The health benefits of dark chocolate, at least when consumed in moderate amounts, have been known throughout history. Exactly why this is the case, though, hasn’t been truly understood until now.

New research presented at the 247th National Meeting & Exposition of the American Chemical Society this week has now shown exactly how dark chocolate affects the human body. The study revealed that dark chocolate can encourage the growth of “good” bacteria in the digestive tract, promoting their anti-inflammatory properties.

“We found that there are two kinds of microbes in the gut: the ‘good’ ones and the ‘bad’ ones,” said Maria Moore, a co-author of the study and an undergraduate student at Louisiana State University. “The good microbes, such as Bifidobacterium and lactic acid bacteria, feast on chocolate. When you eat dark chocolate, they grow and ferment it, producing compounds that are anti-inflammatory.”

According to John Finely, the lead author of the study, these anti-inflammatory compounds can lower the inflammation of cardiovascular tissue. This, in turn, could help reduce stroke risks for those who ingest dark chocolate.

Finely and his colleagues looked at three cocoa powders for the study. Using a simulated digestive tract made of test tubes the team fermented non-digestible materials in human fecal bacteria. Though the antioxidant compounds and fiber contained in the cocoa power are nod easily digested, the “good” microbes in the human colon are able to metabolize the materials, producing small polymers that were observed as having an anti-inflammatory effect.

The study’s authors have also suggested that the benefits of the cocoa powder could be increased by combining it with prebiotics such as those found in raw garlic or whole wheat flour. Doing this could have a similar effect as certain compounds found in common dietary supplements.

“When you ingest prebiotics, the beneficial gut microbial population increases and outcompetes any undesirable microbes in the gut, like those that cause stomach problems,” said Finely.

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