Regularly taking calcium supplements might increase the risk of cardiovascular events, a study from New Zealand suggests.
In the meta-analysis, fifteen randomized controlled trials involving 12,000 people taking calcium supplements were analyzed (1). The researchers found calcium supplementation (500 milligrams or more per day without vitamin D) to be associated with a 20% to 30% increase in heart attack risk, but no increased risk was found for strokes or death from heart disease. Taking the results together with the modest overall efficacy in reducing fracture risk, the scientists suggest that a reassessment of the role of calcium supplements in the prevention and treatment of osteoporosis is warranted. They speculate that calcium supplements may rapidly elevate blood calcium levels, which are believed to lead to hardening of the arteries, which can cause heart attacks.
Experts say that the analysis is interesting but not convincing. You would expect to see an increase in mortality in supplement users along with heart attacks, but the fact that this was not seen makes it hard to understand how calcium could increase the risk for heart attack and not for stroke or death if this association is real, they commented. The findings should encourage more research, but it would be not appropriate at this stage to change public health advice on the use of calcium supplements to maintain bone health.