Another larger study including 345 IBS-D patients evidenced that the increase of Clostridia was associated with the rise of fecal bile acids and with a decrease in serum fibroblast growth factor 19 (FGF19) concentration, a feedback regulator of intestinal transit, possibly explaining the augmented bowel frequency and stool water content in this IBS subtype. This evidence concerns the gene FGF19 and irritable bowel syndrome.