A. Jeffrey Blumberg, PhD, director of Tufts HNRCA Antioxidants Research Laboratory, replies: This can be a challenge, for several reasons. The FDA does not require food producers to list the content of flavonoids such as those that give dark chocolate its health benefits in the Nutrition Facts panel or elsewhere on the label. Moreover, because of lawsuits, some products that used to cite their flavonoid or flavanol or natural antioxidant content (e.g., on chocolate and tea) no longer do so. Because there is no reference standard (RDA or DV) for flavonoids, per FDA guidelines no product can claim to be a good or rich source of them.
What consumers can do, however, is choose dark or bittersweet or baking chocolate, as they contain more flavanols than Dutch chocolate. The process of dutching or alkalinizing cocoa powder can substantially decrease its flavanol content, while it makes the chocolate smoother and less astringent or bitter.