Teen Vogue—April 23, 2009
The answer is simple: The body can't make vitamin D on its own. Few foods naturally contain the nutrient (fish like salmon and mackerel and foods like liver and egg yolks do). For that reason, public health officials mandated decades ago that milk be fortified with vitamin D.
Certain diets may play a role in vitamin D deficiency as well. "Teen girls are more likely to experiment with diets like veganism, which cut out products such as eggs, fish, and fortified dairy, the common dietary sources of vitamin D," says Lisa Callahan, MD, of the Women's Sports Medicine Center at New York's Hospital for Special Surgery. But food is just one way the body gets vitamin D.
The most abundant source of vitamin D by far is the sun (the body uses sunlight to convert a form of cholesterol in the skin into vitamin D).
Which isn't to say you should sunbathe in order to get vitamin D. "Always use SPF and reapply during prolonged exposure," Callahan suggests.
So how can girls guard against skin cancer and still get enough vitamin D? First, check labels to see if any of your favorite foods are already fortified with the nutrient. Many products - like orange juice, cereal, and yogurt - have vitamin D added to them.
If your levels from food are insufficient, then "take a multivitamin that includes D," Callahan advises. "I tell my patients to get between 800 and 1,000 IUs [international units] per day which, between supplements and food, is easily achieved. There's so much that modern medicine can't fix, but solving vitamin D deficiency is simple."