When skin is exposed to the sun’s rays, a compound is released in the blood vessels that helps lower blood pressure, according to the study.
Lead study author Dr Richard Weller said the research calls into question whether the so-called sunshine vitamin, vitamin D, recommended for supplementation by the government in winter, is the only factor in sunlight responsible for good health.
“Everyone’s got hooked up about vitamin D,” said Weller, who is senior lecturer in Dermatology at the University of Edinburgh. “The mechanism we’ve shown is separate to vitamin D, so vitamin D by itself does not account for the benefits of sunlight.”
Study participants’ skin was exposed to ultraviolet (UVA) light from tanning lamps for two 20-minute sessions. The first session they were exposed to UV rays and heat of the lamps; in the second session the volunteers were exposed to heat only.
Blood pressure dropped noticeably for one hour following exposure to UV rays, but not after the heat-only sessions.
The findings showed that sunlight alters levels of nitric oxide in the skin and blood, reducing blood pressure. Yet vitamin D levels remained the same. This could be good news for heart health, reducing the risk of heart attack and stroke.
It is known that blood pressure rates are higher the further people live from the Equator and also lower in summer than winter. Scientists previously attributed this to a change in temperature.
High blood pressure affects approximately 16 million people in the UK and, according to government figures, is the leading factor of 62,000 deaths from stroke and heart attacks per year.
Weller said that while diet, such as the Mediterranean diet, is an important factor in preventing heart disease, the sun may be an additional factor worth considering as well.
“What would be interesting is if sun was not just an additional but an interactive factor,” he said.
Skin experts agree that excessive sun exposure is critical in preventing skin cancer, but warn that not being exposed to it at all, out of fear or as a result of a certain lifestyle, could increase the risk of cardiovascular disease, accounting for 80 times more deaths in the UK than those from skin cancer.
“We need to be reconsidering our advice on sun exposure, Weller said.
Results from a recent study on the total Danish population of 4 million showed that Danes with skin cancer live 10 years longer than Danes without skin cancer.
A Swedish study in 2010 reported that Swedes who regularly sunbathed lived longer and the health benefits of sun exposure outweighed the risk of skin cancer.
“There’s no evidence showing that sunlight protection reduces death from any cause. My concern is that it might be doing the opposite.”