Big Health Benefits of A Little Sun

A number of studies observe that the incidence of hypertension and cardiovascular disease correlates with latitude and rises in winter, but a biological cause has remained unclear. Martin Feelisch, from the University of Southampton (United Kingdom), and colleagues completed a study that suggests that sunlight alters levels of the small messenger molecule, nitric oxide (NO) in the skin and blood, reducing blood pressure.  The researchers exposed the skin of 24 healthy individuals to ultraviolet (UVA) light from tanning lamps for two sessions of 20 minutes each. In one session, the volunteers were exposed to both the UVA rays and the heat of the lamps. In another, the UV rays were blocked so that only the heat of the lamps affected the skin.  The results suggest that UVA exposure dilates blood vessels, significantly lowers blood pressure, and alters NO metabolite levels in the circulation, without changing vitamin D levels. Further experiments indicate that pre-formed stores of NO in the upper skin layers are involved in mediating these effects. The study authors write that: “our data provide mechanistic insights into an important function of the skin in modulating systemic [nitric oxide] bioavailability which may account for the latitudinal and seasonal variations of [blood pressure] and cardiovascular disease.”