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Annual mega-dose of vitamin D doesn't reduce fractures, study finds

May 11, 2010 |  1:30 pm

Sufficient vitamin D is vital to bone health and preventing the bone-thinning disease osteoporosis. But a new study shows an experimental therapy involving a once-a-year mega-dose of vitamin D did not prevent bone fractures and actually increased the risk of falls and fractures.

Researchers in Australia gave a single, annual dose of 500,000 international units of vitamin D or a placebo to 2,256 women, ages 70 and older, at high risk for fracture. But after three to five years, the study showed that 74% of the women in the vitamin D group had at least one fall compared with 68% of the women in the placebo group. Women in the vitamin D group had 171 fractures compared with 135 in the placebo group.

Vitamin D supplementation of 800 IU a day is known to be important for good bone health. It's not clear why an annual mega-dose may backfire. It's possible that vitamin D improved the women's overall health and well-being to the extent that they were more active and mobile and had more opportunities to fall. But no matter, said the authors of a commentary accompanying the study, it's safe and effective to take the vitamin at lower doses daily, weekly or monthly.

The study was published Tuesday in the Journal of the American Medical Assn.

— Shari Roan