Q Can you tell me about vitamin D? I know that sunlight helps our bodies produce vitamin D, but I'm wondering if sunscreens interfere with that process or limit the amount our bodies make. Should I be taking a supplement?
A Yes, sunscreens interfere with your body's vitamin D synthesis, but that's no reason not to wear it, according to Kim Robien, assistant professor at the University of Minnesota's Division of Epidemiology & Community Health.
"We really do recommend that everyone wear sunscreen," she said. "It's not worth the tradeoff to get melanoma [skin cancer]."
And yes, you should probably be taking a supplement. Many health and nutrition experts, including Robien, are taking vitamin D supplements. Here's why.
For years vitamin D, called the sunshine vitamin, was seen as the strong-bones vitamin; deficiencies caused deformations such as rickets. With better nutrition, especially fortified milk, many believed deficiencies to be a worry of the past. However, that view is changing.
Robien said that there's a great deal of discussion about this vitamin now. With new tools and research, scientists are finding that the nutrient is linked to much more than healthy bones. The vitamin plays a role in cancer risk, infections, inflammation, pain, maybe even diseases such as multiple sclerosis and diabetes.
And most people don't get enough vitamin D, she said. A survey of blood tests by the Centers for Disease Control suggests that at least 60 percent of Americans are deficient in vitamin D.
At the very least, the lack of vitamin D can be painful.
A University of Minnesota study of children and adults with nonspecific body aches found that 93 percent of them were deficient in vitamin D. Especially interesting was the fact that every participant of color (of African, Hispanic and American Indian descent) was deficient in the vitamin. Apparently pigment as well as sunscreen can interfere with vitamin D production.
One gets vitamin D from sun exposure, of course, and food. But it's difficult to get enough to meet daily needs.
In Minnesota and other northern states, the sun is not intense enough from October through March to stimulate the body to produce vitamin D. In addition, many people don't eat enough vitamin D-rich foods such as salmon, fortified milk, some breakfast cereals and cod liver oil.
Robien suggests that you talk with your doctor about taking a vitamin D supplement. Sold over the counter at drug and health food stores, vitamin D preparations with cholecalciferol, rather than ergocalciferol listed on the label, are recommended. (Ergocalciferol isn't bad; cholecalciferol is better absorbed and utilized by the body.)
Current recommendations for vitamin D are 200 international units daily, up to 400 units for older Americans, Robien said, but that may change. In light of recent and continuing research, many scientists wonder what optimal vitamin D levels are; some believe current levels are too low. For now, however, don't exceed current recommendations with supplements unless instructed to do so by a doctor.