Findings from a new study examining calcium and bone health are strikingly similar to those published in mid-February from the larger investigation funded by the U.S. National Institutes of Health, known as the Women's Health Initiative (WHI).
In both studies, compliance seemed to be critical.
Calcium supplementation did not seem to reduce the risk of hip fractures among women who took their pills less often than they had agreed to. Supplementation did appear to be modestly protective in women who were scrupulous about taking their calcium as directed.
National OsteoporosisOsteoporosis Foundation president Ethel Siris, MD, tells WebMD that the research as a whole suggests that women who don't get enough calcium in their diets benefit from taking the nutrient in pill form.
She says most women need between 1,200 and 1,500 milligrams of calcium a day. Each serving of dairy, such as an 8-ounce glass of milk or a 6-ounce container of yogurt, contains about 300 milligrams of calcium.
"If you are getting enough calcium, taking more isn't going to make any difference," she says. "If you aren't getting enough, studies suggest that taking supplements can help."
The new study involved 1,460 Australian women over the age of 70 who were followed for five years. Half the women were randomly assigned to take 600 milligrams of calcium carbonate twice a day; the other half took identical placebo tablets.
The WHI study included a younger population of 36,282 women between the ages of 50 and 79 who were followed for seven years. Half of the women were assigned to take 1,000 milligrams of calcium and 400 international units of vitamin D daily, while the other half unknowingly took placebo pills.
In both studies, women were considered noncompliant with treatment if they took less than 80% of the recommended medication.
Richard L. Prince, MD, of the University of Western Australia, and colleagues reported the findings from the smaller study in the April 24 issue of the Archives of Internal Medicine.
During the five-year study, 236 participants (16%) had fractures. Overall, the fracture rate was the same for women in the active calcium arm of the study as in the placebo arm. A protective benefit was seen among women who were compliant with treatment. Among these women, the fracture rate was 10% among the calcium users and 15% among placebo users.
But close to half of the women in the study (43%) were considered noncompliant.
"The calcium supplementation regimen tested currently cannot be recommended as a public health approach to fracture prevention because of the lack of long-term compliance," Prince and colleagues wrote. "However, these data supported the continued use of calcium supplements by women who are able to remain compliant with their use."
Diet and Exercise
Jacques Rossouw, MD, who is project director for the WHI trial, says it is clear that women -- especially older women -- benefit from getting adequate calcium. But he recommends making every effort to get the calcium from food sources, rather than supplements.
The WHI study found that taking calcium in pill form was associated with an increased risk of kidney stoneskidney stones. This association was not seen in the Australian study.
Rossouw and Siris agree that taking vitamin D in pill form is probably a good idea because it is almost impossible to get enough of the nutrient in foods. Vitamin D helps the body absorb calcium.
While younger women may get what they need from 15 to 20 minutes of direct sun exposure two or three times a week, Siris says older women may not be able to produce enough vitamin D through safe sun exposure.
Vitamin D Recommendations
She recommends 800 to 1,000 international units of vitamin D a day but warns that most multivitamins don't contain the optimal form of the vitamin.
"Vitamin D is cheap, but it is hard to find," she says. "We are learning more and more about the importance of this vitamin, but you still might have to search for it."
The experts also agree that getting regular exercise is one of the most important things women can do to protect their bones. Weight-bearing exercise is especially important, but not for the reason most women think, Siris says.
"People believe that weight-bearing exercise builds bone, but this isn't true in a 75-year-old, or in a 50-year-old for that matter," she says. "What it does do is make people stronger and improve their balance and coordination so that they fall down less often. Falls are common among elderly people, and this is how fractures occur. So anything that reduces falls can reduce fractures."