Dark Chocolate: A Sweet Choice for Heart Health

December 20, 2007—Chocolate—long known to soothe the emotional heart—might also be good for the physical heart: A new study has found that eating dark chocolate improves blood flow through the heart.

Although chocolate doesn’t often make the list of healthiest foods, a growing body of evidence suggests that dark chocolate can lower blood pressure and prevent cardiovascular disease. The cacao plant, used to make chocolate, is rich in antioxidant flavonoids that are thought to contribute to its heart-protective effects. In fact, a serving of dark chocolate can have as much or more antioxidant capacity and flavonoid content as a serving of red wine, berries, or vegetables.

After the cacao seed is fermented, roasted, and ground to produce cocoa, it is transformed into a wide variety of delicacies. However, only dark chocolate appears to benefit heart and blood vessels: Most commercial cocoa powder is processed with alkali, which destroys most of its antioxidants. White chocolate, made from cocoa butter and sugar, has no flavonoids. And though milk chocolate and chocolate milk do contain flavonoids, proteins in milk prevent them from being absorbed in the digestive tract.

In the new study, published in the International Journal of Cardiology, 39 healthy men between 23 and 40 years old were randomly assigned to eat 45 grams (about 1.5 ounces) of dark chocolate or 35 grams (just over 1 ounce) of white chocolate per day for two weeks. Blood flow through the vessels of the heart (coronary blood flow) was measured at the beginning and end of the study.

When coronary blood flow is restricted, such as may be caused by hardened arteries (atherosclerosis) or a blood clot, the heart muscle may not be able to get enough oxygen to function properly. Angina, a periodic tightness or pain in the chest, often occurs in people with coronary artery disease, and complete obstruction of blood flow through a coronary artery can result in a heart attack.

All of the men had normal coronary blood flow at the beginning of the study, but the men who ate dark chocolate had a 27% increase in coronary blood flow after two weeks, while the men who ate white chocolate had no change. “This is the first clinical trial to demonstrate an improvement in [coronary blood flow] in healthy adults after short-term consumption of flavonoid-rich dark chocolate,” the authors commented.

It is important to temper the recent excitement about dark chocolate with the reminder that most chocolate products are high in sugar, fat, and calories. Eating the amount of chocolate used in this study would add about 250 calories to each day. Overweight and obesity are major risk factors for heart disease, so adding these calories may not be wise for everyone who wants to improve heart health.

(Int J Cardiol 2007; online publication)

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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