Irritable bowel syndrome (IBS) is a common gut-brain interaction disorder. The etiology of IBS is not entirely elucidated, however, among the risk factors, dietary factors are regarded as crucial. Previous studies have primarily investigated the association of single nutrients and food groups with odds of IBS, rather than diet quality, which considers the interaction of food groups in odds of disease. Thus, the current study sought to investigate the association of dietary quality index-international (DQI-I) and odds of IBS in Iranian adults. In this case-control study, dietary intakes of 100 IBS cases and 310 healthy controls were examined using a validated Dish-based Semi-quantitative Food Frequency Questionnaire (DS-FFQ). DQI-I score was then calculated based and categorized into tertiles. The Persian version of the Rome IV questionnaire was utilized to assess IBS. Multivariable logistic regression was used to assess the association of DQI-I score and the odds of IBS. After controlling for potential confounders, no significant association was shown between DQI-I scores and IBS odds among whole and gender-stratified groups. Although DQI-I represents a healthy diet, the results of the current case-control study demonstrated that, a higher DQI-I score was not associated with reduced odds of IBS in fully adjusted regression models. Considering inherent limitations as well as the scarce evidence regarding the association between DQI-I and odds of IBS, further large-scale, prospective studies are required to confirm our findings.

Evidence of an association between metabolic syndrome (MetS) and irritable bowel syndrome (IBS) is emerging but is still inconclusive. The current cross-sectional study was conducted to explore the relationship between the two syndromes in a sample of Lebanese adults (n 221; mean age: 43·36 years; 62·9 % females), recruited from a large urban university and its neighbouring community. MetS was diagnosed based on the International Diabetes Federation criteria, and IBS was assessed using the Birmingham IBS scale. Logistic regression analyses were performed taking MetS and its components as dependent variables and IBS and its subscales as independent variables. Covariates included socio-demographic, dietary and lifestyle variables. MetS was positively associated with visual analogue scale (VAS) IBS (total scale (Beta = 4·59, P = 0·029) and VAS–diarrhoea subscale (Beta = 4·96, P = 0·008). Elevated blood pressure (Beta = 5·02, P = 0·007), elevated fasting blood sugar (Beta = 4·19, P = 0·033) and elevated waist circumference (Beta = 5·38, P = 0·010) were positively associated with VAS–Diarrhoea subscale. MetS and IBS were found to be positively associated in a sample of the Lebanese adult population. We suggest that it might be of value to screen for either condition if one of the syndromes exists. Future longitudinal studies are essential to establish a causal relationship between the two syndromes to further understand the commonality related to pathogenesis and explore potential underlying mechanisms.

High intake of dietary advanced glycation end products (AGE) could induce oxidative stress, inflammation and the gut microbiota dysbiosis processes that play a major role in the development of functional gastrointestinal disorders (FGID). There is limited data on the association between AGE intake and FGID. Therefore, this study aimed to examine the association of AGE with FGID in Iranian adults. In a cross-sectional analysis under the framework of the Isfahan functional disorders study, data on 1892 Iranian healthy adults aged 18–65 years were examined. Participants’ dietary intakes were collected using a validated dish-based, 106-item FFQ. Dietary AGE content of seventy-two food items was measured for all participants. FGID were assessed using Rome IV criteria. In total, 38 % of subjects had one of the most prevalent upper or lower FGID. The mean of AGE intake was 14690·10 (sd 8797·25) (kU/gr). In the fully adjusted model, being in the highest v. lowest tertile of AGE intake was associated with increased odds of FGID (OR = 1·78; 95 % CI: 1·01, 3·36). In stratified analysis by sex, males in the highest tertile of AGE intake showed higher odds of FGID than those in the lowest tertile (OR = 2·15; 95 % CI: 1·04, 4·45). However, in females, the AGE intake was not significantly associated with the risk of FGID in the fully adjusted model. Higher AGE intake was significantly associated with an increased risk of FGID, particularly in men. Further prospective studies are warranted to confirm these findings.

The low fermentable oligosaccharide, disaccharide, monosaccharide and polyol (FODMAP) diet is recommended as a first line therapeutic management strategy for irritable bowel syndrome (IBS)(1). The low FODMAP diet is supported by meta-analytical evidence(2), and demonstrates acceptability and effectiveness for improving symptoms and quality of life (QoL) in 50-75% of individuals with IBS. However, a subset of individuals (25-50%) do not respond to the diet(3). The identification of individual-level predictors of treatment response across all three phases of the low FODMAP diet is currently lacking. The study aims were to assess psychological predictors of symptom and QoL response to the low FODMAP diet in patients with IBS. Adults with IBS underwent a three-phase low FODMAP diet, guided by individualised dietetic education. Predictor variables included levels of depressive, anxiety, and extraintestinal somatic symptoms, stress, treatment beliefs and expectations, behavioural avoidance, and illness perceptions. Symptom severity and QoL were the main outcomes. Questionnaires assessing psychological predictors, symptoms and QoL were administered at five points: pre-dietitian (week 0), post-dietitian, end of elimination (week 5), end of reintroduction (week 13), and end of personalisation (week 25) phases. Latent class growth analysis was used to identify classes of response trajectories for symptoms. Linear mixed models were used to test the effect of baseline psychological scores on symptoms and QoL over time. Cross lagged panel models determined the directional predictive relationship between psychological predictors and symptom severity. 112 participants (89% F) median age 30 ± 17 years were included. There were three classes of symptom response trajectories, including ‘non-improvers’ (21.3% of participants) with high initial symptom severity and minimal improvement, ‘improvers’ (22.5% of participants) with low initial symptom severity and significant improvement, and an ‘intermediate’ group (56.2% of participants) with moderate initial symptom severity and significant improvement. Higher treatment beliefs predicted a stronger initial symptom response (effect on linear slope p = 0.036). Lower gut-specific anxiety, as well as higher levels of personal and treatment control at baseline predicted a stronger reduction in IBS symptom severity and improved QoL from week 0 to week 25. Participants with higher levels of baseline psychological symptoms and negative illness perceptions (i.e., lower emotional representations) predicted a stronger initial and later QoL response (effect on linear (p = 0.006) and quadratic (p = 0.049) slopes). Increased cyclical time beliefs predicted poorer initial and later QoL response (effect on linear (p = 0.015) and quadratic (p = 0.029) slopes). Individuals experiencing lower to mid-range symptom severity at baseline had greater improvement with the low FODMAP diet. Lower anxiety, positive illness views and higher treatment beliefs predict better QoL and symptom response. Personalised strategies are crucial for optimising low FODMAP diet effectiveness in IBS.

A diet low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) improves functional bowel symptoms and is a second-line dietary management strategy for the treatment of irritable bowel syndrome (IBS). The diet is complex and involves three stages: restriction, reintroduction and personalisation and clinical effectiveness is achieved with dietitian-led education; however, this is not always available. The aim of this review is to provide an update on the evidence for using the low FODMAP diet, with a focus on the impact of FODMAP restriction and reintroduction considering long-term management of IBS in a clinical setting. Randomised controlled trials have assessed symptom response, quality of life, dietary intake and changes to the gut microbiota during FODMAP restriction. Systematic reviews and meta-analyses consistently report that FODMAP restriction has a better symptom response compared with control diets and a network analysis reports the low FODMAP diet is superior to other dietary treatments for IBS. Research focused on FODMAP reintroduction and personalisation is limited and of lower quality, however common dietary triggers include wheat, onion, garlic, pulses and milk. Dietitian-led delivery of the low FODMAP diet is not always available and alternative education delivery methods, e.g. webinars, apps and leaflets, are available but remove the personalised approach and may be less acceptable to patients and may introduce safety concerns in terms of nutritional adequacy. Predicting response to the low FODMAP diet using symptom severity or a biomarker is of great interest. More evidence on less restrictive approaches and non-dietitian-led education delivery methods are needed.

Individuals with coeliac disease (CeD) often experience gastrointestinal symptoms despite adherence to a gluten-free diet (GFD). While we recently showed that a diet low in fermentable oligo-, di-, monosaccharides and polyols (FODMAP) successfully provided symptom relief in GFD-treated CeD patients, there have been concerns that the low FODMAP diet (LFD) could adversely affect the gut microbiota. Our main objective was therefore to investigate whether the LFD affects the faecal microbiota and related variables of gut health. In a randomised controlled trial GFD-treated CeD adults, having persistent gastrointestinal symptoms, were randomised to either consume a combined LFD and GFD (n 39) for 4 weeks or continue with GFD (controls, n 36). Compared with the control group, the LFD group displayed greater changes in the overall faecal microbiota profile (16S rRNA gene sequencing) from baseline to follow-up (within-subject β-diversity, P < 0·001), characterised by lower and higher follow-up abundances (%) of genus Anaerostipes (Pgroup < 0·001) and class Erysipelotrichia (Pgroup = 0·02), respectively. Compared with the control group, the LFD led to lower follow-up concentrations of faecal propionic and valeric acid (GC-FID) in participants with high concentrations at baseline (Pinteraction ≤ 0·009). No differences were found in faecal bacterial α-diversity (Pgroup ≥ 0·20) or in faecal neutrophil gelatinase-associated lipocalin (ELISA), a biomarker of gut integrity and inflammation (Pgroup = 0·74), between the groups at follow-up. The modest effects of the LFD on the gut microbiota and related variables in the CeD patients of the present study are encouraging given the beneficial effects of the LFD strategy to treat functional GI symptoms (Registered at clinicaltrials.gov as NCT03678935).

The study aimed to assess the total prevalence of functional gastrointestinal disorders (FGID), and separately, irritable bowel syndrome (IBS) among adults and to determine their potential association with fructose consumption. Data from the Hellenic National Nutrition and Health Survey were included (3798 adults; 58·9 % females). Information regarding FGID symptomatology was assessed using self-reported physician diagnosis questionnaires the reliability of which were screened using the ROME III, in a sample of the population. Fructose intake was estimated from 24 h recalls, and the MedDiet score was used to assess adherence to the Mediterranean diet. The prevalence of FGID symptomatology was 20·2 %, while 8·2 % had IBS (representing 40·2 % of total FGID). The likelihood of FGID was 28 % higher (95 %CI: 1·03–1·6) and of IBS 49 % (95 %CI: 1·08–2·05) in individuals with higher fructose intake than with lower intake (3rd tertile compared with 1st). When area of residence was accounted for, individuals residing in the Greek islands had a significantly lower probability of FGID and IBS compared with those residing in Mainland and the main Metropolitan areas, with Islanders also achieving a higher MedDiet score and lower added sugar intake, comparatively to inhabitants of the main metropolitan areas. FGID and IBS symptomatology was most prominent among individuals with higher fructose consumption, and this was most conspicuous in areas with a lower Mediterranean diet adherence, suggesting that the dietary source of fructose rather than total fructose should be examined in relation to FGID.

The 10th International Yakult Symposium was held in Milan, Italy, on 13–14 October 2022. Two keynote lectures covered the crewed journey to space and its implications for the human microbiome, and how current regulatory systems can be adapted and updated to ensure the safety of microorganisms used as probiotics or food processing ingredients. The remaining lectures were split into sections entitled “Chances” and “Challenges.” The “Chances” section explored opportunities for the science of probiotics and fermented foods to contribute to diverse areas of health such as irritable bowel syndrome, major depression, Parkinson’s disease, immune dysfunction, infant colic, intensive care, respiratory infections, and promoting healthy longevity. The “Challenges” section included selecting appropriate clinical trial participants and methodologies to minimise heterogeneity in responses, how to view probiotics in the context of One Health, adapting regulatory frameworks, and understanding how substances of bacterial origin can cross the blood–brain barrier. The symposium provided evidence from cutting-edge research that gut eubiosis is vital for human health and, like space, the microbiota deserves further exploration of its vast potential.

Wheat was first cultivated in the Fertile Crescent (South Western Asia) with a farming expansion that lasted from around 9000 BC to 4000 BC. Whilst humans have been exposed to wheat for around the last 10 000 years, humans have existed for greater than 2·5 million years. Therefore, wheat (and thereby gluten) are relatively new introductions to our diet! By the end of the 20th century, global wheat output had expanded by 5-fold, with a corresponding increase in the prevalence of gluten-related disorders. Coeliac disease (CD) is a state of heightened immunological responsiveness to ingested gluten in genetically susceptible individuals. CD now affects 1 % or more of all adults, for which the management is a strict lifelong gluten-free diet (GFD). However, there is a growing body of evidence to show that a far greater proportion of individuals without CD are self-initiating a GFD. This includes individuals initiating a GFD as a lifestyle choice, people with irritable bowel-type symptoms and those diagnosed with non-coeliac gluten (or wheat) sensitivity. Despite a greater recognition of gluten-related disorders, gaps still remain in our understanding of both their aetiology and management. This article explores the role of the gluten-free diet in gluten-related disorders, along with current uncertainties.

Functional constipation is a significant health issue impacting the lives of an estimated 14 % of the global population. Non-pharmaceutical treatment advice for cases with no underlying medical conditions focuses on exercise, hydration and an increase in dietary fibre intake. An alteration in the composition of the gut microbiota is thought to play a role in constipation. Prebiotics are non-digestible food ingredients that selectively stimulate the growth of a limited number of bacteria in the colon with a benefit for host health. Various types of dietary fibre, though not all, can act as a prebiotic. Short-chain fatty acids produced by these microbes play a critical role as signalling molecules in a range of metabolic and physiological processes including laxation, although details are unclear. Prebiotics have a history of safe use in the food industry spanning several decades and are increasingly used as supplements to alleviate constipation. Most scientific research on the effects of prebiotics and gut microbiota has focussed on inflammatory bowel disease rather than functional constipation. Very few clinical studies evaluated the efficacy of prebiotics in the management of constipation and their effect on the microbiota, with highly variable designs and conflicting results. Despite this, broad health claims are made by manufacturers of prebiotic supplements. This narrative review provides an overview of the literature on the interaction of prebiotics with the gut microbiota and their potential clinical role in the alleviation of functional constipation.

Irritable bowel syndrome (IBS) is a disorder of gut–brain interaction with a complex pathophysiology. Growing evidence suggests that alterations of the gut microenvironment, including microbiota composition and function, may be involved in symptom generation. Therefore, attempts to modulate the gut microenvironment have provided promising results as an indirect approach for IBS management. Antibiotics, probiotics, prebiotics, food and faecal microbiota transplantation are the main strategies for alleviating IBS symptom severity by modulating gut microbiota composition and function (eg. metabolism), gut barrier integrity and immune activity, although with varying efficacy. In this narrative review, we aim to provide an overview of the current approaches targeting the gut microenvironment in order to indirectly manage IBS symptoms.

This study evaluated the association between dietary patterns, gas-related symptoms (GRS) and their impact on quality of life (QoL) in a representative sample (n 936) of the French adult population. During the 2018–2019 ‘Comportements et Consommations Alimentaires en France’ survey (Behaviors and Food Consumption in France), online evaluation of GRS in adult participants was performed using the validated Intestinal Gas Questionnaire (IGQ), which captures the perception of GRS and their impact on QoL via six symptom dimensions scores (range 0–100; 100 = worse) and a global score (mean of the sum of the six symptom dimensions scores). Socio-demographics, lifestyle parameters and dietary habits (7-d e-food diary) were also collected online. Quality of diet was determined using the Nutrient-Rich Food 9.3 (NRF9.3) score (range 0–900; 900 = best). Univariate and multivariate linear regression models were applied to identify factors associated with IGQ global score. K-means was used to identify clusters of subjects based on their dietary records. Data from 936 adults who completed both the IGQ and the food diary showed a mean IGQ global score of 11·9 (sd 11·2). Younger age and female sex were associated with a higher IGQ global score. Only 7 % of subjects reported no symptom at all and nearly 30 % of study participants reported a high impact of GRS on their QoL. Two dietary clusters were identified: cluster 1, characterised by a higher consumption of fruits and vegetables, lower sugars intake and higher NRF9.3 score and cluster 2, characterised by higher intake of sugars, lower intake in dietary fibres and lower NRF9.3 score. The IGQ global score was lower in cluster 1 and higher in cluster 2 v. the total sample average (P < 0·001). The prevalence of GRS in the French adult population is high and is associated with impaired QoL and dietary patterns. A change in food habits towards healthier patterns could help reducing the burden of GRS.

Resistant starch 2 (RS2) may offer therapeutic value to irritable bowel syndrome (IBS) patients particularly in combination with minimally fermented fibre, but tolerability data are lacking. The present study evaluated the tolerability of RS2, sugarcane bagasse and their combination in IBS patients and healthy controls. Following baseline, participants consumed the fibres in escalating doses lasting 3 d each: RS2 (10, 15 and 20 g/d); sugarcane bagasse (5, 10 and 15 g/d); and their combination (20, 25 and 30 g/d). Gastrointestinal symptoms were assessed daily. Six IBS patients and five controls were recruited. No differences in overall symptoms from baseline were found across the fibre doses (IBS, P = 0⋅586; controls, P = 0⋅687). For IBS patients, all RS2 doses led to increased bloating. One IBS patient did not tolerate the low combination dose and another the high sugarcane bagasse dose. Supplementation of RS2 ≤ 20 g/d caused mild symptoms and was generally tolerated in IBS patients even when combined with minimally fermented fibre.

Pulses are healthy and sustainable but induce gut symptoms in people with a sensitive gut. Oats, on the contrary, have no fermentable oligo- di-, monosaccharides and polyols compounds and are known for the health effects of their fibres. This 4-day cross-over trial investigated the effects of oat and rice flour ingested with pulses on gut symptoms and exhaled gases (4th day only) in subjects with a sensitive gut or IBS (n 21) and controls (n 21). The sensitive group perceived more symptoms after both meals than controls (P = 0·001, P = 0·001). Frequency, intensity or quality of the symptoms did not differ between meals during the first 3 d in either group. More breath hydrogen was produced after an oat than rice containing meal in both groups (AUC, P = 0·001, P = 0·001). No between-group difference was seen in breath gases. During day 4, both sensitive and control groups perceived more symptoms after the oat flour meal (P = 0·001, P = 0·0104, respectively) as mainly mild flatulence. No difference in moderate or severe symptoms was detected. Increased hydrogen production correlated to a higher amount of perceived flatulence after the oat flour meal in both the sensitive and the control groups (P = 0·042, P = 0·003, respectively). In summary, ingestion of oat flour with pulses increases breath hydrogen levels compared with rice flour, but gastrointestinal symptoms of subjects sensitive to pulses were not explained by breath hydrogen levels. Additionally, consumer mindsets towards pulse consumption and pulse-related gut symptoms were assessed by an online survey, which implied that perceived gut symptoms hinder the use of pulses in sensitive subjects.

This review intends to act as an overview of fructose malabsorption (FM) and its role in the aetiology of diseases including, but not limited to, irritable bowel syndrome (IBS) and infantile colic and the relationship between fructose absorption and the propagation of some cancers. IBS results in a variety of symptoms including stomach pains, cramps and bloating. Patients can be categorised into two groups, depending on whether the patients’ experiences either constipation (IBS-C) or diarrhoea (IBS-D). FM has been proposed as a potential cause of IBS-D and other diseases, such as infantile colic. However, our knowledge of FM is limited by our understanding of the biochemistry related to the absorption of fructose in the small intestine and FM’s relationship with small intestinal bacterial overgrowth. It is important to consider the dietary effects on FM and most importantly, the quantity of excess free fructose consumed. The diagnosis of FM is difficult and often requires indirect means that may result in false positives. Current treatments of FM include dietary intervention, such as low fermentable oligo-, di-, monosaccharides and polyols diets and enzymatic treatments, such as the use of xylose isomerase. More research is needed to accurately diagnose and effectively treat FM. This review is designed with the goal of providing a detailed outline of the issues regarding the causes, diagnosis and treatment of FM.