A 30-minute exposure to visible blue light can achieve the same results as antihypertensive drugs and reduce systolic blood pressure by almost 8mmHg. But the light has other benefits the drugs don't have: they also reduce arterial stiffness and increase blood vessel relaxation.
Blue light also increases levels of nitric oxide, which protects the cardiovascular system, say researchers from the University of Surrey.
They tested blue light on 14 healthy men, who had whole-body exposure to the light—radiating at 450 nanometres, which is similar to daily sunlight—for 30 minutes for two days. They were also exposed to a filtered light, which acted as the control.
After both sessions, their blood pressure, heart rate and blood flow were measured—and there was a significant improvement after blue-light exposure that wasn't seen after the filtered-light sessions.
Similar effects have been seen with UV (ultraviolet) light—which also helps nitric oxide to be released by the skin—but it can cause skin cancer at high doses, the researchers say.