Do calcium supplements really cause heart attack: Controversy

Posted: Sunday, August 8, 2010 | Posted by Debajyoti Datta | Labels:

In a recent study published in the British Medical Journal, researchers found a 30% increase in myocardial infarction (heart attack) with the intake of calcium supplements. Already several other researchers have questioned the validity of the conclusions of the study.

Let us see what the questions raised are.
Firstly, the study included 15 trials, that are 15 different studies, but the caveat is that patient level data was available for only 5 studies. What this means is that direct data was available for only 5 studies, in case of the other 10 studies no direct data was available. But the researchers have based their findings on these other 10 studies also.

The second question that has been raised and which is significant is that there is no linear correlation between the dose of calcium and the incidence of heart attack. This means that increased doses of calcium does not increase the risk of heart attack. Now if calcium really does cause heart attack, the findings should have been opposite, with increased doses of calcium there would have been increased risk of heart attack. This finding seriously contradicts the conclusion that calcium causes heart attack.

Thirdly, out of the 15 trials included cardiovascular outcomes were either incomplete or absent in 7 trials. This means that the data regarding heart attack was either incomplete or absent in 7 of the included studies. Now this is a serious methodological flaw.

Fourthly, the researchers have not mentioned whether there was adequate control for other confounders like smoking or hypertension (increased blood pressure). This is important because smoking or hypertension may them-selves cause heart attack, hence they are called confounders. To explain simply, let us suppose that a smoker is taking calcium supplements and has a heart attack. Now we cannot say that the heart attack was due to calcium supplements because smoking also causes heart attack. Thus the validity of the study can be questioned, as it did not address these issues.

The findings of the study are open to question. We should not adopt a knee-jerk reaction as calcium supplement is a cheap measure to prevent osteoporosis and most Indians are deficient in calcium. The findings need to be validated by further research. In the meanwhile, there is no cause for concern.

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1 comments:

  1. Jack said...
  2. Chances are the calcium supplement you are taking now is a rock source of calcium. The label will say "calcium carbonate", which is nothing more than limestone. AlgaeCal Plus contains an organic, plant-sourced calcium form derived from a unique South American marine algae called Algas Calcareas™.

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