Use of calcium supplements by healthy postmenopausal women may increase risk for myocardial infarction, according to an article published online January 15 by BMJ.

Researchers at the University of Auckland, New Zealand, investigated the effect of calcium supplementation on risk for vascular events--- myocardial infarction, ischemic stroke, and sudden death--- using data for 1,471 healthy postmenopausal women aged 55 years or over who had previously taken part in a study to assess the effects of calcium on bone density and fracture rates and been randomized to calcium or placebo. Dietary calcium intake was assessed and women were seen every six months over five years.

Adverse events were recorded at each visit. Myocardial infarctions were more commonly reported in the calcium group. The occurrence of any three vascular events (infarction, stroke or sudden death) was also more common in this group.

Because of the potential importance of these findings, the authors checked hospital admissions and reviewed all death certificates for study participants to identify any unreported events.

With the additional events, myocardial infarctions remained more common in the calcium group (36 events in 31 women versus 22 events in 21 women on placebo). Rates for myocardial infarction, stroke or sudden death were also increased in this group (76 events in 60 women versus 54 events in 50 women on placebo) although event rates were of borderline significance.

Although the findings are not conclusive, the authors believe they suggest that high calcium intakes might have an adverse effect on vascular health. If confirmed by other studies, this effect could outweigh any beneficial effects of calcium on bone.