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Vitamin D is known to help maintain healthy bones. It has been shown to reduce the incidence of osteoporosis and hip fractures when taken with calcium. In addition, physicians recommend vitamin D supplements to treat a number of other conditions. Some examples include:

• Psoriasis. This disorder causes red, scaly patches to occur on the skin. Topical prescription medications containing vitamin D may reduce symptoms.
  
  
• Familial hypophosphatemia. This inherited disease prevents the body from using phosphate, resulting in skeletal abnormalities similar to those caused by rickets. Physicians may prescribe both oral vitamin D and phosphate supplements to treat this disorder.

Research continues to investigate possible roles of vitamin D in the prevention and treatment of other conditions. These include:

• High blood pressure. There is some evidence that increasing vitamin D intake with supplements or sun exposure may help reduce blood pressure. Recent research shows an association between low blood levels of vitamin D and increased risk of heart attack, stroke and other cardiovascular events.
  
  
• Cancer. Whether from the sun or diet, increased vitamin D has been associated with lower risk of developing some cancers, including colorectal cancer and possibly breast cancer. Study results are mixed, and the amount of vitamin D required is unknown, so supplementation for this reason is not recommended due to the uncertainty of benefits and the potential dangers of vitamin D overdoses. Although sun exposure is important for vitamin D, excessive sun exposure is a leading cause of skin cancer, the most common form of cancer in the United States.
  
  
• Multiple sclerosis. Some studies have found a link between use of vitamin D supplements and a lower incidence of multiple sclerosis. Further research is required before the vitamin can be recommended for this use.
  
  
• Other conditions. Scientists also continue to examine the use of vitamin D to reduce the risk of diabetes, rheumatoid arthritis and other diseases.

Studies continue to find new evidence of additional possible benefits of vitamin D. For example, one study found that some postmenopausal women who take a combination of calcium and vitamin D supplements may gain less weight than women who do not.

Another study found that people with higher levels of vitamin D in their blood have a reduced risk of developing the early stages of age-related macular disease, the most common cause of blindness in older U.S. adults.