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Calcium supplements up heart risk
[Posted: Wed 20/04/2011 by Deborah Condon www.irishhealth.com]
The use of calcium supplements in the management of osteoporosis should be reassessed because of their link to heart health problems, scientists have suggested.
According to the researchers, their findings add to the mounting evidence that calcium supplements increase the risk of cardiovascular events, particularly heart attacks, in older women.
Calcium supplements are often prescribed to older post-menopausal women to maintain bone health. Sometimes they are combined with vitamin D, but it remains unclear whether taking calcium supplements, with or without vitamin D, can affect the heart.
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 the majority of participants were already taking personal calcium supplements, which may have obscured any adverse effects.
As a result, the researchers decided to re-analyse the WHI results in order to provide the best current estimate of the effects of calcium supplements, with or without vitamin D, on the risk of cardiovascular events.
They 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.
However, in women who were already taking personal calcium supplements at the start of the trial, combined calcium and vitamin D supplements did not alter their cardiovascular risk.
The team from the University of Auckland in New Zealand 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. High blood calcium levels are linked to calcification (hardening) of the arteries, which may also help to explain these results, they said.
Meanwhile, further analyses, which added data from 13 other trials involving 29,000 people, also found consistent increases in the risk of heart attack and stroke associated with taking calcium supplements, with or without vitamin D.
According to the researchers, these findings justify a reassessment of the use of calcium supplements in older people.
Details of these findings are published in the British Medical Journal. However, in an accompanying editorial, doctors argue that there is insufficient evidence available to support or refute the association.
"Clearly further studies are needed and the debate remains ongoing," they said.
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