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Healthy Older Women Advised Against Taking Calcium
U.S government experts found no evidence that calcium, vitamin D supplements help prevent fractures
URL of this page: http://www.nlm.nih.gov/medlineplus/news/fullstory_134346.html
(*this news item will not be available after 05/26/2013)
Monday, February 25, 2013
In healthy adults, lower doses of calcium and vitamin D seem to be ineffective. As for higher doses, it's still up in the air, the government group said.
The new recommendations do not apply to people who are known to be vitamin D-deficient or who already have osteoporosis, the U.S. Preventive Services Task Force (USPSTF) noted.
Every year about 1.5 million fractures in the United States are attributed to osteoporosis, which is caused by a decrease in bone mass and density that makes bones fragile and more susceptible to a break. Almost half of all women older than 50 will have an osteoporosis-related fracture in their lifetime, according to the USPSTF.
Calcium is one of the main building blocks of bone growth, and vitamin D (sourced via sunlight's action on the skin, or through diet) helps bones absorb calcium. But at issue is whether people receive enough of these nutrients in their daily diet, or if supplements would help protect them.
Dr. Virginia Moyer, chair of the USPSTF, and a professor of pediatrics at Baylor College of Medicine, said experts know that a "medium dose" of supplements -- less than 400 international units (IU) of vitamin D and less than 1,000 milligrams (mg) of calcium -- does not work.
As for higher doses? "We simply don't know. There are reasons to think they could work, but unfortunately, even though there are a bunch of studies, there are problems with them," Moyer said.
"We know these recommendations will be very frustrating to both physicians and patients, but it's a call to action to the research community," she added.
The USPSTF analyzed a wide range of studies on the effects of supplementation of vitamin D and calcium levels for bone health and the adverse effects of supplementation. The report, published online Feb. 26 in the Annals of Internal Medicine, makes these points about preventing fractures:
- Don't take low doses of daily supplements: Less than 400 IU of vitamin D and less than 1,000 mg of calcium after menopause have no benefit.
- For higher doses: The task force doesn't have sufficient evidence to make a recommendation on daily supplements.
- For men and women younger than 50: The task force also doesn't have enough evidence to make a recommendation on vitamin D and calcium supplements.
Criticism about the USPSTF guidelines comes from a range of perspectives.
The Council for Responsible Nutrition, a trade association representing the dietary supplement industry, criticized the USPSTF for relying too heavily on data from the Women's Health Initiative (WHI), a study that showed little to no effect on fracture rates in the more than 35,000 postmenopausal women in the trial. They also said that the task force ignored a WHI study out this year that showed a notable reduction in fracture among women who adhered to prescribed doses of calcium and vitamin D.
Some experts prefer a report released by the Institute of Medicine (IOM), a nonprofit organization that gives expert, evidence-based advice on public health issues to policy makers and health professionals.
"That took a very in-depth and I would say a very broad look at the vitamin D and calcium question," said Dr. Sundeep Khosla, a past president of the American Society for Bone and Mineral Research and an endocrinologist and research scientist at the Mayo Clinic. The IOM recommended that most adults get 1,000 mg of calcium, and that women older than 50 and men older than 70 get 1,200 mg of calcium, according to Khosla.
Khosla said the IOM and the USPSTF were each "looking at different parts of the elephant." He said that the USPSTF was focused just on what it took to prevent fracture, ignoring the fact that among healthy people who haven't yet had a break, it would be difficult to detect whether supplements are effective.
"With the IOM taking the physiological perspective, their work might be considered more sensitive [more able to pick up potential benefits or risks]," he said
Marion Nestle, a professor of nutrition, food studies and public health at New York University, co-wrote a journal editorial suggesting that statements from the task force are unlikely to settle the ongoing debate about the use of vitamin D and calcium. "The task force looks at one or two nutrients and one condition at a time, but that's not how people eat or live," she said.
Yet Nestle said she thinks the guidelines suggest reasonable approaches to prevention. "Clinicians ought to be advising healthy diets, plenty of activity and at least 15 minutes a day of sun exposure," she said.
Dr. Margery Gass, executive director of the North American Menopause Society, helped create clinical guidelines on osteoporosis for the American College of Obstetricians and Gynecologists published last year. Gass said she thinks the sheer number of guidelines being disseminated from a variety of different groups is "likely to stir up a little confusion and frustration" among clinicians and the public. But she added that the core message of the USPSTF guidelines is actually simple. "The good thing is that healthy people who do eat a variety of foods may not need to feel compelled to take supplements," she said.
Some expressed concern that the guidelines from the USPSTF are often slow to be implemented because doctors typically practice medicine the way they were trained, and are unlikely to respond quickly to new recommendations.
"I think the response will be very similar to the reaction physicians had to the mammogram guidelines [in 2009]," said Dr. Christine Gerbstadt, a registered dietitian and a spokesperson for the Academy of Nutrition and Dietetics. "Most physicians are just sending their patients for annual mammograms despite the recommendations. Dietitians will get the word out, but where the lag is going to be is with physicians who will be a lot slower to stop [recommending] the calcium," she said.
Moyer, the task force chair, suggested that consumers review the guidelines and bring them along when they see their physician. "Just say, 'I've printed this out and let's talk about it.'" Depending on your particular situation, the best option may require a thorough discussion, she said.
Rather than being confused by the debate between constituencies and organizations about how to deal with preventing fractures, Moyer urged consumers to digest the key message: "Don't bother with inadequate supplemental doses and look for new research about how much vitamin D we really need."
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