Sydney: There is growing evidence that calcium supplements increase the risk of heart attacks among older women, say researchers.
Calcium supplements are often prescribed to older (postmenopausal) women to maintain bone health. High blood calcium levels are linked to calcification (hardening) of the arteries, which may also help to explain these results.
Though the Women`s Health Initiative (WHI) study, a seven-year trial of over 36,000 women, found no cardiovascular effect of taking combined calcium and vitamin D supplements, but a team led by Prof Ian Reid at the University of Auckland, re-analysed the WHI results to evaluate the effects of calcium supplements, with or without vitamin D, on the risk of cardiovascular events, the British Medical Journal reports, citing an Auckland varsity statement.
Reid`s team analysed data from 16,718 women who were not taking personal calcium supplements at the start of the trial and found that those allocated to combined calcium and vitamin D supplements were at an increased risk of cardiovascular events, especially heart attack.
Conversely, in women who were taking personal calcium supplements at the start of the trial, combined calcium and vitamin D supplements did not alter their usual cardiovascular risk.
The authors suspect that the abrupt change in blood calcium levels after taking a supplement causes the adverse effect, rather than it being related to the total amount of calcium consumed.
Further analyses -- adding data from 13 other trials, involving 29,000 people altogether -- also found consistent increases in the risk of heart attack and stroke associated with taking calcium supplements, with or without vitamin D.
These analyses led the study authors to conclude that these data justify a reassessment of the use of calcium supplements in older people.