Huberman Lab Podcast Ep. – Using Red Light to Improve Metabolism & the Harmful Effects of LEDs | Dr. Glen Jeffery

Date: December 1, 2025
Host: Dr. Andrew Huberman
Guest: Dr. Glen Jeffery (Professor of Neuroscience, University College London)

Episode Overview

This episode delves deep into the biological effects of light on human health, with a concentrated focus on how different wavelengths—especially red and long-wavelength light—affect mitochondrial function, metabolism, vision, and overall health. Dr. Glen Jeffery brings groundbreaking research on how red and infrared light can improve cellular health and counteract the potentially detrimental effects of modern indoor lighting, particularly LEDs. The conversation spans topics from evolutionarily informed light exposure, the mechanisms by which light affects mitochondria, to actionable, low-cost changes for optimizing health in a modern, LED-dominated environment.

Key Discussion Points & Insights

The Spectrum of Light and Its Biological Effects

• Visible and Invisible Light: Light ranges from deep blue/violet (~400 nm) to deep red (~700 nm), and the sun emits even more light in the infrared (~3,000 nm) and ultraviolet (~300 nm) ranges (04:19).
• Sunlight vs. Artificial Light: While sunlight comprises a broad spectrum, most LEDs emit heavily in the short-wavelength/blue areas and lack significant long-wavelength (red/infrared) emissions (84:52).
• Absorption vs. Reflection: Biological tissues (and water) absorb different light wavelengths differently, which has wide-ranging effects on our physiology—and is key to understanding red light’s benefits (23:23).

Light's Impact on Mitochondria & Cellular Health

• Water as the Absorber: Red and long-wavelength light aren’t primarily absorbed by mitochondria themselves but by the water surrounding them, increasing ATP production via increased rotation of mitochondrial ‘motors’ (18:07–21:50).
• Train Analogy: "Giving red light gets the train to run down the track faster... then something detects the speed and says, lay down more tracks. So we're finding a lot more protein there that is associated with passing that electron down the pathway to make energy." (21:50, Dr. Jeffery)

Experimental Evidence: Metabolism and Vision

• Systemic Effects of Red Light: Exposing even a small patch of skin to red light (e.g., a 4x6 inch area) before a glucose tolerance test leads to a 20% reduction in glucose spike, demonstrating systemic mitochondrial effects and improved blood sugar regulation (35:05–36:10).
• Penetration Depth: Long wavelength light passes through skin, bone, and even the skull, promoting mitochondrial function in deep tissues, including the brain (43:13–44:20).
• Vision Preservation: Brief, daily exposure of the eyes to long-wavelength light (typically 670 nm, 3 minutes per day) improved color vision in older adults by ~20%, with effects lasting about 5 days (56:16–58:44).
• Effect by Age and Time of Day: Benefits of long-wavelength light are most robust in those over 40 and greatest when administered in the morning (64:15–67:57).

Mitochondria as a System-Wide ‘Community’

• Cellular Communication: Mitochondria across tissues communicate and coordinate responses—even between different organs—which may explain why local light exposure produces systemic benefits (42:13–43:13, 75:07–78:07).
• Potential for Disease Mitigation: Red light therapy showed promise in animal models for slowing neurodegeneration, such as in Parkinson’s disease, and in people with certain eye diseases (38:43–38:56, 70:58–73:59).

Modern Lighting: Public Health Risks of LEDs

• Biological Mismatch: LEDs emphasize short (blue) wavelengths, lack red/infrared, and are now pervasive in homes, offices, and schools—a situation Dr. Jeffery describes as a potential public health issue on the scale of asbestos (83:00).
• Animal Data: Mice and flies under LED light exhibit mitochondrial decline, metabolic disturbances (e.g., fatty liver, high blood sugar), abnormal behaviors, and reduced lifespan compared to those under full-spectrum/incandescent lighting (85:34–88:10).
• Indoor Environment Double Hit: Many new buildings use cheap, short-spectrum LEDs and infrared-blocking glass, further depriving people of health-promoting wavelengths (101:57–105:19).

Strategies for Mitigating LED Harm and Maximizing Health

• Sunlight is Best: Outdoor exposure trumps all, as full-spectrum sunlight is unmatched in its health benefits. Even overcast days provide valuable light, though less long-wavelength light penetrates (62:01–63:31).
• Halogen and Incandescent Lights: These closely resemble the solar spectrum and serve as effective indoor alternatives; using desk lamps or occasional exposure is beneficial, especially in winter or for those largely indoors (99:21–101:58, 122:27–123:09).
• Affordable Solutions: Even low-cost, safe exposures like a dim halogen lamp or (careful) use of beeswax candles can increase long-wavelength light indoors (121:48–122:47).
• Red/Infrared Devices: Most commercial red light therapy devices are safe and can offset mitochondrial decline, but Dr. Jeffery cautions about quality and urges avoidance of lasers for general use (98:05–98:55, 111:03–111:20).
• Plants and Windows: Natural light reflected from plants (especially via near-infrared) can improve indoor light quality; use of non-tinted, non-infrared-blocking glass is ideal (113:36–115:55).

Notable Quotes & Memorable Moments

Indoor Lighting—The Modern Health Threat

"There's a group of us shuffling around corridors ... some are saying this is an issue on the same level as asbestos. This is a public health issue and it's big ... because it's time to talk. We've got enough data."
—Dr. Glen Jeffery, [83:00]

Mitochondrial Health and Light Exposure

"When we use LEDs ... looking at mice, we can watch the mitochondria gently go downhill ... Their membrane potentials are coming down, the mitochondria are not breathing very well. Watch that in real time under LED lighting."
—Dr. Glen Jeffery, [00:08], [85:32]

"We can use red light to reduce the pace of cell death [in the retina]."
—Dr. Glen Jeffery, [39:54]

Red Light Across the Body

"Long wavelength light goes through any clothing ... six layers of t-shirt made no difference. It's all over the place inside the body."
—Dr. Glen Jeffery, [28:44–29:57]

Systemic Benefits—Blood Sugar

"The blood glucose levels went up, but they didn’t peak anywhere near as seriously as they did without the red light ... the reduction in the spike was just over 20%."
—Dr. Glen Jeffery, [35:03]

Effects of Circadian Timing

"Your biggest effect is always in the morning—just before perceived sunrise up until about 11 o'clock."
—Dr. Glen Jeffery, [65:26]

Important Segments & Timestamps

• Visible Light & Its Spectrum: [04:19–06:15]
• Ionizing/Non-Ionizing Radiation Explained: [06:15–07:59]
• Sunlight, Skin Cancer, and Mortality: [10:30–14:45]
• How Red/Infrared Light Benefits Mitochondria and Aging: [18:07–25:00]
• How Red Light Penetrates the Body and Clothing: [25:00–29:57]
• Red Light Decreases Blood Glucose Spikes (Human & Animal Studies): [35:05–36:13]
• Red Light and Neurodegeneration Models: [37:05–39:20]
• Vision Improvement—Human Studies (Elderly): [53:49–58:44]
• Action Optimization (Wavelength, Duration, Age, Time of Day): [59:29–67:57]
• Incandescent/Halogen Lamps Mimic Sunlight Best Indoors: [99:21–101:58]
• Economic/Practical Tips for Better Indoor Lighting: [121:48–124:25]

Practical Takeaways

Actionable Solutions

• Prioritize outdoor exposure to natural sunlight daily, especially in the morning, to support mitochondrial health, vision, and metabolic function.
• If primarily indoors:
  • Use incandescent or halogen lamps (ideally dimmed) to supplement indoor lighting.
  • Place plants near windows and seating areas to reflect near-infrared and improve healthful light quality.
  • Avoid LED-only environments when possible, especially in education or care facilities; if LEDs are unavoidable, short exposure to halogen/incandescent can help.
  • For vision maintenance (especially post-40): Use a safe 670nm (or similar) long-wavelength light source for 3 minutes in the morning, every 5 days.
  • Avoid lasers; stick to LEDs or filtered lamps for photobiomodulation.

For Parents, Educators, and Healthcare Leaders

• Open window access and maximize daylight in schools and care facilities.
• Counteract excessive screen/LED exposure in children and youth by encouraging outdoor play and exposure to full spectrum light.
• Investigate replacing some LED lights with halogen/incandescents or installing supplemental lamps in places where people spend significant time.

Final Reflections

Dr. Jeffery and Dr. Huberman urge individuals, institutions, and policymakers to reevaluate lighting environments for immediate and long-term public health. Their research highlights that optimizing light exposure is not just about sleep and circadian rhythms, but is a “foundational” biological input, regulating metabolism, neurodegeneration, vision, and even mental well-being. These changes can be implemented affordably, both for individuals and at the infrastructure level.

"I believe profoundly that we can affect public health and we should affect public health at a highly economic way."
—Dr. Glen Jeffery, [123:16]

For complete details, references, and further resources, see the episode notes at hubermanlab.com.