Source European Heart Journal
Humans evolved being exposed for about half of the day to the light of the sun. Nowadays, exposure to sunlight is actively discouraged for fear of skin cancer, and contemporary lifestyles are associated with long hours spent under artificial light indoors. Besides an increasing appreciation for the adverse effects of these life-style-related behavioural changes on our chronobiology, the balance between the beneficial and harmful effects of sunlight on human health is the subject of considerable debate, in both the scientific and popular press, and the latter is of major public health significance. While there is incontrovertible evidence that ultraviolet radiation (UVR) in the form of sunlight is a significant predisposing factor for non-melanoma and melanoma skin cancers in pale skinned people, a growing body of data suggest general health benefits brought about by sunlight.
The researchers propose that many of the beneficial effects of sunlight, particularly those related to cardiovascular health, are mediated by mechanisms that are independent of melatonin, vitamin D, and exposure to UVB alone. Specifically, they suggest that the skin is a significant store of nitric oxide (NO)-related species that can be mobilized by sunlight and delivered to the systemic circulation to exert coronary vasodilator and cardioprotective as well as antihypertensive effects. They further hypothesize that this dermal NO reservoir is a product of local production and dietary supply with nitrate-rich foods.
The full article (pdf) is available on the European Heart Journal website.