Johns Hopkins professor Michele Bellantoni, M.D discusses the importance of taking calcium supplements despite the disappointing results of the Women’s Health Initiative trial.
The Johns Hopkins Medical Letter: Health After 50 has long recommended calcium supplements with vitamin D to help prevent bone loss. Recently, the Women’s Health Initiative (WHI), a group of large clinical trials sponsored by the National Institutes of Health, found little to support this recommendation—or did it? While the media was quick to report that calcium supplements don’t work, experts at Johns Hopkins caution women to talk to their doctors before they throw out their pills.
Michele Bellantoni, M.D., Associate Professor of Medicine and Medical Director of Long-term Care at Johns Hopkins Bayview Care Center, says, “When a study like this comes out, people need to ask themselves how much they are like the people in the study and how much the study pertains to them.” The WHI applies to women in general, but each woman’s individual health concerns should be her guide in whether to stop taking calcium supplements. Many women will find it’s a good idea to keep taking them.
The calcium and vitamin D trial was one of three studies that make up the WHI. It followed 36,282 postmenopausal women, aged 50 to 79, for an average of seven years. Women received 1,000 mg of calcium with 400 international units (IUs) of vitamin D daily or a placebo. At the end of the study, researchers were surprised to discover that women taking supplements had no fewer fractures than women given a placebo and only a 1% difference in hipbone mineral density.
Researchers also measured whether calcium supplements helped prevent colon cancer. They didn’t. However, colon cancer takes much longer to develop than the seven years that most women were followed. Recognizing this, researchers have asked the women to continue the study for five more years.
The negative findings on calcium supplements and bone health are more complicated. Dr. Bellantoni explains, “We’re asking an awful lot to expect this study to prove that calcium supplements prevent bone loss or reduce the risk of fracture. For starters, the women in the study didn’t have osteoporosis, nor were they known to be deficient in calcium or vitamin D.” In fact, women were allowed to continue any supplements they were taking before the study began, so it’s possible that they were already getting enough calcium. Approximately 38% of women taking calcium supplements and 39% of women in the placebo group ingested more than 1,200 mg of calcium a day. Furthermore, most women in the supplement group did not take their pills every day. According to Dr. Bellantoni, “The fact that researchers found any benefit is amazing.”
According to an analysis of a subgroup of women who took their supplements at least 80% of the time, calcium with vitamin D reduced the risk of hip fracture by 29%. A subgroup of women over 60 also had some benefit from supplements. However, experts caution against reading too much into the results of these subgroups because they were not selected randomly beforehand. Therefore, it is possible that members of the groups shared traits or habits that contributed to their lower risk of fracture—perhaps they exercised more, for example. Still, according to an editorial accompanying the study, “The possible benefits for the risk of fracture cannot be totally ignored.”
Dr. Bellantoni stresses, “The WHI suggests postmenopausal women who have a normal bone density scan probably won’t be helped by the addition of a calcium supplement. But if testing does reveal significant bone loss (some bone loss is normal after age 30) and women have a hard time getting enough calcium from their diet—and many women do—a supplement will probably help.” People over 50 need 1,200 to 1,500 mg of calcium and at least 400 IUs of vitamin D every day. Dr. Bellantoni recommends that people over 65 and anyone with osteoporosis get 800 IUs of vitamin D daily. Weight-bearing and resistance exercises are also essential, and women with osteoporosis should consider medication, such as a bisphosphonate, proven to prevent fracture. All these measures will help slow bone loss. Even if calcium only helps a little, a little can mean a lot.
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