This shows a diagram of the gut

Bacteria in fermented food signal the human immune system, explaining health benefits

A metabolite produced by lactic acid bacteria binds to the third hydroxycarboxylic acid receptor (HCA), signalling the immune system. Researchers believe the receptor evolved to allow great apes to consume foods that were starting to decay. They suggest the receptor could mediate some beneficial and anti-inflammatory effects of lactic acid in humans, and could serve as a target to treat inflammatory diseases.... Read More...