Exposing skin to sunlight may help lower blood pressure and cut the risk of heart attack and stroke, a new study has found.
Research carried out at the Universities of Southampton and Edinburgh found that sunlight alters levels of the small messenger molecule, nitric oxide (NO) in the skin and blood, reducing blood pressure.
"NO along with its breakdown products, known to be abundant in skin, is involved in the regulation of blood pressure," said Martin Feelisch, Professor of Experimental Medicine and Integrative Biology at the University of Southampton.
"When exposed to sunlight, small amounts of NO are transferred from the skin to the circulation, lowering blood vessel tone; as blood pressure drops, so does the risk of heart attack and stroke," Feelisch said.
While limiting sunlight exposure is important to prevent skin cancer, the authors of the study, including Dr Richard Weller of the University of Edinburgh, suggest that minimising exposure may be disadvantageous by increasing the risk of prevalent conditions related to cardiovascular disease.
Cardiovascular disease, often associated with high blood pressure, accounts for 30 per cent of deaths globally each year.
Blood pressure and cardiovascular disease are known to vary according to season and latitude, with higher levels observed in winter and in countries further from the equator, where ultraviolet radiation from the Sun is lower.
During the study, the skin of 24 healthy individuals was exposed to ultraviolet (UVA) light from tanning lamps for two sessions of 20 minutes each. In one session, the volunteers were exposed to both the UVA rays and the heat of the lamps. In another, the UV rays were blocked so that only the heat of the lamps affected the skin.
The results suggested that UVA exposure dilates blood vessels, significantly lowers blood pressure, and alters NO metabolite levels in the circulation, without changing vitamin D levels.
Further experiments indicated that pre-formed stores of NO in the upper skin layers are involved in mediating these effects. The data are consistent with the seasonal variation of blood pressure and cardiovascular risk at temperate latitudes, researchers said. The study was published in the Journal of Investigative Dermatology.