Every time you switch on a room light or step inside a modern glass office, your body may be missing out on a fundamental biological nutrient: red and infrared light. For decades, global efforts to curb energy consumption have driven a rapid transition toward light-emitting diode (LED) technology and heat-filtering window glass. However, growing biological research suggests that by stripping indoor environments of long-wavelength light, modern architecture and lighting may be unintentionally impairing human metabolic health.
Scientists studying photobiology argue that light functions much like a nutrient for animal cells. While plants use sunlight to convert carbon dioxide into carbohydrates through photosynthesis, human tissues rely on long wavelengths of light—specifically visible red light (650 to 750 nanometers) and invisible near-infrared light (up to 2,500 nanometers)—to support cellular energy production. Unlike short-wavelength light such as ultraviolet (UV), which is absorbed primarily by the skin, red and infrared photons penetrate deep into clothing and living tissue. Inside human cells, these photons stimulate the mitochondria, the organelles responsible for generating adenosine triphosphate (ATP), the primary energy currency of biological life.
Historically, humans were continuously exposed to long-wavelength light. Natural daylight is abundant in red and infrared radiation, as were traditional artificial sources such as campfires, candles, gas lamps, and incandescent light bulbs. Because the light spectrum of incandescent bulbs closely mirrored natural sunlight, indoor environments naturally supplied the wavelengths necessary to fuel mitochondrial metabolism.
The shift toward modern energy efficiency dramatically altered this environmental spectrum. Beginning in the early 2000s, incandescent bulbs were largely phased out in favor of LEDs. While LEDs excel at generating visible light while consuming minimal electricity, they emit virtually no light beyond 750 nanometers, rendering them completely dark in the infrared spectrum. Compounding the problem, modern building glass is engineered to block infrared radiation to minimize heating costs. Together, these innovations have eliminated approximately 95 percent of the long-wavelength spectrum from indoor spaces, where modern urban populations spend up to 90 percent of their lives.
Some researchers, including neuroscientist Glen Jeffery of University College London and former European Southern Observatory astrophysicist Bob Fosbury, describe LED light as "ultra-processed light." They warn that chronic deprivation of red and infrared wavelengths could be a significant, unacknowledged factor behind rising global rates of metabolic disorders, including obesity, type 2 diabetes, and age-related cognitive decline.
While research into red-light therapy originated in the late 1980s with Soviet biophysicist Tiina Karu—who demonstrated that red light accelerates mitochondrial ATP synthesis—its implications for everyday indoor environments are only now coming to light. Although therapeutic applications of targeted red light are expanding for wound healing and pain management, researchers emphasize that restoring natural light spectrums to daily life could offer a simple yet profound safeguard for human cellular health.