It’s really true: dark chocolate makes your coronary arteries open up and increases heart blood flow. In a two-week trial, 39 adults ate either 550 milligrams per day of dark chocolate (with a cocoa content of 70 percent or greater), which is full of flavonoids, or the same amount of white chocolate, which has no flavonoids.
By the end of the study, the coronary flow velocity reserve (CFVR) of the dark chocolate eaters had significantly improved. If you want the same health effect, remember to go easy on the chocolate: 550 milligrams is only about 0.0194 of an ounce.
Source: MedlinePlus, November 2007