Importance of the Unseen: Near-Infrared Light Regulates Human Glucose Levels in the Built Environment

Life evolved under broad spectrum sunlight (300-2500nm), but in the modern built environment under standard Light Emitting Diode (LED) illumination is restricted to around 400-650nm. Different wavelengths influence metabolism via mitochondria. 670-900nm support mitochondrial function while those in the Soret band (420-450nm) undermine mitochondrial ability. Under LED lighting, metabolism is challenged with reduced mitochondria ability, and hence, reduced demand for blood sugars that are required to produce adenosine triphosphates (ATP). As longer wavelengths enhance mitochondrial performance, they increase demand for blood sugars, reducing serum glucose. Here we change the lighting in windowless offices providing either standard LED desk lamps or those supplemented with 850nm in real-world environments. This was for two hours every morning over three days. We then assessed blood sugars with two independent methods, an oral glucose tolerance test and continuous glucose monitoring. Subjects exposed to standard LEDs had significantly increased blood sugars, while those exposed to lamps with added 850nm had significantly reduced blood sugars. These real-world data highlight the importance of light in controlling metabolism. They raise issues concerning public health in interior environments where we now spend >90% of our lives.