The findings were published in the Tuesday issue of Circulation: Heart Failure, an American Heart Association journal.
The nine-year study, conducted among 31,823 middle-aged and elderly Swedish women, looked at the relationship between the amount of high-quality chocolate the women ate and compared their risk for heart failure.
The quality of chocolate consumed by the women has a higher density of cocoa content comparable to dark chocolate by American standards, it was observed.
Researchers found that women who ate an average of one to two servings of the high-quality chocolate per week had a 32 percent lower risk of developing heart failure.
Those who had one to three servings per month had a 26 percent lower risk, while those who consumed at least one serving daily or more did not appear to benefit from a protective effect against heart failure.
The lack of a protective effect among women eating chocolate every day is probably due to the additional calories gained from eating chocolate instead of more nutritious foods, said Dr. Murray Mittleman, lead researcher of the study.
“Chocolate is a relatively calorie-dense food and large amounts of habitual consumption is going to raise your risks for weight gain,” said Dr. Mittleman, director of the cardiovascular epidemiology research unit at Harvard Medical School’s Beth Israel Deaconess Medical Center.
“But if you’re going to have a treat, dark chocolate is probably a good choice, as long as it’s in moderation,” he added.
High concentration of compounds called “flavonoids” in chocolate may lower blood pressure, among other benefits, according to mostly short-term studies. This is the first study to show long-term outcomes related specifically to heart failure.
Although 90 percent of all chocolate eaten across Sweden during the study period was milk chocolate, it contains about 30 percent cocoa solids. US standards only require 15 percent cocoa solids to qualify as dark chocolate.
The average serving size for Swedish women in the study ranged from 19 grammes among those 62 and older, to 30 grammes among those 61 and younger. The standard American portion size is 20 grammes.