Eating chocolate has been tied to a reduced risk of heart disease. Now scientists have uncovered one possible reason.

Using data from a large Danish health study, researchers have found an association between chocolate consumption and a lowered risk for atrial fibrillation, the irregular heartbeat that can lead to stroke, heart failure and other serious problems. The study is in Heart.

Scientists tracked diet and health in 55,502 men and women ages 50 to 64. They used a well-validated 192-item food-frequency questionnaire to determine chocolate consumption. During an average 14 years of follow-up, there were 3,346 diagnosed cases of atrial fibrillation.

After controlling for total calorie intake, smoking, alcohol consumption, body mass index and other factors, they found that compared with people who ate no chocolate, those who had one to three one-ounce servings a month had a 10 percent reduced relative risk for atrial fibrillation, those who ate one serving a week had a 17 percent reduced risk, and those who ate two to six a week had a 20 percent reduced risk.