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Let sun shine for your vitamin D

Copyright © 2016 Albuquerque Journal

Avoiding the bright New Mexico sunshine completely may do us more harm than good, according to a new study co-authored by a University of New Mexico researcher.

The public health message about sun exposure needs to change, the study recommends, with more emphasis on the body’s need for sunlight.

For those of us living in one of the nation’s sunniest states, New Mexicans obtain beneficial vitamin D from sunlight even in winter, unlike people who live in the northern half of the U.S., said Dr. Marianne Berwick, a UNM professor of internal medicine.

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The trick is, how do we balance the benefits of sun exposure against the risk of harmful overexposure to ultraviolet radiation?

The key is to spend time in the sun, but not enough time to get a sunburn, which leads to a higher risk for dangerous melanoma.

As for sunscreen, the study says “excessive use” of sunscreen could result in possible Vitamin D deficiency. Berwick defined excessive use as slathering on large amounts of sunscreen with a sunprotective factor, or SPF, of 30 or higher.

People have many different skin types, and some people can tolerate more sun exposure without risking harmful sunburns. But nearly everyone has some tolerance for sunlight.

“You can be out for a certain amount of time without harming yourself,” said Berwick, who often carries a parasol when she walks outdoors for extended periods.

Health officials for decades have warned Americans to cover up – wear long sleeves, hats, etc. – in sunlight to guard against skin cancer, but that message is too simplistic and may be harming us, Berwick says. Instead, we need to “modify the message,” she said.

“I think people can handle slightly more complex ideas,” she said.

“Public health authorities in the U.S. are currently advising that human sun exposure be reduced,” the study said, even as the CDC warns that 32 percent of Americans suffer from insufficient vitamin D.

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The study, based on an examination of decades of research about the risks and benefits of sun exposure, was published Nov. 19 in the journal Dermato-Endocrinology, which is available online without a subscription.

Insufficiency of vitamin D may be linked to a long list of illnesses, including bone disease, high blood pressure, diabetes, heart disease and a variety of cancers, including skin cancer, it said. Lack of vitamin D is most strongly linked to colon cancer, Berwick said.

The link between melanoma and sun exposure is “two-sided: non-burning sun exposure is associated with a reduced risk of melanoma, while sunburns are associated with a doubling of the risk of melanoma,” the study said.

In New Mexico each year, about 400 people are diagnosed with melanoma, the deadliest form of skin cancer, and about 60 die of the disease, according to the state Department of Health. The rate of new melanoma cases was 13.5 per 100,000 in 2013, which was lower than the U.S. rate of 20.7 per 100,000 that year, according to the U.S. Centers for Disease Control and Prevention.

About a third of Americans don’t get enough vitamin D, which the body makes from ultraviolet radiation in sunlight, as well as nutritional sources.

“The association between sun exposure and reduced cancer mortality in North America was identified in the 1960s,” the study said. In the 1980s, vitamin D was identified as a possible protective factor from cancer.

But “instead of pursuing further benefits of sun exposure, scientific inquiry focused on the health risks of sun exposure, especially melanoma and other kinds of skin cancer,” it said.

By way of background, the study notes that the incidence of melanoma increased 23-fold from 1935 to 2012.

At the same time, the share of Americans who work indoors increased from 25 percent in 1910 to 75 percent in 2000.

The study recommends that fair-skinned people who tan only minimally can obtain required vitamin D by spending about 15 minutes in the sun with face, arms and legs exposed, two or three times a week at midday from May through October.

People with darker skin require more time in the sun to produce required vitamin D and have lower risk of non-melanoma skin cancer.

The good news for New Mexicans is that we don’t have to wait until spring to benefit from sunshine.

Like others who live in the southern half of the U.S., New Mexicans get enough UV radiation year-round to produce vitamin D, Berwick said.

“We get vitamin D from sun even in winter,” she said.


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