Supposedly a mood booster, chocolate does contain some phenylalanine, theprecursor of tyrosine, which in turn is made into the "stay alert" neurotransmitters. It also contains caffeine. But chocolate candy is high in fat, which greatly slows the entry of amino acids into the brain. And no tightly controlled studies have yet been done that prove chocolate does anything but taste good. But it's nice to know that the unusual saturated fat in chocolate, stearic acid, does not raise cholesterol. Cocoa powder is nearly fat free, and a good source of copper and other trace minerals. Avoid chocolate with cholesterol-raising hydrogenated fats.