Calcium supplements and heart attack risk

by Dr Norman Swan

New Zealand research has found that older women taking calcium to protect their bones had a higher risk of heart attack.

ust as women are starting to recover from all the bad publicity over drugs for osteoporosis, New Zealand research has questioned calcium supplements, reporting that older women taking calcium to protect their bones had a significantly higher risk of having a heart attack.

It was a randomised trial of calcium supplements versus placebo in 1400 older women – average age 74 – to prevent bone loss and fractures.

While the calcium benefited the bones, the heart attack rate was up to 40 per cent higher, which meant that over five years up to 16 additional women had a heart attack, stroke or sudden death associated with taking calcium. Stroke risk on its own wasn't significantly raised.

The researchers think the finding is real because other studies have gone in the same direction, but it does need to be verified. No-one is sure about calcium supplements in younger women.

So what should women do?

The advice from the New Zealanders is that calcium in whole food is good because it is associated with lower rates of heart disease – you don't get the big hit of a tablet surging into your bloodstream.

They also think the dose in their study – a gram a day – was too high, and lower doses are safer.