We've long known the benefits of vitamin D for strengthening bones, but researchers are finding that it may also play a role in preventing heart disease, certain types of cancer, arthritis and autoimmune diseases such as multiple sclerosis.
"For those of us in nutritional medicine, the whole story is vitamin D is no longer just about bone health," says Dr. Joel Evans, founder and director of The Center for Women's Health in Darien, Conn., and co-author of the upcoming "The Whole Pregnancy Handbook" (Gotham Books, $20).
Says Dr. Richard Cooper, a licensed naturopathic physician in New Canaan, Conn.: "We're starting to get a better understanding of its full effect on the body.
There is increasing evidence that people who live farther from the equator, and therefore get less sunlight, experience a greater rate of incidence of certain maladies, including multiple sclerosis and colon cancer.
"On the down side, there is increased risk of certain types of skin cancer, but if you avoid the sun totally, there is the risk of being deficient in vitamin D. The fact of the matter is when you use a lot of sunscreen, you decrease the amount of vitamin D....
How much sun exposure should be based on what your risks are."
"The biggest factor is that the governing bodies that come up with recommended dietary intake purely base it on a deficiency disease to prevent things like rickets," Evans says.
"Anybody that would be looking to explore this more should be doing so with someone who knows what tests need to be run," Cooper advises.
There are also some who believe that vitamin D isn't actually a vitamin, because it's produced naturally through sun exposure.