Calcium supplementation in healthy postmenopausal women is associated with upward trends in cardiovascular event rates, according to a study published online Jan. 15 in BMJ.

Mark J. Bolland, MBChB, and colleagues at the department of medicine at the University of Auckland in New Zealand conducted the randomized, placebo-controlled trial to determine the effect of calcium supplementation on myocardial infarction (MI), stroke and sudden death in healthy postmenopausal women.

They examined 1,471 postmenopausal women (mean age 74); among whom 732 were randomized to calcium supplementation and 739 to placebo.

The researchers found that MI was more commonly reported in the calcium group than in the placebo group (45 events in 31 women vs. 19 events in 14 women). The composite end point of MI, stroke or sudden death was also more common in the calcium group (101 events in 69 women vs. 54 events in 42 women), the authors wrote.

They found a number of women needed to treat for five years to cause one MI was 44, to cause one stroke was 56, and to cause one cardiovascular event was 29. By comparison, the number needed to treat to prevent one symptomatic fracture was 50.

The findings’ potentially detrimental effect should be balanced against the likely benefits of calcium on bone, according to the researchers.

“The present study does not unequivocally show an adverse cardiovascular effect of calcium but suggests that the matter needs to be considered carefully before calcium supplementation can be broadly advocated,” the authors concluded.