A 20-minute exposure to sunlight can lower blood pressure, as a British study has shown. Too much sun can promote cancer, but a total absence of UV rays risks leading to cardiovascular problems, as researchers claim.
This study mainly focused on the mechanisms of action of UV rays on the skin, we already knew that the tension varied according to the seasons and latitudes. In countries far from the equator, hypertensive patients generally have higher blood pressure in winter than in summer. This study, carried out by the British universities of Southampton and Edinburgh, was published in the journal “Journal of Investigative Dermatology”.
UV exposure lowers blood pressure
The researchers observed that the sun’s rays work by modifying the production of nitric oxide (NO) in the skin and then in the circulation, which causes the blood vessels to widen and leads to a reduction in blood pressure. According to Martin Feelisch, professor of medicine at the University of Southampton, who participated in this study: “NO and its metabolites, abundant in the skin, are involved in the regulation of blood pressure. When exposed to the sun, a small part of NO is transferred from the skin to the bloodstream, which lowers the tension in the vessels. If blood pressure drops, the risk of cardiovascular events such as myocardial infarction and stroke decreases.”
It is estimated that cardiovascular diseases are responsible for 30% of deaths worldwide each year. Hypertension, sometimes called in the Anglo-Saxon world “silent killer”, is responsible for a large proportion of these deaths.
It is interesting to note that beetroot, a plant with a hypotensive effect, also relies on NO and its metabolites (nitrites, nitrates, etc.) to lower blood pressure. This is why doctors and nutritionists advise drinking beetroot juice in case of hypertension.
UVA rays help lower blood pressure
In this study, the skin of 24 healthy volunteers was exposed to rays from an artificial tanning lamp for 2 sessions of 20 minutes each. In the first session, participants were exposed to both UVA and heat from the lamp. In the second session, UVA rays were blocked and the volunteers only received heat. The quantity of UVA rays received corresponds to exposure to the sun for approximately 30 minutes in summer in a country in southern Europe (eg Italy or Spain).
The results showed, according to the researchers, that UVA exposure dilates blood vessels and significantly lowers blood pressure. UVA rays modify the level of NO metabolites in the bloodstream, without however altering the level of vitamin D. This study also shows that the skin is an organ capable of storing a large quantity of NO. To sum up, we can say that the sun promotes the transfer of NO and its metabolites from the skin to the bloodstream.
Although UV rays can be very harmful to the body by causing skin cancer, completely avoiding sun exposure, for example out of fear or because of a certain lifestyle, can increase the risk of cardiovascular disease. . Depending on these results, we may also need to review the health risks of the sun and modify certain public health recommendations. The researchers point out that more research is needed to better understand certain mechanisms.
Source : Journal of Investigative Dermatology
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