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POPSCalcium: Heart Risk for Older Women? The risk of a heart attack was about 1.5 times greater for those in the supplement group, but the link did not reach statistical significance. Considered together, strokes, heart attack, or sudden death were more common in those on supplements than on placebo, but the differences -- when taken as a whole -- were statistically only of borderline significance But he speculates that the calcium supplements may elevate blood calcium levels and possibly speed calcification in blood vessels, which is known to predict the rates of vascular problems such as heart attack. Proceed with caution....