Effects of Low-FODMAPS Diet on Irritable Bowel Syndrome Symptoms and Gut Microbiome

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.

The efficacy and real-world effectiveness of a diet low in fermentable oligo-, di-, monosaccharides and polyols in irritable bowel syndrome: A systematic review and meta-analysis

BACKGROUND & AIMS

A diet low in fermentable oligo-, di-, monosaccharides, and polyols (LFD) has been shown to effectively reduce irritable bowel syndrome (IBS) symptoms. Effects resulting from real-world studies may differ from those seen in efficacy studies because of the diversity of patients in real-world settings. This systematic review and meta-analysis aimed to compare the effect of the LFD on reducing IBS symptoms and improving the quality of life (QoL) in efficacy trials and real-world studies.

METHODS

Major databases, trial registries, dissertations, and journals were systematically searched for studies on the LFD in adults with IBS. Meta-analysis was conducted using a random effects model with standardized mean differences (SMD) and 95% confidence intervals (CI). Outcomes of interest were all patient-reported: stool consistency, stool frequency, abdominal pain, overall symptoms, adequate symptom relief, IBS-specific QoL and adherence to the LFD.

RESULTS

Eleven efficacy and 19 real-world studies were reviewed. The meta-analysis results for abdominal pain (SMD 0.35, 95% CI 0.16 to 0.54) and QoL (SMD 0.23, 95% CI -0.05 to 0.50) showed the LFD was beneficial in efficacy studies with no statistically significant results for stool frequency (SMD 0.71, 95% CI 0.34 to 1.07). Real-world studies found improvements in abdominal pain and QoL. Due to heterogeneity, no meta-analysis was done for stool consistency and overall symptoms. In these outcomes, results were mostly supportive of the LFD, but they were not always statistically significant.

CONCLUSIONS

The results of this systematic review and meta-analysis suggest the LFD improves outcomes compared to a control diet (efficacy studies) or baseline data (real-world studies). Because of diverse study designs and heterogeneity of results, a clear superiority of the LFD over control diets could not be concluded. There are no indications of an efficacy-effectiveness gap for the LFD in adults with IBS.

Role of the gut microbiota in the pathogenesis of endometriosis: a review

Endometriosis is classically defined as a chronic inflammatory heterogeneous disorder occurring in any part of the body, characterized by estrogen-driven periodic bleeding, proliferation, and fibrosis of ectopic endometrial glands and stroma outside the uterus. Endometriosis can take overwhelmingly serious damage to the structure and function of multi-organ, even impair whole-body systems, resulting in severe dysmenorrhea, chronic pelvic pain, infertility, fatigue and depression in 5-10% women of reproductive age. Precisely because of a huge deficiency of cognition about underlying etiology and complex pathogenesis of the debilitating disease, early diagnosis and treatment modalities with relatively minor side effects become bottlenecks in endometriosis. Thus, endometriosis warrants deeper exploration and expanded investigation in pathogenesis. The gut microbiota plays a significant role in chronic diseases in humans by acting as an important participant and regulator in the metabolism and immunity of the body. Increasingly, studies have shown that the gut microbiota is closely related to inflammation, estrogen metabolism, and immunity resulting in the development and progression of endometriosis. In this review, we discuss the diverse mechanisms of endometriosis closely related to the gut microbiota in order to provide new approaches for deeper exploration and expanded investigation for endometriosis on prevention, early diagnosis and treatment.

Diet-microbiota associations in gastrointestinal research: a systematic review

Interactions between diet and gastrointestinal microbiota influence health status and outcomes. Evaluating these relationships requires accurate quantification of dietary variables relevant to microbial metabolism, however current dietary assessment methods focus on dietary components relevant to human digestion only. The aim of this study was to synthesize research on foods and nutrients that influence human gut microbiota and thereby identify knowledge gaps to inform dietary assessment advancements toward better understanding of diet-microbiota interactions. Thirty-eight systematic reviews and 106 primary studies reported on human diet-microbiota associations. Dietary factors altering colonic microbiota included dietary patterns, macronutrients, micronutrients, bioactive compounds, and food additives. Reported diet-microbiota associations were dominated by routinely analyzed nutrients, which are absorbed from the small intestine but analyzed for correlation to stool microbiota. Dietary derived microbiota-relevant nutrients are more challenging to quantify and underrepresented in included studies. This evidence synthesis highlights advancements needed, including opportunities for expansion of food composition databases to include microbiota-relevant data, particularly for human intervention studies. These advances in dietary assessment methodology will facilitate translation of microbiota-specific nutrition therapy to practice.

Revisiting the Intestinal Microbiome and Its Role in Diarrhea and Constipation

The gut microbiota represents a community of microorganisms (bacteria, fungi, archaea, viruses, and protozoa) that colonize the gut and are responsible for gut mucosal structural integrity and immune and metabolic homeostasis. The relationship between the gut microbiome and human health has been intensively researched in the past years. It is now widely recognized that gut microbial composition is highly responsible for the general health of the host. Among the diseases that have been linked to an altered gut microbial population are diarrheal illnesses and functional constipation. The capacity of probiotics to modulate the gut microbiome population, strengthen the intestinal barrier, and modulate the immune system together with their antioxidant properties have encouraged the research of probiotic therapy in many gastrointestinal afflictions. Dietary and lifestyle changes and the use of probiotics seem to play an important role in easing constipation and effectively alleviating diarrhea by suppressing the germs involved. This review aims to describe how probiotic bacteria and the use of specific strains could interfere and bring benefits as an associated treatment for diarrhea and constipation.

The Efficacy of a Diet Low in Fermentable Oligo-, Di-, Monosaccharides, and Polyols in Irritable Bowel Syndrome Compared to Its "Real-world" Effectiveness: Protocol for a Systematic Review

BACKGROUND

Irritable bowel syndrome (IBS) is associated with various gastrointestinal and nongastrointestinal symptoms and reduced quality of life. A diet low in fermentable oligo-, di-, monosaccharides, and polyols (FODMAPs) is one therapeutic option for IBS. Although the efficacy of the low FODMAP diet has been reported in several systematic reviews, the efficacy-effectiveness gap of the low FODMAP diet has not yet been assessed.

OBJECTIVE

This systematic review aims to compare the efficacy of the low FODMAP diet from efficacy randomized controlled trials (RCTs) with the effectiveness of studies conducted in "real-world" settings.

METHODS

RCTs, prospective and retrospective cohort studies, and retrospective audits assessing the low FODMAP diet in adults with IBS will be searched in 4 databases: Embase, MEDLINE, CENTRAL, and CINAHL. Two independent reviewers will perform study selection, data extraction, and risk of bias assessment and assess selected quality aspects from the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) protocol. Outcomes assessed are stool frequency, stool consistency, abdominal pain, overall symptom scores, adequate symptom relief, IBS-specific quality of life, and diet adherence. Data will be summarized with forest plots without summary statistics, tables, and narrative descriptions.

RESULTS

The search, title and abstract screening, and full-text screening were completed in March 2021, and an updated search was done in May 2022. As of May 2023, data analysis is almost finished, and manuscript writing is in progress. Submission of the manuscript is expected by July 2023.

CONCLUSIONS

The findings of this systematic review will compare the efficacy of the low FODMAP diet for IBS found in RCTs to the diet's real-world effectiveness.

TRIAL REGISTRATION

PROSPERO CRD42021278952; https://tinyurl.com/32jk43ev.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/41399.

A Reduced Tryptophan Diet in Patients with Diarrhoea-Predominant Irritable Bowel Syndrome Improves Their Abdominal Symptoms and Their Quality of Life through Reduction of Serotonin Levels and Its Urinary Metabolites

(1). An essential component of any treatment for patients with irritable bowel syndrome (IBS) is an adequate diet. Currently, a low FODMAP diet is recommended as a first-line therapy, but it does not relieve abdominal discomfort in all patients, and alternative nutritional treatment is required. The purpose of this study was to evaluate the effect of a tryptophan-lowering diet (TRP) on abdominal and mental symptoms in patients with irritable bowel syndrome with predominant diarrhea (IBS-D). (2). The study included 40 patients with IBS-D, and 40 healthy subjects served as a baseline for IBS-D patients, after excluding comorbidities. The TRP intake was calculated using the nutritional calculator. The severity of abdominal symptoms was assessed using the gastrointestinal symptom rating scale (GSRS-IBS). Mental state was assessed using the Hamilton anxiety rating scale (HAM-A), the Hamilton depression rating scale (HAM-D), and the insomnia severity index (ISI). The serum levels of serotonin and melatonin and the urinary excretion of their metabolites 5-hydroxyindoleacetic acid (5-HIAA) and 6-sulfatoxymelatonin (aMT6) were determined by the ELISA method. The severity of symptoms and laboratory data were analyzed before and after a 12 week diet with tryptophan restricted to a daily dose 10 mg per kilogram body weight. (3). Compared to the control group, patients with IBS-D had a higher serum level of serotonin (198.2 ± 38.1 vs. 142.3 ± 36.4 ng/mL; p < 0.001) but a similar level of melatonin (8.6 ± 1.1 vs. 9.4 ± 3.0 pg/mL; p > 0.05). The urinary excretion of 5-HIAA was also higher in patients with IBS-D patients (7.7 ± 1.5 vs. 6.0 ± 1.7 mg/24 h; p < 0.001). After nutritional treatment, both the serum serotonin level and the urinary 5-HIAA excretion significantly decreased (p < 0.001). The severity of the abdominal symptoms and anxiety also decreased, while the HAM-D score and the ISI score remained unchanged (4). Lowering the dietary intake of tryptophan may reduce abdominal complaints and does not alter the mental state of IBS-D patients.

Dietary Modification for the Restoration of Gut Microbiome and Management of Symptoms in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder leading to chronic debilitating issues. A healthy diet plays an integral role in maintaining the gut microbiota equilibrium, thus promoting digestive health. The structure and function of gut microbiota are affected by genetics and environmental factors, such as altered dietary habits, gastroenteritis, stress, increased use of alcohol and drugs, and medication use. Whereas there are various management approaches cited in the literature to manage symptoms of IBS, the purpose of this article is to focus on dietary options that will restore the gut microbiome and help in managing IBS symptoms. Some of the diets that are discussed in this article include a low-FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) diet, gluten-free/wheat-free diet, high-fiber diet, dietary and herbal supplements (psyllium, peppermint oil), and probiotics/prebiotics/synbiotics. The clinical practice guidelines recommended by the American College of Gastroenterology outlines evidence-based dietary recommendations for patients with IBS to manage symptoms. Recent advancements in the dietary management of IBS highlighting the use of a patient-centered, personalized nutrition approach along with lifestyle changes, pharmacological therapies, and psychosocial and behavioral interventions are also reviewed and discussed.

Low FODMAP Diet and Probiotics in Irritable Bowel Syndrome: A Systematic Review With Network Meta-analysis

Background: Probiotic and low fermentable oligosaccharide, disaccharide, monosaccharide, and polyol (FODMAP) diet are two commonly used management approaches for patients with irritable bowel syndrome (IBS). We aimed to evaluate the most effective combinations and components among different probiotics or low FODMAP diet through component network meta-analysis (NMA).

Methods: We searched Embase, Ovid Medline, and Web of Science from inception to 21 January 2021. Randomized controlled trials (RCTs) examining the efficacy of probiotics and low FODMAP diet for IBS were included, with placebo, sham diet, or conventional treatments as controls. Binary outcomes were compared among treatments using the relative ratio (RR). A minimally contextualized framework recommended by the GRADE group was used to evaluate the certainty of evidence. The primary efficacy outcome was the relief of global IBS symptoms, and the secondary efficacy outcome was the reduction in IBS symptom scores or abdominal pain scores.

Key Results: We included 76 RCTs (n = 8058) after screening 1940 articles. Eight RCTs were classified as low risk of bias. Standard network meta-analysis (NMA) showed that Lactobacillus (RR 1.74, 95% CI 1.22–2.48) and Bifidobacterium (RR 1.76, 95% CI 1.01–3.07) were the most effective for the primary efficacy outcome (high certainty evidence); component NMA showed that Bacillus (RR 5.67, 95% CI 1.88 to 17.08, p = 0.002) and Lactobacillus (RR 1.42, 95% CI 1.07 to 1.91, p = 0.017) were among the most effective components. The results of standard NMA and CNMA analysis of the improvement of overall IBS symptom scores or abdominal pain scores were consistent with this finding.

Conclusion:Lactobacillus was the most effective component for the relief of IBS symptoms; Bifidobacterium and Bacillus were possibly effective and need further verification.

Systematic Review Registration: website, identifier registration number.

Study of efficacy and mechanism of low FODMAPs diet on diarrhea-type irritable bowel syndrome based on a gut microbiota-dependent metabolite

BACKGROUND

The changes in gut microbiota-dependent metabolites can cause irritable bowel syndrome (IBS). It is important to investigate whether a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) plays a therapeutic role in IBS treatment by affecting the production of phenylalanine (PHE), a gut microbiota-dependent metabolite.

AIM

To investigate the efficacy of a low FODMAPs diet in diarrhea-type irritable bowel syndrome (IBS-D) and its molecular mechanism for regulating GLP-1 secretion by affecting PHE, a gut microbiota-dependent metabolite.

METHODS

Thirty patients who met the Rome IV diagnostic criteria for IBS-D were enrolled and treated with a low FODMAPs diet for 4 wk. Thirty healthy volunteers served as baseline controls. The changes of clinical symptom scores, and serum PHE, GLP-1, and TNF-α, as well as IFN-γ before and after treatment were recorded. In in vitro experiment, different doses of PHE were added into NCI-H716 cells to observe the regulatory effect of PHE on GLP-1.

RESULTS

The clinical symptom scores after treatment in the IBS group were significantly lower than those before treatment (P < 0.0001 & P < 0.001). After treatment, the levels of PHE and GLP-1 increased (P < 0.05), but those of TNF-α and IFN-γ decreased significantly (P < 0.0001 & P < 0.001). No adverse reactions occurred in the IBS group. In in vitro experiment, GLP-1 expression levels were found to rise with increasing PHE concentrations, and 1 mmol/L PHE could significantly increase GLP-1 secretion.

CONCLUSION

Low FODMAPs diet improves the symptoms in IBS-D patients via mechanisms that may be related to the regulation of GLP-1 by affecting PHE and thereby inhibiting the secretion of pro-inflammatory cytokines.

Diarrhea Predominant-Irritable Bowel Syndrome (IBS-D): Effects of Different Nutritional Patterns on Intestinal Dysbiosis and Symptoms

Irritable Bowel Syndrome (IBS) is a chronic functional gastrointestinal disorder characterized by abdominal pain associated with defecation or a change in bowel habits. Gut microbiota, which acts as a real organ with well-defined functions, is in a mutualistic relationship with the host, harvesting additional energy and nutrients from the diet and protecting the host from pathogens; specific alterations in its composition seem to play a crucial role in IBS pathophysiology. It is well known that diet can significantly modulate the intestinal microbiota profile but it is less known how different nutritional approach effective in IBS patients, such as the low-FODMAP diet, could be responsible of intestinal microbiota changes, thus influencing the presence of gastrointestinal (GI) symptoms. The aim of this review was to explore the effects of different nutritional protocols (e.g., traditional nutritional advice, low-FODMAP diet, gluten-free diet, etc.) on IBS-D symptoms and on intestinal microbiota variations in both IBS-D patients and healthy subjects. To date, an ideal nutritional protocol does not exist for IBS-D patients but it seems crucial to consider the effect of the different nutritional approaches on the intestinal microbiota composition to better define an efficient strategy to manage this functional disorder.

Effects of Low and High FODMAP Diets on Human Gastrointestinal Microbiota Composition in Adults with Intestinal Diseases: A Systematic Review

A diet high in non-digestible carbohydrates is known to promote health, in part through its effect on the gut microbiome. While substantially proven for healthy individuals, these effects are more ambiguous in subjects with intestinal diseases. At the same time, a diet low in these fermentable carbohydrates, the low FODMAP (acronym for Fermentable Oligo-, Di-, Mono-saccharides, And Polyols) diet, is gaining popularity as a treatment option for symptom relief in irritable bowel syndrome and inflammatory bowel disease. There are, however, several indications that this diet induces effects opposite to those of prebiotic supplementation, resulting in gut microbiome changes that might be detrimental. Here, we provide a systematic review of the effects of low and high FODMAP diets on human gastrointestinal microbiota composition in adults with intestinal diseases, through literature screening using the databases PubMed, Embase, and Web of Science. We summarize study findings on dietary impact in patients, including the effect on bacterial taxa and diversity. In general, similar to healthy subjects, restricting non-digestible carbohydrate intake in patients with intestinal diseases has opposite effects compared to prebiotic supplementation, causing a reduction in bifidobacteria and an increase in bacteria associated with dysbiosis. Future studies should focus on assessing whether the induced microbial changes persist over time and have adverse effects on long-term colonic health.

Gut Microbiota and Alimentary Tract Injury

The gastrointestinal (GI) tract is inhabited by a diverse array of microbes, which play crucial roles in health and disease. Dysbiosis of microbiota has been tightly linked to gastrointestinal inflammatory and malignant diseases. Here we highlight the role of Helicobacter pylori alongside gastric microbiota associated with gastric inflammation and cancer. We summarize the taxonomic and functional aspects of intestinal microbiota linked to inflammatory bowel diseases (IBD), irritable bowel syndrome (IBS), and colorectal cancer in clinical investigations. We also discuss microbiome-related animal models. Nevertheless, there are tremendous opportunities to reveal the causality of microbiota in health and disease and detailed microbe-host interaction mechanisms by which how dysbiosis is causally linked to inflammatory disease and cancer, in turn, potentializing clinical interventions with a personalized high efficacy.

Researching New Therapeutic Approaches for Abdominal Visceral Pain Treatment: Preclinical Effects of an Assembled System of Molecules of Vegetal Origin

Abdominal pain is a frequent symptom of irritable bowel syndrome (IBS) and inflammatory bowel diseases (IBDs). Although the knowledge of these pathologies is progressing, new therapeutic strategies continue to be investigated. In the present study, the effect of a system of molecules of natural origin (a medical device according to EU Directive 93/42/EC, engineered starting from Boswellia serrata resins, Aloe vera polysaccharides and Matricaria chamomilla and Melissa officinalis polyphenols) was evaluated against the intestinal damage and visceral pain development in DNBS-induced colitis model in rats. The system (250 and 500 mg kg⁻¹) was orally administered once daily, starting three days before the injection of 2,4-dinitrobenzenesulfonic acid (DNBS) and for 14 days thereafter. The viscero-motor response (VMR) to colon-rectal balloon distension (CRD) was used as measure of visceral sensitivity. The product significantly reduced the VMR of DNBS-treated animals. Its effect on pain threshold was better than dexamethasone and mesalazine, and not lower than amitriptyline and otilonium bromide. At microscopic and macroscopic level, the tested system was more effective in protecting the intestinal mucosa than dexamethasone and mesalazine, promoting the healing of tissue lesions. Therefore, we suggest that the described system of molecules of natural origin may represent a therapeutic option to manage painful bowel diseases.

Advanced Organ-on-a-Chip Devices to Investigate Liver Multi-Organ Communication: Focus on Gut, Microbiota and Brain

The liver is a key organ that can communicate with many other districts of the human body. In the last few decades, much interest has focused on the interaction between the liver and the gut microbiota, with their reciprocal influence on biosynthesis pathways and the integrity the intestinal epithelial barrier. Dysbiosis or liver disorders lead to0 epithelial barrier dysfunction, altering membrane permeability to toxins. Clinical and experimental evidence shows that the permeability hence the delivery of neurotoxins such as LPS, ammonia and salsolinol contribute to neurological disorders. These findings suggested multi-organ communication between the gut microbiota, the liver and the brain. With a view to in vitro modeling this liver-based multi-organ communication, we describe the latest advanced liver-on-a-chip devices and discuss the need for new organ-on-a-chip platforms for in vitro modeling the in vivo multi-organ connection pathways in physiological and pathological situations.