HEALTH: Sunshine May Benefit High Blood Pressure. “Blood tests showed that UVA exposure caused a release of nitric oxide from the skin into the bloodstream. Nitric oxide causes arteries to dilate, and this, the scientists believe, accounts for the effect.”

Interestingly, old-timey bodybuilders believed that sunshine was good for muscle growth. Now modern bodybuilders take arginine supplements that boost nitric oxide levels. The old-time guys were ahead of the curve, which often turns out to be the case.