Daily dark chocolate helps middle-aged hearts

A daily nibble of dark chocolate may slash the risk of heart attacks and strokes by more than one-third, a study of 20,000 middle-aged Germans found.

Researchers tracked participants for a decade to unravel the ties between chocolate and heart disease, and unexpectedly found the biggest benefit lay in warding off strokes. Eating an extra 6 grams of chocolate a day, or less than two Hershey's Kisses, could prevent 85 heart attacks and strokes in every 10,000 people over a decade, said Brian Buijsse, lead researcher of the study published by the European Heart Journal.

The report provides more evidence about the beneficial effects of chocolate, particularly the dark variety that's rich in cocoa and potentially protective compounds called flavanols, said Buijsse, a nutritional epidemiologist at the German Institute of Human Nutrition in Nuthetal. Chocolate appeared to have a more powerful effect than fruit and vegetables, a mainstay of a healthy diet. Those who ate the most chocolate also consumed the fewest fruits and vegetables.

The findings shouldn't be used as a license to binge on chocolate, which could lead to obesity and harm the heart, Buijsse said.

"If you want to eat chocolate, keep it at low amounts and leave out something else in the diet, preferably something also rich in calories," he said. "If you chose chocolate rather than a bag of potato chips, that's probably better, because the chips don't have any nutritional benefit other than the calories."

The study, involving healthy volunteers ages 35 to 65 with no signs of heart disease, was part of the European Prospective Investigation into Cancer. Participants underwent a medical checkup at the start of the trial, including blood pressure, weight and smoking status, then answered questions about their diet, lifestyle and health every two to three years.

The researchers divided volunteers into four groups, ranked by the amount of chocolate they ate. Those in the highest quadrant ate about 7.5 grams a day, the equivalent of about one square of a standard 100-gram chocolate bar.

Although chocolate is known to reduce blood pressure, lower levels in chocolate lovers accounted for only a small part of the benefit seen in the study, Buijsse said. Flavanols may add extra protection by boosting the impact of nitric oxide, a gas that relaxes smooth muscle cells lining blood vessel walls and helps reduce clotting, he said.

"The substances in cocoa, flavanols, are making the blood vessels more elastic and less stiff," he said. That's bad news for white chocolate lovers.

"White chocolate doesn't do anything, probably because it doesn't contain any flavanols," he said.