Review article: biological mechanisms for symptom causation by individual FODMAP subgroups ‐ the case for a more personalised approach to dietary restriction

Abstract

Background: Due to the paucity of targeted therapy for irritable bowel syndrome (IBS), many patients turn to dietary modifications for symptom management. The combination of five subgroups of poorly absorbed and rapidly fermented carbohydrates-fructans, galacto-oligosaccharides, lactose, excess fructose and polyolsare thought to trigger gastrointestinal symptoms and are referred to collectively as "FODMAPs". Aims:To examine the biological plausibility and mechanisms by which foods high in specific FODMAP subgroups cause symptoms, and to use this information to explore the possibility of targeting select dietary components to allow for a more personalised approach to dietary adjustment Methods: Recent literature was analysed via search databases including Medline, PubMed and Scopus.Results: Lactose, fructans and galacto-oligosaccharides have strong biologic plausibility for symptom generation due to lack of hydrolases resulting in distention from osmosis and rapid fermentation. However, excess fructose and polyols may only cause symptoms in specific individuals when consumed in high doses, but this remains to be established. There is evidence to suggest that certain patient characteristics such as ethnicity may predict response to lactose, but differentiation of other subgroups is difficult prior to dietary manipulation. Conclusions:While some clear mechanisms of action for symptom generation have been established, further research is needed to understand which patients will respond to specific FODMAP subgroup restriction. We suggest that clinicians consider in some patients a tailored, personalised "bottom-up" approach to the low-FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile and usual dietary intake.

Letter: the gluten‐free diet as a bottom‐up approach for irritable bowel syndrome

“…We read with interest the review article by Wang et al We agree with the authors that dietary restriction should have a more personalised approach, with the “bottom‐up” approach of the low fermentable oligo‐, di‐, mono‐ saccharides and polyols (FODMAP) diet for patients with irritable bowel syndrome (IBS) being a method to avoid patients being on unnecessarily prolonged restrictive diets, potentially avoiding disruption to the gut microbiota and nutritional composition …”

“…The authors mention fructan reduction as one of the potential strategies of a “bottom‐up” approach . Fructan reduction appears to be a key component of the long‐term maintenance phase of the low FODMAP diet, as demonstrated in a prospective study of 103 patients .…”

“…The authors highlight that the ‘bottom‐up’ approach has not been well studied . However, there have been several trials evaluating the ‘bottom‐up’ approach of the GFD in IBS, with a response rate between 34% to 71% being noted in the literature .…”

Letter: the gluten‐free diet as a bottom‐up approach for irritable bowel syndrome. Authors' reply

“…The authors' declarations of personal and financial interests are unchanged from those in the original article …”

“…We thank Rej et al for their discussion of our review and for highlighting a personalised approach to dietary therapies in functional gastrointestinal disorders (FGIDs) as well as the need to use the least restrictive approach under the guidance of a dietitian. We agree that further randomised controlled trials (RCTs) are needed to understand the efficacy and mechanisms of a gluten‐free diet in FGID.…”