German researchers followed nearly 20,000 people
over eight years, sending them several questionnaires about their diet
and exercise habits.
They
found people who had an average of six grams of chocolate per day — or
about one square of a chocolate bar — had a 39 percent lower risk of
either a heart attack or stroke. The study is scheduled to be published
Wednesday in the European Heart Journal.
Previous studies have suggested dark chocolate in
small amounts could be good for you, but this is the first study to
track its effects over such a long period of time. Experts think the
flavonols contained in chocolate are responsible. Flavonols help the
muscles in blood vessels widen, which leads to a drop in blood pressure.
"It's a bit too early to
come up with recommendations that people should eat more chocolate, but
if people replace sugar or high-fat snacks with a little piece of dark
chocolate, that might help," said Brian Buijsse, a nutritional
epidemiologist at the German Institute of Human Nutrition in Nuthetal,
Germany, the study's lead author.
The people tracked by Buijsse and colleagues had no
history of heart problems, had similar habits for risk factors like
smoking and exercise, and did not vary widely in their Body Mass Index.
Since the study only
observed people and did not give them chocolate directly to test what
its effects were, experts said more research was needed to determine the
candy's exact impact on the body. The study was paid for by the German
government and the European Union.
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Doctors also warned that
eating large amounts of chocolate could lead to weight gain, a major
risk factor for heart problems and strokes.
"Basic science has demonstrated quite convincingly
that dark chocolate ... improves vascular and platelet function," said
Frank Ruschitzka in a statement, a cardiologist at the University
Hospital Zurich and spokesman for the European Society of Cardiology.
"However, before you rush to add dark chocolate to your diet, be aware
that 100 grams of dark chocolate contains roughly 500 calories."
Buijsse said people
hoping to benefit from chocolate's heart healthy effects should cut out
other snacks and sweets if they wanted to eat chocolate. "The biggest
problem with this is not to gain weight," said Buijsse. "Eating too much
chocolate will have negative effects that far outweigh the positive
effects of cocoa."