Study: Sunshine lowers blood pressure
By Amanda McMillan, Outside
Scientists have known for years that rates of hypertension are higher in the winter and in countries farther from the equator, but they haven’t known why—until now. A new study from the universities of Southampton and Edinburgh suggests that exposure to sunlight plays a large role, by causing nitric oxide in the skin to be absorbed into the blood stream. Blood vessels widen as a result, causing a modest—but potentially life-saving—drop in blood pressure.
To study the sun’s effect on blood pressure, researchers exposed 24 healthy volunteers to ultraviolet light, mimicking the amount of exposure a person might get wearing short sleeves and shorts outside for 30 minutes on sunny day. In a second session, they were exposed to the same amount of light and heat, but no UV rays.
The UV exposure triggered a small decline in blood pressure—about two to five points—while the “sham” exposure did not. While that may not seem like a lot, the authors write that a even tiny drop can go a long way: A 10-point change in diastolic pressure, for example, can slash your risk of cardiovascular disease and stroke in half.