Research published Jan. 20 in the Journal of Investigative Dermatology shows that light exposure has the ability to change a person's blood levels of nitric oxide (NO), a signaling molecule that protects different organs. As nitric oxide levels increase, blood pressure drops, according to the researchers.
High blood pressure, or hypertension, occurs when there is too much force pushing outwards on the walls of arteries, the American Heart Associationexplains.
Arteries and veins carry blood to other parts of the body in order to keep them functioning. Because arteries are made of muscles and semi-flexible tissue, they have some stretch to them.
However, if the heart pumps the blood too strongly, the arteries won't snap back into place. This can be caused due to the buildup of cholesterol or plaque, or due to scarring from when arteries were stretched too far in the past. Left untreated, high blood pressure can cause stroke, kidney damage, vision loss, erectile dysfunction, memory loss, fluid in the lungs, peripheral artery disease and chest pain.
Researchers exposed 24 participants to ultraviolet A (UVA) light through tanning lamps during two 20-minute sessions. The amount of exposure was set to be about the same as standing in the sun for 30 minutes in southern Europe. During one session, the participants got the full dose of heat and light from the lamps. The other time, they felt the heat but weren't subjected to the lighting.
When participants were exposed to UVA light, the researchers saw their blood vessels dilate, their blood pressure drop and the nitric oxide levels in their bloodstream increase. Vitamin D levels remained unchanged.
The decline in blood pressure was small, but significant enough to show that the UVA exposure had made a difference, according to the researchers.
They found that the UVA rays specifically affected nitric oxide molecules found in the upper layers of the skin and allowed them to be released in the bloodstream. The results correlate with how blood pressure changes throughout the seasons and why people have cardiovascular risk factors if they live in certain areas, the researchers added.
Blood pressure is typically higher in the winter and lower in the summer, the Mayo Clinic points out.
Study co-author Martin Feelisch, a professor of experimental medicine and integrative biology at the University of Southampton, said the study confirms that there are health benefits to getting some sunshine. Even though excess sun exposure has been known to increase risk for skin cancer, not getting enough sun may be detrimental to heart health. Vitamin D supplements haven't been able to provide all the same benefits as natural sunshine can, he said.
"We believe that NO from the skin is an important, so far overlooked contributor to cardiovascular health. In future studies we intend to test whether the effects hold true in a more chronic setting and identify new nutritional strategies targeted at maximizing the skin's ability to store NO and deliver it to the circulation more efficiently," he said in a press release.
But, senior study author Dr. Richard B. Weller, a dermatologist at the University of Edinburgh in Scotland, told the New York Times that if you have high blood pressure to begin with, just standing in the sun likely won't cure your woes.
"Getting sunlight is not enough if your blood pressure is high. And if you have high blood pressure you need to get it controlled," he warned.
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