Harvard Health Letter

By the way, doctor: Calcium supplements and heart attack risk

Q. I read in the newspapers about a study that said older women taking calcium supplements are at increased risk for experiencing a heart attack, stroke, or sudden death. Should I be concerned?

A. Good question, complicated answer. The study findings you are referring to also caught my eye. Researchers in New Zealand reported the results in the journal BMJ (the initials are now the official name of the British Medical Journal) in January 2008. Their study included 1,471 postmenopausal women, half assigned to take 1 gram of elemental calcium (as calcium citrate) daily; the other half, a placebo pill. The main goal was to see whether the calcium pills would influence bone loss and fracture risk over a five-year period. But once a study has created lots of data, researchers often sift through it, conducting "secondary analyses" to see if there might be other effects from the intervention.

This study was one of these secondary analyses. The conclusion was that the women assigned to take calcium supplements were more likely to have heart attacks, strokes, or sudden death compared with those who took a placebo. How much more likely? By one count, 47% more, although when information from a hospital database was added in, the figure dropped to 21%. Because randomized trials are the gold standard for assessing a treatment, these results got a lot of attention.

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