Lastly, two faulty copies of the SI gene result in reduced disaccharide activity responsible for degradation of sucrose and starch, resulting in diarrhea and gas production in the large intestine from bacterial fermentation and is termed congenital sucrase-isomaltase deficiency (CSID), and should not be considered as IBS [125]. Here, SI is linked to congenital sucrase-isomaltase deficiency.