Altered gastrointestinal microbiota in irritable bowel syndrome and its modification by diet: probiotics, prebiotics and the low FODMAP diet

Abstract

Irritable bowel syndrome (IBS) is a functional bowel disorder characterised by abdominal pain or discomfort with disordered defecation. This review describes the role of the gastrointestinal (GI) microbiota in the pathogenesis of IBS and how dietary strategies to manage symptoms impact on the microbial community. Evidence suggests a dysbiosis of the luminal and mucosal colonic microbiota in IBS, frequently characterised by a reduction in species of Bifidobacteria which has been associated with worse symptom profile. Probiotic supplementation trials suggest intentional modulation of the GI microbiota may be effective in treating IBS. A smaller number of prebiotic supplementation studies have also demonstrated effectiveness in IBS whilst increasing Bifidobacteria. In contrast, a novel method of managing IBS symptoms is the restriction of short-chain fermentable carbohydrates (low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet). Studies consistently demonstrate clinical effectiveness of the low FODMAP diet in patients with IBS. However, one unintentional consequence of this dietary intervention is its impact on the microbiota. This leads to an interesting paradox; namely, increasing luminal Bifidobacteria through probiotic supplementation is associated with a reduction in IBS symptoms while in direct conflict to this, the low FODMAP diet has clinical efficacy but markedly reduces luminal Bifidobacteria concentration. Given the multifactorial aetiology of IBS, the heterogeneity of symptoms and the complex and diverse nature of the microbiome, it is probable that both interventions are effective in patient subgroups. However combination treatment has never been explored and as such, presents an exciting opportunity for optimising clinical management, whilst preventing potentially deleterious effects on the GI microbiota. Irritable bowel syndrome: Prebiotic: Probiotic: FODMAP Irritable bowel syndromeFunctional bowel disorders are characterised by chronic lower gastrointestinal (GI) symptoms in the absence of alarm features that suggest presence of other disease (1,2) . The criteria for irritable bowel syndrome (IBS), one of the most common functional bowel disorders, requires the presence of abdominal pain or discomfort together with an alteration in stool output (1) . IBS is a common condition worldwide, contributes up to 30 % of gastroenterology consultations in the UK (3) , affects more females than males and is more prevalent in those under 40 years of age (4) . A pooled prevalence of IBS in 14 % of females and 9 % of males has been reported in a large systematic review and meta-analysis of fifty-five studies conducted across America, Asia, Europe and Africa (4) .Four different IBS subtypes exist based on predominant stool form, and each may differ in their aetiology.

The Predictive Value of the Hydrogen Breath Test in the Diagnosis of Fructose Malabsorption

“…A fructose-reduction diet influences the intraluminal microbiota [15][16][17], which is discussed as a co-factor in the pathophysiology in a subgroup of patients with IBS [18,19]. In our group of patients, diarrhoea was the most prevalent symptom in the no-response-group during the application of fructose.…”

Behavioural and neurochemical consequences of chronic gut microbiota depletion during adulthood in the rat

“…Alterations in the bidirectional microbiota-gut-brain axis are reported to be involved in the pathogenesis of many well described disorders of the gut including irritable bowel syndrome (IBS) and inflammatory bowel disorder (IBD) (De Palma et al, 2014;Distrutti et al, 2016;Staudacher and Whelan, 2016). More recently brain disorders such as autism spectrum disorder (Mayer et al, 2014), and mood disorders have been associated with dysfunctional microbiota-gut-brain axis communication Dinan 2012, Foster andMcVey Neufeld 2013).…”

Low-FODMAP diet reduces irritable bowel symptoms in patients with inflammatory bowel disease

“…Based on these findings the authors recommend a LFD for short-term use only in managing IBS symptoms, after which, high FODMAP foods should be reintroduced. As such, reintroduction of FODMAPs after a 6-wk LFD likewise be encouraged among IBD patients due to a lack of evidence regarding the long-term effects and consequences of the diet[9,43]. …”