Efficacy and Acceptability of Dietary Therapies in Non-Constipated Irritable Bowel Syndrome: A Randomized Trial of Traditional Dietary Advice, the Low FODMAP Diet, and the Gluten-Free Diet.

None

• TDA, LFD and GFD can all lead to significant improvements in non-constipation IBS with no statistically significant difference in effectiveness between the diets.
• Most patients find a TDA easier and cheaper to implement than a LFD or GFD.
• TDA is therefore recommended as a first line approach in non-constipation IBS.

Introduction

The aim of this study was to compare the effectiveness and patient acceptability of traditional dietary advice (TDA) vs a low FODMAP diet (LFD) vs a gluten-free diet (GFD, cross-contamination allowed) in patients with non-constipation irritable bowel syndrome (IBS).

TDA definition: healthy, sensible eating pattern, including regular meals, not eating too little/too much, adequate hydration, and reducing the intake of: alcohol/caffeine/fizzydrinks/fatty/spicy/ processed foods; fresh fruit (maximum of 3 per day); fibre/gas-producing foods and perceived food intolerances.

Methods

This was a randomised dietary trial over 4 weeks. Dietary advice was provided by a specialist dietitian in a session lasting 45-60 minutes. 99 patients completed the study (33 in each group). Stool analysis was performed in “around half“ (study authors terminology) of participants due to disruption of trial caused by COVID-19.

Results:

• Primary endpoint (reduction of 50 points or more on IBS symptom severity score) was met by 42% of patients on the TDA, 55% on LFD and 58% on GFD. The differences between groups were not statistically significant, p=0.43.
• Patients on the LFD had greater improvements in mood compared to the other diets under examination, reaching statistical significance (p=0.03) for Hospital Anxiety and Depression scale and (p<0.01) for dysphoria score on IBS-QOL scale.
• Patients on TDA found their diet cheaper (p<0.01), less time consuming to shop (p<0.01) and easier to follow when eating out with family and friends (p=0.03), whilst TDA and GFD were considered easier to incorporate into daily diet than LFD (p=0.02).
• No significant differences were found between groups in changes to macro- and micronutrient composition, except a trend to lower fibre intake with LFD (p=0.06).
• There was a significant reduction in intake of FODMAPs in all groups, with greatest reduction in LFD (27.7 to 7.6 g/day, p<0.01), followed by TDA (24.9 to 15.2 g/day, p<0.01) and GFD (27.4 to 22.4 g/day, p=0.03). Differences between groups were statistically significant (p<0.01).
• No differences were noted in change to the dysbiosis index between groups.
• Neither clinical characteristics nor dysbiosis index predicted response to any of the diets.

Conclusion

• TDA, LFD and GFD are all effective approaches for non-constipation IBS.
• TDA should be first-line dietary advice due to being the most patient-friendly.

• When working with clients with non-constipation IBS, a TDA approach may be favoured over LFD and GFD as a first line intervention if the patient has not already tried a TDA diet.
• Patient preferences, budget, time and living situation should be taken into account when deciding on best dietary advice for IBS.

• As all 3 approaches led to reduction in FODMAPs, trials comparing different levels of FODMAP exclusion could lead to valuable information, as a strict FODMAP exclusion, which is commonly recommended in IBS, is difficult and may not be necessary.
• Studies of longer duration would be valuable to confirm that benefits observed with the 3 approaches are not short-term only.
• Comparing individual approaches to appropriate control group would ensure that improvements are not due to a placebo effect.