Women who take calcium after menopause to reduce their risk of the bone-thinning disease osteoporosis may be increasing their risk of zinc deficiency. Taking a calcium supplement with a meal can reduce zinc absorption by 50% Already, about half of older women consume less than the recommended dietary allowance (RDA) for zinc, which is 12 milligrams per day for women over age 50. "This observation suggests that elderly women may be particularly vulnerable to factors that can alter zinc bioavailability or the requirement for zinc, such as a high-calcium diet as shown here," reported lead author Richard Wood, of the Mineral Bioavailability Laboratory at Tufts University in Boston.

American Journal of Clinical Nutrition (1997;65:1803-1809)