A Little Dark Chocolate Can Lower Blood Pressure

Healthnotes Newswire (August 23, 2007)—If you needed encouragement to eat a little dark chocolate every day, a new study provides it, showing that this habit can beneficially lower your blood pressure.

The sweet news from the world of nutrition research in recent years is that something about chocolate seems to lower blood pressure. Scientists have speculated that cocoa polyphenols—plant chemicals that have strong antioxidant effects—might be responsible. The color of chocolate tells much about its polyphenol content: dark chocolate, with its deep brown color, has lots of polyphenols, while white chocolate has virtually none. Milk chocolate has not demonstrated the same benefits as dark chocolate because the milk prevents the body from absorbing the polyphenols.

The new study, published in the Journal of the American Medical Association, included 44 healthy adults with borderline high blood pressure (130/85 to 139/89 mm Hg) or stage 1 high blood pressure (140/90 to 160/100 mm Hg). They were randomly assigned to add either 6.3 grams (about one-quarter of an ounce) of dark chocolate or 5.6 grams of white chocolate to their usual daily diet. The amount of dark chocolate was one square of a 16-square commercially available bar of dark chocolate, and the amount of white chocolate was approximately equal in calories, fat, carbohydrate, and protein.

After 18 weeks, the people eating dark chocolate had a modest decline in blood pressure but those eating white chocolate did not. Systolic blood pressure, the “top” number, fell an average of 2.9 mm Hg, and diastolic blood pressure, or the “bottom” number, dropped an average of 1.9 mm Hg in the dark chocolate eating group. People with higher blood pressure at the beginning of the study saw greater reductions in blood pressure over the course of the trial.

While admitting that the blood pressure reductions were small, the study authors emphasized their significance. “On a population basis, it is estimated that a 3 mm Hg reduction in systolic blood pressure would reduce the relative risk of stroke mortality [death due to stroke] by 8%, of coronary artery disease mortality by 5%, and of all-cause mortality by 4%,” they stated in their conclusion.

A previous study seems to illustrate this suggestion that eating chocolate might have a more profound effect on health than expected. In that study, elderly men who ate an average of 4.2 grams of cocoa per day were found to have slightly lower blood pressure than men who didn’t eat any. Even though the differences in blood pressure were small, there was a 50% reduction in cardiovascular mortality and all-cause mortality in the highest cocoa consumers during 15 years of follow-up. This relatively large difference may have been due to the fact that dark chocolate has beneficial effects on other cardiovascular risk factors (such as insulin sensitivity and blood clotting tendency), not just on blood pressure.

To gain the most benefits while indulging your chocolate habit, keep in mind that regularly eating more than the amount used in this study might offset the benefits by adding an unhealthy amount of sugar, fat, and calories to the diet.

In the current study, eating 6.3 grams of dark chocolate added 30 calories to the daily diet and caused no changes in weight, blood sugar levels, or cholesterol levels. “People get such pleasure from eating chocolate,” commented Dr. Julianne Forbes, a naturopathic doctor with a practice in Maine. “Of course, we have to keep promoting fruits and vegetables, but adding dark chocolate to the list of recommendations for people with high blood pressure brings a little lightness, and might just make it seem possible to comply.”

(JAMA 2007;298:49-60.)

Maureen Williams, ND, received her bachelor’s degree from the University of Pennsylvania and her Doctorate of Naturopathic Medicine from Bastyr University in Seattle, WA. She has a private practice in Quechee, VT, and does extensive work with traditional herbal medicine in Guatemala and Honduras. Dr. Williams is a regular contributor to Healthnotes Newswire.

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