Harvard Women's Health Watch

By the way, doctor: Am I taking too much vitamin D?

Q. I take Fosamax with vitamin D and a multivitamin that contains vitamin D. Now I see my calcium tablets also have vitamin D in them. Am I in danger of getting too much of this vitamin?

A. This is a complicated issue, because there's some disagreement over the optimal daily intake for this vitamin. There's no question that vitamin D is essential for healthy bones. It promotes the absorption of calcium and phosphorus from the intestines — a fundamental step in bone growth and repair. Adequate vitamin D is especially important for women who have osteoporosis or are at risk for it. Studies also suggest that vitamin D bolsters the immune system and in sufficient doses helps prevent certain forms of cancer. In September, researchers reported finding a link between vitamin D supplementation and reduced mortality (see "Lower death rate in vitamin-D takers").

Lower death rate in vitamin-D takers

Vitamin D appears to lower the risk of death, according to an analysis of previously published studies in the Sept. 10, 2007, issue of the Archives of Internal Medicine. Researchers in France and Italy analyzed the results from 18 randomized trials involving 57,311 mostly elderly subjects taking daily vitamin D in doses ranging from 300 to 2,000 IU (average dose was 528 IU). After a follow-up of 5.7 years, individuals taking vitamin D had a 7% reduced risk of death from all causes, compared with those who did not.

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