Women already know they need calcium to protect against osteoporosis. But there may be a benefit to drinking milk or taking supplements beyond that. In a study of 36,000 postmenopausal women published in last week's Archives of Internal Medicine, researchers found that those who were given daily supplements containing 1,000 milligrams of calcium and 400 IUs of vitamin D were slightly less likely to gain weight as they aged compared with those who took placebos. The benefits were biggest for the 40 percent of supplement takers who were already calcium deficient: They were 11 percent less likely to experience weight gain over the seven-year span of the study.
Calcium appears to increase fat metabolism and may also bind to small amounts of dietary fat in the intestine, preventing its absorption; vitamin D seems to help with weight maintenance. For postmenopausal women, "calcium might make a difference because changes in weight aren't necessarily due to excess caloric intake or lack of exercise but small changes in metabolism due to age," says study author Bette Caan, a senior epidemiologist at the Kaiser Permanente Medical Care Program in Oakland, Calif.