Does Calcium Cause Heart Attacks?
Maybe you saw the headlines in May saying that calcium supplements double the risk of heart attacks. The headlines were based on a fairly large study published in the peer-reviewed medical journal Heart. That sounds like a pretty big deal. What are we to make of it?
Youíve probably noticed that headlines are often written more for shock value and simplicity than for accuracy. In this case the headlines were misleading right off the bat because of a bedrock scientific principle: correlation is not causality.
What does that mean? A so-called observational study such as this one only establishes that two things happen together, or are associated. That alone does not mean that one causes the otheróor if so, which is the cause and which is the effect. For that purpose a controlled study, say one in which people are randomly assigned to get a calcium pill or an inert substance, preferably without the subject or experimenters knowing which was which, would be the gold standard.
But even then, one study should be considered in light of all the evidence thatís available. This study was shocking because it contradicts other findings, particularly those suggesting that calcium has heart-protective functions, such as lowering blood pressure.
You can further question how applicable the study is. Although nearly 24,000 people were followed over 11 years, they all lived in Heidelberg, Germany. Maybe itís the water, the brand of supplements, or any number of other things peculiar to that population.
Yet another issue is that the study was not set up to discover influences on heart attacks, but cancer. For statistical reasons, thatís grounds to give it less weight, along with the fact that the number of subjects actually taking calcium supplements was rather small.
If you read the news articles through to the expertsí conclusions, youíll get what should be familiar nutrition wisdom: This study is not conclusive but is worthy of concern. Food is the best source of nutrients because it provides them gradually in a broad-spectrum, balanced way. You should work with your chosen health professionals in addressing any health concern.
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