Calcium supplements may double heart attack risk: Study

However, experts said it was "irresponsible" to advise people with osteoporosis not to take supplements "on the basis of one flawed study".

Millions of people worldwide have been prescribed to take calcium pills daily as a safe way to help fight osteoporosis.

But researchers from the University of Zurich and German Cancer Research Centre in Heidelberg claimed their study adds to mounting evidence that the supplements are "not safe or particularly effective".

For their study, the researchers followed 23,980 people for 11 years and found that those taking calcium pills roughly doubled the risk of having a heart attack.

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 per cent more likely to have had a heart attack during the study.

Detailing their findings in the journal Heart, the team said heart attack risk "might be substantially increased by taking calcium supplements".

The pills "should be taken with caution", they concluded, as they raise the annual risk of a heart attack from about one in 700 people to one in 350, the Daily Telegraph reported.

Instead, people should eat more calcium-rich foods like milk, cheese and green, leafy vegetables, they suggested.

The new findings are at odds with Department of Health in UK which says "taking 1,500mg or less of calcium supplements is unlikely to cause any harm". It only warns: "Taking high doses of calcium could lead to stomach pain and diarrhoea."

Dr Carrie Ruxton of the Health Supplements Information Service also said: "Osteoporosis is a real issue for women and it's irresponsible for scientists to advise that women cut out calcium supplements on the basis of one flawed survey, particularly when the link between calcium, vitamin D and bone health is endorsed by the European Food Safety Authority."

She claimed that the study lacked information on calcium doses and its results could have been skewed by differences between participants underlying health. (More)