A new study has shown that calcium supplementation might increase vascular events in elderly women. The findings are somewhat unexpected, because previous trials have shown that calcium improves blood cholesterol levels.
Dr Mark J Bolland (University of Auckland, New Zealand) and colleagues published the findings online in BMJ January 15, 2008.

"This is quite controversial, given that the worldwide calcium-supplement market is worth $3 billion a year," says Reid. "The trial was primarily looking at what calcium supplements do to bone density, but we had a secondary hypothesis right from the outset that calcium might actually prevent heart attack. What we found, to our surprise, was that we didn't see a decrease but an increase, and the findings appear to be quite robust." Reid added, however, that there have been some clues from three other recent studies, including one from Women's Health Initiative (WHI) in the US "these three did not find significant increases in the number of heart attacks [with calcium], but they have found upward trends."

Dr Erin D Michos (Johns Hopkins University, Baltimore, MD), who was not involved with this new study but cowrote an editorial accompanying the publication of the WHI study on vitamin-D/calcium supplements last year says "This is a thought-provoking study, although not definitive, but further work should be done."
Others warned that it is premature to make any treatment decisions on the basis of this new study. British Heart Foundation spokesperson Judy O'Sullivan said more rigorous research was needed before any firm conclusions could be drawn. "Anyone who has been advised by their doctor to take calcium supplements to protect their bones should not stop doing so in light of this study alone without medical advice," she said.

Reid says his team has a number of plans to look at this issue going forward. "We are going to try to access the radiographs from women in the study and see if we can quantify calcification in them." They also have another study that has just finished, this time in a few hundred men, in which they are looking at coronary artery calcium. "In the men's study, they are younger, and there is an adverse trend, but it's much smaller," he noted.
And he hopes to coordinate a meta-analysis of the UK, US, and Australian studies and his own "to see if we can use all the available evidence to determine whether there really is something solid here."

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