October 18/Canberra Times -- A recent study in the British Medical Journal saw researchers pool the results of 15 medical trials in which a total of about 12,000 people were given calcium-supplement pills.

They found that the people taking the calcium had a 30% increase in the risk of heart attack compared to those who did not. There was also an insignificant increase in the risk of stroke and death.

The risk of heart attack was greater among those with the highest intake of calcium pills (more than 800mg a day); it was not dependent on the age or sex of the participants, or the type of calcium supplement.

Further, a randomized, controlled trial published in 2008 looked at the effects of calcium supplements on vascular disease.

In this study, 1471 postmenopausal women were randomised to receive a supplement (1000mg per day of elemental calcium in divided doses) versus a placebo for five years.

At the end of the study, the women taking calcium pills had a greater risk of heart attack, stroke and sudden death compared with those taking the placebo; the risk of having a heart attack was about 50% higher, the risk of stroke almost 40% higher.

Why might calcium increase the risk of vascular disease?

Observational studies in the past have suggested that people with higher intakes of calcium actually had a lower risk of vascular disease; this is medically plausible because calcium does seem to slightly increase the amount of good cholesterol (HDL) in the blood and lower the bad cholesterol (LDL).

However, calcium can also cause mischief in the arteries.

When arteries are inflamed from poor diet, obesity, smoking and couch-potato lifestyles, calcium is pulled into that inflamed area from the bloodstream. It then gets laid down in the blood vessels, leading to atherosclerosis or hardening of the arteries. Hence, a higher calcium score on a CT scan implies more disease in the arteries that feed the heart.

So is all calcium problematic?

The studies above involved people who took calcium pills. What about foods that are high in calcium? Do they increase the risk of heart disease, too? Probably not.

When someone takes a calcium pill, this leads to an acute increase in blood-calcium levels, and this rapid increase likely delivers more calcium to the arteries, where it can cause damage.

Calcium in food, on the other hand, is absorbed much more slowly and does not lead to a significant change in blood levels; hence it does not seem to cause the problems that pills do.

From the November 1, 2010, Prepared Foods E-dition