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

This discussion with Dr. Glen Jeffery, a professor of neuroscience at University College London, delves into how various wavelengths of light, particularly red and near-infrared, influence human health at the cellular level. Focusing primarily on mitochondria, the energy producers within cells, the conversation spans from the benefits of long-wavelength light to the emerging concerns regarding the harmful effects of modern LED lighting enriched in short-wavelength light. They explore light's impact on metabolism, vision, aging, indoor lighting environments, and public health implications, providing practical insights into harnessing light for improved well-being.

Understanding Light and Its Biological Impact

Light encompasses a broad range of wavelengths beyond what humans can perceive visually, generally between 400 to 700 nanometers (nm). Sunlight emits a continuous spectrum extending from the ultraviolet (around 300 nm) through visible light, and well beyond 700 nm into infrared territory, up to nearly 3,000 nm. The energy carried by shorter wavelengths, such as ultraviolet (UV) and the blue-violet spectrum (around 420-440 nm), is much higher and can cause cellular damage through ionizing effects, such as DNA alterations, sunburn, and cataracts. These high-energy short wavelengths are largely blocked by the skin and ocular lenses to protect underlying tissues. In contrast, long wavelengths such as those found in red and near-infrared light carry less energetic but deeply penetrating energy capable of influencing cellular function, particularly within mitochondria.

The Role of Long Wavelength Light on Mitochondria

Research pioneered by Tina Karu and others has demonstrated that long-wavelength light, primarily in the red to near-infrared range (approximately 650-900 nm), benefits mitochondrial function. Mitochondria do not directly absorb this light; instead, it is the water molecules surrounding them, including the so-called "nanowater" within cells, that absorb light and influence mitochondrial bioenergetics. Long-wavelength light increases the viscosity and spin rate of molecular pumps involved in the mitochondria's ATP (energy molecule) production process. This stimulation enhances mitochondrial efficiency and encourages the synthesis of more protein complexes involved in energy generation. Thus, exposure to red and near-infrared light not only produces immediate improvements in cellular energy output but also promotes longer-term mitochondrial health and resilience.

Light Penetration Through the Body and Implications

Contrary to common intuition, long-wavelength light can penetrate deeply through skin, muscle, bone, and even the skull, scattering within internal tissues. Dr. Jeffery and colleagues verified this by measuring transmitted light energy through the human body and clothing, finding that several percent of red and near-infrared light passes entirely through limbs and the head. This has remarkable implications, as it suggests that even targeted exposure to long-wavelength light can exert systemic effects on mitochondrial function throughout the body and brain. The scattering of light inside the body enables widespread stimulation beyond the illuminated area, and this effect is under active investigation to understand its mechanisms and clinical significance.

Red Light and Blood Glucose Regulation

A particularly groundbreaking finding discussed concerns the systemic metabolic effects of red light exposure. Experiments began with bumblebees, where red light reduced blood glucose spikes after feeding, indicating increased mitochondrial activity and glucose utilization. Extending this work to humans, subjects exposed to brief, localized red light on their back prior to a glucose tolerance test exhibited a roughly 20% reduction in the peak blood glucose spike. This systemic modulation of glucose metabolism, caused by localized light exposure, supports the concept of mitochondrial communities communicating across tissues. It reveals a promising, non-invasive method to improve metabolic health and blood sugar regulation through light therapy.

Red Light and Retinal Aging

The retina holds the highest concentration of mitochondria in the human body and is particularly susceptible to mitochondrial decline with age. Rod photoreceptor cells, responsible for vision in low-light conditions, degenerate with aging, diminishing visual function. Dr. Jeffery's research demonstrated that daily brief exposures to 670 nm red light slowed the loss of these rods and improved color vision thresholds in older adults, with effects lasting approximately five days after only a few minutes of exposure. This enhancement of mitochondrial function in retinal cells presents a potential intervention to mitigate age-related visual decline and diseases involving retinal degeneration, provided the treatment begins early in disease progression. Notably, the effects are most pronounced in individuals over 40 years old, consistent with the mitochondrial theory of aging.

The Importance of Timing and Wavelength Specificity

The efficacy of light therapy is influenced by circadian biology. The greatest improvements in mitochondrial function from long-wavelength exposure occur in the morning hours, roughly before 11 AM. This timing corresponds to natural peaks in mitochondrial activity and metabolic readiness. Regarding wavelength, red and near-infrared light above 670 nm are most effective, while shorter wavelengths in that range show reduced effects. The energy or brightness required is surprisingly low; even very dim red light (around 1 mW/cm²) can stimulate the mitochondrial response. Importantly, long-wavelength light passes well through closed eyelids, so eyes need not remain open during exposure.

Long Wavelength Light's Impact on Neurodegenerative Disease

In models of Parkinson's disease, red and near-infrared light targeted to body regions distant from the brain, such as the abdomen, reduced symptom severity and slowed neuronal degeneration. This systemic benefit aligns with long-wavelength light's deep penetration and the concept of mitochondria operating as a signaling community. By improving mitochondrial function and reducing apoptotic signaling, light therapy may offer neuroprotective effects in conditions characterized by mitochondrial dysfunction and excessive cell death, including Parkinson's and other neurodegenerative disorders.

Long Wavelength Light and Mitochondrial Disease in Children

There have been encouraging anecdotal and preliminary clinical observations of children with mitochondrial genetic disorders benefiting from red light therapy. Some individuals who previously exhibited severe impairment showed significant improvements in mobility and muscle function after receiving targeted red light treatments. Although larger clinical trials have been challenging due to the rarity of these diseases, these cases suggest light therapy may be a low-risk adjunct approach for enhancing mitochondrial performance in serious inherited conditions.

Indoor Lighting and the Rise of LED Concerns

The discussion raises an urgent concern regarding modern indoor lighting's heavy reliance on LED technology, which emits a pronounced spike in short-wavelength blue and violet light (420-440 nm) but lacks sufficient emission of longer wavelengths. Unlike natural sunlight, which provides a smooth and broad spectrum of visible and infrared wavelengths, LED lights present an unbalanced spectrum that overexposes mitochondria to potentially harmful short wavelengths without the protective balancing from long wavelengths. This imbalance has been associated with mitochondrial dysfunction, reduced energy production, metabolic dysregulation, increased fat deposition in animal models, and behavioral changes indicative of stress or anxiety.

Public Health Implications of Excessive Short Wavelength Exposure

Experts, including Dr. Jeffery and colleagues, are increasingly considering the unfiltered short-wavelength exposure from LEDs a potential public health hazard comparable in seriousness to asbestos. Research shows that animals exposed solely to short-wavelength dominant LED lighting suffer systemic harm, including fatty liver disease, smaller vital organs, and impaired sperm motility. In people, continuous exposure to LED lighting, especially indoors in absence of natural sunlight, may contribute to metabolic and visual health declines, circadian disruption, increased disease risk, and negatively modulated immune responses. There is concern this factor may partially explain observed plateaus or declines in lifespan gains in developed countries since the widespread adoption of LED lighting.

The Balancing Role of Long Wavelength Light in Mitigating Damage

Short-wavelength light's detrimental effects on mitochondria appear to be significantly counteracted by concurrent exposure to long-wavelength light. Red and near-infrared light provide a protective and restorative influence, improving mitochondrial respiration and signaling mitochondrial biogenesis. Without sufficient long-wavelength photons, unopposed blue and violet light act more as mitochondrial stressors than stimuli. Given that human biology evolved under sunlight's continuous full spectrum, the modern LED-dominated environment represents an evolutionary mismatch with potential consequences for widespread mitochondrial health.

Incandescent and Halogen Light as Beneficial Indoor Sources

Incandescent and halogen bulbs more closely mimic the smooth continuous spectral output of natural sunlight, including robust long-wavelength and infrared light components. Though incandescents are largely being phased out or banned in many regions due to energy inefficiency, halogen bulbs remain more widely available and share similar spectral properties. Exposure to such lighting indoors has been shown to improve visual function significantly beyond red light alone, with benefits lasting for weeks. Dimmed incandescent or halogen desk lamps can provide ample long-wavelength exposure without raising energy costs or disturbing circadian rhythms and melatonin production, making them valuable tools for balancing indoor light environments.

Architectural Design and Indoor Environmental Considerations

The built environment often compounds the lighting challenges through the widespread use of LED lighting and infrared-blocking window glass intended to reduce heating costs. This combination deprives occupants of both beneficial long-wavelength light and sunlight's thermal effects. Architects and designers are beginning to incorporate these considerations, exploring ways to reintegrate full-spectrum lighting and maximize natural light access indoors. The presence of plants and trees outside can also reflect beneficial infrared radiation into indoor spaces, further supporting mitochondrial health. Such ecological and architectural interventions may become critical components of public health strategies to mitigate the downsides of modern living environments.

Effects on Vision and Myopia Concerns in Children

Beyond metabolic and mitochondrial issues, long-wavelength light deficiency impacts eye development and vision, particularly in children. The increase in myopia worldwide correlates with increased indoor living, reduced outdoor time, and insufficient long-wavelength light exposure. Animal studies have demonstrated that lack of red and near-infrared light contributes to abnormal eye growth and myopia progression. While red light therapy shows promise in experimental control of myopia, proper application is essential as some clinic-based interventions using lasers have caused retinal damage due to uneven energy distribution, emphasizing that LEDs or tailored full-spectrum lighting with long wavelengths are preferable over monochromatic laser exposure for safety.

Practical Recommendations for Lighting and Light Exposure

For most individuals, maximizing time outdoors during daylight hours remains the best strategy to obtain balanced spectral exposure, including long-wavelength light that permeates clothing and skin. When outdoors exposure is limited, supplementing indoor lighting with halogen or dimmed incandescent lamps can be beneficial, especially during winter or in windowless environments. Utilizing safe, well-designed red or near-infrared light therapy devices for short daily sessions enhances mitochondrial function and may improve metabolic and visual health. Careful management of evening screen exposure, including blue light filtering or use of short-wavelength blocking glasses, helps preserve circadian rhythms and metabolic balance. Special attention should be given to children, who are particularly vulnerable to the effects of lighting on eye development and metabolic regulation.

Advancing Clinical and Public Health Applications

Clinical translation of light therapy shows growing promise not only in ophthalmology but also in critical care, neurodegenerative diseases, and mitochondrial disorders. Trials are underway to evaluate red light therapy's efficacy in retinitis pigmentosa and other degenerative eye conditions, with encouraging preliminary results. Efforts are also focused on reforming lighting policies in hospitals, nursing homes, and schools to incorporate healthy lighting principles that optimize mitochondrial function and overall well-being. The intersection of neuroscience, physiology, architecture, and public health is driving innovative approaches that integrate knowledge about light's biological effects into practical, large-scale solutions.