Role of Fructose Malabsorption in Patients With Irritable Bowel Syndrome

c 2018 The Korean Society of Neurogastroenterology and Motility J Neurogastroenterol Motil, Vol. 24 No. 2 April, 2018 www.jnmjournal.org Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders. About 5-11% of the population in most countries is assumed to have IBS. The symptoms of this disorder include recurrent abdominal pain or discomfort related to bowel habit changes that continue for > 6 months, causing heavy burden on the quality of life of some affected persons. The mechanism behind IBS is considered to be multifactorial, including altered motility, visceral hypersensitivity, altered gut microbiota, and dysfunction of the brain-gut axis and the immune system. Likewise, there are multiple treatment options for this disorder, and selecting the appropriate treatment may be challenging for patients and clinicians in the presence of limited evidence. Recent studies have shed new insights about the role of food on the etiologies of IBS. There are many evidences indicating that certain foods cause IBS symptoms. The elimination diets, such as low fermentable, oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs), have been shown to alleviate symptoms. Fructose is a monosaccharide that is increasingly consumed as dietary habits become Westernized worldwide. The more extensive use of fructose-containing artificial sweeteners and high-fructose corn syrup are definitely contributing to this increased intake. A French cohort study showed that this Westernized dietary pattern moderately increased the risk of IBS, and one of the reported foodrelated etiologies of IBS is fructose malabsorption (FM). The ability of the human intestines to absorb fructose is limited. Specific intestinal fructose transporters (glucose transporter-5) in the intestines of humans may be easily overwhelmed by fructose > 50 g. FM leads to a variety of gastrointestinal intolerance symptoms that resemble the symptoms presented by patients with IBS. When patients with unexplained symptoms were administered 50 g fructose and underwent breath tests, 73% tested positive for elevated hydrogen or methane, providing evidence of FM. Moreover, approximately 80% of these positive-tested patients experienced symptoms such as flatus, pain, bloating, belching, and altered bowel habit. The osmotic load that the unabsorbed fructose creates passes into the colon, which houses a variety of fermenting microbiomes that produce these unpleasant symptoms. The physiological connection between FM and IBS is becoming more concrete. Patients with IBS without small intestine bacterial overgrowth (SIBO), confirmed with the glucose hydrogen JNM J Neurogastroenterol Motil, Vol. 24 No. 2 April, 2018 pISSN: 2093-0879 eISSN: 2093-0887 https://doi.org/10.5056/jnm18057 Editorial Journal of Neurogastroenterology and Motility