Creative Commons image credit, below.
I treat dark chocolate as another food group, myself. There's nothing like a small little sliver of dark chocolate to add some get-up-and-go to a morning. According to highlights from the Mayo Clinic Health Letter, May, 2011, dark chocolate contain flavenols, which "appear to play a protective role in heart health." Generally, the darker the chocolate, the better, according to the highlights.
I've never met a dark chocolate I didn't like (I once was able to sample many varieties as part of a focus group), but I do eat a lot of Lindt 90% Cocoa Supreme Dark chocolate. I noticed one day, looking at the ingredients, that not only was there no gluten, but that it didn't look like there was any dairy, either. The ingredients: chocolate, cocoa powder processed with alkali, cocoa butter, sugar, bourbon vanilla beans. The allergy info notes: "May contain traces of peanuts/soybean/tree nuts/milk.
Now, the only other question arising in my mind involves the alkali used to process the cocoa powder. According the Mayo Clinic, above, (and I've read this in other reliable health sources), another good source of flavenols is "unsweetened 100 percent cocoa powder that hasn’t been alkalized (in other words, Dutch processed)." Because the Lindt cocoa powder appears to have been alkalized, however, maybe I'll have to be content knowing that I'm getting really dark chocolate as well as great taste. Image unrelated to Lindt chocolate, it's just a nice photo licensed by Creative Commons.