Calcium supplements increase risk of heart attack

Study:  They raise blood calcium  level and leads to plaque in blood vessels

Calcium supplements, which many people consume hoping to ward off osteoporosis, increase the risk of heart attack by as much as 30 per cent, researchers reported.

These tiny tablets, which carry concentrated doses of calcium, were also associated with a higher incidence of stroke and death, but this was not statistically significant.

The researchers advised people consuming calcium supplements to seek advice from their doctors, take more calcium-rich food and try other methods, like exercise, not smoking and keeping a healthy weight, to prevent osteoporosis.

Said Professor Ian Reid of the Faculty of Medical and Health Sciences at the University of Auckland: “People regard calcium supplements as natural, but they are really not natural at all.”

Prof Reid and his colleagues in Britain, New Zealand and the United States had conducted a meta-analysis encompassing 11 studies which tracked nearly 12,000 elderly people over four years.

Half of them were given calcium supplements, and the other half, placebos, or dummy pills with no therapeutic content. The results were published in the British Medical Journal.

“What we found was a 30 per cent increase in heart attacks in the people who were randomised to take calcium,” Prof Reid said.

“If you have 1,000 people taking calcium for five years, we would expect to find 14 more heart attacks, 10 more strokes and 13 more deaths in the people given calcium than…if they hadn’t been treated with calcium.

“That is 37 more adverse events, and we expect 26 fractures being prevented. So calcium is associated with bad things prevented,” he added.

The link was consistent across trials and was independent of age, sex, and type of supplement.

While experts are not certain about the biological mechanism by which calcium supplements may damage the body, studies in the past have linked high levels of blood calcium to more heart attacks and damage to blood vessels, Prof Reid said.

“When you take calcium supplements, your blood calcium level goes up over the following four to six hours and goes up to the top end of the normal range.

“That doesn’t happen when you eat calcium in your diet because the calcium from food is very slowly absorbed and so the blood calcium level hardly changes at all,” the professor said.

Higher blood calcium may lead to the formation of plaque, or fatty deposits, in blood vessels, which can lead to heart attack, stroke and other cardiovascular disease, Prof Reid explained.

“People have always focused on fat levels in the blood as driving that process (plaque formation), but there is increasing evidence now that calcium levels in the blood might drive that as well,” he added.

In a commentary, Professor John Cleland of the University of Hull in Britain and his colleagues pointed out that – regardless of their possible impact on heart attack rates – calcium supplements are not very efficient in reducing fractures, in any case.

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Category: Features, Health alert