Review article: epidemiology of IBS and other bowel disorders of gut-brain interaction (DGBI)

Sports Dietitians Australia and Ultra Sports Science Foundation Joint Position Statement: A Practitioner Guide to the Prevention and Management of Exercise-Associated Gastrointestinal Perturbations and Symptoms

It is now well-established that exercise can disturb various aspects of gastrointestinal integrity and function. The pathophysiology of these perturbations, termed "exercise-induced gastrointestinal syndrome (EIGS)," can lead to exercise-associated gastrointestinal symptom (Ex-GIS) inconveniences. EIGS outcomes can impact physical performance and may lead to clinical manifestation warranting medical intervention, as well as systemic responses leading to fatality. Athlete support practitioners seek prevention and management strategies for EIGS and Ex-GIS. This current position statement aimed to critically appraise the role of EIGS and Ex-GIS prevention and management strategies to inform effective evidence-based practice and establish translational application. Intervention strategies with mostly consistent beneficial outcomes include macronutrient (i.e., carbohydrate and protein) intake and euhydration before and during exercise, dietary manipulation of fermentable oligo-, di-, and mono-saccharides and polyols (FODMAP), and gut training or feeding tolerance adjustments for the specific management of Ex-GIS from gastrointestinal functional issues. Strategies that may provide benefit and/or promising outcomes, but warrant further explorations include heat mitigating strategies and certain nutritional supplementation (i.e., prebiotics and phenols). Interventions that have reported negative outcomes included low-carbohydrate high-fat diets, probiotic supplementation, pharmaceutical administration, and feeding intolerances. Owing to individual variability in EIGS and Ex-GIS outcomes, athletes suffering from EIGS and/or support practitioners that guide athletes through managing EIGS, are encouraged to undertake gastrointestinal assessment during exercise to identify underlying causal and exacerbation factor/s, and adopt evidence-based strategies that provide individualized beneficial outcomes. In addition, abstaining from prevention and management strategies that present unclear and/or adverse outcomes is recommended.

Attention in irritable bowel syndrome: A systematic review of affected domains and brain-gut axis interactions

BACKGROUND

Irritable bowel syndrome (IBS) is a disorder characterized by gut-brain interactions, leading to abdominal pain and altered stool patterns, which significantly affect patients' quality of life. Recent research suggests that attention may be impaired in individuals with IBS, potentially influencing symptom perception and emotional distress.

OBJECTIVE

This systematic review aims to examine the relationship between attention and IBS, focusing on the affected domains of attention and the interactions within the brain-gut axis.

METHODS

A comprehensive search was conducted across MEDLINE/PubMed, PsychINFO, and Scopus from January 1990 to December 2024. Studies included were those that assessed attention in adult IBS patients using valid measurement tools. A total of 24 studies were analyzed, incorporating neuroimaging and behavioral methods.

RESULTS

IBS individuals exhibit specific attentional impairments, including deficits in sustained attention, selective attentional biases toward gastrointestinal (GI)-related and symptom-specific stimuli, and heightened vigilance to threat and pain cues. Neurofunctional studies reveal altered brain activity in areas such as the insula, anterior cingulate cortex, and amygdala, indicating increased interoceptive awareness and cognitive load. Pre-attentive processing and sensory gating show exaggerated responses, while sustained attention and attentional control demand additional cognitive resources. These patterns reflect an interplay between heightened sensitivity to internal stimuli and cognitive processing challenges in IBS.

CONCLUSION

This review highlights specific attentional deficits and biases in IBS, suggesting they may contribute to symptom exacerbation and emotional distress. Further research is needed to explore the underlying mechanisms and potential therapeutic interventions.

Patients with Irritable Bowel Syndrome Exhibit Aberrant Expression of Endogenous Retroviruses and SETDB1

Irritable bowel syndrome (IBS) is a common disease, whose etiopathogenesis is poorly understood. Human endogenous retroviruses (HERVs) originate from ancient infections of germinal cells and represent 8% of our DNA. Most HERVs have become defective due to the accumulated mutations; some can, however, still be activated, and their altered expressions have been associated with a number of chronic inflammatory and immune-mediated disorders, including gastrointestinal diseases. Retroviral transcription is modulated by TRIM28 and SETDB1, which also participate in the regulation of epigenetic mechanisms and in shaping the immune system. Expressions of HERVs and TRIM28/SETDB1 have not been investigated in patients affected by IBS. Using a PCR real-time Taqman amplification assay, we explored the RNA levels of HERV-H-pol, HERV-K-pol, and HERV-W-pol; syncytin 1 (SYN1), SYN2, and HERV-W-env; and TRIM28 and SETDB1 in the peripheral blood of 37 IBS patients and healthy controls (HCs) of similar age. The transcript levels were higher in IBS patients than in HCs for all HERVs except for HERV-W-pol, with significant p-values for HERV-H-pol, HERV-K-pol, and SYN1 and borderline p-values for SYN2 and HERV-W-env. The RNA levels of SETDB1 were significantly enhanced in IBS patients, while those of TRIM28 were in the normal range. Patients with severe disease had significant upregulation of SETDB1 compared to those with mild or moderate symptoms. These findings suggest that overexpression of HERVs and SETDB1 may contribute to the development of IBS and open the way to innovative therapeutic strategies.

A New Strategy for Dietary Nutrition to Improve Intestinal Homeostasis in Diarrheal Irritable Bowel Syndrome: A Perspective on Intestinal Flora and Intestinal Epithelial Interaction

BACKGROUND AND OBJECTIVES

Although a reasonable diet is essential for promoting human health, precise nutritional regulation presents a challenge for different physiological conditions. Irritable Bowel Syndrome (IBS) is characterized by recurrent abdominal pain and abnormal bowel habits, and diarrheal IBS (IBS-D) is the most common, seriously affecting patients' quality of life. Therefore, the implementation of precise nutritional interventions for IBS-D has become an urgent challenge in the fields of nutrition and food science. IBS-D intestinal homeostatic imbalance involves intestinal flora disorganization and impaired intestinal epithelial barrier function. A familiar interaction is evident between intestinal flora and intestinal epithelial cells (IECs), which together maintain intestinal homeostasis and health. Dietary patterns, such as the Mediterranean diet, have been shown to regulate gut flora, which in turn improves the body's health by influencing the immune system, the hormonal system, and other metabolic pathways.

METHODS

This review summarized the relationship between intestinal flora, IECs, and IBS-D. It analyzed the mechanism behind IBS-D intestinal homeostatic imbalance by examining the interactions between intestinal flora and IECs, and proposed a precise dietary nutrient intervention strategy.

RESULTS AND CONCLUSION

This increases the understanding of the IBS-D-targeted regulation pathways and provides guidance for designing related nutritional intervention strategies.

Effects of Physical Exercise on the Microbiota in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal disorder characterized by abdominal pain, bloating, diarrhea, and constipation. Recent studies have underscored the significant role of the gut microbiota in the pathogenesis of IBS. Physical exercise, as a non-pharmacological intervention, has been proposed to alleviate IBS symptoms by modulating the gut microbiota. Aerobic exercise, such as running, swimming, and cycling, has been shown to enhance the diversity and abundance of beneficial gut bacteria, including Lactobacillus and Bifidobacterium. These bacteria produce short-chain fatty acids that possess anti-inflammatory properties and support gut barrier integrity. Studies involving IBS patients participating in structured aerobic exercise programs have reported significant improvements in their gut microbiota's composition and diversity, alongside an alleviation of symptoms like abdominal pain and bloating. Additionally, exercise positively influences mental health by reducing stress and improving mood, which can further relieve IBS symptoms via the gut-brain axis. Long-term exercise interventions provide sustained benefits, maintaining the gut microbiota's diversity and stability, supporting immune functions, and reducing systemic inflammation. However, exercise programs must be tailored to individual needs to avoid exacerbating IBS symptoms. Personalized exercise plans starting with low-to-moderate intensity and gradually increasing in intensity can maximize the benefits and minimize risks. This review examines the impact of various types and intensities of physical exercise on the gut microbiota in IBS patients, highlighting the need for further studies to explore optimal exercise protocols. Future research should include larger sample sizes, longer follow-up periods, and examine the synergistic effects of exercise and other lifestyle modifications. Integrating physical exercise into comprehensive IBS management plans can enhance symptom control and improve patients' quality of life.

Understanding Gut Sensations: Irritable Bowel Syndrome and Diagnostic Fluidity in Danish Clinical Practice

Irritable bowel syndrome (IBS) is a prevalent health challenge in a Danish welfare context. Drawing on ethnographic fieldwork at two Danish gastroenterology clinics, and inspired by Charles E. Rosenberg's idea of styles of explaining widespread diseases, we outline three styles of understanding and treating gut trouble in daily clinical work: "The microbial gut," "the mindful gut," and "the lifestyled gut." Moreover, we suggest the concept of fluidity to characterize IBS as a diagnostic category that allows clinicians and patients to operate through complex understandings of permeable boundaries between body, mind, and environment to negotiate personalized solutions for embodied gut sensations.

A pharmacokinetic evaluation of tenapanor for the treatment of irritable bowel syndrome with constipation: an update of the literature

INTRODUCTION

Tenapanor is the latest addition to the second-line pharmacotherapeutic options for the treatment of irritable bowel syndrome with constipation. It is a first-in-class inhibitor of type 3 sodium/hydrogen exchanger (NHE3), characterized by very low oral absorption. Its pharmacological properties are discussed here based on the latest literature.

AREAS COVERED

A general description of tenapanor is provided, highlighting those pharmacokinetic and pharmacodynamic characteristics of the drug which may be of major importance for tolerability and safety. This description is associated with a summary and analysis of currently available toxicological data.

EXPERT OPINION

Plasma concentrations of free tenapanor after oral administration are well below the half maximal inhibitory concentration for NHE3, so that systemic effects of the drug are minimal. Therefore, the action of tenapanor is limited to NHE3 located on the apical membrane of enterocytes. The consequent reduction in intestinal sodium absorption increases the intraluminal content by osmosis, which in turn enhances the propulsive activity of the colon. Diarrhea is the most frequent adverse effect of tenapanor. Increased fecal sodium and water excretion do not appear to expose patients to short- and long-term hydro-electrolyte imbalances.

Exploring new subgroups for irritable bowel syndrome using a machine learning algorithm

Irritable bowel syndrome (IBS) is a complicated gut-brain axis disorder that has typically been classified into subgroups based on the major abnormal stool consistency and frequency. The presence of components other than lower gastrointestinal (GI) symptoms, such as psychological burden, has also been observed in IBS manifestations. The purpose of this research is to redefine IBS subgroups based on upper GI symptoms and psychological factors in addition to lower GI symptoms using an unsupervised machine learning algorithm. The clustering of 988 individuals who met the Rome III criteria for diagnosis of IBS was performed using a mixed-type data clustering algorithm. Nine sub-groups emerged from the proposed clustering: (I) High diarrhea, pain, and psychological burden, (II) High upper GI, moderate lower GI, and psychological burden, (III) High psychological burden and moderate overall GI, (IV) High constipation, moderate upper GI, and high psychological burden, (V) moderate constipation and low psychological burden, (VI) High diarrhea and moderate psychological burden, (VII) moderate diarrhea and low psychological burden, (VIII) Low overall GI, and psychological burden, (IX) Moderate lower GI, and low psychological burden. The proposed procedure led to the discovery of new homogeneous clusters in addition to certain well-known Rome sub-types for IBS.

HLA-DQ and alcohol in the pathogenesis of irritable bowel syndrome in college students: a case-control study

Some researchers have shown that genetics contribute to the incidence of IBS. However, no research has focused on the interaction between HLA-DQ and living habits in the pathogenesis of IBS. The present study explored the risk factors for IBS in college students of Guangxi Han nationality and explored the interaction between HLA-DQ and living habits on the pathogenesis of IBS. Univariate and multivariate analyses were used to determine the risk factors for IBS. Logistic interaction analysis and the Excel table made by Andersson were used to explore the interaction between genes and living habits in the context of IBS. We found that low expression of HLA-DQ2 and DQ8 were associated with the pathogenesis of IBS, while mild to moderate alcohol consumption was associated with the occurrence of IBS symptoms. Only the HLA-DQ8 gene and alcohol consumption had additive interactions in the context of the occurrence of IBS. In other words, for college students of Guangxi Han nationality, HLA-DQ2 and HLA-DQ8 might be protective against IBS, while alcohol consumption might be an independent risk factor. There was an additive interaction between HLA-DQ8 and alcohol consumption in the occurrence of IBS.

Does sourdough bread provide clinically relevant health benefits?

During the last decade, scientific interest in and consumer attention to sourdough fermentation in bread making has increased. On the one hand, this technology may favorably impact product quality, including flavor and shelf-life of bakery products; on the other hand, some cereal components, especially in wheat and rye, which are known to cause adverse reactions in a small subset of the population, can be partially modified or degraded. The latter potentially reduces their harmful effects, but depends strongly on the composition of sourdough microbiota, processing conditions and the resulting acidification. Tolerability, nutritional composition, potential health effects and consumer acceptance of sourdough bread are often suggested to be superior compared to yeast-leavened bread. However, the advantages of sourdough fermentation claimed in many publications rely mostly on data from chemical and in vitro analyzes, which raises questions about the actual impact on human nutrition. This review focuses on grain components, which may cause adverse effects in humans and the effect of sourdough microbiota on their structure, quantity and biological properties. Furthermore, presumed benefits of secondary metabolites and reduction of contaminants are discussed. The benefits claimed deriving from in vitro and in vivo experiments will be evaluated across a broader spectrum in terms of clinically relevant effects on human health. Accordingly, this critical review aims to contribute to a better understanding of the extent to which sourdough bread may result in measurable health benefits in humans.

Irritable bowel syndrome - controversies in diagnosis and management

INTRODUCTION

The irritable bowel syndrome (IBS) is the best-recognized disorder of gut brain interactions (DGBI). However, it is controversial if the Rome IV criteria iteration for IBS diagnosis is fit for purpose.

AREAS COVERED

This review critically evaluates Rome IV criteria for diagnosis of IBS and addresses clinical considerations in IBS treatment and management, including dietary factors, biomarkers, disease mimics, symptom severity, and subtypes. The role of diet in IBS is critically reviewed along with the influence of the microbiota, including small intestinal bacterial overgrowth.

EXPERT OPINION

Emerging data suggest the Rome IV criteria are more suitable for identifying severe IBS and least useful for sub-diagnostic patients who are still likely to benefit from IBS treatment. Despite convincing evidence that IBS symptoms are diet-driven and often postprandial, a relationship to eating is not a Rome IV diagnostic criterion. Few IBS biomarkers have been identified, suggesting the syndrome is too heterogeneous to be measured by a single marker, and combined biomarker, clinical, dietary, and microbial profiling may be needed for objective characterization. With many organic diseases mimicking and overlapping with IBS, it's important clinicians are knowledgable about this to mitigate the risk of missing comorbid organic intestinal disease and to optimally treat IBS symptoms.

Abdominophrenic Dyssynergia: A Narrative Review

Chronic bloating and abdominal distension are common and highly bothersome gastrointestinal symptoms. Although the differential diagnoses for bloating and distension are broad, these symptoms are frequently associated with disorders of the gut-brain interaction. Functional abdominal bloating may be a result of visceral hypersensitivity, whereas abdominal distension seems to be a somatic behavioral response associated with abdominophrenic dyssynergia, featuring diaphragmatic contraction and abdominal wall relaxation. We review the available literature regarding abdominophrenic dyssynergia and comment on its epidemiology, diagnosis, treatment, and avenues to address in the near future.

Prevalence, epidemiology and associated healthcare burden of Rome IV irritable bowel syndrome and functional dyspepsia in the adult population of Gibraltar

OBJECTIVE

Gibraltar is a unique densely populated multicultural British Overseas Territory for which no population data on disorders of gut-brain interaction have existed.We aimed to provide the first-ever assessment of prevalence of irritable bowel syndrome and functional dyspepsia in Gibraltar in relation to their diagnostic recognition and healthcare burden.

DESIGN

An internet survey was carried out in Gibraltar in 2019-2020. The study survey included demographic questions, the Rome IV diagnostic questions for functional dyspepsia and irritable bowel syndrome, relevant medical history, previous surgeries, medication use, healthcare visit frequency and a quality-of-life questionnaire.

RESULTS

888 individuals (3.5% of all Gibraltar adults) completed the survey anonymously. Irritable bowel syndrome prevalence was 5.2% (95% CI 3.7% to 6.6%). Functional dyspepsia prevalence was 9.9% (95% CI 7.9% to 11.9%). The two conditions overlapped substantially. Women had higher mean prevalence than men of both disorders. People meeting criteria for either or both disorders were prone to surgeries, had more frequent healthcare visits, higher medication use and lower quality-of-life scores compared with people without these disorders. Diagnostic recognition by healthcare providers was low, leaving 58.3% of irritable bowel syndrome and 96.9% of functional dyspepsia individuals undiagnosed.

CONCLUSION

This first-ever population-based study of Rome IV defined irritable bowel syndrome and functional dyspepsia in Gibraltar indicates that the prevalence rates of these disorders are similar to the recently reported data for the UK and Spain, but they remain poorly recognised despite substantially affecting the quality of life of individuals who have them in the Gibraltar community.