Studies have shown that the sweet treat can also lower your blood pressure and reduce your risk of diabetes, she says.
Dark Chocolate Rich in Flavonoids
The study involved 39 healthy men who ate a 1.4-ounce candy bar of either dark chocolate or white chocolate daily for two weeks.
Shiina says the dark chocolate was rich in a potent flavonoid known as cacao polyphenol, while the white chocolate contained no flavonoids.
The researchers measured what doctors call coronary flow velocity reserve (CFVR). It's an indicator of the ability of the coronary arteries to dilate and allow more blood flow to heart muscle tissue.
After two weeks, coronary circulation significantly improved in participants who ate dark chocolate. There was no change among those who ate white chocolate.
4 Times as Many Flavonoids
Cacao polyphenol contains four times as many disease-fighting flavonoids per serving than red wine or tea, Shiina says.
That's not to say you can indulge in dark chocolate with impunity, says Sidney Smith, MD, a past president of the American Heart Association and professor of medicine at the University of North Carolina in Chapel Hill.
"You have to balance the fats and calories of the candy bar against the benefits of flavonoids," he tells WebMD.
Shiina says that in the future, development of a cacao polyphenol supplement could overcome the problem.
The study was presented here at the American Heart Association's Scientific Sessions 2007.