Calcium Supplements Linked to Boost in Heart Attack Risk

Although millions of people take calcium supplements to boost bone health and ward off osteoporosis, New Zealand researchers say the supplements have little effect on bone strength and contribute to a small increase in the risk for heart attack among older people. The report is published online in BMJ.

Rather than relying on calcium supplements, the researchers suggest that people get their required calcium, if possible, from foods.

"When you look at major trials where people have been randomly assigned to take calcium or placebo, there is an increase in the risk of heart attack in the people who were randomly assigned to take calcium," says the study's lead researcher, Ian Reid, MD, from the department of medicine in the Faculty of Medical and Health Sciences at the University of Auckland.

Reid was careful to note that people need calcium in their diet. "What we are saying is that calcium supplements don't appear to be a good thing, based on the current evidence," he explains.

For the study, Reid's team did a meta-analysis of 11 randomized, controlled trials involving 11,921 people. In other words, the researchers reviewed already published studies and teased out data on any connection between calcium supplements and heart attacks.

Their analysis found nearly a 30% increased likelihood of having a heart attack among people older than 40 who were taking calcium supplements. In addition, there was a small but statistically insignificant increase in the risk for stroke and death among those taking supplements.

The findings remained consistent even after taking into account age, sex, and the type of supplement, the researchers say.

The increased risk for a heart attack was a modest one, the researchers note.

Though a 30% increased risk is, in absolute terms, small, it still could reveal a large problem because so many people take calcium supplements, Reid says.

Moreover, noting that calcium supplements appeared to have only a minor effect on bone health and perhaps no effect in preventing fractures, the researchers suggested that their use in preventing or treating osteoporosis (thinning of the bones) should be reconsidered.

Reid speculated that calcium supplements can increase blood levels of calcium above the normal level, causing changes in blood chemistry, which could be dangerous in people at risk for heart attacks.

"We advise our patients to move away from calcium supplements and move toward eating calcium-rich food as part of a normal balanced diet and to remain physically active," he says.

The researchers noted that the study had certain limitations, including excluding studies in which participants took both vitamin D and calcium supplements, and added that some of the trials they reviewed did not collect data on heart problems in a standardized manner.

Source: Brigham and Women's Hospital