Dark chocolate really does a body good, and scientists now have a better idea why. Gut bacteria break down large compounds in its key ingredient, cocoa powder, into smaller molecules that can curb harmful inflammation, researchers reported today at the American Chemical Society meeting in Dallas, Texas. In test-tube experiments, scientists treated the cocoa with stomach and pancreatic enzymes and washed the sample to remove water-soluble molecules. They then fed the remaining insoluble material to bacteria cultured from lab members’ stool samples (yes, they pooped in a cup for this study) and fermented it in anaerobic conditions similar to those in the ileum and colon. The fermentation products acted as anti-inflammatories when applied to monolayers of digestive tract cells that the researchers had exposed to inflammatory stimulants. The findings suggest that we can thank our gut bacteria for giving dark chocolate its touted health benefits.

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