Calcium plus Vitamin D -- Little Effect on Fracture Rates

Home>
Primary Care>
General Medicine>
Summary and Comment

Calcium plus Vitamin D — Little Effect on Fracture Rates

A large trial from the Women's Health Initiative showed no significant effect on rates of hip and other fractures.

Despite exhortations that postmenopausal women should take supplemental calcium and vitamin D, unequivocal evidence to support this practice has remained elusive. In this randomized trial from the Women's Health Initiative, more than 36,000 women (age range, 50–79) received either the combination of daily elemental calcium (1000 mg as calcium carbonate) plus vitamin D₃ (400 IU), or placebo. At baseline, mean daily calcium intake was 1151 mg, and mean daily vitamin D intake was 366 IU.

During an average follow-up of 7 years, rates of hip fracture were slightly, but not significantly, lower in the calcium/vitamin D group than in the placebo group (14 vs. 16 fractures per 10,000 person-years). Total fracture rates (at all sites) were also similar in the two groups (164 vs. 170 per 10,000 person-years). In an analysis limited to women who took at least 80% of their pills, the calcium/vitamin D group had significantly fewer hip fractures than did the placebo group (10 vs. 14 per 10,000 person-years), but numbers of total fractures were similar. Calcium/vitamin D recipients had a small but significant increase in risk for kidney stones compared with placebo recipients (hazard ratio, 1.17).

Comment: Calcium and vitamin D supplementation had little effect on fracture rates in this large 7-year trial. However, the relatively high baseline intake of calcium and vitamin D might have diminished the likelihood that supplementation would prevent additional fractures, and other data suggest that 800 IU of vitamin D might be more effective than 400 IU (Journal Watch Jun 3 2005). Moreover, these findings don't apply to women with osteoporosis, who comprised only about 4% of subjects. Although these findings hint at benefit in some subgroups, an editorialist concludes that "calcium with vitamin D supplementation by itself is not enough to ensure optimal bone health."

— Allan S. Brett, MD

Published in Journal Watch General Medicine February 24, 2006