ChocOholic gut bacteria may be one of the chief reasons why dark chocolate is good for the heart, research suggests.
By breaking down indigestible chocolate compounds and fermenting cocoa fibre, they generate a potent anti-inflammatory effect.
Scientists believe this helps to protect the heart and arteries and prevent killer strokes.
Researcher Maria Moore, from Louisiana State University, said: "We found there are two kinds of microbes in the gut: the 'good' ones and the 'bad' ones.
"The good microbes, such as Bifidobacterium and lactic acid bacteria, feast on chocolate."
"Bad" gut bacteria, such as Clostridia and some strains of Escherichia coli (E.coli), help to trigger inflammation, leading to bloating, diarrhoea and constipation.
The team tested three types of cocoa powder, in an artificial digestive tract consisting of a series of modified test tubes.
Cocoa contains antioxidant polyphenol compounds such as catechin and epicatechin and a small amount of dietary fibre.
Both components are poorly digested and absorbed, but are readily processed by the friendly bacteria in the colon.
"In our study we found that the fibre is fermented and the large polyphenolic polymers are metabolised to smaller molecules, which are more easily absorbed," said Dr John Finley, who led the Louisiana team.
"These smaller polymers exhibit anti-inflammatory activity. When these compounds are absorbed by the body, they lessen the inflammation of cardiovascular tissue, reducing the long-term risk of stroke."