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Healthnotes Newswire (April 21, 2006)- Eating dark chocolate can lower blood pressure and improve insulin sensitivity, reports the American Journal of Clinical Nutrition (2006;81:611–4). Because high blood pressure and impaired insulin sensitivity are heart disease risk factors, the results of this study suggest that eating dark chocolate might help prevent heart disease. That possibility is supported by previous research showing that chocolate inhibits both platelet aggregation and the oxidation of LDL ("bad") cholesterol, effects that would also be expected to reduce heart-disease risk. However, as chocolate also has a number of adverse effects, the "chocolate cure" for heart disease may not be for everyone.

In the new study, healthy volunteers were randomly assigned to eat 100 grams (approximately 3.5 ounces) of dark chocolate each day for 15 days. The average systolic blood pressure (the higher number on a blood pressure reading) fell by 6.4 mm Hg and insulin sensitivity (a measure of how effectively insulin works in the body) improved significantly. In contrast, when the same volunteers ate white chocolate there was no significant improvement in these measures. Dark chocolate is rich in certain types of flavonoids, whereas white chocolate contains them in negligible amounts. Previous research has suggested that these flavonoids are responsible for the beneficial changes reported in dark-chocolate consumers.

The improvement in heart-disease risk factors associated with eating chocolate should be weighed against its negative effects. For many people, chocolate is addictive, and getting into a chocolate habit could lead to obesity. Chocolate has been implicated as a possible cause of acne, and for some people it is a triggering factor for migraines. Chocolate also contains various "mind altering" substances, including an amphetamine-like compound (phenylethylamine) and a chemical that mimics some of the effects of the active ingredient in marijuana. In addition, eating chocolate causes heartburn or symptoms of esophageal reflux in some people.

Furthermore, flavonoids that have similar effects to the ones in chocolate are present in a wide variety of fruits, vegetables, whole grains, and other plant foods. Many of those foods also contain other heart-protecting nutrients such as essential fatty acids, potassium, vitamin C, magnesium, folic acid, vitamin E, vitamin B6, and fiber. While it is generally agreed that eating fruits, vegetables, and whole grains can help prevent heart disease, it is not known whether adding chocolate to a diet that is already high in flavonoids would provide any additional benefit.

Despite the concerns about chocolate, eating a small amount of dark chocolate every day might be beneficial for some people. Milk chocolate, on the other hand, would not be expected to provide the same benefits, because milk strongly inhibits the absorption of the flavonoids in chocolate.