Taking a daily vitamin D supplement might extend your life, at least if you’re an older woman. That’s the suggestion of a comprehensive review published this week by the Cochrane Collaboration.
The analysis looked at 50 prior trials, including 94,148 people—mostly women living in nursing homes, with an average age of 74—from high-income countries. Researchers concluded that over a two-year period, one life was saved for every 161 people who took an average daily dose of less than 800 international units of vitamin D3 (cholecalciferol). Other forms, including vitamin D2 (ergocalciferol) and the active forms of vitamin D (alfacalcidol and calcitriol), did not show the same benefit. People who took vitamin D3 with calcium were more likely to develop kidney stones.
Bottom line: None of the trials included in the analysis were designed to detect a reduction in mortality, so the findings need to be confirmed. And more research is still needed comparing different doses of vitamin D3, alone or combined with calcium, on mortality. Meanwhile, the best way to get vitamin D is through dietary sources, such as fortified milk and fatty fish such as salmon or sardines. Limited exposure to sunlight can also provide vitamin D, but talk with your doctor first, to assess your risk of skin cancer. And if, in consultation with your doctor, you decide to take vitamin D supplements, choose one labeled "USP Verified", which indicates that it meets standards for purity and potency set by the U.S. Pharmacopeia, a nongovernmental authority, and have what the USP considers acceptable limits of contaminants. For a list of products that have been verified by the USP, go to www.uspverified.org.
Source
Vitamin D supplementation for prevention of mortality in adults (Review) [The Cochrane Library]
—Doug Podolsky
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