Effects of a Low FODMAP Diet in Inflammatory Bowel Disease and Patient Experiences: A Mixed Methods Systematic Literature Review and Meta-Analysis

Abstract

Introduction: A low FODMAP diet reduces symptoms of irritable bowel syndrome (IBS), but its impact on inflammatory bowel disease (IBD) is less established. This systematic review aimed to: (1) assess the effect of a low FODMAP diet in IBD and (2) understand patient experiences when implementing the low FODMAP diet.

Methods: Four databases (Medline, Embase, CINAHL and CENTRAL) were systematically searched. RCTs evaluating a low FODMAP diet in IBD on disease activity, inflammatory markers, gastrointestinal symptoms, and quality of life (QoL), and qualitative studies reporting patient experiences of low FODMAP interventions (in either IBS or IBD), were included. Outcome data were meta-analysed as standardised mean differences or odds ratios. Qualitative data underwent content analysis using the Health Belief Model.

Results: Five RCTs (n = 224) and two qualitative studies (n = 30 IBS patients, no studies in IBD) were included. Compared with controls, there was no effect of a low FODMAP diet on disease activity (Crohn's disease: SMD -0.33; -0.77, 0.11; ulcerative colitis: SMD -0.31; -0.78, 0.15) or faecal calprotectin (SMD -0.20; -0.49, 0.09), but lower severity of global IBS symptoms (SMD -0.56; -0.90, 0.23) and higher QoL scores (SMD 0.43; 0.05, 0.81) at end of intervention. Patients with IBS described implementation as burdensome (Severity, Barriers), inadequate professional support (Susceptibility) and found it difficult to interpret information (Susceptibility, Barriers). Meal plans and recipes (Cue to action and Self-efficacy) gained through dietitian-led information sessions were valued (Benefits).

Conclusions: A low FODMAP diet does not impact IBD disease activity and inflammation markers, but leads to improved gastrointestinal symptoms compared with controls. The diet should be considered for improving functional gastrointestinal symptoms, but not an IBD treatment. There are minimal studies about patient experiences implementing the low FODMAP diet, all in IBS. Future research should assess patient experiences of low FODMAP diet implementation, specific to IBD.

Protocol registration: PROSPERO CRD42023480762, Open Science Framework.

Keywords: Crohn's disease; FODMAP; RCT; inflammatory bowel disease; irritable bowel syndrome; qualitative; ulcerative colitis.

Figure 1

Prisma flow chart. From Page et al. [25].

Figure 2

Forest plot for disease activity scores at the end of intervention.

Figure 3

Forest plot for inflammatory markers scores at the end of intervention.

Figure 4

Forest plot for global gastrointestinal symptoms severity score at the end of intervention.

Figure 5

Forest plot for improvement of individual symptom scores.

Figure 6

Forest plot for quality of life scores at the end of intervention.

Figure 7

Interrelated domains of the Health Belief Model [34]. Oversimplified information from general practitioners (GPs) and gastroenterologists (GEs) may increase perceived susceptibility to negative effects of a restrictive diet, creating barriers to low FODMAP diet implementation. Perceived severity related to the impact on the individual's household and social impacts when implementing a low FODMAP diet. External cues, such as information sessions and meal ideas, were found to enhance knowledge and self‐efficacy, aiding individuals in successfully adopting dietary changes.