Effects of a gluten challenge in patients with irritable bowel syndrome: a randomized single-blind controlled clinical trial.

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• The results of this study suggest that a strict gluten-free, low FODMAP diet could be used in Individuals with IBS for anxiety reduction and improvement in quality of life.
• However, only a small number of participants were included and followed for a short duration.
• IBS is a complex disorder the cause of which is largely unknown. It requires a multidisciplinary approach in its treatment.

Irritable bowel syndrome (IBS), a functional disorder of the lower gastrointestinal tract, is characterized by various somatic and psychological manifestations. Evidence suggests IBS and non-celiac gluten sensitivity (NCGS) overlap. The development of IBS is thought to be multifactorial. Low-grade inflammation and food intolerances including to gluten and fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP), may play a role. Gluten tolerance is a major dilemma in medical practice.

The aim of this randomized controlled trial is to evaluate tolerance to gluten, anxiety and quality of life in irritable bowel syndrome (IBS). Prevalence of non-celiac gluten sensitivity (NCGS) was also reported. This trial was conducted in Tehran, Iran, in adults aged 18-80 years and with symptoms of IBS according to the ROME-IV criteria.

In informing their research question, the authors reference evidence of the efficacy of a gluten-free diet (GFD) and a low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet on IBS symptoms.

One hundred and seven subjects were enrolled into phase I of the study, when a strict low-FODMAP and GFD was introduced for six weeks. Seventy subjects completed phase 1, of which twenty subjects declined to continue, leaving fifty subjects. These fifty subjects were enrolled into phase 2 and randomized into three groups (i) an unrestricted gluten diet (n=10), (ii) continuation of the low-FODMAP/GFD (n=15), and (iii) a gluten challenge group (n=25), for a further six weeks.

Reductions in bloating (3.5±2.6 to 2.5±2.1, p=0.03) and pain severity (2.9±2.8 to 2±2.2, p=0.02) were observed in the GFD, and a reduction in total VAS score (45.6±15.9 to 27.8±12.8, p=0.05) in the high-gluten group. The satiety score increased (2.3±1 to 3.8±3.1, p=0.04) in the unrestricted gluten diet group. At the end of the study, differences for pain frequency, pain severity and impact on community function were observed between the groups.

In this study, a low-FODMAP strict GFD was shown to reduce anxiety and improve the quality of life.

• In the gluten challenge phase of the study, between-group analysis revealed significant differences for pain and impact on community function No significant differences were found for bloating, satiety, defecation, total score, anxiety scores or quality of life between the groups. These mixed results, also found in other studies, add weight to the fact that the cause of IBS is unclear. The authors hypothesize that there may be an IBS subtype or new medical term, categorized as gluten sensitivity-IBS.
• Symptoms were evaluated but not objective outcomes, for example blood biomarkers. No aggravation of symptoms was observed in this study following the gluten challenge. Other non-gluten components of food may be responsible for IBS symptoms. Recent evidence suggests that fructans may be responsible in individuals with IBS and a low-FODMAP diet may be beneficial.
• Biopsychological factors are important to consider in the duration and severity of IBS symptoms.
• A strict GFD can come with problems, as mentioned, nutritional deficiencies, difficulty finding GF foods, high cost, altered taste, impacts on social/quality of life.
• Results were mixed, however suggest a low-FODMAP strict GFD could be a therapeutic choice for the management of IBS particularly in reducing anxiety and improving quality of life.

• Randomized controlled trials with greater numbers of participants and longer durations assessing the impact of a low-FODMAP strict GFD in IBS, are warranted.
• Including food sensitivity/intolerance testing may be useful to distinguish which individuals might benefit from a GFD alone, a low-FODMAP diet alone or a low-FODMAP GFD.
• Small intestinal bacterial overgrowth (SIBO) testing would be of interest to understand who might benefit from a low-FODMAP diet.
• Studies assessing baseline stress levels and stress management interventions in combination with dietary interventions such as low-FODMAP GFD could be important avenues of research.