If you have high blood pressure, then you likely already know that it's the leading cause of stroke, and a major risk factor for cardiovascular disease. So, besides things like medication, diet changes, weight loss and exercise, what can be done to reduce it? Well, it turns out that exposure to blue light may help.

In a randomized study recently conducted at Britain's University of Surrey, 14 healthy male volunteers received full-body exposure to visible blue light for 30 minutes on one day, followed by 30 minutes of exposure to a control light on a subsequent day. The blue light had a wavelength of about 450 nanometers, which is similar to that of the visible blue light contained within sunlight.

Before, during and for two hours after both of the light-exposure sessions, scientists assessed each test subject's blood pressure, artery stiffness, blood vessel dilation and blood plasma levels of nitric oxide. It was found that while exposure to the control light had no effect, the blue light sessions resulted in a systolic blood pressure reduction of almost 8 mmHg (millimeters of mercury). According to the university, that sort of reduction is similar to what is seen in trials of blood pressure-lowering medications.

The blue light additionally appeared to reduce artery stiffness and to increase levels of nitric oxide, which is a signalling molecule associated with cardiovascular health. It is believed that the blue light exposure triggered a release of nitric oxide from the skin, allowing it to enter the bloodstream. There, it proceeded to relax the blood vessels and increase blood flow, resulting in a decrease in blood pressure.

"Exposure to blue light provides an innovative method to precisely control blood pressure without drugs," says U Surrey's Prof. Christian Heiss. "Wearable blue light sources could make continued exposure to light possible and practical. This would be particularly helpful to those whose blood pressure is not easily controlled by medication, such as older people."