Characterization of a low fermentable carbohydrate diet and its treatment effects in an Asian setting for patients with functional dyspepsia and irritable bowel syndrome

Abstract

The etiopathogenesis of functional gastrointestinal disorders (FGID) includes visceral hypersensitivity, and impaired gastrointestinal motility. Functional dyspepsia (FD) and irritable bowel syndrome (IBS) are two of the most prevalent FGID in Asia, affecting 15% and 7% population respectively. Patients with FD have overlapping symptoms with IBS in the Asian population, such as epigastric pain, postprandial fullness and excessive gas production (manifest as self-perceived excessive belching and flatulence). Patients with FD and IBS commonly associate their symptom development with the ingestion of meals. There has been an accumulation of data regarding the effects of a group of fermentable and osmotically active carbohydrates, collectively known by acronym FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) as major dietary triggers in patients with IBS. There is an abundance of data demonstrating the efficacy of the low FODMAP diet in IBS in western populations yet, there are no high-quality studies in Eastern populations. Given the significant symptom overlap between FD and IBS, the low FODMAP diet could also be a solution for FD in East Asia. This thesis is the first study investigating the possible effect of the low FODMAP diet in East Asian patients with FD and/or IBS. This thesis consisted of three studies; i) Evaluation of the pattern of lactulose, lactose and fructose hydrogen breath tests (HBT) in healthy controls, FD and/or IBS, ii) Investigation of the habitual FODMAP content in the diet in the Hong Kong Chinese and finally iii) a randomized double-blinded cross-over interventional dietary study examining the efficacy of the low vs. typical FODMAP diet in symptom genesis in FD and/or IBS. ROME IV suggests the distribution of gastrointestinal syndromes is different in between FD and/or IBS1, 2. In the study on hydrogen breath test, there were clearly differentiated patterns of symptom genesis between FD, IBS, FD-IBS overlap and healthy controls. Chinese IBS patients experience both upper and lower gastrointestinal symptoms3, 4. In the study on the habitual diet, the dietary FODMAP content is at least 5 grams lower than that of the western population, therefore supporting a role for dietary manipulation of FODMAP content in this region as a treatment for FD and/or IBS. In the interventional study, patients with FD had reduced belching and postprandial fullness as charted by the Visual Analogue Scale (VAS) on the low FODMAP diet as compared to the typical Hong Kong diet. In IBS, belching, postprandial fullness, abdominal pain/discomfort, and flatulence as charted by the VAS were also significantly reduced. The FD-IBS overlap group showed reduction of both upper and lower gastrointestinal symptoms. In summary, this is the first study to examine a large Asian cohort for their lactulose, lactose and fructose HBT, with findings suggestive of a differential pattern genesis among groups. Furthermore, unique information about the relatively lower habitual FODMAP content in Hong Kong diet was confirmed and the efficacy of the low FODMAP diet has been proven to reduce gastrointestinal symptoms in both patients with FD and/or IBS, adding another tool to the management of FGID in East Asia.