Randomised studies suggest that calcium supplements without coadministered vitamin D are associated with an increased incidence of myocardial infarction.
Dr Mark J Bolland and team carried out a meta-analysis of cardiovascular events in randomised trials of calcium supplements. (Posted: 08/31/2010; BMJ © 2010 BMJ Publishing Group). In the five trials where details of patient outcomes were available (over 8000 patients), 143 people allocated to calcium had a myocardial infarction compared with 111 allocated to placebo (hazard ratio 1.31, 95% confidence interval 1.02 to 1.67, P=0.035). Non-significant increases occurred in the incidence of stroke (1.20, 0.96 to 1.50, P=0.11), the composite end point of myocardial infarction, stroke, or sudden death (1.18, 1.00 to 1.39, P=0.057), and death (1.09, 0.96 to 1.23, P=0.18).
Although the magnitude of the increase in risk is modest, the widespread use of calcium supplements means that even a small increase in incidence of cardiovascular disease could translate into a large burden of disease in the population. The likely adverse effect of calcium supplements on cardiovascular events, taken together with the possible adverse effect on incidence of hip fracture, and its modest overall efficacy in reducing fracture (about 10% reduction in total fractures), suggest that a reassessment of the role of calcium supplements in the prevention and treatment of osteoporosis is warranted, and the vascular effects of calcium supplements, especially without Vitamin D, should be studied further.