Calcium Supplements Increase Risk of Heart Attack

[Original author: Fran Lowry for Medscape, August 17, 2010]

A meta-analysis of 15 randomized trials with over 11 thousand participants suggest that taking calcium supplements without also taking vitamin D can increase the risk of myocardial infarction. The findings, prepared by Dr. Mark J. Bolland of University of Auckland, New Zealand and colleagues, imply that additional study should be performed to reconsider the role of calcium supplements in managing osteoporosis.

Interpretation of the studies showed conflicting results — some indicated that high calcium intake proved protective against vascular disease while others indicated detrimental results, including an increase in the speed of vascular calcification and mortality in patients with kidney failure, and an increase in myocardial infarction in women.

A Misdiagnosis?

Dr. John Cleland of Castle Hill Hospital, Kingston, UK and his colleagues contributed an editorial with the study presenting a discussion on why calcium supplementation may have been seen to increase cardiovascular risk. In it, they argued that the negative effects of calcium build-up on arterial walls, should they occur, would be expected to take much longer to show up than that observed in the meta-analysis. The team suggested that the increase in myocardial infarction might simply be a misdiagnosis of gastrointestinal symptoms caused by the calcium (i.e., it was heartburn, not MI).

Recommendation

The consensus recommendation of the editorial team was that women should discuss the study findings with their physicians and, in most cases, consider discontinuing calcium supplementation unless specific medical conditions make them appropriate. They suggest that those with osteoporosis generally not be given calcium supplements, either alone or with vitamin D, unless they are also receiving effective therapy for osteoporosis for a recognized indication.

They concluded by underscoring the important need for additional research on whether such supplements are needed at all as an addition to effective osteoporosis therapy.

References

Bolland MJ, Avenell A, Baron JA, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ 2010; DOI:10.1136/bmj.c3691.

Bolland MJ, Barber PA, Doughty RN, et al. Vascular events in healthy older women receiving calcium supplementation: Randomized controlled trial. BMJ 2008; 336:262-266.

Cleland JG, Witte K, Steel S. Calcium supplements in people with osteoporosis. BMJ 2010; 341; DOI:10.1136/bmj.c3856.