Inside a human brain when reading a book.

LEDs are more energy-efficient, yet they also pose a threat to human health. For the past two decades the global shift toward energy-efficient light-emitting diodes has drastically altered how we light our homes and offices. While highly beneficial for reducing electricity bills, these lights emit a narrow spectrum dominated by short blue wavelengths and entirely lack the long-wavelength red and infrared light found in natural sunlight and older incandescent bulbs. Emerging research led by Professor Glen Jeffery at University College London shows that our cells’ powerhouses, the mitochondria, rely on these missing red wavelengths to function. Without them, mitochondrial respiration is suppressed, leading to systemic infrared starvation that can disrupt cellular energy production, cause chronic inflammation, and accelerate aging. This lack of natural spectrum light is more than a matter of eye strain; it has deep metabolic consequences. Studies show that exposing the body to specific red and near-infrared light stimulates mitochondria to consume more glucose and oxygen, dramatically reducing blood glucose spikes and regulating insulin levels. Conversely, prolonged indoor exposure to red-deficient, blue-heavy LEDs is linked to metabolic dysfunction and cellular degeneration, contributing directly to chronic conditions such as type 2 diabetes, cognitive decline, and vision loss. As public health researchers warn of this modern environmental hazard, experts suggest reintroducing balanced full-spectrum lighting or simple red-light exposure to help restore our natural metabolic rhythms and protect long-term health. [Barrett, E. M., & Jeffery, G. (2026). LED lighting (350-650nm) undermines human visual performance unless supplemented by wider spectra (400-1500nm+) like daylight. Scientific Reports, 16(1), 3061. DOI: 10.1038/s41598-026-35389-6]