New research from Louisiana State University offers the first-ever glimpse of the mechanism by which dark chocolate benefits cardiovascular health, a complex biological process that has traditionally been shrouded in mystery.

Maria Moore, an undergraduate student at Louisiana State and co-author of the study, said in a press release that the process requires a distinction between “good” and “bad” gut bacteria. "The good microbes, such as Bifidobacterium and lactic acid bacteria, feast on chocolate," she explained. "When you eat dark chocolate, they grow and ferment it, producing compounds that are anti-inflammatory."

To investigate, the researchers tested three cocoa powders using a laboratory model of the human digestive tract. Non-digestible materials were then broken down with human fecal bacteria.

The findings, which were announced at the National Meeting & Exposition of the American Chemical Society, show that this fermentation process releases and promotes the uptake of antioxidant compounds like catechin and epicatechin. "When these compounds are absorbed by the body, they lessen the inflammation of cardiovascular tissue, reducing the long-term risk of stroke," the team told reporters.

The key, according to senior author Dr. John W. Finely, is that these microbes are able to break down complex antioxidants, or polyphenols, into much smaller metabolic products. “The large polymers are generally poorly absorbed,” he wrote in an email to Medical Daily. “But the microbes in the lower GI tract break them down to smaller molecules which are absorbed.”

The new study comes only days after researchers at Brigham and Women’s Hospital announced a five-year, double-blind observational study aimed at quantifying the health benefits of flavanols — a group of metabolites that include both catechin and epicatechin. Earlier this year, a study from the University of East Anglia in the UK found that the same compounds may also lower the risk of diabetes.

Cardiovascular disease is currently the leading cause of death in the United States, killing about 600,000 people each year. According to the Centers for Disease Control and Prevention (CDC), that is about one-fourth of all fatalities. On average, deaths and illnesses associated with coronary heart disease cost the nation $109 billion annually.