Chocolate contains some interesting natural compounds, including xanthine, theobromine and phenylethylamine. They sound powerful, but there's not enough of any of them to really cause any reaction in the body. Significant amounts of xanthine, which is similar to caffeine, may make you jittery.

Theobromine can stimulate your central nervous system and relax the bronchi of the lungs and your blood vessels. Phenylethylamine (PEA) is similar to amphetamine.

Actually, it's possible that a little bit of chocolate may be good for you. Dark chocolate has antioxidants that may prevent damage due to free radicals. Chocolate also has some positive impact on the function of blood vessels, but unfortunately, probably doesn't lower high blood pressure as much as some people had hoped.

You don't need much chocolate to get the antioxidant benefit. You only need about one and one-half ounces of dark chocolate per day, and dark chocolate has more of the antioxidants than milk chocolate.

Remember that chocolate treats and candy typically have lots of sugar and fat that can add extra calories you probably don't need and undo all the good that might be done by the antioxidants.

By Shereen Jegtvig, About.com Guide
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