Vitamin D Meta-Analysis on Fracture Risks

A new meta-analysis on vitamin D finds that a high dose of the ingredient may be best for reducing one’s risk of bone fractures. Results are available online at the New England Journal of Medicine.

Academic researchers from eight countries reviewed 11 clinical trials on more than 31,000 elderly participants, most of whom were women. Each clinical trial compared vitamin D supplementation (daily, weekly, or every four months), with or without calcium, to placebo or calcium supplementation.

The researchers found that vitamin D supplementation was associated with a 10% reduction in hip fractures and a 7% reduction in non-vertebral fractures compared to placebo.

But the likelihood of subjects experiencing significant risk reduction may rely on the vitamin dosage.

When breaking down risk reduction based on dosage-the trials used anywhere from 792 to 2000 IU of vitamin D-the researchers determined that the highest quartile of vitamin D intake provided the most clinically relevant risk reduction (30% at hip and 14% at non-vertebral locations). Still, an editorial accompanying the study calls for more rigorous methodology before calling this conclusive.

“Despite the consensus that more is not better, we have continued to conduct trials (and include them in meta-analyses) without regard to ensuring the presence of two key features: baseline status and dose adequacy,” said the editorial's author, Robert Heaney, MD, from the Osteoporosis Research Center at Creighton University Medical Center. “The question of how much vitamin D is enough is likely to remain muddled as long as meta-analyses focus on trial methodology rather than on biology.”

The meta-analysis on vitamin D and bone fractures was funded by grants from the Swiss National Foundations, the European Commission’s Framework 7 Program, and DSM Nutritional Products.