For years, chocolate lovers have remained blissfully unaware of the precise reason bittersweet dark chocolate seems to improve cardiovascular health. At least until, now that is.

Researchers at a meeting of the American Chemical Society in Dallas said they had solved the confection conundrum: Specific chocolate-loving microbes in the gut convert an otherwise indigestible portion of the candy into anti-inflammatory compounds, they said.

Using a series of modified test tubes to simulate humans’ gurgling guts, researchers exposed several forms of cocoa powder to digestive juices and enzymes, and then to bacteria found in samples of human feces.

What they found was that after cocoa was “digested,” long molecules called polyphenolic polymers remained within the gastrointestinal, or GI, tract.

“They do nothing for us except travel down the GI tract after we consume them,” Finley said.

That is until they encounter some of the many microbes that inhabit the human colon, particularly Bifidobacterium and lactic acid bacteria, researchers said.

“These little guys say, ‘Hey — there’s something in there that I can use,’ and they start to break it down,” Finley said.