Huberman Lab
Using Red Light to Improve Metabolism & the Harmful Effects of LEDs | Dr. Glen Jeffery
01 Dec 2025
Dr. Glen Jeffery, PhD, is a professor of neuroscience at University College London and a leading expert on how different colors (wavelengths) of light impact cellular, organ and overall health. He explains that long-wavelength light (red, near-infrared and infrared) can enter the body and brain to enhance mitochondrial function and thereby improve metabolism, eyesight, blood glucose regulation, mood, hormones and more. We also discuss how short-wavelength light from LED bulbs can impair mitochondrial health and why balanced, full-spectrum light is essential for health. Dr. Jeffery shares simple yet powerful ways to use natural and artificial light sources to enhance your metabolic function, eyesight and longevity. Sponsors AG1: https://drinkag1.com/huberman Wealthfront*: https://wealthfront.com/huberman Joovv: https://joovv.com/huberman Rorra: https://rorra.com/huberman Function: https://functionhealth.com/huberman Timestamps 00:00 Glen Jeffery 03:12 Light, Ultraviolet (UV), Visible & Infrared (IR) Light 06:25 Light's Impact on the Body & Light, Sunburn, Cataracts 09:55 UV Light, All-Cause Mortality, Skin Cancer 14:55 Sponsors: Wealthfront & Joovv 17:58 Light Impacts Mitochondria Function & Structure, Long-Wavelength Light (Red/IR), Nano Water 25:00 Long-Wavelength Light Passes Through Clothing & Body; Tissue Scattering 30:08 Long-Wavelength Light & Blood Glucose; Mitochondria 36:19 Red Light, Parkinson's Disease, Cell Death; Eye Rods & Aging; Mitochondria Community 42:46 Red/IR Light, Skull & Brain; Safe Non-Ionizing Radiation 48:22 Sponsors: AG1 & Rorra 51:04 Offsetting Retinal Aging, Improve Vision & Long-Wavelength Light 59:28 Tool: Long-Wavelength Light & Preserve Retinal Mitochondria; Sunlight 1:03:50 Mitochondrial Theory of Aging, Circadian Rhythm & Mitochondria 1:07:57 Tool: Improve Vision with Long-Wavelength Light 1:10:44 Macular Degeneration, Rescuing Vision, Early Intervention 1:13:59 Light Effects at Local vs Distant Tissues, Immune System, Body Communication 1:19:09 Sponsor: Function 1:20:56 Short-Wavelength Light, LED Light, Mitochondria & Serious Health Detriments 1:28:39 Lifespan, LED Lights; Sunlight & Balanced Wavelengths; "Sunlike" Marketing 1:34:45 Fires, Incandescent Lights vs LED Lights, Lasers; Long-Wavelength Devices 1:39:07 Incandescent & Halogen Bulbs, Mitochondria & Built Environments 1:45:19 Windows, Light & Office Work; Screens, Kids & Myopia; Tools: Plants; Lighting 1:55:56 Bring the Outdoors Indoors 2:00:35 Tool: Candlelight; Dim Halogen Lamps 2:05:06 Mitochondrial Diseases, Children & Long-Wavelength Light; Light Bulbs 2:11:53 Zero-Cost Support, YouTube, Spotify & Apple Follow, Reviews & Feedback, Sponsors, Protocols Book, Social Media, Neural Network Newsletter *This experience may not be representative of other Wealthfront clients, and there is no guarantee of future performance or success. Experiences will vary. The Cash Account, which is not a deposit account, is offered by Wealthfront Brokerage LLC, member FINRA/SIPC.Ā Wealthfront Brokerage is not a bank. The base APY is 3.50% on cash deposits as of November 07, 2025, is representative, subject to change, and requires no minimum. If eligible for the overall boosted rate of 4.15% offered in connection with this promo, your boosted rate is also subject to change if the base rate decreases during the 3 month promo period. Funds in the Cash Account are swept to program banks, where it earns the variable APY. New Cash Account deposits are subject to a 2-4 day holding period before becoming available for transfer. Investment advisory services are provided by Wealthfront Advisers LLC, an SEC-registered investment adviser. Securities investments: not bank deposits, bank-guaranteed or FDIC-insured, and may lose value. Learn more about your ad choices. Visit megaphone.fm/adchoices
Chapter 1: What is discussed at the start of this section?
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.
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 change. gently go downhill.
They're far less responsive. Their membrane potentials are coming down. The mitochondria are not breathing very well. Watch that in real time.
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. Glenn Jeffrey, 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. Jeffrey'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. Jeffrey 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.
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Chapter 2: How does light impact mitochondrial function?
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 drive 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.
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Chapter 3: What are the effects of long-wavelength light on blood glucose?
And now for my discussion with Dr. Glenn Jeffrey. Dr. Glenn Jeffrey, welcome. Thank you. Thank you very much. We go way back. Later, I'll tell a little bit of the story and why it is truly fascinating. unforeseen that we'd be sitting here talking about what we're talking about, but it's great to see you again.
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. 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.
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.
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.
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Chapter 4: How can red light therapy improve vision and cellular health?
That's our spectrum. Nanometers. Yeah, nanometers.
And there we're talking about the wavelength, how bumpy those wavelengths of light are.
Yeah. Sunlight extends out almost to 3,000 nanometers. Just think about it. 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.
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...
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 sunburn 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 colours, 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. red, orange, yellow, green, blue, indigo, violet, right?
We can separate those out by shining light through a prism. I think the cover of the Pink Floyd, Dark Side of the Moon album. 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? 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.
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Chapter 5: What role does morning light play in mitochondrial function?
Yes, we've got more room to lift them up and improve their function.
What was the time of day, so-called circadian effect of this?
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. So, 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, 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 account of time a 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 as 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.
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 9 o'clock in the morning was not a mitochondria at 4 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.
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Chapter 6: How can long-wavelength light improve vision?
No. No, you don't. So we were, 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. So people started off at, say, 40 milliwatts per centimeter squared. And I looked at that and I thought, crikey. That's bright.
That's bright.
That's very bright.
Big after effect. Yeah, that's going to make someone wince. 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. But then we had someone in the lab do an experiment and we had the flashlights that had batteries in them, which got a lovely effect, and we found out the batteries had been run down.
She was getting an effect close at one milliwatt per centimeter squared. That is low. That's dim red light.
That is low. Okay. So it sounds like one can use dim to moderately bright red light that's comfortable. I say red, but I mean long white light that's comfortable and likely get the effect. 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.
You've also looked at this in the context of macular degeneration, which is a very common form of blinding, especially in people as they get older. What were the results in terms of rescuing vision in people with macular degeneration?
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 100 years, probably 20% of you will have macular degeneration. Remember, the retina is 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.
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Chapter 7: What are the negative effects of short-wavelength light from LEDs?
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. 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 there will be these systemic effects those mitochondria are talking other mitochondria i mean i'm fascinated by how mitochondria are perhaps transported between cells and around the body there's there's a not even a cottage industry anymore i think a lot of biologists are thinking about this seriously but let's say i want to improve the function the mitochondrial function in it in my gallbladder um should i shine the red light on my gallbladder it seems to stands to reason that that
the answer would be yes.
I think the answer is yes. The issue is how quickly the effect takes place in distal and proximal tissues. So if you shine the light on your kneecap, something will probably happen within one to two hours. At the kneecap. At the kneecap. Right, right, right. But then if you're examining the response of that on your hand, it's 24 hours later, right?
So the message has to get out and things have to, the story has to spread. And the spreading of the story, that's an intense kind of area of activity. What is the signal? Where is it coming from? What is the signal? And I think we poked our finger at that slightly because we found that cytokine expression in the serum changed a lot. Inflammatory cytokines are going down? No.
Increase in cytokine expression at low levels is protective. So what it's saying to the body is brace yourself. Something's coming. Immune system is getting mobilized. Yeah. So that was very, very clear. So animals that had improvements in physiology also had changes in cytokine expression. 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, there. 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 cargoes. Now, they carry all different sorts of cargoes. 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.
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Chapter 8: How can we balance light exposure for better health?
It's just that the red light isn't penetrating that far.
It gets absorbed.
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 red fish are still there deeper, but it disappears to you. 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.
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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 slash Huberman. Function currently has a wait list of over 250,000 people, but they're offering early access to Huberman podcast listeners.
Again, that's functionhealth.com slash 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.
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