The flavonoids in dark chocolate -- the antioxidant compounds that give it its bittersweet taste -- promote a variety of cardiovascular benefits. The antioxidants in dark chocolate can also lower blood pressure, increase good cholesterol, decrease oxidation of bad cholesterol, which leads to plaque accumulation in the arteries, and promote blood sugar regulation. Dark chocolate can also lengthen the time it takes blood to clot and increase healthy blood flow by making blood vessels more elastic.