Vitamin D helps bones and muscles grow strong and healthy. Low levels of vitamin D can lead to problems like rickets and osteoporosis. Rickets is a deformity mainly found in children. Osteoporosis is the thinning of bone, a common problem as people, especially women, get older.

Studies in recent years have suggested that vitamin D may also have other uses. Studies have shown that low levels of D may increase the risk of heart attacks in men and deaths from some cancers. Other studies have shown that people with rheumatic diseases often have low levels of D.