Low FODMAP diet reduces gastrointestinal symptoms in irritable bowel syndrome and clinical response could be predicted by symptom severity: A randomized crossover trial.

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A low (4 g/day) FODMAP diet could provide clinical benefits in the context of an acute strategy for IBS clients with frequent loose stools (IBS-Diarrhoea and/or IBS-Mixed) compared to those with hard and less frequent stools (IBS-Constipation) to improve the severity of GI symptoms, including lower abdominal pain intensity and frequency, bowel habits, daily life interference, and psychological distress.

Introduction

The aim of this paper was to investigate the effects of diets with low vs. moderate FODMAP content on gastrointestinal (GI) symptoms and bowel habits, and to identify possible predictors of clinical response to a low FODMAP diet and FODMAP sensitivity in Irritable Bowel Syndrome (IBS).

Methods

• This study involved a double-blind, randomised, controlled, crossover trial of 29 participants (18-75 years), mostly female, diagnosed with IBS (Rome IV)
• The primary outcome was to assess the effects of a low (4 g/day) vs. moderate (23 g/day) FODMAP diet on GI symptoms over a 7-day period
• Secondary outcomes involved assessing the effects of low vs. moderate FODMAP diets on i) somatic symptoms, ii) psychological distress, iii) predictors of clinical and IBS-Severity Scoring System (IBS-SSS) sensitivity to FODMAP
• Breakfast was standardised, with prescribed low FODMAP list deviations recorded
• Main dishes and snacks were also provided
• Participants were requested to limit alcohol, caffeine, fatty- and spicy foods, ate regularly, chewed thoroughly and drank enough water
• GI symptoms and bowel habits were recorded during the 7-day screening period, then participants undertook a Lactulose Nutrient Challenge Test (LNCT)
• The first 7-day diet started one day after the LNCT
• A 14-day wash-out period allowed participants to eat and drink as usual, thereafter following the second 7-day diet period as part of the cross over design.

Results

A low FODMAP intervention (compared to a moderate FODMAP diet); resulted in:

• Reduced overall IBS rating (10 ± 72 vs. 57 ± 108, P=0.04)
• Improved abdominal pain frequency (10 ± 32 vs. 18 ± 29 (P=0.02)
• Improved stool consistency (0.2 ± 1.0 vs. 0.6 ± 1.2, P= 0.01) and frequency (0.1 ± 0.7 vs. 0.4 ± 0.7, P= 0.01)
• Overall, 34% of participants positively responded to the low FODMAP diet, which could be predicted based on higher baseline IBS-SSS scores (P=0.02)
• Participants sensitive to FODMAPs had increased pre- and postprandial ratings of gas, abdominal pain and bloating and higher exhaled methane concentrations compared to non-sensitive participants to FODMAPs
• Authors highlighted a non-significant association between FODMAP sensitivity and GI symptoms during the LNCT, with higher visceral hypersensitivity (45 ± 20, P=0.73) after ingestion of poorly absorbed and fermentable carbohydrates, with no independent predictors identified.

Conclusions This study showed that a diet low in FODMAPs reduces GI symptoms and positively impacts bowel habits in IBS, compared with a moderate FODMAP diet.

• While this was a short term study, a low FODMAP diet reduced GI symptoms and affected bowel habits (more firm and less frequent stools) in IBS, compared with a diet containing moderate amounts of FODMAPs
• Knowing the above, an assessment of overall IBS severity and predominant bowel habits before the intervention may be helpful for clinicians working with younger females in their IBS management before considering a trial period with the low FOD-MAP diet as a treatment option.

• Future trials could target a larger sample size with a more representative population, as well as assessing low FODMAP interventions over longer timeframes
• . Additionally, the assessment of biological measures such as microbiota diversity and stability, as well as metabolites (such as short chain fatty acids) could be important to understand mechanistic attributes of low FODMAP diets in IBS.