German researchers have found that people who take calcium supplements could be increasing their risk of having a heart attack.
Calcium is often taken by older people to strengthen bones and prevent fractures.
But the study, published in the journal Heart, said the supplements “should be taken with caution”.
Experts say promoting a balanced diet including calcium would be a better strategy.
The researchers at the German Cancer Research Centre, in Heidelberg, followed 23,980 people for more than a decade.
They compared the number of heart attacks in people who were taking calcium supplements with those who did not.
There were 851 heart attacks among the 15,959 people who did not take any supplements at all. However, people taking calcium supplements were 86% more likely to have had a heart attack during the study.
The researchers said that heart attacks “might be substantially increased by taking calcium supplements” and that they “should be taken with caution”.
Ian Reid and Mark Bolland, researchers at the University of Auckland in New Zealand, said: “The evidence is also becoming steadily stronger that it is not safe, nor is it particularly effective.
“Therefore, the administration of this micro nutrient should not be encouraged; rather people should be advised to obtain their calcium intake from an appropriately balanced diet.
“We should return to seeing calcium as an important component of a balanced diet and not as a low cost panacea to the universal problem of postmenopausal bone loss.”