Vitamin D consumption has been associated with a decreased risk of multiple sclerosis (MS), a condition affecting approximately 400,000 Americans. The study tracked more than 187,000 women for 10 to 20 years and found that subjects who took at least 400 International Units (IU) daily — the amount found in most multivitamins — had about a 40 percent decreased chance of developing MS. Vitamin D also appears to prevent or slow MS-like symptoms in animals.

Produced naturally by the body when it is exposed to sunlight, vitamin D is a fat-soluble vitamin and a hormone precursor, thus playing an important role in several biological functions. Experts recommend taking no more than 1,000 IUs daily, as excessive amounts of vitamin D can be toxic. However, most cases of toxicity reports involve intake of 25,000 to 60,000 IUs daily for one to four months.