Blue LED light linked to obesity and dementia, while red-light therapy shows disease-fighting potential
New studies warn that blue light from screens and LEDs could disrupt sleep and metabolism, even as researchers test red light for eye disease, diabetes, and nerve injuries.
A wave of research is examining how different wavelengths of light affect human health. While red light therapy is being tested as a drug-free treatment for conditions from age-related macular degeneration to diabetes and spinal injuries, blue light from screens and LED bulbs is linked by some studies to obesity, sleep disruption and other health risks. Health authorities have begun to weigh these findings: the NHS recommends red light therapy for oral mucositis caused by cancer treatment, and in January the FDA authorized red light for the treatment of dry age-related macular degeneration.
Blue light risk and timing: The debate centers on how high energy blue light can affect brain and body clocks, the retina and cellular energy. Scientists highlight mitochondria as a key mediator, because blue light can suppress their function while red light can energize them. Animal experiments and human epidemiology are cited to illustrate potential harms and benefits, though researchers caution that more work is needed to translate findings to broad public health guidance. Research published in Scientific Reports this year found that mice exposed to high levels of blue light rapidly gained weight and showed significantly raised levels of anxiety. In contrast, a 2020 study of 2,000 people by the Barcelona Institute for Global Health, published in Epidemiology, found those with the highest exposures to nocturnal blue light had a 60 percent higher risk of bowel cancer—an association researchers say may relate to sleep disruption.
In contrast, older lighting such as incandescent bulbs provided a spectrum closer to daylight, but those bulbs were banned in the UK in 2016 to cut energy use. Proponents argue that modern LEDs emit very little red light and more blue light, which some experts say can disrupt mitochondria and metabolic and retinal function. The discussion underscores a broader question about how much light might be contributing to public health trends as our environments transition to round-the-clock illumination.
Glen Jeffery, a professor of neuroscience at the University College London Institute of Ophthalmology, says red light boosts mitochondrial energy while blue light depletes it and harms cell function. He notes that animal studies show a much better recovery rate from stroke with red light exposure than with blue light, and that red light therapies are inexpensive to develop. He adds that devices producing deep red light can be made for modest costs, though consumer products vary in quality and safety. Jeffery has conducted several trials exploring red light's potential, including a claim that red light exposure can recharge energy deficits in retinal cells and support vision in aging eyes. A 2020 study in the Journal of Gerontology reported that healthy volunteers aged over 40 who received a 670-nm red light in their eyes for three minutes a day over two weeks showed improved low-light vision and color discrimination, with the eyelids left closed since red light passes through them.
In recent work, red light therapy has been explored for metabolic health as well. A study reported in the Journal of Biophotonics last year exposed the skin on the backs of 15 people to red light for 15 minutes before they drank a sugary beverage. Blood glucose was monitored for two hours, and those who received red light exhibited smaller glucose spikes and lower total sugar levels than those who did not, suggesting a possible effect on how mitochondria use sugar to generate energy. Researchers caution that these findings are early, and larger trials are needed to determine practical benefits and safety.
Meanwhile, researchers at the Technical University of Denmark are pursuing a different light-based approach for dementia. A technique that beams flickering light through the eyes aims to induce gamma brainwaves, which some studies have linked to the destruction of toxic amyloid plaques associated with Alzheimer's disease. Early clinical results suggest that daily 30-minute sessions for three months may improve speech and memory in people with mild to moderate Alzheimer's, though the Alzheimer's Society says the work is promising but not yet ready for broad clinical use.
In Birmingham, red-light therapy is being explored as an emergency treatment for spinal injuries. Lab tests indicate red light can boost mitochondrial energy in damaged nerve cells, potentially helping them to regrow and restore movement and sensation. One of the device developers, Zubair Ahmed, a professor of neuroscience at the University of Birmingham, says a red light device could be implanted rapidly into patients with spinal trauma to balance an energy deficit in injured neurons. While the potential is intriguing, experts caution that these results are preliminary and largely derived from lab studies.
Not everyone is convinced that red light is a universal cure-all. Russell Foster, a professor of circadian neuroscience at the University of Oxford, told Good Health that many of the studies have major flaws and that extrapolating results from mice to humans is problematic given differences in light sensitivity and biology. Some researchers argue that the simplest way to obtain beneficial light exposure remains natural sunlight, noting that humans evolved under a broad spectrum of light across the day and that balance is key.
What this means for everyday life remains a topic of debate among scientists and clinicians. Some experts suggest that ensuring adequate daytime light and limiting excessive blue light exposure at night could help support healthy circadian rhythms and metabolic function, while others see red light therapies as a potential adjunct for specific conditions after more robust trials. Those considering consumer red light devices are advised to be cautious: while inexpensive devices exist, there is no universal safety guarantee, and the quality and safety of at-home devices can vary widely. Proponents urge patients and caregivers to consult medical professionals before pursuing any new light-based treatment.
For now, the public health conversation continues to balance emerging evidence of potential risks from blue-rich lighting with promising early data on red light therapy as a nonpharmacologic approach to several conditions. As researchers expand trials and refine methodologies, clinicians caution against drawing broad conclusions until larger, well-controlled studies establish clear benefits and safety profiles for widespread use.