For years, doctors have been telling women to take calcium after menopause to keep their bones strong and prevent fractures. And women have complied, making calcium the top seller in the multibillion-dollar dietary-supplement industry. In 2004 alone, the total calcium tab was about $993 million. But last week a study from the Women's Health Initiative (WHI) questioned whether women were wasting their money. The study of 36,282 postmenopausal women ages 50 to 79 found that calcium had only a small effect on bone density and no significant effect on the rate of fractures. And although calcium is generally considered safe, researchers found a 17 percent increase in kidney stones among women taking the supplements.
This is the second time in a month that results from a WHI study have challenged long-held beliefs about nutrition and health. Another WHI study reported that low-fat diets do not protect against breast or colorectal cancer or heart disease. And in 2002, the WHI issued the bombshell finding that hormone treatment after menopause did not protect against heart disease in most women and had more risks than benefits. Although some of those results have been questioned and critics have claimed the WHI overall was badly designed, many scientists still regard it as a landmark in women's health research. "When you think back to the 1980s, the early 1990s, we had very little clinical data on issues that affect women's health," says Dr. Elizabeth Nabel, director of the National Heart, Lung and Blood Institute, which sponsors the WHI.
In the calcium and vitamin D study, half of the women received a daily dose of 1,000 milligrams of elemental calcium in the form of calcium carbonate combined with 400 units of vitamin D. The other half received placebo pills. The women were observed for an average of seven years; by the end of the trial, three quarters were still taking their pills. Scientists found that women taking the supplements had only 1 percent higher hip-bone density than women on the --placebo. Although the overall reduction in hip fractures was not statistically significant, some women did see a benefit. Women who consistently took the full supplemental dose had a 21 percent decrease in hip fractures, and women older than 60 had a 21 percent reduction. Some scientists think the results might have shown even more of a benefit from calcium if the women had stuck with the dose for a longer time. Reducing a woman's risk of hip fracture is important because it's one of the most debilitating injuries, especially for older women, says Dr. Rebecca Jackson, an endocrinologist at Ohio State University. Still, women shouldn't toss out their calcium supplements before checking with their doctors, especially if they're older than 60 or are at high risk of osteoporosis, a skeletal disorder that weakens bones (go to www.nlm.nih.gov/medlineplus/osteoporosis.html for more information). Women who don't have enough calcium (1,000 to 1,200 milligrams a day) in their diets should also consider supplements. Good food sources include dairy products, fortified orange juice, salmon, sardines, fortified ready-to-eat cereals, almonds and soybeans. Weight-bearing exercises, like walking or jogging, also increase bone density. Yoga and Pilates improve flexibility and help prevent falls. All these improve your general health as well, so there's no downside to giving them a try.