Vitamin D has the potential to ward off a number of serious diseases

September brings the end of summer in the northern hemisphere and, for many, that means getting less sunshine. Our skin uses the sun's rays to make vitamin D. Without it, the body can’t absorb dietary calcium, so it steals calcium from bones, increasing the risk of osteoporosis and fractures. But missing out on the “sunshine vitamin” has consequences for more than just bone health, reports the September 2008 issue of Harvard Women’s Health Watch.

Vitamin D would be essential if it just protected bone health. But researchers have discovered that it’s active in many other tissues and cells and controls many genes, including some associated with cancer, autoimmune disease, and infection. Hardly a month goes by without news about the risks of too little vitamin D or about a potential role for the vitamin in warding off diseases, including breast cancer, multiple sclerosis, and even schizophrenia. More trials are needed to confirm vitamin D’s benefits and risks. In the meantime, the evidence is so compelling that some experts already recommend at least 800 to 1,000 IU of vitamin D per day for adults.

Harvard Women’s Health Watch notes that unless you live in the South and spend a fair amount of time outdoors, or you eat lots of vitamin D–fortified foods, supplements are the best way to get 800 to 1,000 IU of vitamin D a day. Most multivitamins contain only 400 IU, but don’t just take two — getting double doses of other vitamins and minerals can be unsafe. Instead, you can take a vitamin D pill to round out your daily needs. Until we know more, make sure your vitamin D intake from supplements does not exceed 2,000 IU per day.