Chocolate is a source of polyphenols (the same type of antioxidants found in red wine). Stearic acid, the fat it contains, doesn't affect cholesterol levels, and studies have shown that flavonoids in dark chocolate help reduce the stickiness of platelets, cells that play an important role in blood clotting. As a result, blood takes longer to clot, reducing the danger of coronary artery blockages. Chocolate's polyphenols also appear to boost levels of HDL (the "good" cholesterol) and lower LDL (the "bad" cholesterol), at least in the lab. I recommend consuming good-quality dark chocolate that is at least 70 percent cocoa as a healthy snack, as long as you don't go overboard. An ounce or two a few times a week is good for you.
Article courtesy of Dr. Andrew Weil's website, found here.