Calcium Supplements May Increase Heart Attack Risk in Older Women

A new study suggests that calcium supplementation in postmenopausal women results in a significantly increased rate of adjudicated vascular events.

Researchers at the University of Auckland (New Zealand) conducted a secondary analysis of an existing randomized placebo controlled trial involving 1,471 postmenopausal women over 55 (average age 74), randomly assigned to receive a calcium supplement or a placebo. The women were asked questions about calcium in their diet, and they were assessed every six months for five years. The researchers calculated that including the daily supplement, women in the calcium group were getting on average about 1,861 mg of calcium a day, while those in the placebo group--who got their daily calcium only from their diet--averaged about 853 mg a day. Main outcome measures noted in the new study were the following cardiovascular-related events: death, sudden death, angina, myocardial infarction (MI), chest pains, stroke, and transient ischemic attack (TIA).

The results showed that reports of MI were significantly higher in the calcium group than in the placebo group (45 events in 31 women versus 19 events in 14 women). The occurrence of any three vascular events, MI, stroke, or sudden death was also significantly more common in the calcium group (101 events in 69 women versus 54 events in 42 women). The researchers went back and checked hospital records and death certificates to look for any unreported events; after adjusting the figures for the newly found and previously unreported events, they discovered that MI was still more common in the calcium group (36 events in 31 women versus 22 events in 21 women on placebo).
The study was published in the January 15, 2007, issue of the British Medical Journal (BMJ).

"Calcium supplementation in healthy postmenopausal women is associated with upward trends in cardiovascular event rates,” concluded Mark J Bolland, M.D., and colleagues of the faculty of medical and health sciences. "This potentially detrimental effect should be balanced against the likely benefits of calcium on bone, and is particularly important in the case of elderly women.”


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