The results of a randomized, placebo-controlled trial of calcium and vitamin D supplements in more than 36,000 postmenopausal women, conducted as part of the Women’s Health Initiative (RD Jackson et al. N Engl J Med 2006; 354:669), have been misinterpreted by some patients to mean that they should stop taking such supplements.
At the time of recruitment, the participants in this study had an average daily calcium intake of 1100-1200 mg. They were randomized to take either 1000 mg of calcium carbonate plus 400 IU of vitamin D3 or a placebo for an average of 7 years. Both groups were permitted to take calcium and vitamin D supplements on their own as well. In the intention-to-treat population, the study supplements increased hip bone density but did not decrease the incidence of hip fractures. The subgroup of women who adhered to the protocol and actually took the study supplements showed a significant reduction in hip fractures compared to the control group.
Men and women over age 50 should have a total calcium intake of about 1200 mg per day (Treat Guidel Med Lett 2005; 3:69). If they need a supplement to achieve that, calcium citrate is more expensive, but it offers some advantages over calcium carbonate: it can be taken without food, causes less GI disturbance and may be less likely to cause kidney stones.
With any calcium salt, vitamin D is necessary for optimal absorption. The recommended minimum daily requirement of vitamin D (vitamin D3 is preferred) is 400 IU for people 50-70 years old and 600 IU for those over 70. But those infrequently exposed to the sun may need 800- 1000 IU of vitamin D daily, and many experts recommend 800 IU or more for all postmenopausal women.