Dark Chocolate

Dark chocolate without milk as an additive is also called plain chocolate. The US Government calls this sweet chocolate, and requires a 15% concentration of chocolate liquor. European rules specify a minimum of 35% cocoa solids.
Dark Chocolate is the healthiest type of chocolate. Dark chocolate has ingredients that lower blood pressure and fight disease, but white chocolate and milk chocolate don't, studies show. It is a potent antioxidant. Antioxidants remove free radicals which are destructive molecules that are implicated in heart disease and other illnesses.
It is the cocoa phenols in the dark chocolate that have been shown to reduce blood pressure. European chocolates typically have greater concentrations of cocoa phenols than those from the United States.
However the addition of milk to create milk chocolate or white chocolate may interfere with the absorption of antioxidants. So if you want to be as healthy as possible when eating chocolate then eat dark chocolate!