A slew of recent books and studies have touted the benefits of vitamin D and the perils of not getting enough vitamin D; some even encourage lying in the sun and taking vitamin supplements in order to prevent depression. But dermatologists say more time soaking up the rays isn't necessary—most Americans get all the vitamin D they need just by going outside in the course of their daily duties, and beyond that, it's easy to get adequate levels of the vitamin through nutrients in food. "Sunlight helps us produce vitamin D, but the amount of sunlight you need is so low that you could walk outside for probably five minutes and have enough," says Craig Austin, a New York-based dermatologist and founder of AB Skincare.
Vitamin D is important because it helps with calcium absorption; it's found in foods ranging from milk and cheese to liver, beef, fish and eggs. Many cereals are now fortified with vitamin D, as well; most people who follow normal diets probably don't need to take vitamin D or calcium supplements, Austin says. "Vitamin D deficiency, I don't think, is really all that common."
During the winter, people who live in northern climates might consider taking daily supplements, says New Jersey-based dermatologist Eric Siegel. But overdoing the vitamins has side effects, too, including nausea, vomiting, poor appetite and constipation. "You can also start suffering kidney disease, and, believe it or not, once you go past a certain dose of vitamin D, you can start clogging up the kidneys, because there's too much calcium absorbed into the blood," he says.
So don't use vitamin D as a reason to lie in the sun that extra half hour, Siegel says. "Why not get [vitamin D] out of food or supplements?" he asks. "Why give yourself skin cancer?"