Harvard Health Letter

Vitamin D: Enjoying its day in the sun

New study summing up anticancer research adds to its luster.

We met someone the other day who had just been told by his doctor to give up his daily vitamin E pill. The vitamin's reputation has slid as studies have challenged the view that it prevents heart disease, Alzheimer's disease, or cancer — and in the large daily doses of 400 International Units (IU) that people have been taking, it may actually do harm. "But," our health-conscious acquaintance asked, "should I be taking vitamin D instead?"

Cancer prevention

That question is on many people's minds these days. A study published by the American Journal of Public Health in late 2005 concluded that taking vitamin D pills could substantially reduce the risk for breast, colon, prostate, and ovarian cancer. The study itself was just a summary of previously published research. But the University of California, San Diego, researchers spiced it up with a strongly worded conclusion scolding the public health and medical communities for not adopting vitamin D supplementation for cancer prevention sooner. They contrasted the nickel-a-day cost of a 1,000-IU vitamin D pill with "the high human and economic costs of treating cancer attributable to insufficiency of vitamin D."

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