Research carried out in New Zealand on healthy, postmenopausal women found that they were more likely to have an MI if they were taking regular calcium supplements.
Rates of stroke and sudden death were also found to be higher, said the newspapers.
Previous studies have claim-ed that calcium supplements can lower LDL cholesterol and protect against cardiovascular disease (CVD).
What is the research?
The newspaper reports stem from a randomised controlled trial to determine how adverse vascular events in healthy older women are affected by taking calcium supplements.
University of Auckland researchers carried out a secondary analysis of data looking at the effect of calcium supplements on bone density.
Women were included in the initial study if they were over 55 years of age, had been postmenopausal for more than five years and had a life expectancy greater than five years.
Anyone already receiving treatment for osteoporosis, taking calcium supplements or with major co-morbidities was excluded from the study.
The team prescribed 732 women 1g of calcium daily and gave placebo to 739 women. Participants were followed up every six months for five years.
Results showed that women taking calcium supplements were twice as likely to suffer an MI as those taking placebo.
Also, composite endpoint, including MI, stroke or sudden death, was 47 per cent more likely in the calcium group.
What do the researchers say?
Professor Ian Reid, lead researcher, said that the negative effects of calcium supplements on cardiovascular health 'clearly outweighed' the LDL-lowering properties of the calcium supplements.
The average age of women in the study was 74 and Professor Reid said: 'We cannot say that the effect will be the same in 50-year-old women.'
He advised GPs to carry on prescribing calcium supplements to women, providing they have 'clear coronary arteries and low CVD risk factors'.
What do other experts say?
West London GP Dr Sarah Jarvis, RCGP spokeswoman on women's health said: 'It is important to get the whole picture in order to weigh up the risks and benefits of prescribing supplements to a particular patient.'
- Calcium supplements have been shown to double the risk of MI in postmenopausal women.
- This cardiovascular risk may outweigh the LDL-lowering properties of calcium in at-risk women.
- Patients with a healthy cardiovascular profile can continue to take the supplements.