Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) disorder with a global prevalence of about 11.2%. In recent times, non-pharmacological options, in particular dietary management, have grown in importance in management of IBS due to the poor performance of pharmalogical treatment options. Dietary treatment options include i) traditional dietary advice (TDA); ii) low fermentable oligosaccharide, dissacharide, monosaccharide and polyols (FODMAP) diet (LFD) and iii) a gluten-free diet (GFD). A range of studies assessing efficacy of a short-term LFD in patients with IBS showed an improvement in both symptoms and quality of life (QoL) in around 70% of patients. There is emerging data on the long-term efficacy of the LFD in IBS patients. However, in Asia, the low FODMAP diet is a relatively novel treatment approach and there is little data on the short-term efficacy of LFD and no data on the reintroduction of FODMAPs. Due to the wide variation in diets worldwide, as well as within Asia, it is important to study the role of this dietary treatment option in this population group. This study aimed to assess the efficacy and acceptability of a short-term strict LFD and long-term ‘modified’ FODMAP diet in patients with diarrhoea-predominant IBS (IBS-D).
This prospective, randomised, single-blind trial was undertaken in northern India between 2019 and 2020. Study participants were aged between 18-65 years of age with a diagnosis of IBS-D and moderate to severe disease (IBS symptom severity score (SSS) ≥ 175). Exclusion criteria included any other IBS subtypes, other GI disease, alarm symptoms, patients already on a restricted diet, consumption of bowel preparation/antibiotics/probiotics or change in IBS medication in the 4 weeks prior to the study and significant comorbidities or addictions.
Patients were randomised to a strict LFD (n=52) or TDA (n=49) groups in phase I (4 weeks) under dietetic guidance. Diet history as well as IBS-SSS and IBS-QoL questionnaires and the Bristol Stool Form Chart were administered at baseline. Comprehensive written information on the dietary approach was provided along with a food and stool diary. Telephone dietetic input between days 10-14 was given to resolve any issues. At the start of phase 2 (4 weeks), IBS-SSS and IBS-QoL questionnaires were repeated and dietary compliance was assessed with patients who had >50% compliance of the time able to progress to phase II. Regular dietetic support was provided during this phase and the intake of FODMAPs and macronutrients was calculated at baseline, 4 and 16 weeks. Study questionnaires and food and stool diaries were collected at the end of the study period (16 weeks).
The primary outcome was the change in IBS-SSS at 4 weeks and proportion of responders (based on the recommended cut off of reduction in IBS-SSS ≥50). In addition, ‘adequate symptom relief’ at 4 weeks was a primary outcome. Secondary outcomes included change in IBS-SSS and proportion of responders at 16 weeks, improvement in QoL and change in individual GI symptoms at 4 and 16 weeks.
94 patients completed phase 1 with the majority being always or frequently compliant with the dietary treatment. As a result, 87 patients (LFD=43 and TDA=44), who completed phase 1 with >50% compliance, entered into phase II. At 4 weeks, IBS-SSS significantly reduced in both groups compared with baseline, however, mean IBS-SSS in the LFD group was significantly lower than the TDA group. The proportion of responders in the LFD group was significantly higher than the TDA group. This was also seen at 16 weeks. In terms of secondary outcomes, IBS-SSS sub-scores for frequency of abdominal pain, severity of abdominal distention and dissatisfaction with bowel habits showed significantly greater reduction in the LFD group compare with the TDA group, both at 4 and 16 weeks. Stool form and consistency showed improvement only in the LFD group whilst the IBS-QoL was significantly higher in the LFD group than the TDA group. Whilst the macroutrient intake all reduced in the LFD group at 4 weeks, this gradually improved at 16 weeks. At the end of the study period (16 weeks), the total number of patients still taking >50% of baseline medications was significantly lower in LFD group (60.8%) compared with TDA group (81.6%), however, 7 patients in the LFD group and 4 in the TDA group needed an addition to or increase in their medication.
This study shows that dietitian-delivered LFD advice in patients with IBS-D significantly improves symptoms and QoL compared with TDA. Implementing both a short-term ‘strict’ low FODMAP diet and a long-term ‘modified’ FODMAP diet was found to be feasible and acceptable. With adequate guidance and support, nutritional adequacy and compliance can be achieved.