THURSDAY, July 29 (HealthDay News) -- 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.

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," said the study's lead researcher, Dr. Ian Reid, from the Department of Medicine in the Faculty of Medical and Health Sciences at the University of Auckland.

"The extent of that increased risk is enough to completely counterbalance the small beneficial effect that calcium tablets have on numbers of fractures," he said.

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 explained.

The report is published online July 30 in BMJ.

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 percent 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, gender and the type of supplement, the researchers said.