Even though irritable bowel syndrome (IBS) has been known for more than 150 years, it still remains one of the research challenges of the 21st century. According to the current diagnostic Rome IV criteria, IBS is characterized by abdominal pain associated with defecation and/or a change in bowel habit, in the absence of detectable organic causes. Symptoms interfere with the daily life of patients, reduce health-related quality of life and lower the work productivity. Despite the high prevalence of approximately 10%, its pathophysiology is only partly understood and seems multifactorial. However, many patients report symptoms to be meal-related and certain ingested foods may generate an exaggerated gastrointestinal response. Patients tend to avoid and even exclude certain food products to relieve their symptoms, which could affect nutritional quality. We performed a narrative paper review of the existing and emerging evidence regarding dietary management of IBS patients, with the aim to enhance our understanding of how to move towards an individualized dietary approach for IBS patients in the near future.

Fermentable oligo-, di-, monosaccharides and polyols (FODMAPs) can provoke symptoms in patients with irritable bowel syndrome (IBS). We aimed to compare 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 IBS. Adult participants with IBS (Rome IV criteria, n = 29) were included and adhered to two 7-day diet periods, with either low (4 g/day) or moderate (23 g/day) amounts of FODMAPs, in this randomized, double-blind, crossover study. The periods were separated by a wash-out period (≥14 days). IBS-Severity Scoring System (IBS-SSS) and a stool diary (Bristol Stool Form) were completed before and after the diet periods. At baseline, severity of GI symptoms and gut microbial fermentation were assessed (every 15 min, 4 h) during the Lactulose Nutrient Challenge Test (LNCT). Clinical response and FODMAP sensitivity were defined by reduction after low FODMAP period, and increase after moderate FODMAP period in IBS-SSS (≥50 points), respectively. Severity of GI symptoms (P = 0.04), stool consistency (P = 0.01), and stool frequency (P = 0.01) differed between the interventions, with reduced overall GI symptom severity, abdominal pain intensity and frequency, bowel habits dissatisfaction, and daily life interference (P < 0.05 for all), as well as more firm (P = 0.03) and less frequent (P < 0.01) stools after low FODMAP intervention, but not after moderate FODMAP intervention. A third (34%) responded clinically to the low FODMAP diet, and the response could be predicted by higher IBS-SSS at baseline (P = 0.02). Although modest associations between FODMAP sensitivity (22%) and GI symptoms during LNCT were observed, no independent predictors could be identified. A diet low in FODMAPs reduces GI symptoms and affects bowel habits in IBS, compared with a moderate FODMAP diet. Assessment of IBS severity before the intervention may be used to predict clinical response to a low FODMAP diet. Trial registry (http://www. gov): Registered under Clinical Trial number NCT05182593.

INTRODUCTION: This study focused on defining the global prevalence of clinically relevant levels of psychological distress and somatic symptoms and the prevalence of coexistence between these symptoms and disorders of gut-brain interaction (DGBI). We also analyzed how clinically relevant psychological distress and somatic symptoms and coexistent DGBI are associated with health-related outcomes. METHODS: We included a representative sample of 54,127 adult participants (49.1% women; mean age of 44.3 years) from 26 countries worldwide. Participants completed an Internet survey (the Rome Foundation Global Epidemiology Study) with validated self-report questionnaires. RESULTS: Clinically relevant psychological distress and/or somatic symptom severity was reported by 37.5% of the sample. These participants had 4.45 times higher odds to have at least one DGBI than individuals without psychological distress and/or somatic symptoms. Compared with participants with psychological distress and/or somatic symptoms with vs without DGBI, participants with a DGBI reported increased healthcare and medication utilization (with OR from 1.6 to 2.8). Coexistent DGBI in participants with psychological distress and/or somatic symptoms was the variable most strongly associated with reduced mental (β = −0.77; confidence interval [−0.86 to −0.68]) and physical (β = −1.17; confidence interval [−1.24 to −1.10]) quality of life. DISCUSSION: This global study shows that psychological distress, somatic symptoms, and DGBI are very common and frequently overlap. The coexistence between psychological distress/somatic symptoms and DGBI seems to be especially detrimental to quality of life and healthcare utilization. Individuals with psychological distress/somatic symptoms and DGBI coexistence seem to be a group vulnerable to psychosocial problems that should be studied further and would likely benefit from psychological/psychiatric interventions.

Summary: Background: A gluten‐free diet reduces symptoms in some patients with irritable bowel syndrome (IBS) through unclear mechanisms.Aims: To assess the effects of gluten‐free versus gluten‐containing diet on symptoms and the gut microenvironment, and to identify predictors of response to the gluten‐free diet in IBSMethods: Twenty patients with IBS and 18 healthy controls (HC) followed a gluten‐free diet during two 14‐day intervention periods where they sprinkled either gluten (14 g/day) or rice flour powder over their meals. Primary outcomes included effects of the interventions on IBS symptoms (IBS‐SSS) and bowel habits. Secondary outcomes included effects of gluten‐free diet on faecal microbiota and metabolite profile.Results: IBS symptoms improved during the gluten‐free (p = 0.02), but not the gluten‐containing period, with no difference between the interventions. IBS patients reported fewer loose stools during the gluten‐free intervention (p = 0.01). Patients with IBS and HC presented distinct metabolite profiles based on the effects of the gluten‐free diet (p < 0.001). True responders (reduced IBS‐SSS by ≥50 solely after gluten‐free period) and non‐responders were discriminated based on the effects of the gluten‐free diet on the microbiota (p < 0.01) and metabolite profiles (p < 0.001). The response to the gluten‐free diet could be predicted by the metabolite profile before the intervention (p < 0.001).Conclusions: A gluten‐free diet may influence symptoms in a subset of patients with IBS, with a particular effect on bowel habits. A gluten‐free diet seems to impact the gut microenvironment. Responsiveness to the gluten‐free diet may be predicted by the metabolite profile. Clinicaltrials.gov: NCT03869359.

Wheat contains several components, including gluten and fructan, that may be associated with gastrointestinal symptoms (GI) in irritable bowel syndrome (IBS). The aims of the study were to determine the average daily intake of gluten, investigate the association of gluten and GI symptoms, as well as the association between fructan and GI symptoms in IBS subjects. We assessed dietary intake, including total energy, and calculated average gluten and fructan intake in this 4-day food diary study. The subjects reported GI symptoms using the validated Gastrointestinal Symptom Rating Scale-IBS (GSRS-IBS). In total, 147 IBS subjects (116 females) were included in this study. The median (IQR) intake of gluten was 11.0 (7.5-15.4) (range: 0.6-52.1) g/day, and this intake was significantly higher for males (16.2 (11.5-18.8), g/day) compared with females (10.3 (7.3-13.2), g/day) (P ≤ 0.001). For analyses purposes, the subjects were stratified in tertiles of gluten intake. Median (IQR) overall GI symptom severity (GSRS-IBS) was significantly worse for the subjects with the lowest (52 (45-57)) and intermediate gluten intake (51 (43-58)), compared with the highest gluten intake (45 (37-50), P ≤ 0.05, and P ≤ 0.01 respectively). In addition, caloric intake was significantly lower in subjects with the lowest (1905 ± 446, kcal/day) and intermediate gluten intake (1854 ± 432, kcal/day), compared with subjects with the highest gluten intake (2305 ± 411, kcal/day), P < 0.001 for both. Analyses of the stratified fructan tertiles resulted in no significant differences in GSRS-IBS. The mean intake of gluten varies substantially among subjects with IBS, and IBS subjects with more severe GI symptoms have lower intake of gluten and calories. (http://www.clinicaltrials.gov): Registered under Clinical Trial number NCT02970591.

Background: Abnormal oroanal transit time (OATT) and visceral hypersensitivity are key pathophysiological factors in irritable bowel syndrome (IBS). The lactulose nutrient challenge test (LNCT) has been developed to assess the postprandial symptoms and gut microbial fermentation. We aimed to investigate associations between OATT, rectal sensitivity, and LNCT in IBS patients.Methods: We included 263 IBS patients from two study cohorts, where the link between pathophysiology and symptoms was investigated. During the LNCT, severity of postprandial symptoms was graded, and breath hydrogen/methane concentrations were measured after ingestion of a combined lactulose nutrient drink every 15 min for 4 h. The patients underwent rectal sensitivity (rectal barostat) and OATT (radiopaque markers) investigations. Comorbid conditions (functional dyspepsia, anxiety, depression, and somatization) were assessed with questionnaires.Key Results: After controlling for comorbid conditions, rectal sensitivity was associated with abdominal pain (p < 0.05), and more rapid OATT was associated with higher severity of abdominal discomfort, rumbling, nausea, and urgency (p < 0.05 for all) both pre‐ and post‐prandially. Postprandial nausea, urgency, and abdominal pain changed differently over time depending on OATT (p < 0.05 for all). OATT, but not rectal sensitivity, was associated with hydrogen and methane concentrations (p = 0.002 for both). Trajectories over time of postprandial symptoms and exhaled hydrogen/methane concentrations were correlated with different correlations depending on OATT.Conclusion and Inferences: This study highlights the importance of oroanal transit and hydrogen and methane production in the pathophysiology of IBS and increases our understanding of pathophysiological factors involved in postprandial symptom generation. Treatments targeting oroanal transit and hydrogen and methane production may improve specific postprandial symptoms.