1 consistently helps my digestion, keeps my immune system strong, and it ensures that my mood and mental focus are always at their best. AG1 is now available in three new flavors: berry, citrus, and tropical. And while I've always loved the AG1 original flavor, especially with a bit of lemon juice added, I'm really enjoying the new berry flavor in particular. It tastes great, but then again, I do love all the flavors. If you'd like to try AG1 and try these new flavors, you can go to drinkag1.com/huberman to claim a special offer. Just go to drinkag1.com/huberman to get started. Today's episode is also brought to us by Rorra. Rorra makes what I believe are the best water filters on the market. It's an unfortunate reality, but tap water often contains contaminants that negatively impact our health. In fact, a 2020 study by the Environmental Working Group estimated that more than 200 million Americans are exposed to PFAS chemicals, also known as forever chemicals, through drinking of tap water. These forever chemicals are linked to serious health issues such as hormone disruption, gut microbiome disruption, fertility issues, and many other health problems. The Environmental Working Group has also shown that over 122 million Americans drink tap water with high levels of chemicals known to cause cancer. It's for all these reasons that I'm thrilled to have Rorra as a sponsor of this podcast. I've been using the Rorra countertop system for almost a year now. Rorra's filtration technology removes harmful substances, including endocrine disruptors and disinfection byproducts, while preserving beneficial minerals like magnesium and calcium. It requires no installation or plumbing, it's built from medical-grade stainless steel, and its sleek design fits beautifully on your countertop. In fact, I consider it a welcome addition to my kitchen. It looks great, and the water is delicious. If you'd like to try Rorra, you can go to rorra.com/huberman and get an exclusive discount. Again, that's Rorra, R-O-R-R-A.com/huberman. Let's talk about the two sort of bookends of age. You just mentioned babies, and we'll return to babies, children, and youth. Let's talk about some of the work you've done on retinal aging and using long wavelength light. I'm being very careful with my language here, because if I say red, people think you have to see it, but there's red, near-infrared, NIR, it's typically shown as NIR, infrared light. And I think we batch those when we say long wavelength light. It's going, what? 650 nanometers would be red out to, I guess it's as far as 900 nanometers or so?

Glen Jeffery: Yeah, and then beyond 900 is infrared. So we've got the near-infrared, and we've got the infrared. Now, you're right. We've got to start defining these terms a little bit more clearly. But I think for nearly all of the research we're talking about, we're talking about where vision stops, which is around 700, and we're talking about the near-infrared, which is, for practical purposes, is going up to around 900.

Andrew Huberman: Mm-hmm. Mm-hmm.

Glen Jeffery: But I remember doing an experiment with UV once, and it was a bizarre experiment, trying to work out if a reindeer could see UV light.

Andrew Huberman: Do they?

Glen Jeffery: Yeah, they do actually. But then, while we were doing the experiment, I was beginning to say, "Look, I'm not believing any of this data because I can see this flashing now." And as was pointed out to me, you will see wavelengths of light that you shouldn't see if you just turn the energy up.

Andrew Huberman: Mm-hmm.

Glen Jeffery: So, if I put you in a room with UV and I pump loads of energy into that UV, you'll see things that you shouldn't.

Andrew Huberman: Mm.

Glen Jeffery: And likewise with the reds, you shouldn't really see much above 700. I can get you to see 850 if I just turn the energy up a bit, and you see these little red glows.

Andrew Huberman: Yeah, this explains a lot of people's ideas about whether or not they've seen ghosts, but that's a different podcast, ghosts and UFOs. But an interesting discussion but for another time.

Glen Jeffery: Yeah.

Andrew Huberman: But I can't help but mention that, okay, maybe we'll return to this later, but Glen has worked on a variety of species, as have I over the years. So maybe at the end, we'll do a quick catalog of the species that we've worked on over the years. So, I'm not surprised to learn that you worked on reindeers, given the other species you've worked on. But returning to the human, you published some papers over the last five, six years or so, looking at how, when the eyes specifically are exposed to long-wavelength light, it can do excellent things for preserving vision or off-setting some loss of visual function. Could you detail those experiments for us?

Glen Jeffery: Yeah. So, let's take two pieces of information first. So one of the main theories of aging is the mitochondrial theory of aging. Mitochondria regulate the pace of aging. So if you can regulate mitochondrial health, you can regulate aging. That's relatively clear. So, that's the first thing. And then the second thing to remember is that there's more mitochondria in your retina than there is in any other part of your body. Your retina has got the highest metabolic rate in the body, ages fast, and my argument always is, it's the sports car. Bangs out of the garage, but after so many thousand miles, you've got to service it, otherwise it falls apart. So there was a very strong argument for trying to manipulate mitochondria in the retina, which is great for me because I'm a retinal person, I'm a visual person, so I had the tools to do it. So, the first experiment we did, which was very gratifying, was to actually measure people's ability to see colors. Now, we used a rather sophisticated test, first of all, and that was we'd put on a very high resolution monitor, say, the letter T in blue, and then we'd add loads and loads of visual noise to it in the background, or we'd have an F in red, visual noise. And then we found the threshold at which they could see that letter and happily identify it. So, we found out what their visual ability was for colors. We then gave them a burst of red light to improve their mitochondria in cells that are very mitochondria-dependent, and we then brought them back, and we found the threshold had changed. Their threshold had improved in every one of those subjects bar one.

Andrew Huberman: They could see something they couldn't see before.

Glen Jeffery: See before.

Andrew Huberman: By one, I think it's hard for... What scale is it on? Some of these tests, this is like the tritan test.

Glen Jeffery: Well, so we tested tritan and protan, so...

Andrew Huberman: Okay, so this is nerd speak for the different visual tests. Most people are familiar with the Snellen chart. When you go to get your driver's license, you have to read the letters of different sizes.

Glen Jeffery: Yeah.

Andrew Huberman: Very different. This is measuring the just noticeable difference between you can see something, you can't see something.

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: When you say there was an improvement of but one, could you frame that in a real-world context for people who are not thinking about visual psychophysics?

Glen Jeffery: Okay. It's very simple. Of all the people we've tested, we've got an improvement, and there's very large numbers of them, except one subject. So, all right?

Andrew Huberman: Yeah. Ah, you're saying but one.

Glen Jeffery: No, no, no.

Andrew Huberman: I thought you meant that was the numerical the size of the effect. Okay.

Glen Jeffery: No. No. No. No. If you look over the population, the size of the effect is around 20%. It's very substantial. All right? But our ability to improve visual function varies enormously between individuals.

Andrew Huberman: You said but one.

Glen Jeffery: Yeah.

Andrew Huberman: This is a UK/US nome...

Glen Jeffery: Yeah. Sorry.

Andrew Huberman: No, but don't apologize. I should apologize.

Glen Jeffery: Yes.

Andrew Huberman: Okay. An improvement of 20%, improvement in threshold, so people are seeing better than they did prior. Could you explain what they did for the intervention? How many times a week, a day? How long are they shining red light in their eyes? Excuse me, long wavelength light. What's the nature of that light? Maybe even tell us how far away from it they are.

Glen Jeffery: Okay. So in our first experiments, we used 670 nanometers, right? Which is a deep-ish red light. The only reason we used that is because all the studies before us, doing different things, had used 670, consequently there was a database. So that's why we did it, and we did it with a little torch that we put in front of someone's eye...

Andrew Huberman: Flashlight. I'll translate the flashlight. Not a torch with fire near the eye.

Glen Jeffery: No, definitely not.

Andrew Huberman: Oh my goodness.

Glen Jeffery: And we did that for three minutes. And originally, we did that every day for a number of weeks.

Andrew Huberman: Eye open, not eye closed.

Glen Jeffery: Makes very little difference because the long wavelength light passes through the lid without it being affected very much. So, I said to people, "Whatever you're comfortable with. You're doing me a favor. You're being a subject in my experiment. I'm not paying you for it. You want to keep your eyes closed, you keep your eyes closed." And those people all had an improvement in their color vision. Now, we then titrated that down. So instead of doing it every day for so many days, we just did it for one day, and three minutes of that light, one day, and we brought them back. I think it was an hour later. They all improved.

Andrew Huberman: How stable was the effect? I mean, did they have to only do one treatment ever?

Glen Jeffery: No. I wish that was the case.

Andrew Huberman: Okay.

Glen Jeffery: In all of those people, and I have to say, we've done similar experiments on flies, on mice, on humans. It's five days.

Andrew Huberman: It lasts five days.

Glen Jeffery: Five days. It's a solid five-day effect. So something very fundamental that is conserved across evolution is playing a role here. And I have to say that to a first approximation, anything I find in a fly, I find in a mouse, anything I find in a mouse, I find in a human. I can't find a big disjuncture between those things. So, it lasted five days. And the real big point to take on board is it's a switch. There's not a dose response curve here. It is a switch. You put enough energy in at a certain wavelength of light, and it goes bang and click, and then five days later, it goes chunk and stops.

Andrew Huberman: I have a lot of questions about these studies, so I'm going to try and be as precise about them. I know it's on people's minds. If people are going to get in front of a long-wavelength light-emitting device, do you think it's critical that it be 670 nanometers, or could it be 650 out to 800? How narrow band does the light actually have to be in terms of wavelength?

Glen Jeffery: Pretty much anything works to a rather similar extent at 670 going upwards. When you go below 670 towards 650, the effects tend to be somewhat reduced.

Andrew Huberman: If this is happening very quickly, you said an hour later, the vision is better, thresholds have changed, and it lasts five days.

Glen Jeffery: Yeah.

Andrew Huberman: Do you think we can get the same effect from sunlight, given that sunlight contains these long wavelengths of light? Or is it that the sunlight isn't of sufficient energy for most people? I mean, with this, what you call torch, I call flashlight, light source, the way you described it and showed it with your hand for those listening is fairly close to the eye, maybe eyelids closed or maybe open if people can tolerate that, and you're shining that light in their eyes for a couple of minutes. How different is it than stepping outside on a really bright day, closing my eyes if I look in the direction of the sun because that's pleasant, or just walking in the sunlight and getting long wavelength exposure?

Glen Jeffery: Well, I'm a big fan of natural sunlight because life has evolved for billions of years under sunlight, right? It's only recently changed. I don't know that cutoff point, but there's an enormous difference between the light produced by a flashlight and sunlight. Sunlight is an enormous broad spectrum, and that flashlight is just a little window of light that happens also to be present in sunlight.

Andrew Huberman: Mm-hmm.

Glen Jeffery: Now, I think the two situations are probably incomparable.

Andrew Huberman: Mm-hmm.

Glen Jeffery: Right? And I'm not going to spend whatever is left of my career hunting that down.

Andrew Huberman: Mm-hmm. Mm-hmm.

Glen Jeffery: We know, and I think this is the global concept I've got, which is that we can do much with single wavelengths of long wavelength light, right? Like a flashlight, which is 850 or 860. We can do a lot. But we can never do the same as you can get from sunlight. But you can't do those tight controlled experiments with sunlight that I can do much more easily with specific wavelengths.

Andrew Huberman: Mm-hmm. Yeah, and you're in the UK, so you'd have a lot of days where you couldn't do experiments at all.

Glen Jeffery: We don't do sunlight.

Andrew Huberman: I'm just kidding. Well, I must say oftentimes when I tell people to get sunlight in their eyes in the morning to set their circadian rhythm, I'm like a repeating record with that, and I will be till the day I die. People will say, "There's no sunlight where I live." And I remind them that even on a very overcast day, there's a lot of photon energy coming through, but the long wavelength light is cut off. So they're still getting a lot of photons. I mean, compare how bright it is at 9:00 a.m. versus midnight the night before.

Glen Jeffery: Yeah.

Andrew Huberman: Their sun is that they can't see the outline of the sun as an object is what they're referring to.

Glen Jeffery: Right. I think the important point there is that long wavelength light gets scattered by water. It gets absorbed and scattered by water. So, on a winter's day, we've got a cloud, and that cloud contains water.

Andrew Huberman: Mm-hmm.

Glen Jeffery: There will be an attenuation of the longer wavelength light. It won't be vast, but there will be an attenuation, but it will start coming at you in different angles. So when you're walking on a sunny day, and you're walking down the road, sun's in front of you, you feel warm on your chest when you've got clothes on, and it's the longer wavelength light doing it because it's relatively focused. On that winter's day, you're still getting a lot of long wavelength light, but it's coming at you in a lot of different angles, and it's slightly attenuated. So my argument, which is the new mantra of the lab to some extent, is get a dog, right? Get a dog because you'll have to go out in daylight two or three times a day.

Andrew Huberman: You'll get no argument from me. You're making me very happy, Glen. I love dogs. Listeners of this podcast will know I absolutely love dogs, and my last dog was an English bulldog, half English bulldog, half mastiff. So, the next one will also be an English bulldog. A couple more questions because I know people are curious about long wavelength light-emitting devices for their eyes and other tissues. You mentioned that one subject did not respond, and if I'm not mistaken, these effects, at least on the eyes, I don't know about the other effects on blood sugar, et cetera, but on the eyes and visual function seem to be gated by age, right?

Glen Jeffery: Yeah.

Andrew Huberman: If I recall, people younger than 40, you saw less of an effect.

Glen Jeffery: Overall, statistically, we saw less of an effect. My youngest son responded very, very strongly. And at the time, I think he was about 25. So, you have to look at a population level to get that. But okay, look, this all makes sense. Mitochondrial theory of aging means that we should have more room to improve mitochondria in the elderly than the young. But we all age at different rates. One of the biggest problems about doing experiments on humans as opposed to mice is we all do radically different things. Some take exercise, some have very good diets, some have poor diets. And mice sitting in our animal house, eating the same food, they're very, very similar to one another. Everything is the same. So, we have to accept that noise. But generally, when your mitochondria are in a poor state, which is consistent with aging, yes, we've got more room to lift them up and improve their function.

Andrew Huberman: What was the time of day, so-called circadian effect, of this?

Glen Jeffery: Very clear. Again, same in flies, mice, and humans. Your biggest effect is always in the morning, and it's always generally just before perceived sunrise up until about 11 o'clock. And it's very, very clear. But let's look at the backdrop to this. Your mitochondria, they're not doing the same thing all the time. So, if we did this experiment for 24 hours, looking at mitochondria. And if you look at what mitochondria are doing over 24 hours, it's shifting. It's not the same even over a three-hour period. It's shifting. And so the proteins that we have in different parts of mitochondria are changing in concentration radically. It's a very, very active area. So if you're doing research on mitochondria, and you're not taking into account the time of day, you may have a problem. But the mornings are very, very special. In the morning, there are lots of things changing in your body. Your hormone levels are very, very different. Your blood sugars tend to be picking up. You've been asleep. A predator may have been watching you. You need to wake up, and you need to be ready on the road. You can't be like a lizard that's got to wait for the sun to rise and to get themselves into a position where you can get your body temperature up. So the morning is very important. You're making more ATP, this petrol that mitochondria make in the morning, than at any other time. Now, I can improve function across a wide range of issues in the morning. I can't do it very easily in the afternoon. And I think this comes from a very myopic point of view, which is we think about mitochondria purely as things that make energy. They do lots of other things. And my interpretation is that in the afternoon, well, the standard lab joke is they're doing the ironing. They're doing other things that, as organelles, they need to do.

Andrew Huberman: Interesting. Mm-hmm.

Glen Jeffery: They are over a period of a day, they're making contact with other organelles in the cell, particularly something called the endoplasmic reticulum. They're junctioning with that. We've got such a limited view of what they do. I was surprised to find that a mitochondria at nine o'clock in the morning was not a mitochondria at four o'clock in the afternoon. That poses some very serious problems about the interpretation of our data if people are doing things at different times of day.

Andrew Huberman: So, if somebody wants to improve their vision with long-wavelength light exposure, maybe we can just give them a rough contour of what this would look like. A long wavelength of 670, and greater, emitting flashlight torch at a comfortable distance from the eye so it could be three inches, six inches, a foot, depending on how bright it is. But if I were going to run the experiment, I'd probably want to bring it about as close as people felt like they wanted to close their eyes, but then move it back just a little bit, just below the threshold of kind of, I don't want to say discomfort, but where it's just too bright. And then you're saying it doesn't matter if their eyelids are closed or open, you give it three minutes, five minutes of exposure once every five days or so. And is that going to be sufficient?

Glen Jeffery: There is the difference between something that has an effect and then the efficiency of that effect.

Andrew Huberman: Mm-hmm. Mm-hmm.

Glen Jeffery: So, if you take a 670 nanometer light source and you do exactly that, you will have an effect.

Andrew Huberman: Mm-hmm.

Glen Jeffery: Now, as we're going forward, certainly we're finding the energy at which you give that wavelength is dropping and dropping and dropping and still effective.

Andrew Huberman: So, you don't need a very bright light?

Glen Jeffery: No. No, you don't. The original experiments, they used watts. They measured it in watts, not lux. Lux is not very meaningful to this situation because that's adjusted for the human eye. We want to know what was the energy that the cell experienced.

Andrew Huberman: Mm-hmm.

Glen Jeffery: So, people started off at, say, 40 milliwatts per centimeter squared, and I looked at that and I thought, "Crikey."

Andrew Huberman: That's bright.

Glen Jeffery: That's bright.

Andrew Huberman: That's very bright.

Glen Jeffery: Big after effect.

Andrew Huberman: Yeah, that's going to make someone wince. Yeah.

Glen Jeffery: It is. So, then we got ourselves down to what we do in the lab now generally, which is around eight, which is very comfortable, has the same effect.

Andrew Huberman: Mm-hmm.

Glen Jeffery: But then we had someone in the lab do an experiment, and we had the flashlights that had batteries in them. She got a lovely effect, and we found out the batteries had been run down, and she was getting an effect close at one milliwatt per centimeter squared. That is low.

Andrew Huberman: That's dim red light.

Glen Jeffery: That is low.

Andrew Huberman: Okay. So, it sounds like one can use dim to moderately bright red light that's comfortable. I say red, but I mean long-wavelength light that's comfortable and likely get the effect.

Glen Jeffery: Well, yeah.

Andrew Huberman: Sounds like the effect can occur at any age, but it's going to be more pronounced in people that have experienced some loss of vision because of age, which everybody does.

Glen Jeffery: Yes.

Andrew Huberman: You've also looked at this in the context of macular degeneration, which is a very common form of blinding, and especially in people as they get older. What were the results in terms of rescuing vision in people with macular degeneration?

Glen Jeffery: Okay. So, macular degeneration is when, you could put it crudely, that the center of your retina that you're using for reading, degenerates, and you could say it's part of an aging process. If I get you all to live to 50, so if I get you all to live to a 100 years, probably 20% of you will have macular degeneration. Remember, the retina's a sports car, it burns out. So, I had a very significant failure in a clinical trial because we took a whole group of patients, who had macular degeneration, we treated them with red light, and we treated their part... More women have macular degeneration than men. We took their husbands as the control subjects. And to a first approximation, we got absolutely no effect whatsoever. This is kind of a point where people working with Glen are losing enthusiasm. But lo and behold, their husbands, their vision... They didn't have macular degeneration, but their vision was improving enormously, particularly the way in which they could deal with darkness. So, we stomped around over this. Something was wrong. And we found that when we looked back at it, we found that the subjects that we were dealing with, the patients, their disease had reached a certain point. It had gone beyond a certain point. Now, when that study was replicated by someone who thought about it a bit more than me, an ophthalmologist called Ben Burton in the UK, he got a great result. He started to get a really good result. And when you talk to people about red light, and I talk to people, I talk to Parkinson's societies, I talk to various groups, and I talk to the researchers, and there is one thing that's very clear, is that red light can impact on aging, it can impact on disease, but it can't do it if that disease has really got its teeth into you.

Andrew Huberman: Mm-hmm.

Glen Jeffery: Right? So, where we need to get into situations is early on in disease. So, we thought very much at one point about rheumatism, rheumatoid arthritis.

Andrew Huberman: Yeah, very common autoimmune condition. Yeah.

Glen Jeffery: Yeah. And, we had absolutely zero effect, but all the subjects we dealt with already had hands that were quite twisted. It wasn't people coming in saying, "I've got this ache in my hand," which is where we should have intervened. So, early intervention is absolutely critical. We don't have to give high energies. We don't have to give long exposures. We can improve situations, but where we need to put our effort is the efficacy of how we improve things. If I can improve something 20%, well, that's great for that person, but can we improve it 80%?

Andrew Huberman: Mm-hmm.

Glen Jeffery: And that's all about wavelengths. It's all about energies. It's all about us thinking a little bit more carefully before we set up the experiment.

Andrew Huberman: It also makes me think that even though long-wavelength light can penetrate the body and it scatters, like for instance, the shining of light on a four-by-six inch rectangle on the back impact blood glucose regulation everywhere.

Glen Jeffery: Mm-hmm.

Andrew Huberman: Shining long-wavelength light into the eyes improved presumably mitochondrial function in order to increase the visual detection ability, and on and on. Presumably, the tissue that you focus the light on, if it's a focused light, is going to derive the greatest benefit, right? Or at least the most opportunity for mitochondrial change. Then there will be these systemic effects. Those mitochondria are talking to other mitochondria. I mean, I'm fascinated by how mitochondria are perhaps transported between cells and around the body. There's not even a cottage industry anymore. I think a lot of biologists are thinking about this seriously.

Glen Jeffery: Mm.

Andrew Huberman: But let's say I want to improve the mitochondrial function in my gallbladder, should I shine the red light on my gallbladder? It stands to reason that the answer would be yes.

Glen Jeffery: I think the answer is yes. The issue is how quickly the effect takes place in distal and proximal tissues.

Andrew Huberman: Mm-hmm.

Glen Jeffery: So, if you shine the light on your kneecap, something will probably happen within one to two hours.

Andrew Huberman: At the kneecap?

Glen Jeffery: At the kneecap.

Andrew Huberman: Right. Right, right.

Glen Jeffery: But then if you're examining the response of that on your hand, it's 24 hours later.

Andrew Huberman: Mm-hmm.

Glen Jeffery: Right? So, the message has to get out and things have to... The story has to spread. And the spreading of the story, the spreading... That's an intense kind of area of activity. What is the signal? Where is it coming from? What is the signal?

Andrew Huberman: Mm-hmm.

Glen Jeffery: And I think we poked our finger at that slightly because we found that cytokine expression in the serum changed a lot.

Andrew Huberman: Inflammatory cytokines are going down?

Glen Jeffery: No. Increase in cytokine expression at low levels is protective.

Andrew Huberman: Okay.

Glen Jeffery: Right? So, what it's saying to the body is, "Brace yourself, something's coming."

Andrew Huberman: Sure. Yeah. Mm-hmm. Immune system is getting mobilized.

Glen Jeffery: Yeah.

Andrew Huberman: Yeah.

Glen Jeffery: So, that was very, very clear. So, in animals that had improvements in physiology also had changes in cytokine expression.

Andrew Huberman: Mm-hmm.

Glen Jeffery: And I looked at that and I thought, "Is that the real reason, or is this a secondary, third or fourth level effect?" Now, there's some stunning stuff that I'm waiting to come out from Westminster University in the UK, being done by a great scientist, Ify, and what she's showing is a means of communication that we are very really rather unaware of, which is these microvesicles that go around the body, go around the serum, and these microvesicles carry cargos. Now, they carry all different sorts of cargos, and people have played with them a little bit in terms of changes in the gut microbiome. How does that affect the whole body? They've been talking about microvesicles, and she's showing that microvesicle concentration is changing quite significantly with... In fact, what we did with her was we didn't give her a red light. We gave her an LED light where we changed the LEDs in there to put some long wavelength elements in it. So, the communication around the body, what is doing... We've got to break that one.

Andrew Huberman: Mm-hmm.

Glen Jeffery: It's probably not one thing. Again, scientists always think about one thing. It's a complex pattern. When I looked at the changes in cytokine expression, my first reaction was, "I need a mathematician sitting next to me." All these things are changing in a complex manner, and I'm only looking at 50 of them, and there's probably over 300, so I could be missing the point. But communication... And you're right, mitochondria, you can see cells come along to a sick cell, and they join together, and the mitochondria is pushed in to the sick cell. How amazing.

Andrew Huberman: Mm-hmm.

Glen Jeffery: We'd have never thought about that.

Andrew Huberman: Mm-hmm.

Glen Jeffery: Your mitochondria are ill. I'm going to come along, and I'm going to give you some fresh mitochondria.

Andrew Huberman: Mm-hmm. They, the mitochondria, are amazing, and it's amazing how little we really understand about how they work, and yet what we do understand points to how spectacularly important they are for energy, longevity, and as you pointed out, how malleable they are.

Glen Jeffery: Yeah.

Andrew Huberman: And it all makes sense in the evolutionary context of water and the absorption of red light. Another way that's kind of fun to illustrate this red light absorption by water thing is if anyone ever goes snorkeling on a tropical reef, you'll notice that in the first 10 feet of water from the surface down, you can see beautiful oranges and reds.

Glen Jeffery: Mm.

Andrew Huberman: And then if you go deeper, those seem to disappear. They haven't disappeared. It's just that the red light isn't penetrating that far.

Glen Jeffery: Yeah.

Andrew Huberman: Right? It gets absorbed.

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: Now, if you bring a flashlight down with you, as night divers do, or even day divers will do that sometimes in order to see those, those red fish are still there deeper. But it disappears to you.

Glen Jeffery: Yeah, yeah.

Andrew Huberman: So, it's very interesting. I'd like to take a quick break and acknowledge one of our sponsors, Function. Last year, I became a Function member after searching for the most comprehensive approach to lab testing. Function provides over one hundred advanced lab tests that give you a key snapshot of your entire bodily health. This snapshot offers you with insights on your heart health, hormone health, immune functioning, nutrient levels, and much more. They've also recently added tests for toxins such as BPA exposure from harmful plastics and tests for PFAS, or forever chemicals. Function not only provides testing of over a hundred biomarkers key to your physical and mental health, but it also analyzes these results and provides insights from top doctors who are expert in the relevant areas. For example, in one of my first tests with Function, I learned that I had elevated levels of mercury in my blood. Function not only helped me detect that but offered insights into how best to reduce my mercury levels, which included limiting my tuna consumption, I'd been eating a lot of tuna, while also making an effort to eat more leafy greens and supplementing with NAC, N-Acetylcysteine, both of which can support glutathione production and detoxification. And I should say, by taking a second Function test, that approach worked. Comprehensive blood testing is vitally important. There are so many things related to your mental and physical health that can only be detected in a blood test. The problem is blood testing has always been very expensive and complicated. In contrast, I've been super impressed by Function's simplicity and at the level of cost. It is very affordable. As a consequence, I decided to join their scientific advisory board, and I'm thrilled that they're sponsoring the podcast. If you'd like to try Function, you can go to functionhealth.com/huberman. Function currently has a wait list of over 2,50,000 people, but they're offering early access to Huberman podcast listeners. Again, that's functionhealth.com/huberman to get early access to Function. I'd like to talk a little bit about the other end of the wavelength spectrum, short-wavelength light. And here I'd like to move to artificial lighting, and point to what I think is a very serious concern. I know it might seem a little bit extreme, but I am very concerned about the fact that people are exposed to so much short wavelength, what's commonly referred to as blue light, but I don't think that really captures it because people hear the words, "Blue Light," and they think, oh, if a light source appears blue, then that might be messing with my melatonin at night, and might be messing with my mitochondria even. But it's the white light coming from LED sources, which are basically what we use as lighting sources nowadays, that, yes, they contain blue light, but they also contain violet light and stuff that doesn't appear blue because you've got the other wavelengths in there. In other words, white light coming from LEDs is very short wavelength enriched. To me, that's a problem if short-wavelength light is causing dysfunction of mitochondria, and I do believe that's the case, unless it's balanced by the longer wavelengths.

Glen Jeffery: Mm-hmm.

Andrew Huberman: And at the same time, like anything, it can be remedied if we do the right thing. So, could you illustrate for us what happened over the last 30 years or so in most every country as we moved from... Well, actually, let's take it further back. Let's go from candlelight and firelight to incandescent bulbs. Let's also talk about halogen bulbs, and now LED bulbs. I know people like to focus on screens, but we'll set aside screens for the moment.

Glen Jeffery: Mm-hmm.

Andrew Huberman: Let's talk about indoor lighting.

Glen Jeffery: Mm-hmm.

Andrew Huberman: Because I am very concerned about the amount of short-wavelength light that people are exposed to nowadays, especially kids, especially given what you told us about blood glucose regulation. What's known about this?

Glen Jeffery: Okay, there's a group of us shuffling around corridors, all mumbling to one another saying, "How big a stink is this?" And some people are... I reviewed a document that was sent to the European Commission last week just before I came over here from a very balanced, Dutch lighting engineer when he wrote to the European Commission saying, "We've got to rethink this." And so, the group of us that are shuffling around, some of them are saying this is an issue on the same level as asbestos. This is a public health issue, and it's big. And I think it's one of the reasons why I'm really happy to come here and talk because it's time to talk, right? We've got enough data. So, LEDs came in, and people won the Nobel Prize for this, very rightly at the time, because they save a lot of energy. They are very energy efficient because they do not produce on the whole light that we do not see. So, the effort is all in what we see. Now, as you pointed out, the LED has got a big blue spike in it, although we tend not to see that, and that is even true of warm LEDs, and there is no red. Remember? So, we're talking about billions of years of evolution under broad-spectrum sunlight. When we had fires, that was pretty much the same. A fire is pretty much broad spectrum, candles pretty much broad spectrum. So, nothing really changed in our world until around 2000. As we get to 2005, we're starting to find that the incandescent lights with their loads of infrared start being pushed off the market.

Andrew Huberman: And that was purely because they take more energy.

Glen Jeffery: Yeah.

Andrew Huberman: Electric bills are higher, and they don't last as long.

Glen Jeffery: Yeah, exactly.

Andrew Huberman: Okay.

Glen Jeffery: So, when we use LEDs, the light found in LEDs when we use them, certainly we use them on the retina looking at mice, we can watch the mitochondria gently go downhill. They're far less responsive. Their membrane potentials are coming down. The mitochondria are not breathing very well. We can watch that in real time.

Andrew Huberman: Under LED lighting.

Glen Jeffery: Under LED lighting at the same energy levels that we would find in a domestic or a commercial environment.

Andrew Huberman: That's very concerning to me.

Glen Jeffery: It is. It was never picked up. Then also, if you do experiments, say for instance, on flies, flies don't live as long under blue light, right? Their mitochondria, again, decline quite markedly. You produce less ATP. If you look at mice, you find mice start putting on a lot of weight. They start putting on a lot of weight because their mitochondria are not taking that glucose out, and it's being deposited as fat. Their control of their blood glucose, not surprisingly, becomes unbalanced, and they start to behave slightly peculiarly in open field situations. Now, you and I know that when you put a mouse in an open field situation, it's a measure of how confident it feels. So, it runs around the edge at first until it feels happy, and then it wanders around the middle and all the rest of it. Mice under LED lighting do not make that transition from working around the edge and coming into the center, and that is possibly consistent with the notion they have low-level infection, chronic infection. That's all published. Now, there's some stunning data coming out of another lab, it will come out early next year, showing that these same mice have fatty livers. Again, not really desperately surprising.

Andrew Huberman: So, same food chow as their full-spectrum light counterparts, but they're under LED lighting, and they've got fatty livers.

Glen Jeffery: Yeah. They've got fatty liver. But there's a clear systemic effect here because their livers are smaller, their kidneys are smaller, and their hearts are slightly smaller. With the liver problems, we get a raise in what we'll call liver distress signals, proteins coming round, one's called ALT, which tells you your liver is not happy at all. Interestingly, where do you also find vast numbers of mitochondria? You find them in sperm. So, there is a greater concentration of sperm with abnormal swimming capacity and abnormal morphology in those mice, and the testicles have abnormal morphologies. Now, these are animals that are really running towards the end of their life, okay? But again, let's put all these things together. This is clearly telling us that it's not just the LED, it's the LED range, which is 420 to 440. It's a specific range that the mitochondria absorb, and it's the absence of the red light to counter balance that.

Andrew Huberman: Got it. So, this is so important for people to hear, and I just want to reiterate something you said earlier. You said that, at least to your mind, this exposure to excessive amounts of short-wavelength light, because of LEDs, is possibly as serious as asbestos exposure in terms of its detrimental effects to human biology. Possibly.

Glen Jeffery: Possibly. That's what we're shuffling around saying, getting confident about it. I'd point out another issue. Now, your colleagues, some are a bit more excitable than others. Some of them are very conservative and sit there...

Andrew Huberman: It depends on how much red light they're getting under.

Glen Jeffery: Yeah.

Andrew Huberman: Bad joke, I know.

Glen Jeffery: Yeah, bad joke.

Andrew Huberman: Yeah.

Glen Jeffery: Let's look at growth in lifespan in Western Europe. Chunks up, chunks up, chunk, chunk, chunk, chunk. Slowly, you know, we're living slightly longer on average one year than the next. And really you could draw a line along that curve. Yeah, it's relatively straight. We get a dent in the curve and the tendency towards asymptote, which means flattening out, after about 2010. Now, that can be corrected for COVID. Something is turning that down. Now, I'm not going to say LEDs are shortening the lifespan, but I've got a number of colleagues around me who are saying, "You need to take this one into account."

Andrew Huberman: Mm-hmm. And you did say earlier that amount of sunlight exposure, which includes balanced wavelengths of short, medium, and long wavelengths, is associated with longer life, less all-cause mortality.

Glen Jeffery: Yes, definitely.

Andrew Huberman: And that brings me to the other point that you made, so I'm aware that I'm just restating what you said. But it's really hovering in my mind as so important that I think people need to hear it again, which is it may not be that short-wavelength light is detrimental to mitochondria, per se. It's that in the absence of balanced light, you're taking whatever mechanisms that short-wavelength light have on mitochondria, and you're tipping the seesaw in that direction, and the other side of the seesaw would be weighted by long-wavelength light. So, presumably, because mitochondria evolved under short, medium, and long-wavelength light, I mean, let's be fair, it's not like they evolved under red torches, as you call them, right?

Glen Jeffery: Mm-hmm.

Andrew Huberman: The balance between these wavelengths is really what's key, and LEDs are just shifting the balance very heavily to short wavelengths. So, I realize that we're framing long wavelengths as great and short wavelengths as bad, but like so many things in biology, it seems that it may just be the balance that's important, and that long wavelengths can have this kind of protective effect, to some extent. But the way I'm thinking about it is that LEDs may be problematic because of just how heavily they weigh one side of the mechanism. Is that...

Glen Jeffery: I think you've got it in one there. It's a balance.

Andrew Huberman: As opposed to, being quote-unquote, "Toxic," right? It would be like saying, we need all three macronutrients. I suppose you could live without carbohydrates, but fats, proteins, and carbohydrates, and people will try and demonize any one of those depending on who they are.

Glen Jeffery: Yeah, yeah.

Andrew Huberman: But most cultures, most humans evolved in the context of eating some amount of all three of those macronutrients, maybe to varying degrees, different seasons, et cetera. So, you can't just say that one is bad, you know? Fats are bad, proteins are bad, carbohydrates are bad. It's the weighting of them that's going to influence biology differently. It seems like the same thing would hold for light. So, under... So, let's frame this in people's minds. Under typical lighting conditions with LEDs. So, if I go buy a LED light, light bulb, and it doesn't say sunlight mimicking or full spectrum, how little long-wavelength light is there in that bulb compared to sunlight, and how much short-wavelength light is there compared to sunlight? And not in terms of intensity, because obviously the sun is generally far more intense than any bulb, but in terms of the distribution of wavelengths. What sort of situation are we creating with those bulbs?

Glen Jeffery: Okay. So, first of all, you know, the way you've described it is absolutely the way I think about it, and I think all our colleagues. It's balance. It's balance. You should be very careful about what you read on an LED box because people are saying sun-like, right?

Andrew Huberman: Mm-hmm.

Glen Jeffery: Now, I've never found, commercially, an LED that says that that's really gone anything significantly beyond 700.

Andrew Huberman: Mm-hmm.

Glen Jeffery: Right? So, it doesn't matter what they're telling you, I'm exceedingly doubtful that commercially anyone has got anything that does that.

Andrew Huberman: Mm-hmm.

Glen Jeffery: Because the only way you could do that is to have a vast array of LEDs in a single device. So, you know, have an LED at 670, an LED at 700, an LED at... All the way up to over a 1000. It's not realistic because it's expensive and it draws lots of energy.

Andrew Huberman: Mm-hmm.

Glen Jeffery: And the other thing is that we now have found that the mitochondria knows that it's a compressed load of LEDs, because if you put people under a compressed series of LEDs like that, you don't get the same response or the same positive effect as you do if you put them under an incandescent light where the spectrum is totally smooth.

Andrew Huberman: Mm-hmm.

Glen Jeffery: There's no ups and downs at the top of them. It's totally smooth. Now, how a mitochondria does that is completely and utterly beyond me.

Andrew Huberman: But it makes sense. The mitochondria evolved under sunlight.

Glen Jeffery: Under sunlight, yeah.

Andrew Huberman: And sunlight is a smooth, when you say smooth, as opposed to bumps, what Glen is referring to is, short wavelengths leading, you said it's a continuum leading up to long wavelengths.

Glen Jeffery: Yeah, it's a continuum.

Andrew Huberman: Sunlight has that. We'll talk about incandescents in a moment. And these LEDs have these spikes of short, medium, and longish wavelength light, but they're not actually mimicking sunlight.

Glen Jeffery: Yeah. No. And isn't it amazing that mitochondria can sort that one out?

Andrew Huberman: I think it's really cool.

Glen Jeffery: And just makes me feel, by the time it's all over for me, I'll have got one bite at this apple, but there's a load more there that I think we're going to find out. They're doing things that are just inconceivable at the moment.

Andrew Huberman: What about incandescent bulbs and fire? I mean, aside from being concerned that people are going to burn their apartments and homes down if they use candlelight or firelight at night, how healthy is candlelight?

Glen Jeffery: Mm-hmm.

Andrew Huberman: How healthy is incandescent light with respect to the mitochondria?

Glen Jeffery: So, look, well, I think we're going to leave candlelight out of it, because to get enough light out of a candle, we're going to have to have copious amounts of candles.

Andrew Huberman: And that's where people burn down structures.

Glen Jeffery: Yeah, yeah. And, I noticed here in California people have got lots of wooden houses. Let's stay away from that one.

Andrew Huberman: Got a lot of what?

Glen Jeffery: Wooden houses.

Andrew Huberman: Well, we had a serious fire issue this very area.

Glen Jeffery: Yes, I know.

Andrew Huberman: I mean, as you're coming in the Pacific Coast Highway, you may have noticed.

Glen Jeffery: You can see it.

Andrew Huberman: That used to be covered with homes. I mean, it was a devastating fire, yeah.

Glen Jeffery: Yeah. To a first approximation, the spectrum of light that you get from an incandescent light bulb is highly similar to solar light, right? So, it covers almost the same range. It's a smooth function. We drift gently from short wavelengths into medium wavelengths into long wavelengths. So, in evolution, we were wandering around in sunlight. We then made the transition to fires producing the same light, and that's quite interesting. Where do we use fires? We use fires as we move further north, as we come out of Africa, as we move into... I mean, why did people... It's beyond me, having come for this interview from northern Europe in winter, it's beyond me as to why they ever did that because it's grim. But they had a light source that was very solar-like. And so, there was no issue there, I don't think. So, it's that really very dramatic change that happens in the early 2000s. Your body has never experienced such confined, limited spectrum of light, never experienced it before. And one of the other issues that relates particularly to devices that people may use to increase the amount of long-wavelength light they get, some of these devices are lasers. No living entity has ever seen monochromatic light before. It is a totally alien thing to life.

Andrew Huberman: Yeah, but please folks, do not shine lasers into your eyes.

Glen Jeffery: No. Do not.

Andrew Huberman: And in fact, don't shine lasers on your skin. The only people who should be shining lasers on bodies are trained medical professionals for which there's an important medical procedure being done. I'm going to encourage you to be willing to answer this even though I realize it's a bit of an uncomfortable space for you. For artificial long wavelength light-generating devices, like the red, near infrared, and infrared, some of these are fairly high power. There are a growing number of papers, certainly in dermatology and pain relief.

Glen Jeffery: Mm-hmm.

Andrew Huberman: I mean, not a ton of papers, but actually it was a cover of what I was told was one of the more prestigious dermatology journals. It's starting to evaluate what we call photobiomodulation with long-wavelength light.

Glen Jeffery: Mm-hmm.

Andrew Huberman: When you look at those devices, do you think that exposure to those can offset the negative effects of LED lighting in a meaningful way?

Glen Jeffery: First of all, I think the majority of them do no harm.

Andrew Huberman: Mm-hmm.

Glen Jeffery: I suspect that the majority of them have a positive impact. But we've opened up a lot of those devices, and they're pretty poor.

Andrew Huberman: Poor in terms of the amount of energy?

Glen Jeffery: Poor in terms of how they're put together, first of all. The value of the components.

Andrew Huberman: Okay, got it.

Glen Jeffery: When you get an LED, an LED's like buying a car. You can buy a bad car or you can buy a very good car. A lot of the LEDs are not what they say they are, certainly when it comes to things like 670 nanometers, which is popular. They're hard to get, so they're not what they say they are. And very often they're not what they say they are a year down the road when they've been on and off for a long period of time.

Andrew Huberman: Well, I think there's a range of qualities, as well. Some are medical grade, some are not.

Glen Jeffery: Yeah.

Andrew Huberman: Some are used actively by medical clinics, some are not. I hear you. I think it's like any industry associated with health and wellness, as it's called. I think there's a range. So, in terms of prescriptives as it relates to indoor lighting, let's set aside long-wavelength light emitting devices, incandescent sound like the perfect solution. But can I still buy incandescent bulbs?

Glen Jeffery: Not in North America. You can't buy classic incandescents.

Andrew Huberman: They're gone?

Glen Jeffery: Yeah, I think I signed a petition to try and keep them about six months ago, and I don't know what the status of it is now. You should still be able to get halogen bulbs, which are almost identical to incandescent. They're a type of incandescent.

Andrew Huberman: Mm-hmm.

Glen Jeffery: And the point here is that you can't have LED lights in ovens because they melt, okay? So, generally, incandescents are retained for a few special reasons. The importance of these I think is highlighted by something that should come out just before Christmas, one of our studies, where at University College London, we have some buildings without windows. And they've got some pretty harsh LED lighting in them. And what we did last year, with those is we went in there and we measured all the people, the staff in there, we measured their ability to detect color. Then we gave them a whole series of desk lamps, 40-watt incandescent desk lamps, and we said, "You don't have to look at this. Just move around." You know, if that's on your desk... But a lot of them were architectural model makers. So, they'd be sitting at their desk for a little bit of the time, then they'd be going off gluing two bits of wood together.

Andrew Huberman: Where's the light directed for these people?

Glen Jeffery: Just directed down.

Andrew Huberman: It's directed down, not at their eyes.

Glen Jeffery: No, no.

Andrew Huberman: Okay.

Glen Jeffery: It's supplementing their whole environment. So, we walked away from that, and we left them... I think we left them for two weeks. And we came back, and we measured their color perception again. And we got so much better an effect than we ever got with reduced-spectrum long-wavelength LEDs. It was... Well, I may just go back and do all the analysis again. I was really surprised. So, with the LEDs, what you tend to do is, the long-wavelength ones, you improve your perception of blue a bit more than your perception of red, and this is a bit of a complex story, and it's all over in five days. These characters, their perception of blue and red, both improved to the same extent, and it was very significant. And then we took the bulbs away, and we thought, "Well, we'll come back six days later, and we'll see where they are." And we came back. They were exactly the same. Their perception hadn't declined.

Andrew Huberman: The improvement was maintained.

Glen Jeffery: The improvement was maintained.

Andrew Huberman: Mm-hmm.

Glen Jeffery: We went back a month later. The improvement was maintained. We went back a month later. The improvement was maintained.

Andrew Huberman: Hmm.

Glen Jeffery: So I'm tracing all these people, what their lives are like, and the rest of it. It was in November, December, so they weren't getting much daylight. They were rather... Yeah. Well, they were in a situation that all people are in northern Europe. And then we had a problem. It was Christmas. Experiment ended. But let's think about this. These people not only had more significant improvement than they would get with red light, the effect lasted much longer. Now, one of the things that makes me think now, I go back, and I think about our experimental results. Why did I get such good experimental results in whatever it was I was doing? Is it simply because I'm drawing my subjects from a population of human beings who are living under LED lights? If I went and did those same experiments on a group of farm assistants, or people who are doing surveying of the countryside, would I get the same effect? I think that in the built environment, we are suffering from a suppression of our physiology. I have to be careful here about not going over the top. But we're suffering from a suppression of our physiology via mitochondria, that is just being produced by the built environment. And a point that I really need to make here, because I now spend a lot of time talking to architects. I spend more time talking to architects than I do talking to ophthalmologists or medics. You put a building up, invariably, the majority of the phases of that building will go over budget. It's rare for a building to come in under budget. The last thing to go into a building is the lighting. It is the very last. It goes in after the glass. Okay? Where do you take your cut on your overexpenditure? You take your cut on the lighting. You buy the cheapest LEDs you can, and the cheapest LEDs have got the restricted spectrum. And to add insult to injury on this, to retain thermal regulation of the building, all commercial buildings and all big buildings, now, not domestic ones, will invariably have infrared blocking glass. So you get the first hit on the fact that your LEDs are pretty awful, undermining your mitochondria. The second is, you're isolated from the visual world outside by the infrared blocking glass. This is a double hit, and I think that double hit is quite significant. Now, we have had a major, probably one of the world's largest architects firms that have just won a very big contract in the USA for a hospital, walk through the door and say, "What is this about healthy lighting?" And I know they're putting their money on the table on this one, because they have a vast area where all the architects sit. It's like an aircraft hangar. And they're stripping out all the LEDs.

Andrew Huberman: So, what I'm gathering is that if people spend a lot of time outside, A: that's a good thing.

Glen Jeffery: Mm-hmm. Yeah.

Andrew Huberman: B: You probably don't need to supplement your indoor lighting environment. LEDs might even be fine for those folks. Although you wouldn't recommend it. Doesn't sound like they need to, quote-unquote, "supplement" with incandescent or with long-wavelength light exposure from a device. For people, which I think is most people nowadays, who are under LED lighting, a significant portion of the day, in a building with glass that filters the bright sunlight to control the temperature and make sure there isn't a lot of glaringly bright light coming in at certain phases of the day, they certainly should try and get outside.

Glen Jeffery: Yeah.

Andrew Huberman: But when they can't take their lunch outside, take a call outside, get outside.

Glen Jeffery: Yeah.

Andrew Huberman: Light clothing is going to be fine because the long-wavelength light will pass through, as your colleague discovery, literally go through their body, scatter, et cetera. But they may choose to supplement with a halogen or incandescent, even just a table lamp for a short period of time, now and again, especially, it seems, in winter, this would be beneficial.

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: And where I worry the most about light environments as it relates to diminishing mitochondrial function is in kids who are staring at screens, not getting outside enough because of screens, classrooms, et cetera. What do we know about screen light? You know, I, like many people, will dim down my screen in the evening if I'm going to be on my computer. I do wear short-wavelength-blocking glasses; I wouldn't say after sundown, but after dark, really helps my transition to sleep for obvious reasons.

Glen Jeffery: Yeah. Mm-hmm.

Andrew Huberman: I learned that people's sensitivity to light, in terms of how it impacts sleep, varies quite a lot.

Glen Jeffery: Yes, it does.

Andrew Huberman: Some people can stare at blue light and fall asleep, no problem. Other people do that; they're waking up in the middle of the night. I'm very sensitive to it. But the blood glucose-elevating effects of short-wavelength light at night seem pretty ubiquitous. There's this study, I don't know if you're familiar with it. It was done, and it was published in the proceedings of the National Academy of Sciences. They had people, I think it was kids actually, sleep under a one-hundred-lux overhead light. So their eyes are closed. One hundred lux is very dim.

Glen Jeffery: Yeah.

Andrew Huberman: And as compared to complete darkness, or it wasn't complete darkness, I think it was, like, a one-to-ten lux lighting condition, you saw elevated blood morning glucose.

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: Which is not good, right? That reflects a cortisol increase. So it's not just about sleep, it's about blood glucose regulation, et cetera. So, I'm summarizing here quite a lot of things, and I'm speculating here and there as well. Do you think people need to supplement with long-wavelength light if they're not getting outside enough, or they work in one of these LED-rich environments?

Glen Jeffery: Okay, let's backtrack a little bit, particularly about the kids and screens. So, myself and a load of my colleagues have sat with a blue screen staring at it all day, for days. Mind-bogglingly boring thing to do. It had almost no effect on it.

Andrew Huberman: Oh, you've done that experiment?

Glen Jeffery: We've done that experiment.

Andrew Huberman: Oh, I thought you were just describing your life.

Glen Jeffery: No, no.

Andrew Huberman: Okay. Yeah, yeah.

Glen Jeffery: And I think the answer is that the blue in most of those screens is actually rather long-wavelength blue.

Andrew Huberman: Mm-hmm.

Glen Jeffery: So it's blue, pushing 450 plus. So, it's not in that danger zone, which I regard as 420 to 440.

Andrew Huberman: Mm-hmm.

Glen Jeffery: I think it's outside it. And I know we talked at one point to a major American computer manufacturer about this issue, about the screen. So, I am not as worried about that as I thought I would've been.

Andrew Huberman: Mm-hmm.

Glen Jeffery: But there is a separate issue, and it's one that the pediatric ophthalmologists are very concerned about, and that is particularly close work in kids. Close work combined with a lot of screen work and the issue of myopia.

Andrew Huberman: Close work being, staring at something within a foot or, or two?

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: Yeah.

Glen Jeffery: And myopia. Now, this is a very big issue in Asia, and in China.

Andrew Huberman: Mm-hmm.

Glen Jeffery: And we know that the absence of long-wavelength light is a driver. My problem is, I can't work out why. Now, I should fundamentally be a pragmatist and say, "If we know it's a driver, then let's just supplement it."

Andrew Huberman: When you say it's a driver, it's creating this problem.

Glen Jeffery: It is part of the thing that's creating this problem.

Andrew Huberman: Mm-hmm.

Glen Jeffery: Now, myopia is a really big issue because, okay, we can control myopia by just giving you different lenses, right? So, your child will be able to read the text even though they've got myopia. The trouble is that when that child reaches 40 or 50, the retina has been stretched because the eye has grown too long. And as the retina stretches, as you age, and you lose cells, so the retina becomes a little less cohesive, you get tears, and you can get a form of macular degeneration.

Andrew Huberman: Yikes.

Glen Jeffery: So, this is a major concern, particularly in China, and they've taken a number of steps to deal with it. One of which, for instance, is in the classroom, they put a bar on the desk, so the kids can't actually sit too far forward to read the text.

Andrew Huberman: Whoa.

Glen Jeffery: Right? So, to increase the distance. They've also got into the red light, but part of the problem there is they've used lasers. So they've got a restriction in myopic development. But at the same time, when you go back and look at them, there are spots in the retina where the laser has affected.

Andrew Huberman: Negatively.

Glen Jeffery: Negatively.

Andrew Huberman: It is burning out pieces of retina.

Glen Jeffery: Yeah. But you know, people come along, and they say, "Well, look, we only used 10 milliwatts per centimeter squared." Same as an LED. The thing that they don't get is that laser light scatters in a very different way from LEDs. LED light scatters uniformly.

Andrew Huberman: Why do you think they use lasers?

Glen Jeffery: Because it sounds good. We're using light. We're doing something more powerful. That's a problem around this whole industry. We're doing powerful things.

Andrew Huberman: Hmm.

Glen Jeffery: Now, laser light does not scatter evenly when it hits tissue. It forms something called caustics. And caustics are the sorts of things you see, sometimes, on a shallow lake where it's rippling, and you get bright spots, and you get dark spots. Those bright spots are what you get in laser light, these caustics. So the energy is tripling or quadrupling in certain areas. So, I mean, I didn't know what a caustic was until I started to talk to physicists. Reiterate on you, never ever use a laser, unless there is a profound medical reason for doing so. And certainly, myopia, which is going to be a ticking time bomb. No current politician is particularly concerned, because it's going to be another person's problem in the future. So, windows in classes, very important.

Andrew Huberman: And not tinted windows.

Glen Jeffery: Not tinted windows. We're currently talking about putting a few incandescent lights in. Schools generally are stretched for money.

Andrew Huberman: Mm-hmm.

Glen Jeffery: And their first reaction is "This is going to cost us a lot more." Well, the answer actually is to put a dimmer switch on the incandescent light bulb. Even though it appears dim to you, still producing loads of infrared light because it's getting warm. The other thing that we've not touched on, which is, I think, very important in the architectural world and the school world, is that all plant matter reflects infrared light. You grab a plant out here in California, where maybe it's 80 degrees, the leaf is not hot. Why does that happen? It's because it reflects infrared light. Now, if you go up to a plant in brilliant sunlight and you put your measuring equipment on it, the light that's being reflective is just a small reach away from what we think of the smallest therapeutic dose could be. So, planting trees to reflect the infrared light that is available to you is very important. Architects are really getting that one.

Andrew Huberman: Does it have to be trees, or can it just be indoor plants, and having an incandescent sort, sometimes?

Glen Jeffery: Well, okay, have an incandescent source, but have also plants on the outside that are getting sunlight, because they're going to bounce the infrared back to you.

Andrew Huberman: Mm-hmm.

Glen Jeffery: One of the physicists in our lab, Edward Barrett, has a fantastic infrared camera, and he goes around taking infrared photographs. And we were in an office building, and there was some blackout blinds or very thick blinds, and when we looked through the infrared camera, there was a small fire at the bottom of these curtains. I mean, just really surprised. And then we pulled back the curtain, and there was a row of plants.

Andrew Huberman: Mm-hmm.

Glen Jeffery: And there is... The name completely escapes me. There is a city in the Midwest where the authorities planted something like 1,000 trees. And what they did was they measured blood markers, that were blood markers of stress, including complement-related protein, which is a sign of systemic inflammation. And they planted these trees, and they went back, I think two or three years later, and measured these metrics, and they got a significant reduction. Now, that is interesting, right? So, my big question, and it's one that I'm trying to get ethics to do now, is what happens to your blood as you pass from a concrete building? You sit in a concrete building for five hours. It's horrible. You're getting no infrared light. You've got infrared blocking windows. You've got LEDs. What happens when I wheel you into a park? What happens when I wheel you into Woodland? You know you feel so much better. Everybody says, "I feel so much..." Well, if you feel better, something's happening. What is happening? So it's not only about the light that we have in the built environment, it's about the glass that we have in the built environment, and it's about plant matter. Plant matter, should we be planting plants, for instance, on the north side of buildings, which are tall, because they will hit the light level, and they have the capacity to reflect it back through, into the building?

Andrew Huberman: I can tell you've been spending a lot of time with architects. And there are a couple of things that are really striking. One, it's very clear that as we become more and more modern as a species, we're going to look for more cost and energy-efficient ways to do things. LEDs are a good example of that.

Glen Jeffery: Yeah.

Andrew Huberman: And I think LEDs have been very beneficial across a number of different industries. But that, you know, as we move away from agricultural living for most people, nowadays, people even will just have food delivered as opposed to going to restaurants.

Glen Jeffery: Yeah.

Andrew Huberman: That's happening more and more. And I think it's a required effort to bring the critical elements of the outside indoors.

Glen Jeffery: Yes.

Andrew Huberman: And it sounds kind of crazy, but people will exercise indoors. I try and exercise outside if I can, but I can't always do that. But we're now talking about bringing long-wavelength light indoors, and bringing balanced full-spectrum light indoors. And if it's as simple as bringing some plants, you know, putting plants around a building, keeping the tinting off of windows, maybe I could see where that might cause some issues with regulating temperature and the downstream costs of that, et cetera. But, having some long-wavelength emitting sources, maybe it's an actual long-wavelength, AKA red light, somewhere near a plant or a series of plants in a...

Glen Jeffery: Hmm. Hmm.

Andrew Huberman: Because not everyone can change their internal environment, their apartments, et cetera.

Glen Jeffery: No, no.

Andrew Huberman: I must say, in the last, probably, 18 months, I've made some pretty serious efforts to get in front of a long-wavelength emitting device. My own personal experience is that by doing that... And I do do it early in the day, I do not use protective eye covering because I'm comfortable with those wavelengths. I sometimes will close my eyes for portions of it. But I must say, and I don't think this is a placebo, but who knows, I find that it produces a tangible increase in energy and feelings of well-being, for a substantial amount of time afterwards for me. But that's on a backdrop of already doing a number of other things, including trying to get outside for brief 20-minute or even 10-minute walks, grab a little gulp of sunshine, as I call it. It's not really a gulp. I think that the more we can get outdoors, great, provided we don't sunburn.

Glen Jeffery: Mm-hmm. Yep.

Andrew Huberman: But we need to start bringing certain elements of the outdoors into classrooms and hospitals. I mean, there's this phenomenon, ICU psychosis, where people don't have access to sunlight and circadian rhythm information. They're being woken up in the middle of the night, and they're not psychotic, and they develop a transient psychosis that resolves when they leave the hospital.

Glen Jeffery: Hmm.

Andrew Huberman: I mean, I feel, as you can probably tell, very-very strongly that lighting is so critical for immediate and long-term health. And I agree with you. I think we, not to sound catastrophic, but if we don't, no pun intended, short-circuit this excessive short-wavelength light issue, that we are going to see more and more metabolic dysfunction, more and more visual dysfunction, myopia.

Glen Jeffery: Yeah. Yeah.

Andrew Huberman: And for people with neurodegeneration or a genetic bias toward it, or you know, maybe the occupational hazard-related bias toward it, that if they don't get the protective effects of long-wavelength light, I think it's going to be really serious.

Glen Jeffery: Hmm. Yeah. I completely agree with you. And we weren't sticking our head above the parapet three or four years ago, but we are now. We think this is a significant public health problem. We've been approached by a few critical care units saying, "What about changing our lighting?" I mean, the architects have taught me one or two things. So, they say cost to me, because they're commercial. So, they say things like "Okay, well, if that gets your patient out of intensive care unit one day earlier, what does it save you?"

Andrew Huberman: Mm.

Glen Jeffery: With one group of architects, we've talked about changing the lighting in a building that's having major refurbs on it. And oh, you know, the owners are going, "Oh, we're doing... Do we need this?" Et cetera, et cetera. And the architect turned around and said, "How many days did you lose to sickness in this building last year?" And, of course, they didn't know the answer, but it put them, really, on the spot. But the architect said, "You should look at the larger economic model here, and that includes the health, perceived health of the individual. But it may have beneficial effects for you in terms of reducing costs."

Andrew Huberman: Mm-hmm.

Glen Jeffery: I think they put their finger on that, really, quite sharply.

Andrew Huberman: Hmm. For people that are on a real budget, and like most of us, have to rely on LED lighting, hopefully they're dimming their lighting a bit in the evening, not relying so much on overhead lighting, trying to get their circadian rhythm correct.

Glen Jeffery: Hmm.

Andrew Huberman: And in the daytime, getting outside, get their sunlight in the morning, et cetera. And they want to get some more balanced or long-wavelength light, and they want to do it in the least expensive way possible. Even though candlelight is not very bright, I would recommend getting an odorless, because we're learning all this stuff about the odors from candles. A, you know, an odorless, like a pure beeswax candle, provided it's safe, they can put at their desk in the evening or maybe even on their nightstand, they can have a candle while they read. Just getting a bit more long-wavelength light. As you say, supplementing with long-wavelength light here and there. Maybe, while even they're on their phone or their tablet before sleep.

Glen Jeffery: Yeah.

Andrew Huberman: I feel like these things ought to make a meaningful difference over time. They're very low-cost. Provided you don't burn your structure down, they're safe. And even better, it sounds like it would be to get a hold of an incandescent or a halogen bulb. But I feel like this is something that almost anyone could do, and it seems very, very healthy to do.

Glen Jeffery: Well, I am 100% behind the idea that, firstly, this can change public health; and secondly, that it should be done at almost zero-cost, because that is a potential. Okay? So, if you look at, say, a number of my colleagues, and this includes myself, in the kitchen, I have got a halogen lamp. So, when I get up in the morning and, you know, you're spending that 45 minutes that really should be 10 minutes, but you're faffing around, doing stuff, there's a halogen lamp there, on at the right time. It's not desperately bright, but it's there at a critical time during the day.

Andrew Huberman: What color does it appear?

Glen Jeffery: Ordinary white light.

Andrew Huberman: Okay. But it's full spectrum?

Glen Jeffery: But it's full... A proper halogen lamp is just a certain kind of incandescent that has potential, longer life, in terms of its shelf life, because there are reasons you should keep it, reasons you should have it.

Andrew Huberman: Hmm. Mm-hmm. Mm-hmm.

Glen Jeffery: And just do that.

Andrew Huberman: Great.

Glen Jeffery: A halogen lamp, and particularly if you can afford to dim it, it'll last almost forever. Because if you just turn the power down, which increases the amount of infrared light, the bulb will last for ages. Absolutely ages.

Andrew Huberman: Mm-hmm. And you're using this in the morning, you could also use it in the evening. And if you dim it down, it's not going to alter your melatonin level, circadian rhythm much.

Glen Jeffery: No. And if you dim it down, your energy bills should not go up.

Andrew Huberman: Mm-hmm.

Glen Jeffery: So I believe, profoundly, that we can affect public health, and we should affect public health at a highly economic way. So we are working hard on what's the minimum? What's the minimum? What's the minimum?

Andrew Huberman: Mm-hmm.

Glen Jeffery: In critical care units, a big one that we really are trying to dent is nursing homes, where these people spend all their time in beds, or they're away from windows. Can we wheel them all in for breakfast and actually have a heat source, an incandescent heat source, to provide incandescent light, but at the same time use that heat?

Andrew Huberman: Mm-hmm.

Glen Jeffery: So the architects used to say, "Well, if you want me to change all these lighting, what am I going to do with all this excess heat coming off ceiling lamps?" Well, they've turned around now, they're saying, "We'll put them lower down and maybe we'll use the heat circulating in the room." There's lots of imaginative ways around this.

Andrew Huberman: Mm-hmm. Mm-hmm.

Glen Jeffery: There's 50 PhDs in this, with some really simple winner experiments.

Andrew Huberman: It's great. I mean, I'd like everyone to think about their indoor lighting environment, how much sunlight exposure, and short-wavelength-shifted LED exposure they're getting during the day. Not because I'm really into extreme biohacking. I'm actually not. I just think that whatever we're missing from the out-of-doors that we need and is healthy for our mitochondria, which clearly involves long-wavelength light; your work has demonstrated that beautifully, and the work of others, of course.

Glen Jeffery: Hmm.

Andrew Huberman: You're always so good at attribution, so I want to acknowledge you for that by doing it as well. I think people should do it. And if it's an incandescent bulb, or a halogen, or candlelight, it seems like it would make a meaningful difference.

Glen Jeffery: Yeah.

Andrew Huberman: Speaking of meaningful differences, before we part ways here, I would love to hear a story that you were starting to tell me before we recorded, about a child with a mitochondrial disease. And how some of this stuff about light and mitochondria was actually useful in that context.

Glen Jeffery: Yeah. So, we're doing clinical trials, and I'm quite optimistic about some of them. But there is a specific group of diseases called mitochondrial diseases, where the genetic code, because mitochondria have got their own DNA, the genetic code for making ATP gets disrupted. And that can be mild, or it can be very severe. Some of these children do not make it beyond 25. Typical reasons are heart failure, et cetera. Some of them are very bed-bound and crippled by the disease. Others manage to walk around and function to a first approximation. And I started to get emails from people who said, "You were showing red light, you're using the word red light and mitochondria, improving mitochondria. My child's got mitochondrial disease." And I said, "I don't have ethics for that. I can't pass any real comment. If you chose to do something, then I suggest you might consider doing this." And the first child that did do that had a, I would say, gut-wrenching improvement. We were devastated by its effect.

Andrew Huberman: Positive effect?

Glen Jeffery: Positive.

Andrew Huberman: Over here, when we say gut-wrenching, we mean it was negative.

Glen Jeffery: Oh, no, no.

Andrew Huberman: You're saying, "eye-watering" for you guys is negative, "gut-wrenching is positive. Over here, "eye-watering" is positive, and "gut..." I'm just teasing.

Glen Jeffery: Okay.

Andrew Huberman: Yeah.

Glen Jeffery: So, we were looking at simple metrics, which is, how much they could open their eyelids. It's called ptosis, right? Couldn't open their eyes. This child, the first child within a month or so, had semi-mobility.

Andrew Huberman: Amazing.

Glen Jeffery: I got a video of her walking to school.

Andrew Huberman: Amazing.

Glen Jeffery: I went to the bathroom and sobbed. "Done something that's really helped someone." Then we had another couple of kids, and they all had small improvements. We got a clinical trial for it. And our biggest problem is, we couldn't get enough kids into the study. The density of kids with mitochondrial disease in the UK, we got funding for it, was just too low. So one of the things I've got to do, sadly, when I go back, certainly before Christmas, I've got to wrap that up and hand the money back. I'm just going to say, "Just could not get the kids." And some of them, as I told you, when that disease digs in badly, we can't do anything about it. Some of those kids were just so sick. You know, it was a major effort to get them to the hospital to assess them.  But let's take a defocused image on this. In theoretically, red light should help kids with mitochondrial disease. It will do absolutely no harm whatsoever. And I generally say, if all of this is a pile of rubbish, A: I'll look an idiot, but I don't think I am going to look an idiot. B: You will not have wasted money on something that's just completely worthless. So, I'm talking to people now, and I'm saying, "Okay, why don't you think about changing the light bulbs in the home to just get that extra bit of red light to help you through?" We've got a trial for a retinal disease coming out shortly. I don't know the results. They won't show me, probably because they know I'll talk. And it's for a disease called retinitis pigmentosa.

Andrew Huberman: Very common.

Glen Jeffery: And we've had a fantastic response from a donor in the States, who has given us some money. And the next project in that line is changing the light bulbs for patients with retinitis pigmentosa. Now, I'm partly working at Moorfields Eye Hospital. Supposedly, it's got the biggest ophthalmic outpatient population in the world. And we do have enough people with retinitis pigmentosa. So I'm going to kick that off towards the end of this year. Everything's pointing towards light bulbs. Everything's pointing towards... And I would, at this point, say, and I'm not saying it for the first time here, I've shouted about it for the last six months, Moorfields Eye Hospital is building a brand-new hospital. Looks great. It's all in glass. It blocks infrared. And it's going to have the world's worst LEDs put in it. You know? We need to learn, but it's apparent to me, we're going to have to learn slowly.

Andrew Huberman: As with so many things with human health. But listen, Glen, I want to thank you on many levels. First of all, for taking the long trek over here from the UK. We have some sunlight to offer you.

Glen Jeffery: Oh, let's look. I'm on the Huberman podcast. That's a big pro, plus in life.

Andrew Huberman: All right, well.

Glen Jeffery: I got out of London, which was gray, grim, cold, and wet. You didn't have to talk too hard to get me over here.

Andrew Huberman: All right. Well, we're happy to have you here in the studio sharing all this knowledge. And also, I really want to thank you for shifting your focus of research. We won't waste people's time by talking about the various things that you and I worked on for years. We were in slightly overlapping fields, and then, different fields, and we would overlap again. But we go way back, and you've always done such meticulous and really beautiful work. But I think you and I have shared with one another, and I'll share now, that, at some point, one reaches a juncture in their career, where you kind of go, "How can I make the most positive impact?"

Glen Jeffery: Hmm. Hmm.

Andrew Huberman: And a few years back, when I started seeing the studies that you were doing on bees and mice, and then, humans, evaluating how different wavelengths of light can impact visual function, mitochondrial health, and the number of really terrific collaborators that you've brought in around that. And again, I love the way that you give such ready attribution to the other people in the field, and also that you are willing to be vocal about what people can do. Scientists are often afraid of that. You give people meaningful suggestions about how they can, perhaps, improve their health, their vision, et cetera, using low-cost or even, in some cases, cost-saving technology. I could go on and on here, but I really want to thank you for sharing all this knowledge, for doing the work you do, and for being a voice for public health, as it relates to indoor and outdoor lighting. And I really look forward to seeing what you do next, and it's a real pleasure for me to sit down with a long-term colleague. So thank you.

Glen Jeffery: I thoroughly enjoyed it.

Andrew Huberman: Yeah.

Glen Jeffery: Thank you.

Andrew Huberman: Thank you for joining me for today's discussion with Dr. Glen Jeffery. To learn more about his work and to find links to the various resources we discussed, please see the show note captions. If you're learning from and/or enjoying this podcast, please subscribe to our YouTube channel. That's a terrific zero-cost way to support us. In addition, please follow the podcast by clicking the "Follow" button on both Spotify and Apple. And on both Spotify and Apple, you can leave us up to a five-star review. And you can now leave us comments at both Spotify and Apple. Please also check out the sponsors mentioned at the beginning and throughout today's episode. That's the best way to support this podcast. If you have questions for me or comments about the podcast, or guests, or topics that you'd like me to consider for the Huberman Lab podcast, please put those in the comments section on YouTube. I do read all the comments. For those of you that haven't heard, I have a new book coming out. It's my very first book. It's entitled "Protocols: An Operating Manual for the Human Body." This is a book that I've been working on for more than five years, and that's based on more than 30 years of research and experience. And it covers protocols for everything from sleep to exercise, to stress control, protocols related to focus and motivation, and of course, I provide the scientific substantiation for the protocols that are included. The book is now available by presale at protocolsbook.com. There, you can find links to various vendors. You can pick the one that you like best. Again, the book is called "Protocols: An Operating Manual for the Human Body." And if you're not already following me on social media, I am hubermanlab on all social media platforms. So that's Instagram, X, Threads, Facebook, and LinkedIn. And on all those platforms, I discuss science and science-related tools, some of which overlaps with the content of the Huberman Lab podcast, but much of which is distinct from the information on the Huberman Lab podcast. Again, it's hubermanlab on all social media platforms. And if you haven't already subscribed to our Neural Network Newsletter, the Neural Network Newsletter is a zero-cost monthly newsletter that includes podcast summaries as well as what we call protocols, in the form of one-to-three-page PDFs that cover everything from how to optimize your sleep, how to optimize dopamine, deliberate cold exposure. We have a foundational fitness protocol that covers cardiovascular training and resistance training. All of that is available, completely zero cost. You simply go to hubermanlab.com, go to the Menu tab in the top right corner, scroll down to Newsletter, and enter your email. And I should emphasize that we do not share your email with anybody. Thank you once again for joining me for today's discussion with Dr. Glen Jeffery. And last but certainly not least, thank you for your interest in science.

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