March 11, 2005 -- Now here's a prescription that chocoholics will gladly follow: Eat a healthy dose of dark chocolate every day to lower your blood pressure and reduce your risk of developing diabetes.
A new study shows that eating dark chocolate decreases blood pressure and improves insulin sensitivity in healthy people. Impaired insulin sensitivity is a major risk factor for diabetes and reduces the body's ability to process blood sugar (glucose) effectively.
Flavonoids are a larger family of compounds found in the seeds and skins of plants, such as grapes, cocoa beans, and citrus fruits. Recent studies have shown that these compounds may be responsible for many of the heart-healthy effects associated with red wine and diets rich in fruits and vegetables.
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In the study, which appears in the March issue of the American Journal of Clinical Nutrition, researchers compared the effects of adding 100 grams (3.5 ounces) of dark chocolate or 90 grams (3.2 ounces) of white chocolate to the normal diets of 15 healthy Italians.
Dark chocolate is rich in flavonoids due to their high cocoa content, but white chocolate contains no cocoa, and, therefore, no flavonoids.
The participants ate a daily dose of dark chocolate for 15 days, followed by a seven-day no-chocolate phase, and then ate the white chocolate for another 15 days.
Researchers found that blood sugar metabolism was significantly improved after the dark chocolate phase, as evidenced by reduced insulin resistance and higher insulin sensitivity. But no such healthy effects were found after the white chocolate phase.
The study also showed that the participants' systolic blood pressure (the top number in a blood pressure reading) was significantly lower after 15 days of eating dark chocolate -- an average of 108 mm Hg compared with 114 mm Hg. Again, no effects were found after eating white chocolate.
Other studies have shown similar effects with other flavonoid-containing foods, such as tea and wine, on blood pressure.
Researchers say the antioxidant-rich compounds improve blood pressure by helping the lining of the blood vessels expand and contract better to control blood flow more effectively.
In an editorial that accompanies the study, Cesar G. Fraga, of the department of nutrition at the University of California, Davis, says "the findings of this study are of particular interest in terms of identifying potentially healthy foods."
He says other studies with flavonoid-containing foods, such as tea and wine, have shown similar effects on vascular and blood pressure regulation.