German researchers report that eating just a square of chocolate a day may reduce the risk of myocardial infarction (heart attack) and stroke, as well as reduce blood pressure. But are the findings too sweet to be true? Some critics remain skeptical of the study’s results.

Those eating the most chocolate also enjoyed lower blood pressure, but only about one point lower, on both systolic (top number) and diastolic (bottom number) measures.

The study, published in the March 30, 2010 online edition of the European Heart Journal, followed over 19,000 people for ten years, periodically asking them questions about their diets and exercise habits. Lead researcher Brian Buijsse and his team found that those who ate the most chocolate (7.5 grams per day, equivalent to just over a square of chocolate in a typical candy bar) were at a 39% reduced risk of having a heart attack or stroke over the course of the study, compared to those who ate the least (1.7 grams/day). Those eating the most chocolate also enjoyed lower blood pressure, but only about one point lower, on both systolic (top number) and diastolic (bottom number) measures.

While these numbers may sound encouraging, don’t run out and buy a king-size candy bar just yet. One potential issue with the study involves the average amounts of chocolate consumed by the participants. The highest and lowest amounts of chocolate consumed, 7.5 grams and 1.7 grams, are both very low, and only represent averages (in other words, no one would actually eat 1.7 grams of chocolate every day). It’s more likely that people are eating one candy bar a week, or one candy bar every month or two, which averages out to the low average amounts per day. While some critics say that the averages in the study may lead to problems in interpreting the data accurately, there is clearly something at play to explain the rather large difference between the groups (39%). The authors of the study say that more research will be needed – in the form of randomized trials, rather than questionnaires (on which people are likely to misreport their chocolate consumption) – to better understand the relationship between chocolate and heart health.

The study was conducted by researchers at the German Institute of Human Nutrition in Nuthetal, Germany.