A new study has backed claims that older women who take calcium supplements are increasing their risk of heart attack.
Post-menopausal women often take the supplements to maintain healthy bones, but researchers in New Zealand have said the method of managing osteoporosis should be reassessed.
The study was led by Professor Ian Reid at the University of Auckland and follows a seven-year Women's Health Initiative trial of more than 36,000 women, which found no negative cardiovascular effects of taking combined calcium and vitamin D supplements.
However, the majority of participants in that study were already taking personal calcium supplements, which may have obscured any adverse effects.
Prof Reid's study looked at data from 16,718 women who were not taking personal calcium supplements at the start of the trial.
It found that those allocated to combined calcium and vitamin D supplements were at an increased risk of cardiovascular events, especially heart attack.
But women who were taking personal calcium supplements at the start of the trial, combined calcium and vitamin D supplements did not alter their cardiovascular risk.
The authors said they suspect abrupt changes in blood calcium levels after taking a supplement causes the adverse effect, rather than it being related to the total amount of calcium consumed.