A Square of Chocolate a Day Linked to Lower Risk of Heart Attack and Stroke
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Reviewed By Laura J. Martin, MD
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March 30, 2010 -- Just in time for the Easter Bunny's arrival, researchers have more sweet news about chocolate and heart disease.
Researchers in Germany say that people who ate the equivalent of one square of a 100 gram (3.5 oz) chocolate bar per day had a 39% lower risk of having heart attack or stroke than people who ate much less chocolate.
But before you stock up on chocolate Easter eggs, researchers warn that the key to reaping the health benefits of chocolate is moderation. A single 100-gram bar of chocolate contains about 500 calories, and eating too much can contribute to unhealthy weight gain.
"Small amounts of chocolate may help to prevent heart disease, but only if it replaces other energy-dense food, such as snacks, in order to keep body weight stable," researcher Brian Buijsse, a nutritional epidemiologist at the German Institute of Human Nutrition in Nuthetal, Germany, says in a news release.
Chocolate and Heart Attack Risk
The study, published in the European Heart Journal, followed 19,357 adults for 10 years. The participants received medical checkups at the start of the study in 1994-1998, and every two to three years filled out questionnaires about how often they ate a 50 gram bar of chocolate. They could also indicate if they ate half or a bar or more than one.
The participants were not asked about what kind of chocolate they ate, but researchers asked a subset of 1,568 participants to describe the chocolate they ate in the last 24 hours to give an indication of what proportions might be found in the entire study. The results within this subset showed 57% ate milk chocolate, 24% dark chocolate, and 2% white chocolate.
By the end of the study, researchers found that people who ate the most chocolate, an average of 7.5 grams per day, had a 27% lower risk of heart attack and a 48% lower risk of stroke than people who ate the least amount of chocolate, an average of 1.7 grams per day.
"To put it in terms of absolute risk, if people in the group eating the least amount of chocolate (of whom 219 per 10,000 had a heart attack or stroke) increased their chocolate intake by six grams a day, 85 fewer heart attacks and strokes per 10,000 people could be expected to occur over a period of about 10 years," Buijsse says.
People who ate the most chocolate also had blood pressure that was about 1 point systolic (the top number in a blood pressure reading) and 0.9 point diastolic (the bottom number) lower than people who ate the least amount of chocolate.
Flavanols in Chocolate Help Heart
Researchers say the benefits of chocolate on reducing heart disease risk appear to be because of the high flavanol content of cocoa. Flavanols are a type of antioxidant, and chocolates with a higher percentage of cocoa, such as dark chocolate, contain more flavanols.
"Flavanols appear to be the substances in cocoa that are responsible for improving the bioavailability of nitric oxide from the cells that line the inner wall of blood vessels," Buijsse says. "Nitric oxide is a gas that, once released, causes the smooth muscle cells of the blood vessels to relax and widen; this may contribute to lower blood pressure. Nitric oxide also improves platelet function, making the blood less sticky."
Experts say together with previous research the results of this study build a strong case that eating a daily dose of chocolate is healthy for the heart.
"Basic science has demonstrated quite convincingly that dark chocolate particularly, with a cocoa content of at least 70%, reduces oxidative stress and improves vascular and platelet function," Frank Ruschitzka, professor of cardiology and director of heart failure/transplantation at the University Hospital Zurich in Switzerland, says in the release.
SOURCES: Buijsse, B. European Heart Journal, March 31, 2010, online advance
News release, European Heart Journal.
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