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

Episode 257 Dec 1, 2025 Episode Page ↗
Overview

Dr. Glen Jeffery, a professor of neuroscience at UCL, explains how long-wavelength light (red, near-infrared) boosts mitochondrial function, improving metabolism and eyesight. He warns against excessive short-wavelength LED light and provides actionable ways to optimize light exposure for health.

At a Glance
25 Insights
2h 14m Duration
15 Topics
5 Concepts

Deep Dive Analysis

Introduction to Light Spectrum and Health Impacts

UV Light, Sunburn, Cataracts, and All-Cause Mortality

How Long-Wavelength Light Enhances Mitochondrial Function

Deep Penetration and Scattering of Long-Wavelength Light

Long-Wavelength Light's Systemic Effects on Blood Glucose

Red Light's Role in Reducing Cell Death and Neurodegeneration

Mitochondria as a Communicating Community Across Tissues

Offsetting Retinal Aging and Improving Vision with Light

Mitochondrial Theory of Aging and Circadian Rhythm

Short-Wavelength LED Light's Detrimental Health Effects

Comparing Incandescent, Halogen, and LED Light Spectra

Impact of Built Environments and Glass on Light Exposure

Myopia in Children and the Role of Light Environment

Low-Cost Strategies for Healthier Indoor Lighting

Long-Wavelength Light for Mitochondrial Diseases in Children

Nanowater Viscosity

Mitochondria produce ATP in a viscous 'nanowater' environment. Long-wavelength light is absorbed by this water, reducing its viscosity, which increases the spin rate of the ATP-producing motor and enhances mitochondrial function.

Mitochondrial Community

Mitochondria across different cells and tissues in the body act as a community. Positive or negative information and effects can be shared systemically, meaning localized light exposure can have widespread benefits.

Mitochondrial Theory of Aging

This theory posits that mitochondria regulate the pace of aging. By improving mitochondrial health and function, it's possible to regulate or slow down aspects of the aging process.

Caustics in Laser Light

Unlike LED light which scatters uniformly, laser light when hitting tissue forms 'caustics' – bright spots where energy is concentrated and can be significantly higher, potentially causing damage.

Infrared Blocking Glass

Modern commercial buildings often use infrared-blocking glass to regulate thermal temperatures. This inadvertently prevents beneficial long-wavelength light from entering, contributing to a 'double hit' of poor light exposure when combined with LED lighting.

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How does long-wavelength light (red, near-infrared) impact cellular health?

Long-wavelength light is absorbed by nanowater surrounding mitochondria, increasing the efficiency of ATP production and stimulating the synthesis of more energy-producing proteins. This improves mitochondrial function and overall cellular health.

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Can long-wavelength light penetrate deep into the body and brain?

Yes, long-wavelength light can pass through skin, clothing, and even bone (like the skull) into the body, where it scatters and can impact mitochondria in deep tissues and organs.

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Does long-wavelength light exposure affect blood sugar regulation?

Yes, studies show that a brief exposure to long-wavelength light on a small area of the body can significantly reduce the spike in blood glucose levels after consuming sugar, indicating improved glucose utilization by mitochondria.

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Can long-wavelength light improve vision and offset retinal aging?

Yes, exposing the eyes to specific long-wavelength light (e.g., 670 nanometers) for a few minutes can improve color vision thresholds and reduce the pace of cell death in the retina, particularly in older individuals, with effects lasting about five days.

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Is modern LED lighting detrimental to health?

Yes, LED lighting, especially those with a strong blue spike (420-440 nanometers) and lacking balanced long-wavelength light, can impair mitochondrial function, reduce ATP production, lead to weight gain, unbalanced blood glucose, and negatively impact organ health and lifespan in animal models.

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What are the best types of indoor lighting for health?

Incandescent and halogen bulbs are preferable to LEDs because they produce a broad, smooth spectrum of light, similar to sunlight, including beneficial long wavelengths. Dimming these bulbs can extend their lifespan and still provide therapeutic infrared light.

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How can people on a budget improve their indoor light environment?

Simple, low-cost methods include using halogen lamps (especially dimmed), candlelight (safely), and ensuring natural light through untinted windows. Getting outside for regular daylight exposure is also critical.

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What is the optimal time of day for long-wavelength light exposure?

The most significant positive effects of long-wavelength light exposure occur in the morning, from just before perceived sunrise until about 11 AM, as mitochondrial activity and hormone levels are shifting during this period.

1. Leverage Long Wavelength Light

Utilize red, near-infrared, and infrared light to improve overall health, as these long wavelengths support mitochondrial function and can penetrate deep into the body.

2. Protect Mitochondria From LEDs

Employ long-wavelength light, such as red light, to protect against mitochondrial damage caused by excessive exposure to LED bulbs and screens, which contain detrimental short wavelengths.

3. Use Incandescent/Halogen Lighting

Replace or supplement LED indoor lighting with incandescent or halogen bulbs, especially in environments where you spend significant time, as they provide a full, balanced spectrum of light similar to solar light.

4. Enhance Vision With Light

Expose your eyes to long-wavelength light (e.g., 670 nanometers) for three minutes, once every five days, ideally in the morning, to improve color vision and overall visual function.

5. Red Light for Blood Glucose

Apply red light to a small area of skin (e.g., a 4x6 inch rectangle on the back) to significantly reduce post-meal blood glucose spikes by stimulating mitochondrial function.

6. Daily Sunlight Exposure

Get sunlight exposure both in your eyes and on your skin regularly, as it contains a balanced spectrum of light beneficial for health, but always avoid burning.

7. Prevent Sunburn

While seeking sunlight for its health benefits, always avoid sunburn, as it is linked to DNA mutations and skin cancers.

8. Shield From Excessive UV

Protect your skin and eyes from excessive UV and other short wavelengths to prevent mutations, sunburn, and conditions like cataracts.

9. Get Some UV Exposure

Ensure you get some UV light exposure, as it is necessary for processes like Vitamin D production.

10. Morning Light Therapy Optimal

For maximum benefit from long-wavelength light therapy, apply it in the morning, ideally from just before perceived sunrise until about 11 AM, as mitochondrial activity is highest then.

11. Comfortable Eye Light Intensity

When applying long-wavelength light to the eyes, use a dim to moderately bright intensity (e.g., around 1-8 milliwatts per centimeter squared) that feels comfortable, as high brightness is not necessary for effect.

12. Early Disease Light Intervention

For conditions like macular degeneration or other diseases, apply red light therapy early in the disease progression for the most effective impact on aging and disease mitigation.

13. Red Light for Mitochondrial Disease

For children with mitochondrial disease, consider introducing red light exposure (e.g., from specific light bulbs) in the home, as it theoretically helps and poses no harm.

14. Reduce Cellular Death

Utilize red light to reduce the pace of cell death, as it positively impacts mitochondria and their signaling for cell demise, contributing to longevity.

15. Systemic Light Benefits

Understand that long-wavelength light penetrates and scatters throughout the entire body, supporting mitochondria in all organs, so direct exposure to any part of the body can be beneficial.

16. Boost Brain Health With Light

Expose your head to certain long wavelengths of light, as they can pass through the skull into the brain to promote brain health.

17. Mitochondrial Community Response

Understand that mitochondria throughout the body act as a community, communicating and influencing each other, so local light exposure can have systemic benefits.

18. Utilize Plants for Infrared

Incorporate plants indoors and around buildings, especially on sun-exposed sides, as they reflect beneficial infrared light back into the environment, contributing to a healthier light spectrum.

19. Dim Incandescent for Longevity

Dim incandescent or halogen light bulbs to extend their lifespan and increase their output of beneficial infrared light, without significantly raising energy bills.

20. Take Lunch/Calls Outside

Maximize outdoor time by taking lunch breaks or phone calls outside to increase exposure to natural, full-spectrum light.

21. Wear Light Clothing Outdoors

When outdoors, wear light clothing to allow beneficial long-wavelength light to penetrate and scatter throughout your body.

22. Get A Dog For Outdoor Time

Consider getting a dog to ensure you go outside in daylight two or three times a day, increasing your consistent exposure to natural, full-spectrum light.

23. Increase Screen Distance (Kids)

For children, ensure they maintain an increased distance from screens and close-up work to help prevent the development of myopia.

24. Avoid Laser Light Therapy

Never use lasers for light therapy on your eyes or skin unless administered by a trained medical professional for a specific medical procedure, due to the risk of uneven energy distribution and tissue damage.

25. Avoid Infrared-Blocking Glass

Be aware that infrared-blocking glass in modern buildings can isolate you from beneficial long-wavelength light; advocate for or seek environments with non-infrared blocking windows.

This is an issue on the same level as asbestos. This is a public health issue, and it's big.

Glen Jeffery

When we use LEDs... 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. You can watch that in real time.

Glen Jeffery

Mitochondria themselves are not absorbing long wavelength light. It's the water that they're surrounded by. It's their environment.

Glen Jeffery

If you've got bad mitochondria... they're a community. You can't deal with them in isolation. Even across cells in different areas of the body, they're a community.

Glen Jeffery

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, you know, but after so many thousand miles, you've got to service it, otherwise it falls apart.

Glen Jeffery

No living entity has ever seen monochromatic light before. It is a totally alien thing to life.

Glen Jeffery

Improve Vision with Long-Wavelength Light

Glen Jeffery
  1. Use a long-wavelength light source (e.g., 670 nanometers or higher, up to near-infrared) that is comfortable and not excessively bright (e.g., 1 to 8 milliwatts per centimeter squared).
  2. Position the light source a comfortable distance from your eyes (e.g., 3-6 inches).
  3. Expose your eyes to the light for approximately three minutes. You can keep your eyelids closed or open, whichever is more comfortable.
  4. Perform this intervention once every five days.
  5. Apply this protocol in the morning, ideally between perceived sunrise and 11 AM, for the most significant effects.
400 to 700 nanometers
Visible light spectrum Wavelength range that humans can see.
Up to 3,000 nanometers
Sunlight wavelength range Includes ultraviolet, visible, and infrared light.
Just over 20%
Reduction in blood glucose spike Observed after a burst of red light exposure on the back in human subjects.
One third
Percentage of rod photoreceptor loss over life Typical loss in the retina due to aging.
Around 20%
Improvement in color vision threshold Observed after three minutes of 670 nanometer red light exposure to the eyes.
Five days
Duration of vision improvement effect After a single three-minute exposure to 670 nanometer red light.
670 nanometers and upwards
Optimal long-wavelength light for vision Wavelengths below 670 nm tend to have reduced effects.
As low as 1 milliwatt per centimeter squared
Effective energy level for vision improvement Original experiments used 40 mW/cm², but effects are seen at much lower, comfortable levels.
420 to 440 nanometers
Harmful blue light wavelength range Specific range that mitochondria absorb and is detrimental when unbalanced by long wavelengths.
20%
Percentage of people with macular degeneration by age 100 If all individuals lived to 100 years.