By now, it is commonly understood that too much sun exposure poses such health risks as premature aging, skin cancer and other skin damage. But more sun protection can mean less production of vitamin D, a vital nutrient the skin makes when it absorbs ultraviolet-B rays from sunlight.
Vitamin D, also known as the “sunshine vitamin,” is a fat-soluble vitamin responsible for regulating blood levels of calcium and phosphorous, two minerals necessary for bone production. It helps the body absorb calcium, helping to form and maintain strong bones and teeth, and is used, often in combination with calcium, to increase bone mineral density and decrease fractures.
It is so essential to the human body that virtually every tissue — including the brain, heart, muscles and immune system — has vitamin D receptors.
Studies have shown that vitamin D could play a role in preventing a number of diseases, including Alzheimer’s, autoimmune disorders, cardiovascular disease, depression, diabetes and even obesity.
It may also help prevent many types of cancer. A 2012 study in Oxford’s cancer research journal Carcinogenesis found that, among breast cancer patients, women with higher vitamin D levels had smaller tumors and higher survival rates. Another recent study linked higher vitamin D levels to lower likelihoods of lethal prostate cancer.
Because it plays a role in skin cell metabolism and growth, vitamin D can help prevent premature aging and other skin damage, and treat such skin conditions as psoriasis, eczema, acne, scleroderma and rosacea, which typically worsen in winter months, when most people receive little or no sun exposure.
For example, a 2010 study of psoriasis sufferers in Dublin, Ireland, not only found vitamin D deficiencies in 75 percent of patients during wintertime, but also showed that UVB treatments, which stimulate vitamin D production in the skin, both doubled patients’ vitamin D levels and cleared their psoriasis.
And, in 2008, researchers at the University of California, San Diego, found that vitamin D supplements boost production of protective compounds in the skin and help prevent skin infections that result from atopic dermatitis, a common form of eczema characterized by severe itchiness, redness and scaling. Researchers at Massey University in New Zealand are currently conducting trials to determine whether such supplements are an effective treatment for psoriasis.
Just as vitamin D can help prevent many health problems, the inverse also applies: A vitamin D deficiency can increase the risks for all of the above conditions and others, including osteomalacia, a softening of the bones, and rickets, which causes skeletal deformities in children.
And most of us don’t get enough.
A 2010 study in the Nutrition Research Journal found that 42 percent of American adults were vitamin D deficient, with the highest rates among African Americans at 82 percent and Hispanics at 69 percent. Vitamin D deficiency was “significantly more common” among obese individuals, those without a college education, those with poor health and those who did not consume milk daily.
But that doesn’t mean you should bake in the sun.
Too much sun exposure can increase one’s risk of two types of non-melanoma skin cancer — basal cell carcinoma and squamous cell carcinoma. It can also cause premature aging and other skin problems.
Sources of Vitamin D
Although sunlight is the primary source of vitamin D for most people, there are other ways of obtaining this essential nutrient.
Sunscreen, even with as little protection as SPF 8, can reduce the skin’s ability to make vitamin D by 95 percent, according to a report in The Journal of Nutrition. Therefore, most experts agree that 10 to 15 minutes of unprotected sun exposure three times a week should be enough to satisfy vitamin D requirements without increasing other risk factors. However, a broad-spectrum sunscreen with SPF 15 or higher should be applied after that time.
But, depending upon where you live, the time of year and your skin color, that’s not always possible. Sunlight during the winter months is so weak throughout most of the country that the skin cannot get enough UVB rays to make vitamin D. Even during the summer months, a darker-skinned person takes twice as long to make vitamin D as a lighter-skinned person.
That’s why it’s important to obtain as much as possible from food. Although vitamin D is naturally present in only a few foods, it is added to many others. Good sources include:
- Cod liver oil
- Fortified milk, soy milk, yogurt, butter, margarine, cheese, orange juice, cereal
If you’re still not getting enough, supplements may be necessary. But be careful: They are not regulated by the FDA, and expert recommendations range from as little as 400 IU to as much as 4,000 IU of vitamin D per day. Too much supplementation can make the intestines absorb too much calcium, potentially causing calcium deposits to build up in soft tissues, kidney stones, kidney damage and a variety of other problems.
Ask your health care provider how vitamin D can help you.