D Is for … Death Defying?
Why are conditions such as colon cancer, multiple sclerosis and type 1 diabetes less common in areas with plentiful sunlight? Some research points to an abundance of vitamin D, the only nutrient our bodies synthesize from sunlight. Vitamin D, it turns out, plays an important role in regulating the immune system.
It may even lengthen your life. In 2007, a study analyzing 18 clinical trials found that people who took vitamin D supplements regularly had a 7 percent lower death rate over five and a half years. "That could translate into one or two more years of life," says Philippe Autier, M.D., of the International Agency for Research on Cancer, one of the study authors. Other conditions that may be deterred by vitamin D:
- Cancer. A 2007 controlled study of nearly 1,200 postmenopausal Nebraska women linked supplements of vitamin D and calcium to a 77 percent lower risk of all cancer, but the strongest evidence is for prevention of colon cancer, according to several large-scale studies. Evidence that vitamin D prevents other cancers is preliminary.
- Heart disease. Adequate vitamin D may help control high blood pressure, studies show.
- Multiple sclerosis (MS). Researchers at Harvard studied blood samples of military personnel and found that white Americans with the highest levels of vitamin D were 62 percent less likely to develop MS, an autoimmune neurological disease. The finding didn't extend to people of other races, though, possibly because of inadequate sample size.
- Depression. Vitamin D deficiency has been linked to mood disorders, especially in the elderly. However, taking vitamin D supplements doesn't relieve depression, studies show. Too much vitamin D can be a problem too: one study found brain lesions, albeit reversible, in elderly people with the highest levels of vitamin D.
- Other conditions. There is some preliminary evidence that vitamin D may play a role in preventing some infections, rheumatoid arthritis, diabetes (type 1 and type 2), dementia and macular degeneration, a common eye disease.