The Dietary Management of Patients with Irritable Bowel Syndrome: A Narrative Review of the Existing and Emerging Evidence

Abstract

Even though irritable bowel syndrome (IBS) has been known for more than 150 years, it still remains one of the research challenges of the 21st century. According to the current diagnostic Rome IV criteria, IBS is characterized by abdominal pain associated with defecation and/or a change in bowel habit, in the absence of detectable organic causes. Symptoms interfere with the daily life of patients, reduce health-related quality of life and lower the work productivity. Despite the high prevalence of approximately 10%, its pathophysiology is only partly understood and seems multifactorial. However, many patients report symptoms to be meal-related and certain ingested foods may generate an exaggerated gastrointestinal response. Patients tend to avoid and even exclude certain food products to relieve their symptoms, which could affect nutritional quality. We performed a narrative paper review of the existing and emerging evidence regarding dietary management of IBS patients, with the aim to enhance our understanding of how to move towards an individualized dietary approach for IBS patients in the near future.

Keywords: dietary fiber; dietary management; exclusion diets; gluten-free diet; irritable bowel syndrome; lactose-free diet; low FODMAP diet.

Figure 1

An overview of important pathophysiological factors in IBS. The current view of the heterogeneous IBS pathophysiology is that it is caused by altered brain-gut interactions, with various alterations and abnormalities along the brain-gut axis in subsets of IBS patients. Created with BioRender.

Figure 2

Advise on dietary habits, lifestyle, and how to avoid symptom triggers. Guidelines regarding dietary habits, lifestyle, and avoidance of symptom triggers were already described in early 1990s and were based on clinical experience. This approach can still be used to work towards a personalized dietary management of IBS patients. Abbreviation: IBS: irritable bowel syndrome. Created with BioRender.

Figure 3

Diagnostic work-up and interventions in patients with IBS, derived from the NICE guidelines. Primary care physicians should apply step 1–4, and can refer patients to secondary care (step 5) if they develop refractory IBS. Abbreviations: FODMAP: fermentable oligo-, di-, monosaccharides and polyols; IBS: irritable bowel syndrome; NICE: National Institute for Health and Care Excellence. Created with BioRender.

Figure 4

Mechanism of action of FODMAPs. When FODMAPs pass the small intestine where they are incompletely absorbed and can pass into the colon. In the colon the osmotically active short-chain carbohydrates increase the luminal water content. Fermentation of FODMAPs by colonic bacteria causes the production of gas. Increased luminal water content and gas production result in a distention of the large intestine, which in turn could generate GI symptoms. Abbreviations: FODMAPs: Fermentable oligosaccharides, disaccharides, monosaccharides and polyols; GI: gastrointestinal. Created with BioRender.

Figure 5

The digestion of lactose in the small intestine. (1) Hydrolyzation of lactose by lactase, located in upper layer of enterocytes. (2) Rapid absorption of monosaccharides, glucose and galactose, which is maximal in the proximal jejunum. (3) Glucose will be used for energy, galactose as a part of glycoproteins. Created with BioRender.

Figure 6

Schematic overview of wheat grain components and relation to gastrointestinal symptoms in IBS. Abbreviations: ATIs: amylase-trypsin inhibitors; GI: gastrointestinal; IBS: irritable bowel syndrome. Created with BioRender.

Figure 7

Timeline of dietary trials and diagnostic criteria for irritable bowel syndrome. Abbreviation: FODMAP: fermentable, oligo-, di-, monosaccharides and polyols. Created with BioRender.