Researchers at the University of Auckland (New Zealand) conducted a patient level and trial level meta-analyses of randomized, placebo controlled trials of calcium supplements, to investigate whether calcium supplements increase the risk of cardiovascular events. Medline, Embase, the Cochrane central register of controlled trials, reference lists of meta-analyses of calcium supplements, and two clinical trial registries were included. Initial searches were carried out in November 2007, with electronic database searches repeated in March 2010. The eligible studies included 100 or more participants of mean age more than 40 years, with a study duration of more than one year. Cardiovascular outcomes were obtained from self-reports, hospital admissions, and death certificates.

The researchers found 15 trials that were eligible for inclusion, five with patient level data and 11 with trial level data; in the five studies contributing patient level data, 143 people allocated to calcium had a myocardial infarction (MI), compared with 111 allocated to placebo. Nonsignificant increases occurred in the incidence of stroke, the composite end point of MI, stroke or sudden death, and death. The meta-analysis of trial level data showed similar results: 296 people had a MI (166 allocated to calcium, 130 to placebo), with an increased incidence of MI in those allocated to calcium. According to the researchers, the results demonstrate a 30% increased risk for cardiovascular events in those taking calcium supplements. The study was published in the July 29, 2010, issue of BMJ.

"We advise our patients to move away from calcium supplements and move toward eating calcium-rich food as part of a normal balanced diet and to remain physically active,” said lead author Ian Reid, M.D., of the department of medicine. "People should have a bone density test to assess their risk for osteoporosis. If their risk is high, they should consider using medications rather than calcium supplements.”

"When you look at major trials where people have been randomly assigned to take calcium or placebo, there is an increase in the risk of heart attack in the people who were randomly assigned to take calcium,” added Dr. Reid. "The extent of that increased risk is enough to completely counterbalance the small beneficial effect that calcium tablets have on numbers of fractures.”

Related Links:
University of Auckland