Study shows health benefits of non-burning exposure to UV light

Moderate exposure to sunlight that does not cause sunburn can prevent vitamin D deficiency with minimal risk of individuals developing skin cancer, a recent British study found.

The study, published in the December issue of the British Journal of Dermatology, is believed to be the first to examine both the health benefits of sunlight along with the ability of the skin to repair itself after exposure to low-level ultraviolet radiation.

The main way for the body to produce vitamin D is by exposing skin to ultraviolet B rays in sunlight. While over-exposing skin to the sun until it burns can increase the risk of developing skin cancer, the benefits of sensible sun exposure are numerous and extend beyond vitamin D. They include the production of nitric oxide, which improves blood flow and decreases blood pressure, and the release of feel-good beta-endorphins that reduce depression.

However, the dermatology community has long recommended that sunlight should largely be avoided in order to prevent skin cancer – advice that some doctors see as having increased the rate of vitamin D deficiency globally.

Vitamin D deficiency plagues a large percentage of the population. It increases the risk of many types of cancers, diabetes, cardiovascular disease, multiple sclerosis, dementia and numerous other illnesses. In children, a lack of vitamin D impacts growth and increases the risk of rickets and asthma, among other problems.

Led by Dr. S.J. Felton of the University of Manchester, the study examined volunteers from the Manchester, U.K. area with both lighter skin that sunburns easily and darker skin that rarely burns. Individuals with light skin can more easily produce vitamin D, while those with dark skin have more melanin that blocks some of the sun’s rays, thereby making it more difficult to generate vitamin D.

Adult participants were exposed to tanning beds that emitted 95 percent UVA rays and 5 percent UVB rays, a close simulation to summer sunlight in the U.K. Individuals were exposed to the UV light three times a week in January and February, when the sun’s rays in the U.K. are not strong and when vitamin D production is low. The doses of UV exposure took about 6 minutes to administer, equating to 13-17 minutes of exposure to midday sun in June in the U.K.

The study illustrated how skin has evolved over time to receive the benefits of sunlight while also repairing any UV-induced damage to the DNA in the skin, which protects it from non-melanoma skin cancer.

“What this study shows is that you can get a reasonable amount of sunlight that would make enough vitamin D in your skin living in the U.K. Yes, the DNA is somewhat damaged, but because the body has adapted to its environment, it has the ability to repair it,” said Dr. Michael Holick, professor of medicine, physiology and biophysics at Boston University Medical Center and a leading authority on vitamin D.

“You have to ask the question, why would the human body have evolved for tens of thousands of years to depend on sun for its vitamin D requirement? And that’s the explanation: because the skin is able to respond,” Holick said in an interview with Life Science Daily.

Holick, the author of numerous studies on the health benefits of sun exposure and vitamin D, wrote an editorial on Felton’s study in the British Journal of Dermatology that said he hopes it will give health regulators a new perspective.

“I would hope that the study would make people out there recommending that individuals never be exposed to direct sunlight realize that in fact some sun exposure has a healthy benefit and that we should be promoting sensible sun exposure,” Holick said.

He is advocating that public health officials change their recommendation on avoiding the sun in favor of moderate sun exposure. The goal is for more individuals to become educated about the wide range of health benefits from modest sunlight exposure, which is superior to taking vitamin D pills as a supplement, Holick added.