Surrounded by winter’s gloomy gray skies, many of us believe that a little bit of sunshine will be good for our health — helping our bodies synthesize vitamin D and improving mood. And now scientists have found a new way that sunshine may be good for our health: Exposure to the ultraviolet components of sunlight can lower blood pressure.
For decades, scientists have noticed a link between geography and risk of high blood pressure. The average blood pressure in a population increases as distance from the equator increases, as does the prevalence of hypertension, or abnormally high blood pressure. Researchers have also noted that people with mild hypertension have higher blood pressure measurements in the winter. What scientists couldn’t figure out was whether sunlight or temperature was causing these differences.
Controlling Blood Pressure
A clue came in the form of a signaling molecule known as nitric oxide.
In 2009, a group of Scottish scientists discovered a vast repository of nitric oxide in the surface of the skin — far greater than anything in the blood. They also showed that exposure to a component of ultraviolet radiation known as UVA light could make the nitric oxide biologically active, converting it to nitrate or nitrite.
Martin Feelisch, a biologist at the University of Southampton in England, believed that these results could explain why individuals living nearer the equator were less prone to hypertension. He hypothesized that the UVA rays from sunlight activated the nitric oxide, which entered the bloodstream and lowered blood pressure by dilating blood vessels.