The study involved shining two different doses of ultraviolet light (specifically UVA light—wavelengths between 315 and 400 nanometers) on ten volunteers, then measuring its effects on a range of outcomes like blood pressure, resting metabolism, and nitrite and nitrate levels. It’s this last bit that caught my attention, because the rise of beet juice as an endurance-boosting supplement is due to its high levels of nitrate. The body converts that nitrate to nitrite and then to nitric oxide, which seems to make your muscles work more efficiently during endurance exercise. These studies have also found that boosting levels of nitric oxide has other health benefits, like acutely lowering blood pressure and regulating blood sugar. (In fact, one recent study found that using mouthwash twice a day or more, which wipes out the oral bacteria that convert nitrate to nitrite, was associated with a 50 percent increase in the risk of developing prediabetes or diabetes.) - www.outsideonline.com