The increased risk for a heart attack was a modest one, the researchers noted.
Though a 30 percent increased risk is, in absolute terms, small, it still could reveal a large problem because so many people take calcium supplements, Reid said.
Earlier studies did not find a similar risk when people get calcium through eating foods rich in the mineral, which suggests that supplements may be an independent risk factor.
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 said.
In addition, Reid said, people should have a bone density test to assess their risk for osteoporosis. "If their risk is high, they should consider using medications rather than calcium supplements," he said.
He and other 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.
Dr. John Cleland, from the Department of Cardiology at Castle Hill Hospital and Hull York Medical School at the University of Hull in Kingston upon Hull in the United Kingdom, who wrote an accompanying journal editorial, said that "calcium supplements probably don't reduce fractures and certainly don't reduce mortality and can now be considered ineffective."
"It is not c
All rights reserved