Blue LED lighting linked to obesity, diabetes risk and dementia concerns as red-light therapy shows promise

A wave of research into lighting and health suggests that blue-rich LED lamps and screens may be linked to rising rates of obesity, type 2 diabetes and cognitive decline, even as red-light therapy emerges as a potential treatment for a range of conditions.

Experts caution that more evidence is needed to establish cause and effect, but the mix of findings has prompted discussion about how much of modern life is shaped by the light we use indoors.

The spectrum of light produced by contemporary LEDs differs markedly from older incandescent bulbs, which were banned in the UK in 2016 to curb energy use. Incandescent lighting provided a spectrum more similar to sunlight, while LEDs emit far less red light and more blue light. In turn, blue light is a high-energy form that, in excess, can disrupt body clocks, suppress melatonin and influence how the body metabolizes sugars.

A study published this year in Scientific Reports found that mice exposed to high levels of blue light rapidly gained weight and showed higher levels of anxiety, highlighting potential metabolic and mental-health implications of prolonged blue-light exposure. In another line of inquiry, a 2020 study of about 2,000 people by the Barcelona Institute for Global Health reported that those with the highest exposure to nocturnal blue light had a 60 percent higher risk of bowel cancer, a link researchers counted as likely related to sleep disruption and breakdowns in circadian regulation. While ^these studies do not prove causation, they add to a growing caution about how modern lighting may influence health over time.

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Proponents of red-light therapy point to the opposite effect: red light appears to energize mitochondria, the energy-producing structures inside cells, while blue light can disrupt mitochondrial function. Glen Jeffery, a professor of neuroscience at the University College London Institute of Ophthalmology, notes that modern lighting is skewed toward blue, with little red light, and that mitochondria respond to the different wavelengths of light in distinct ways. He and colleagues have explored red-light exposure for various conditions, including age-related retinal changes and metabolic responses.

Red light therapy has already shown therapeutic potential in several hard-to-treat conditions. The NHS has already approved red light for the treatment of oral mucositis, a painful side-effect of chemotherapy and radiotherapy for head and neck cancer. In eye research, red light has been studied for dry age-related macular degeneration, the leading cause of sight loss in the UK. In a trial reported last year in Retina, patients received six cycles of red-light treatments—five minutes per eye every four months—and about 55 percent of treated eyes showed a notable improvement of at least five letters on an optician’s chart after 13 months. A larger study is ongoing to confirm these results. Separately, researchers have explored red-light therapy as a means to modulate glucose spikes in people with type 2 diabetes. In a small study published in the Journal of Biophotonics, 15 participants had red light exposure on the back of the body for 15 minutes before a sugary drink; blood sugar spikes and total sugar levels were lower than in a control group and over the two hours following the test, suggesting mitochondria may be nudged to use blood sugar more efficiently.

Beyond metabolic and eye health, researchers at the Technical University of Denmark are pursuing a different light-based approach to dementia. The method uses flickering light beamed into the eyes to elicit gamma brain waves, which have been linked to the brain’s ability to clear toxic plaques associated with Alzheimer’s disease. Early clinical results suggest that for some people with mild to moderate Alzheimer’s, daily 30-minute exposures over three months may improve language and memory. The Alzheimer’s Society has described the technique as promising but notes that it is too early to recommend for routine use.

In Birmingham, researchers at the University of Birmingham are pursuing red-light therapy as an emergency treatment for severe spinal injuries. Preclinical work indicates that red light can boost mitochondrial energy in damaged nerve cells, potentially helping cells to regrow and restore some function after injury. Zubair Ahmed, a neuroscience professor involved in device development, says a compact red-light system could be implanted in patients with spinal trauma to help balance the energy crisis that follows injury.

But not all scientists are convinced that red light is a universal remedy. Russell Foster, a professor of circadian neuroscience at the University of Oxford, cautions that many studies have major flaws and that extrapolating animal findings to humans is risky given different light sensitivities. Others stress that while red-light therapy is intriguing, it does not replace the benefits of natural light. Professor Jeffery points out that sunlight remains the most accessible source of red and other wavelengths and notes that being outdoors each day carries broad health benefits beyond any single therapy.

Overall, the emerging picture is nuanced. Red-light therapy is being explored as a simple and potentially safe way to support energy production in cells, with early signals of benefit in eye health, metabolic control and nerve injury. Yet the research is still evolving, and experts urge rigorous, large-scale trials to confirm effectiveness and determine optimal exposure parameters. At the same time, concerns about blue-rich LED lighting and screen exposure are driving calls for balanced lighting in homes, offices and schools, alongside continued innovation in therapies that leverage the power of light. In the meantime, health professionals emphasize practical steps such as getting regular daylight exposure, maintaining consistent sleep schedules, and using indoor lighting that includes a spectrum closer to natural daylight when possible.