Researchers say sunlight exposure could help lower high blood pressure.
New research, published in the latest Journal of Investigative Dermatology, is causing waves in the medical media beat ― or should that be UV waves?
According to the report, exposure to sunlight alters levels of the small messenger molecule, nitric oxide (NO) in the skin and blood, dilating blood vessels and thus easing hypertension. However, this goes against years of warnings that sunlight exposure can cause life-threatening skin cancer.
While agreeing that avoiding excess sunlight exposure is critical to prevent skin cancer, the authors say 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. Moreover, 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.
Martin Feelisch, Professor of Experimental Medicine and Integrative Biology at the University of Southampton, explained in a press release that “NO along with its breakdown products, known to be abundant in skin, is involved in the regulation of blood pressure. 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.”
During the study, the skin of 24 healthy volunteers 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 suggest 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 indicate 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.
Professor Feelisch adds that “these results are significant to the ongoing debate about potential health benefits of sunlight and the role of Vitamin D in this process. It may be an opportune time to reassess the risks and benefits of sunlight for human health and to take a fresh look at current public health advice.”
The researchers also say they believe that NO from the skin is an important, so far overlooked contributor to cardiovascular health. In future studies, they 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.