Chocolate lovers, take heart: A Japanese study finds that flavonoid-rich dark chocolate can improve coronary blood flow.

The study looked at what's known as coronary flow velocity reserve (CFVR), an indicator of the ability of the coronary arteries to dilate and allow more blood flow in response to medications.

The two-week trial included 39 healthy adults, average age 29, who ate either 550 milligrams per day of dark chocolate versus white chocolate with no flavonoids.

The researchers used Doppler echocardiography to assess CFVR at the start and end of the study. They also measured the participants' blood pressure, blood lipids and two markers of oxidative stress.

Participants who ate dark chocolate showed significantly improved CFVR after two weeks, while those who ate white chocolate showed no change, the study found.

"Flavonoid-rich dark chocolate intake had acute effects in improving coronary function in healthy adults, as compared to non-flavonoid white chocolate, independent of changes in oxidative stress parameters, blood pressure and lipid profile," wrote the researchers from Chiba University.

However, they noted that difficulties in blinding (preventing participants from knowing which kind of chocolate they were eating) may have affected the results.

The study was to be presented Sunday at the American Heart Association annual meeting in Orlando, Fla.

More information: The Linus Pauling Institute at Oregon State University has more about flavonoids.

SOURCE: Nov. 4, 2007, presentation, American Heart Association annual meeting, Orlando, Fla.