Compliance Important with Calcium Supplements
Posted April 27, 2006
CHICAGO - Two months after a huge clinical trial concluded that calcium supplements don't do much to protect older women from bone fractures, a new study has found just the opposite. Or so it would appear.
The paper released Monday in the Archives of Internal Medicine said older women who consistently took calcium for five years had significantly fewer broken bones than those who did not. But in February, the Women's Health Initiative - a mammoth government-sponsored study - reported that calcium supplements had little effect.
What's a person to do?
Keep taking your calcium, doctors say, either as part of your diet or in supplement form.
That's what Ethel Liten does. Liten, 84, of Evanston, Ill., has been taking calcium chews "for at least 30 years," she said. "It's like chicken soup: It may not help, but it wouldn't hurt."
The U.S. government currently recommends that women over 50 get 1,200 mg of calcium a day, along with at least 400 IU (international units) of vitamin D. Perhaps surprisingly, the data compiled by the two most recent bits of research both support that recommendation.
The answer to the puzzle lies in how you look at the data. In both studies, no clear benefit was found for women who were assigned to take calcium. But that is probably because many who were supposed to be taking the pills didn't actually do so.
When researchers looked only at those women who took their pills regularly, both studies showed a clear benefit on bone fractures.
So, why were consumers jerked around by the confusing results? That's just how science works, experts say.
Researchers who took part in the Women's Health Initiative, or WHI, say they had a duty to report the answer to the main question they had posed: Did calcium and vitamin D supplements protect older women from hip fractures, in the real world?
"As an investigator and a scientist, you're obligated to report results the way the study was designed," said research nutritionist Linda Van Horn of Northwestern Memorial Hospital, one of the WHI investigators. "Then people have the liberty to provide additional interpretation."
The WHI study involved signing up more than 36,000 women ages 50-79 and randomly assigning half of them to take a calcium supplement (1,000 mg plus 400 IU of vitamin D) and half to take an identical-looking dummy pill, or placebo. After an average of seven years, the group taking the real thing had fewer broken hips, but the difference was not statistically significant.
That finding led to the negative headlines and sound bites.
But buried deeper in the paper was another finding: Women who took the pills consistently had a 29 percent lower risk of breaking their hip than those taking a placebo, a statistically significant difference. In absolute terms there were 10 hip fractures per 10,000 women per year in the calcium group, compared to 14 in the placebo group.
The study also found that, in the calcium group, women over 60 - who are more likely to suffer osteoporotic fractures in the first place - had a 21 percent reduced risk, whether or not they took the pills every day.
Other factors, too, may have affected the overall findings. A majority of women in the WHI - including those in the placebo group - were taking calcium supplements on the side, because researchers felt it would have been unethical to tell participants they could not take something they believed was good for their health.
In addition, many of the women in the WHI were overweight, on hormone replacement therapy or taking medications to prevent bone loss - all of which reduce the risk of hip fractures. (The fewer fractures occur during a trial, the harder it is to show significant differences between groups.)
Another possible factor was that the supplement contained only 400 IU of vitamin D. That was what the government recommended when the WHI study began in the 1990s. But Dr. Andrew Davis, a preventive medicine specialist at the University of Chicago Hospitals, advises his patients to get at least 800 IU a day.
Vitamin D is necessary for absorption of calcium, and it seems to improve muscle strength and balance (which can help prevent falls). Davis said recent evidence indicates it may also reduce the risk of cancer.
In the study reported Monday, Australian researchers recruited 1,460 women over 70. Half took 600 mg of calcium twice a day and half took a placebo. (All the women had sufficient vitamin D, blood tests showed.)
After five years, there was no difference in the number of osteoporotic fractures in the two groups as a whole. But among those who took at least 80 percent of the pills they were given (either active or placebo), the ones on calcium had 44 percent fewer fractures.
The researchers concluded: "Supplementation with calcium ... is ineffective as a public health intervention in preventing clinical fractures in the ambulatory elderly population owing to poor long-term compliance, but it is effective in those patients who are compliant."
Liten's neighbor in Evanston, Anne Chalecki, says she takes 1,200 mg a day of calcium in supplement form and is also careful to eat calcium-rich foods such as broccoli, yogurt and occasionally tofu - "though that's not one of my favorite things."
Chalecki, 70 and a retired school secretary, said she didn't know about the importance of calcium until 10 or 12 years ago and now suffers from osteoporosis, or brittle bones.
"I wish I had started a lot earlier," she said.
Date: April 25, 2006
© 2006, Chicago Tribune. Distributed by Knight Ridder/Tribune News Service.