Leyla Weighs In: How Natural Light Supports Metabolic Health and Blood Sugar Control

Registered dietitian nutritionist Leyla Muedin discusses how exposure to natural daylight may improve metabolic health beyond diet and exercise, highlighting a controlled crossover study of 13 adults aged 65+ with type 2 diabetes published in Cell Metabolism. Participants spent 4.5 days in living spaces lit by either natural light through large windows or artificial light, with identical meals, sleep, activity, and screen time; after a 4-week washout they switched conditions. Natural light was associated with more hours of blood glucose in the normal range, less glucose variability, higher evening melatonin, and improved fat oxidative metabolism, suggesting effects on circadian “body clocks” and coordination between central and peripheral clocks. Muedin recommends getting morning light on the face, reducing sunglasses and high SPF use, dimming lights at night, keeping consistent sleep, and spending more time outdoors; she also notes that architecture can limit sunlight exposure.