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

Welcome to the Huberman Lab Podcast. I’m Andrew Huberman, and today I’m joined by Dr. Glen Jeffery of University College London to explore how light—especially red, near infrared, and infrared—can enhance cellular health, metabolism, and even brain function. We’ll cover how long wavelengths support mitochondria, how they pass through the body, and how to apply them safely in daily life.

I’m deeply worried about indoor light. The short-wavelength heavy output from LEDs is a public health issue. In our lab we can watch mitochondria lose vigor under LED-like spectra at everyday intensities.

Set up the basics for us. What’s the light spectrum, what’s outside what we can see, and how does that matter for cells?

We see roughly 400 to 700 nanometers, but sunlight stretches far beyond—to about 300 nanometers in the ultraviolet and out near 3000 in the infrared. Short wavelengths carry more punch and drive sunburn, while long wavelengths carry energy without that damaging kick. The eye blocks most UV, which is why snow blindness and cataracts happen at the front of the eye.

We should protect skin and eyes from too much UV, yet sunlight is linked to lower all-cause mortality. Some melanomas aren’t sun-driven, so the story is nuanced. I’m keen on the newer data that more sunlight tracks to longer life.

Dermatologist Richard Weller has reanalyzed this and argues that avoiding sunburn while getting sunlight associates with lower mortality. The field followed assumptions for years; now the balance of risks and benefits is being rethought.

Let’s move to mitochondria. How do long wavelengths help them?

Early work suggested mitochondria absorb red and near infrared, but the big insight is water. Long wavelengths alter the properties of nanowater around the ATP motor, letting it spin more easily. You also get more of the proteins that move electrons, so there’s an immediate boost and a longer-term buildout.

That fits with mitochondria’s watery, bacterial heritage. And it’s helpful to remember that what looks red reflects red, while water and tissue absorb it.

Exactly. The absorption profile that drives the benefits matches water’s absorption, including known peaks. We should have looked at the milieu sooner.

How deep do these long wavelengths go? Through skin and clothing? Do they scatter?

Most of the long-wavelength energy that hits you goes in and scatters widely. Only a small fraction exits out the other side. It even goes through common fabrics—multiple layers of t-shirt material—and color doesn’t matter. In rooms, beams bounce, so a point source is not the only source if walls are close.

You ran a striking study on blood sugar. Can you walk us through it?

After seeing red light lower glucose excursions in starved bumblebees and blue make them worse, we did a glucose tolerance test in humans. A brief red light exposure to a small patch of back skin before the drink reduced the glucose spike by a bit over twenty percent. There was no heat sensation. The area was tiny, yet the effect was systemic, which fits the idea that mitochondria signal as a network.

There are primate data on Parkinson’s where abdominal light reduced symptoms. What might be happening there?

Long wavelengths tamp down pathways to programmed cell death, so stressed cells are less likely to die. We’ve also slowed age-related rod photoreceptor loss with daily red light. Mitochondria behave as a community, so local improvements can ripple outward, and damaged mitochondria can spread trouble too.

Can long wavelengths reach the brain through the skull?

Yes. They pass through bone. Deoxygenated blood absorbs some, so you see veins in transillumination, but most structures are traversed. Clinically, red and near infrared pass through neonatal heads to monitor mitochondrial status, and ethics boards view this as safe, non-ionizing light.

Define the useful bands for us, and note that very intense light can appear visible even beyond typical limits.

Vision fades around 700 nanometers, and we work mostly from there to near 900. Push the energy high enough and people can perceive beyond, but for biology we target the near infrared band.

You’ve shown that brief eye exposure to long wavelengths improves color vision. How big is the effect and how long does it last?

Three minutes at 670 nanometers improved color contrast thresholds by around twenty percent in most people. Eyes could be open or closed. A single exposure works, and the benefit lasts about five days. It behaves like a switch rather than a gradual dose response.

What’s the best time of day, and how bright does the light need to be?

Mornings are best across flies, mice, and humans, likely because mitochondria prioritize ATP then. We used to think you needed high irradiance, but we see effects at very low levels—down near one milliwatt per square centimeter.

So sunlight is always beneficial, but devices give control. Cloud cover will scatter and trim long wavelengths, yet there’s still plenty outside. Get out when you can.

Yes. Sunlight is broad and rich, devices are narrow but precise. On overcast days long wavelengths are attenuated and arrive from many angles, but you still get meaningful exposure. My mantra is: get outside, often.

Do younger people benefit less? And how should someone set this up at home?

Older individuals often show bigger gains, but responses vary widely. Practically, a comfortable red or near infrared source a few inches away for about three minutes in the morning, every five days or so, is a simple starting point.

What about macular degeneration and other diseases? Is timing critical?

Late-stage disease didn’t improve in our early trial, but earlier disease did in follow-ups. The pattern repeats in other conditions: intervene early, keep energy modest, and tune wavelength and timing to drive larger gains.

If I target the light to a specific organ, do I help that organ most, then see systemic effects later?

Local effects arrive first, distant tissues follow hours later. We see shifts in serum cytokines at low levels that look protective, and microvesicles likely carry signals. Cells can even donate healthy mitochondria to neighbors.

Let’s tackle LEDs and indoor lighting. Why do you see this as a big problem?

LEDs are efficient but heavily weighted to short wavelengths and lack red. In animals, that profile lowers mitochondrial performance, pushes weight gain and glucose dysregulation, induces fatty liver, alters open-field behavior, and worsens sperm quality. The core issue is spectral imbalance.

So balance matters. Sunlight is smooth across wavelengths, while many LEDs have spiky outputs. And lasers are not a good idea for self-use.

Right. Stacking multiple LEDs still doesn’t recreate a smooth incandescent-like spectrum, and mitochondria seem to notice. Lasers create hot spots in tissue, so they’re for medical professionals only.

Can red and near infrared devices offset LED-heavy environments? And what about bulbs we can actually buy?

Many devices likely help, but component quality is uneven. Classic incandescents are largely gone in North America, yet halogens remain and are close in spectrum. In a windowless UCL building, adding incandescent desk lamps led to large, lasting improvements in color perception over weeks.

Buildings often use cheap LEDs and infrared-blocking glass, so it’s a double hit. For people inside all day, get outside when possible and consider a halogen or incandescent source to balance the spectrum.

Agreed. Architects are now asking for healthy lighting. Retrofitting away from poor LEDs and avoiding infrared-blocking glass can make a real difference.

What about screens and kids? And can plants help indoors?

Most screens emit longer blue, outside the worst band. The bigger pediatric issue is near work plus low long-wavelength exposure driving myopia. Don’t use lasers. Bring in daylight, use dimmable incandescent or halogen where possible, and add plants outside windows—leaves reflect infrared and can feed it back in. Tree planting even tracks to lower inflammatory markers.

Modern life pushes us inside, so we need to bring key parts of the outside in. I find early-day long-wavelength exposure boosts my energy, and I’d love to see hospitals and schools adopt these principles.

It’s a health and economic win. Better lighting can shorten ICU stays and reduce sick days. That matters to administrators.

For low-cost options, people can use a clean-burning candle or a simple lamp. Any final practical tip?

Keep a halogen lamp in the kitchen for morning use, and dim it in the evening. It’s full spectrum with plenty of infrared, and dimming makes bulbs last while maintaining the helpful wavelengths.

We can boost public health cheaply by rethinking indoor lighting; dimmed incandescent sources add long-wavelength light without driving up energy bills.

We’re testing practical setups for places like nursing homes, even using lower, heat-emitting fixtures so the warmth is useful rather than wasted.

This isn’t about extreme biohacking; check your sunlight versus blue-shifted LED exposure, and consider safe long-wavelength light from incandescent, halogen, or even candles.

Before we wrap, could you share the story about the child with a mitochondrial disorder and how light helped?

Mitochondrial diseases impair ATP production and range from mild to severe, and families started asking if red light could help.

I didn’t have ethics approval, but one family tried it and the improvement was dramatic in a positive way.

Just to be clear, you mean it helped a lot.

We tracked simple measures like eyelid opening, and within about a month that child was walking to school; I cried in the bathroom.

A few others showed smaller gains, so we started a trial but could not recruit enough children in the UK and will have to return the funds.

Stepping back, red light looks safe and plausibly helpful, so I tell families to consider swapping household bulbs to increase the red component.

We also have a Moorfields Eye Hospital study in retinitis pigmentosa queued up with support from a US donor.

Ironically, the new Moorfields building blocks infrared and plans harsh LEDs, which shows how slowly institutions adapt.

Thank you for making the trip from the UK; we can at least offer some sun.

Happy to be here, and it was easy to leave cold, grey London.

I appreciate how you pivoted your work to show how wavelength shapes vision and mitochondrial health, and how you share practical, low-cost guidance.

It’s an honor to have you here, and I’m excited for what you do next.