Calcium supplements, which are often prescribed to post-menopausal women to help strengthen their bones, may boost the risk of heart problems and stroke, a news study found.

University of Auckland researchers in New Zealand analyzed data from a study on bone density in which nearly 1,500 healthy women aged over 55 were enrolled.

The women were randomly divided in two groups, the first group being given daily calcium supplements. The second group was given placebo. The participants’ health was monitored every six months over five years.

Researchers discovered that 60 women who were give calcium had 76 so-called cardiovascular events, which means either they suffered heart attacks, strokes or they died. In the placebo group, 50 of the women had 54 such events.

“Loading with high doses of calcium reduces bone loss but at a cost in heart health that is not justified,” said researcher Ian Reid, MD, professor of medicine and endocrinology at the University of Auckland.

Some members of the medical field welcomed the results of the study with criticism, showing their doubt or calling the results “implausible,” as Robert P. Heaney, MD, John A. Creighton University professor at Creighton University in Omaha, Neb., and a long-time researcher of calcium’s effect on health, said.

“Extra calcium doesn't build up in your arteries. The body regulates the blood concentration of calcium. Postmenopausal women should be getting 1,500 milligrams [a day] through diet and supplements. Even if it turns out this [proposed link between calcium supplements and heart attacks] is true and replicated [with further research] you have to weigh that against fracture protection," Heaney says of calcium supplements.

Reid disagreed, suggesting women over the age of 70 and some others should rethink calcium supplements calling it a “primarily” problem for elderly women because they are more predisposed to coronary heart disease than younger subjects are.

“Therefore it seems wise to advise against [high amounts of] calcium supplementation in those over the age of 70 years and in those known to have coronary heart disease. Aiming at a total calcium intake of approximately 1 gram [1,000 milligrams] a day [equivalent to four servings of dairy products] seems sensible in these subjects,” Reid said.

However, rigorous research is needed before any firm conclusions are drawn, as Judy O’Sullivan, a cardiac nurse at the British Heart Foundation said. O’Sullivan also suggested that women who were prescribed calcium supplements to protect their bones should not stop doing so just because of the results of this study alone.

The results of the study were published in the Wednesday issue of the British Medical Journal.