Sun light reduces blood pressure, improves mood and cardiovascular health plus suppresses multiple sclerosis symptoms.

The health benefits of sunlight are not just vitamin D, but those related to the release of nitric oxide, and the production of beta-endorphin,.

In addition to the benefits of vitamin D, several human skin diseases, like psoriasis, vitiligo, atopic dermatitis and localized scleroderma, can be treated with solar radiation (heliotherapy) or artificial UV radiation (phototherapy). UV exposure can suppress the clinical symptoms of multiple sclerosis independently of vitamin D synthesis. Furthermore, UV generates nitric oxide (NO), which may reduce blood pressure and generally improve cardiovascular health. UVA-induced NO may also have antimicrobial effects and furthermore, act as a neurotransmitter. UV exposure may also improve mood through the release of endorphins, regulation of circadian rhythms which are all important components of life-long health and well-being  (Asta Juzenienea, Johan Moanab. Beneficial effects of UV radiation other than via vitamin D production,  Dermato-Endocrinology, Volume 4, Issue 2, 2012)

beta-endorphin

UV-exposer increases levels of a molecule called beta-endorphin, which acts similarly to morphine and heroin in the body. Endorphins circulating in the blood are able to carry feel-good messages to the brain.

This endorphin production may also explain why people are more generally drawn to sunny spots and often go to the beach on vacation.

Nitric oxide

Normal human keratinocytes secrete nitric oxide (NO) in response to UVA and UVB radiation, and In humans, NO is a powerful vasodilator with a short half-life of a few seconds in the blood. Long-known pharmaceuticals such as nitroglycerine and amyl nitrite were found to be precursors to nitric oxide more than a century after their first use in medicine.

Importantly Low levels of nitric oxide production such as synthesised by sun exposure are important in protecting organs such as the liver from ischemic damage (Nitric oxide produced by ultraviolet-irradiated keratinocytes stimulates melanogenesis.  J Clin Invest. 1997 Feb 15; 99(4): 635–642).