Schematic illustration for the possible mechanisms by which FODMAPs can trigger IBS symptoms. Upon reaching the large intestine FODMAPs can exert direct or indirect effect on the intestinal endocrine cells. They act as prebiotics and change the intestinal flora and they are fermented by the intestinal microbiota with gas production. The production of gas increases the luminal pressure and stimulates the release of serotonin from serotonin (EC) cells. Serotonin act on the intrinsic sensory nerve fibres (ISNF) of the submucosal and myenteric ganglia, which in turn convey the activation to the extrinsic sensory nerve fibres (ESNF) to the central nervous system.