Abstract and Introduction
Background: Irritable bowel syndrome (IBS) is a heterogeneous disorder of gut-brain interaction (DGBI) maintained by interacting biological, psychological, and social processes. Interestingly, there are two contrasting yet evidence-based treatment approaches for reducing IBS symptoms: exclusion diets such as those low in fermentable oligo-, di-, monosaccharides and polyols (FODMAPs) and exposure-based cognitive-behavioural therapy (CBT). Exclusion diets recommend patients avoid foods thought to be symptom-inducing, whereas exposure-based CBT encourages patients to expose themselves to foods.
Aims: To address the paradox of conceptually opposite exclusion diets and exposure-based CBT for IBS.
Methods: In this conceptual review, we describe the rationale, practical implementation, evidence base and strengths and weaknesses of each treatment. We conducted up-to-date literature search concerning the low FODMAP diet and CBT, and performed a secondary analysis of a previously conducted trial to illustrate a key point in our review.
Results: The low FODMAP diet has demonstrated efficacy, but problems with adherence, nutritional compromise, and heightened gastrointestinal-specific anxiety raise caution. Exposure-based CBT has demonstrated efficacy with substantial evidence for gastrointestinal-specific anxiety as a key mechanism of action. Mediation analysis also showed that increased FODMAP intake mediated decreased symptom severity in exposure-based CBT. However, there is minimal evidence supporting which treatment "works best for whom" and how these approaches could be best integrated.
Conclusions: Even though exclusion diets and exposure-based CBT are conceptually opposite, they each have proven efficacy. Clinicians should familiarise themselves with both treatments. Further research is needed on predictors, mechanisms and moderators of treatment outcomes.
Irritable bowel syndrome (IBS) is a prevalent disorder of gut-brain interaction, formerly called functional gastrointestinal disorders, defined by recurrent abdominal pain associated with defaecation or change in bowel habits. Its aetiology and pathophysiology remain incompletely understood, but there is consensus that IBS symptoms result from complex interactions between biological, psychological and social processes, for which the microbiota-gut-brain axis constitutes the mechanistic basis. Mechanisms shown to be involved in IBS are manifold, including but not limited to altered microbiota composition and function, low-grade inflammation, nutrient intolerances, visceral hypersensitivity, altered motility and dysfunction of the neural and neuroendocrine stress response systems. In addition, psychological processes including (symptom-specific) anxiety and heightened attention towards gastrointestinal sensations (i.e. hypervigilance) and social events (i.e. observational learning) may influence these biological processes. IBS is a heterogeneous condition, and the relative contribution of different pathophysiological mechanisms may vary widely between patients. In other words, different mechanisms along the microbiota-gut-brain axis may result in very similar phenotypical presentations at the symptom level.
This pathophysiological heterogeneity renders IBS treatment difficult. Various treatments including pre-, pro-, and antibiotics, neuromodulators, exclusion diets and brain-gut behavioural therapies[5,7] all have proven some effectiveness, but the numbers needed to treat are relatively high (ranging from 3 to 9), indicating that a substantial number of patients do not benefit from these treatments. Curiously, two conceptually opposite treatments are both efficacious in IBS (Table 1). On the one hand, exclusion diets recommend that patients avoid foods that are thought to be symptom-inducing. On the other hand, exposure-based cognitive behavioural therapy (CBT) encourages patients to expose themselves to these foods with the aim of improving gastrointestinal symptom severity via a reduction in gastrointestinal-specific fear and anxiety. In this perspective paper, we analyse this paradox and its implications for the status of IBS as a disorder and its treatment. Before doing so, we first discuss both treatments in detail.
Aliment Pharmacol Ther. 2022;56(4):592-605. © 2022 Blackwell Publishing