Lighting and your health

The problem with modern LEDs

Standard LED lighting disproportionately emits light in the 460-495nm blue wavelength range. This specific wavelength is detected by intrinsically photosensitive retinal ganglion cells (ipRGCs), which signal directly to the suprachiasmatic nucleus, the brain's master circadian clock. The result: blue light exposure in the evening suppresses melatonin production by up to 42%, delays sleep onset, and shifts the circadian phase.

In 2023, 248 leading scientists from 43 countries signed a consensus statement warning about the health effects of artificial light at night (ALAN), including disrupted circadian rhythms, melatonin suppression, and increased risk of breast cancer, obesity and type 2 diabetes through circadian disruption pathways.

The mechanism connecting disrupted circadian rhythm to metabolic and oncological outcomes is melatonin's role as an antioxidant and immune modulator, not simply as a sleep hormone. Suppressing melatonin in the evening does not merely affect sleep quality. It affects immune surveillance, tumour suppression, insulin sensitivity and cortisol regulation.

What incandescent and halogen light does differently

Incandescent and halogen bulbs operate by heating a filament to incandescence. This produces a continuous blackbody radiation spectrum spanning from infrared through visible light, closely approximating natural sunlight. The blue wavelength proportion in incandescent output is significantly lower than in LED or fluorescent lighting, and the infrared output is substantially higher.

The regulatory phaseout of incandescent bulbs in many jurisdictions was driven by energy efficiency considerations, not health considerations. From a circadian and photobiological perspective, incandescent and halogen lighting used in the evening is meaningfully different from LED lighting. Replacing bedroom and living room bulbs with incandescent or low-colour-temperature halogen options for evening use is a straightforward, low-cost intervention.

The case for infrared and near-infrared light

Photobiomodulation (PBM) describes the use of specific wavelengths of red and near-infrared light to stimulate cellular responses. The mechanism involves absorption of photons by cytochrome c oxidase, the terminal enzyme in the mitochondrial respiratory chain, which increases electron transport and ATP production. The most studied therapeutic wavelengths are 630-660nm (visible red) and 810-880nm (near-infrared).

Documented effects in randomised controlled trials include: reduced inflammatory markers, improved wound healing, reduced musculoskeletal pain, improved skin collagen density, improved mood via retinal photoreception pathways, and accelerated muscle recovery. Professor Glen Jeffery at University College London has published extensively on the mechanisms of red light on retinal function and mitochondrial health.

Practical application: a red or near-infrared therapy panel used for 10-15 minutes daily in the morning provides photobiomodulation benefits while also reinforcing the morning light signal that anchors the circadian rhythm. Andrew Huberman and Glen Jeffery discussed the specific mechanisms in a widely shared 2023 podcast episode.

Lighting in the context of your home

Lighting changes are most impactful in the rooms where you spend evening hours and sleep. The bedroom and living room are the highest priority. The bedroom is particularly important: even dim blue-enriched light during the hour before sleep measurably delays sleep onset and reduces slow-wave sleep duration.