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Doubts About Calcium
There were, and that's why many doctors aren't telling patients to stop taking their calcium and vitamin D supplements. Not all study participants took the supplements as directed. Some began taking prescription medications to ward off bone thinning. And some women in the placebo group took supplements on their own, making it harder to discern differences between the intervention group and the placebo group.
Researchers have also raised questions as to whether the vitamin D dose was high enough or the study large enough to detect differences in fracture risk .
Why do doctors recommend women take calcium supplements as they approach menopause?
The idea is to protect bones against age-related thinning thought to make them more susceptible to fracture. Calcium is the "most abundant mineral in the human body," according to the federal Office of Dietary Supplements (ODS), and more than 99 percent of it is stored in the bones and the teeth.
"Bone undergoes continuous remodeling," the ODS explains, with constant bone breakdown and formation, which involves the depositing of calcium into the newly formed bone. With age, says the ODS, eventually "bone breakdown exceeds formation, resulting in bone loss, which increases the risk for osteoporosis," a condition that increases the risk of fractures.
Vitamin D, whether from food, sunlight or as a supplement, is recommended to promote the absorption of calcium.
This isn't the first study to cast doubt on the value of taking calcium supplements, is it?
Previous findings have been mixed, said Joan McGowan, a project officer for the WHI study and director of the musculoskeletal diseases branch at the National Institute of Arthritis and Musculoskeletal and Skin Diseases. A few recent studies have shown little bone benefit from calcium supplementation, experts said; getting some participants to take their supplements as directed was a problem, just as it was in the WHI study. But in another bone study involving frail older women, calcium supplementation appeared beneficial. Researchers say additional study is needed to provide more conclusive results.
How could calcium be shown to increase bone density but not decrease fracture risk? Aren't the two tied?
Not necessarily. "Low bone density is only one of the risk factors for fracture," McGowan said in an e-mail interview. Other factors include age, genetics and propensity to fall ,she said.
How reliable are bone density tests in assessing my risk of future fractures?
The Mayo Clinic calls the tests a "fairly accurate predictor of your risk of fractures" and a "valuable tool in the diagnosis of osteoporosis." Some studies have cast doubt on the tests' ability to predict fractures, but for now they are the best tool available.