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.