A growing number of health experts and consumers are raising concerns about the widespread adoption of LED (light-emitting diode) lighting and its potential effects on human health. Since incandescent bulbs were phased out in many regions, including under a European Union directive beginning in 2009 with a full ban by 2016, LED bulbs have become the dominant source of artificial lighting in homes, workplaces, and public spaces. While LEDs are more energy-efficient and cost-effective, emerging research suggests they may have unintended physiological consequences.

Incandescent bulbs, first developed in the late 19th century, produce light by heating a tungsten filament, resulting in a broad spectrum of light that includes significant amounts of red and infrared wavelengths. These long-wavelength lights are similar to components of natural sunlight and have been linked to various biological benefits. In contrast, LED bulbs emit primarily short-wavelength blue light, which is known to increase alertness but can also disrupt circadian rhythms and interfere with sleep patterns.

Glen Jeffery, professor of neuroscience at University College London, explains that modern indoor environments, dominated by LED lighting and limited exposure to natural sunlight due to window filtration, reduce the amount of long-wave red and infrared light that humans receive. According to Jeffery, this shift in light exposure may negatively impact cellular function, particularly within mitochondria—the cell's energy producers—and has been associated with health conditions such as type 2 diabetes, anxiety, obesity, skin aging, and cancer.

Supporting this view, a 2024 study published in the Journal of Biophotonics found that brief exposure to red light lowered blood sugar levels significantly after glucose intake. Additionally, research from Maastricht University observed that type 2 diabetes patients working under natural light had more stable blood sugar levels compared to periods spent under LED lighting. Jeffery suggests that the absence of infrared light from LED sources could contribute to pre-diabetic metabolic states by impairing mitochondrial function.

Circadian neuroscience professor Russell Foster of the University of Oxford acknowledges the complex effects of blue light on the body's internal clock. Foster notes that while blue light exposure during the day can promote alertness, prolonged exposure to bright LED light in the evening may shift circadian rhythms and disrupt sleep. He advocates for balanced lighting use, recommending different lighting for daytime versus evening environments to minimize disruption.

Some individuals report severe sensitivity to LED lighting. Rachel Mitchell, a former management consultant from Cheltenham, began experiencing headaches and eye discomfort after switching her home and work environments to LED bulbs in 2021. Despite consulting specialists and trying various remedies, her symptoms persisted until she reverted to incandescent bulbs and reduced screen time. As a result, she left her corporate career and now works from home using older lighting technologies, emphasizing her need for gentler illumination.

Advocacy groups like LightAware have noted a rise in public concern about LED lighting’s health effects, including issues related to flicker caused by faulty bulbs or dimmers. John Lincoln, co-founder of the charity, calls for more thorough research on the biological impacts of LED lighting, which he says was introduced widely without sufficient study.

Researchers recommend incorporating sources of red and infrared light in everyday settings to mitigate potential adverse effects. Jeffery suggests placing incandescent or red-enriched bulbs in frequently used areas such as kitchens to ensure at least 45 minutes of exposure to long-wavelength light daily. Meanwhile, spending more time outdoors remains a natural way to obtain the full spectrum of sunlight.

As LED lighting technology continues to evolve, experts emphasize the need for further investigation into its long-term health implications, as well as considerations for public health guidance on lighting environments.