A story in The New York Times Sunday Magazine credits LSU researchers with figuring out the reason people who eat dark chocolate have a lower risk of heart disease. The chocolate is indigestible.

“Researchers at Louisiana State reached this conclusion after simulating the human digestive system in glass vessels. One represented the stomach and the small intestine, with their digestive enzymes, and a second reproduced a large-intestine-like environment, with gut microbes from human volunteers. The scientists then added cocoa powder to the stomach vessel.

The lab stomachs and small intestines broke down and absorbed some cocoa powder. But the undigested cocoa ended up in the “colon” where some was broken down into metabolites known to reduce cardiac inflammation. The rest of the undigested cocoa began to ferment and released substances that improve cholesterol levels, the research found. In addition, the gut microbes that digest cocoa were desirable probiotics, which increased after the cocoa was introduced.

Less desirable microbes like staphylococcus declined.