A study looking at 15 randomized trials finds the use of calcium supplements without coadministered vitamin D is associated with an increased risk of heart attack.

Most guidelines for the prevention or treatment of osteoporosis recommend the use of calcium supplements, despite the fact that they reduce the risk of fracture only marginally, write Dr Mark J Bolland (University of Auckland, New Zealand) and colleagues.

Studies have yielded conflicting results about their use, with some observational studies suggesting that high calcium intake is protective against vascular disease, and others showing that calcium supplements speed vascular calcification and increase mortality in patients with kidney failure and increase cardiovascular events and MI in women.

Senior author Dr Ian R Reid (University of Auckland) told heartwire that women should discuss the finding from his study with their doctors, but that in most cases, "discontinuation of calcium would seem appropriate."

There are those that disagree with the studies findings.  In an editorial accompanying the article [3], Dr John Cleland (Castle Hill Hospital, Kingston upon Hull, UK) and colleagues wonder why calcium supplements should increase cardiovascular risk, as found in this meta-analysis. "Accumulation of calcium in the arterial wall leading to reduced compliance would be expected to take years, but the increased risk of myocardial infarction reported by Bolland and colleagues occurred early after calcium supplementation (median follow-up of 3.6 years)."

Until more becomes known about the best way to prevent osteoporotic fractures, the editorialists conclude that "patients with osteoporosis should generally not be treated with calcium supplements, either alone or with vitamin D, unless they are also receiving an effective treatment for osteoporosis for a recognized indication." They add that research on whether such supplements are needed in addition to effective osteoporosis treatment is "urgently required."

Researchers are starting to look at gender differences to see if this may be a factor.  Eighty percent of the studies participants were women.  More study is needed to determine if the current recommendations for calcium supplementation need to be revised.