Taking a calcium supplement to help stop bones from thinning puts people at a greater heart attack risk, a report in the journal Heart said Wednesday.
The study of about 24,000 people ages 35 to 64 found those who regularly took calcium supplements were 86% more likely to have a heart attack than those who didn't. Those who took only calcium supplements were twice as likely to have a heart attack as those who didn't take any vitamin supplements. Calcium supplements have been linked to kidney stones and bloating in other studies, according to the National Institutes of Health (NIH).
"Calcium supplements have been widely embraced by doctors and the public, on the grounds that they are a natural and therefore safe way of preventing osteoporatic fractures," the authors write. "We should return to seeing calcium as an important component of a balanced diet."
The study, aimed at seeing if calcium supplements affect cardiovascular risk, found no direct link between the supplements and heart attacks, nor did they identify brands of supplements. Participants answered questions about supplement use and diet in an 11-year health study.
The study did not look at what caused the heart attacks, but "supplements cause calcium levels to soar above the normal range, and it is this flooding effect which might ultimately be harmful," the authors write.
"Doctors who work with the elderly and people who are postmenopausal routinely tell them to take a calcium supplement," says Linda Russell, a rheumatologist and osteoporosis specialist at Hospital for Special Surgery in New York. "It's really time to re-examine that philosophy. Other studies about calcium have been suggesting this in recent years, but maybe this study really should get doctors to rethink this approach."
Strategies for preventing bone thinning in postmenopausal women have recently come under review; the Food and Drug Administration warned in the New England Journal of Medicine May 9 about risks associated with some bisphosphonates and how long to take them. Some bisphosphonates, widely prescribed to treat osteoporosis and prevent fractures, have been linked to a rare atypical thigh bone fracture.
"It's very important for people to be vigilant, keep track of medications and talk with their doctors," says Elizabeth Shane, professor of medicine at Columbia University's Department of Medicine and spokeswoman for the American Society of Bones and Mineral Research. "The knowledge base is continually changing."
Russell says she re-evaluates a patient's need for bisphosphonates every year.
Shane advises patients to get their calcium naturally from their diet in small doses so it is absorbed throughout the day and to use a supplement only to make up a difference if they fall short of the daily requirement.
For a postmenopausal woman age 51 to 70, when osteoporosis becomes a greater danger, the recommended range is 1,000 to 1,200 mg. After age 71, it's 1,200 mg.
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