Overview
- A randomized within-subject crossover study of 13 older adults with type 2 diabetes found that daytime natural light led to more hours with glucose in the normal range and reduced daily glucose variability versus standard artificial office lighting.
- Participants spent 4.5 days under each lighting condition in tightly controlled settings with standardized meals, sleep, activity and medication, separated by at least a four-week washout.
- Natural daylight shifted metabolism toward greater fat oxidation without changing average glucose levels and was associated with slightly higher evening melatonin secretion.
- Muscle biopsies and exploratory multi-omic analyses indicated daylight-related changes in clock gene expression and systemic lipid and metabolite patterns consistent with circadian alignment effects on metabolism.
- Authors emphasize the small, short, controlled nature of the trial and report plans for longer real-life studies; the work was published in Cell Metabolism and supported by VELUX Stiftung/Daylight Academy, the Swiss National Science Foundation and the Vontobel Foundation.