The gut microbiome as a predictor of low fermentable oligosaccharides disaccharides monosaccharides and polyols diet efficacy in functional bowel disorders

A Low FODMAP Diet Supplemented with L-Tryptophan Reduces the Symptoms of Functional Constipation in Elderly Patients

(1) Background: The elderly suffer from functional constipation (FC), whose causes are not fully known, but nutritional factors may play a role. The aim of the present study was to assess the effect of a low FODMAP diet supplemented with L-tryptophan (TRP) on its metabolism and symptoms of functional constipation in elderly patients. (2) Methods: This study included 40 people without abdominal complaints (Group I, controls) and 60 patients with FC, diagnosed according to the Rome IV Criteria (Group II). Two groups were randomly selected: Group IIA (n = 30) was qualified for administration of the low FODMAP diet, and the diet of patients of Group IIB (n = 30) was supplemented with 1000 mg TRP per day. The severity of abdominal symptoms was assessed with an abdominal pain index ranging from 1 to 7 points (S-score). The concentration of TRP and its metabolites, 5-hydroxyindoleacetic acid (5-HIAA), kynurenine (KYN), and 3-indoxyl sulfate (3-IS) in urine were determined using the LC-MS/MS method. (3) Results: In Group II, 5-HIAA concentration in urine was lower, and KYN and 3-IS concentrations were higher than in the control group. A negative correlation was found between the S-score and urinary concentration of 5-HIAA (p < 0.001), and 3-IS concentration was positively correlated with the S-score. However, the correlation between the S-score and 3-IS concentration was negative (p < 0.01). After a dietary intervention, 5-HIAA concentration increased in both groups, and the severity of symptoms decreased, but the decrease was more pronounced in Group IIB. (4) Conclusion: A low FODMAP diet supplemented with L-tryptophan has beneficial effects in elderly patients suffering from functional constipation.

Evolutionary medicine approaches to chronic disease: The case of irritable bowel syndrome

Irritable bowel syndrome (IBS), a gastrointestinal disease, is a global phenomenon correlated with industrialization. We propose that an evolutionary medicine approach is useful to understand this disease from an ultimate perspective and conducted a scoping literature review to synthesize the IBS literature within this framework. Our review suggests five potential evolutionary hypotheses for the cause of IBS, including (a) a dietary mismatch accompanying a nutritional transition, (b) an early hygienic life environment leading to the immune system and microbiotic changes, (c) an outcome of decreased physical activity, (d) a response to changes in environmental light-dark cycles, and (e) an artifact of an evolved fight or flight response. We find key limitations in the available data needed to understand early life, nutritional, and socioeconomic experiences that would allow us to understand evolutionarily relevant risk factors and identify a need for further empirical research to distinguish potential causes and test evolutionary hypotheses.

Exploring the gut microbiota: lifestyle choices, disease associations, and personal genomics

The gut microbiota is a rich and dynamic ecosystem that actively interacts with the human body, playing a significant role in the state of health and disease of the host. Diet, exercise, mental health, and other factors have exhibited the ability to influence the gut bacterial composition, leading to changes that can prevent and improve, or favor and worsen, both intestinal and extra-intestinal conditions. Altered gut microbial states, or 'dysbiosis', associated with conditions and diseases are often characterized by shifts in bacterial abundance and diversity, including an impaired Firmicutes to Bacteroidetes ratio. By understanding the effect of lifestyle on the gut microbiota, personalized advice can be generated to suit each individual profile and foster the adoption of lifestyle changes that can both prevent and ameliorate dysbiosis. The delivery of effective and reliable advice, however, depends not only on the available research and current understanding of the topic, but also on the methods used to assess individuals and to discover the associations, which can introduce bias at multiple stages. The aim of this review is to summarize how human gut microbial variability is defined and what lifestyle choices and diseases have shown association with gut bacterial composition. Furthermore, popular methods to investigate the human gut microbiota are outlined, with a focus on the possible bias caused by the lack of use of standardized methods. Finally, an overview of the current state of personalized advice based on gut microbiota testing is presented, underlining its power and limitations.

Gut Microbiome-Brain Alliance: A Landscape View into Mental and Gastrointestinal Health and Disorders

Gut microbiota includes a vast collection of microorganisms residing within the gastrointestinal tract. It is broadly recognized that the gut and brain are in constant bidirectional communication, of which gut microbiota and its metabolic production are a major component, and form the so-called gut microbiome-brain axis. Disturbances of microbiota homeostasis caused by imbalance in their functional composition and metabolic activities, known as dysbiosis, cause dysregulation of these pathways and trigger changes in the blood-brain barrier permeability, thereby causing pathological malfunctions, including neurological and functional gastrointestinal disorders. In turn, the brain can affect the structure and function of gut microbiota through the autonomic nervous system by regulating gut motility, intestinal transit and secretion, and gut permeability. Here, we examine data from the CAS Content Collection, the largest collection of published scientific information, and analyze the publication landscape of recent research. We review the advances in knowledge related to the human gut microbiome, its complexity and functionality, its communication with the central nervous system, and the effect of the gut microbiome-brain axis on mental and gut health. We discuss correlations between gut microbiota composition and various diseases, specifically gastrointestinal and mental disorders. We also explore gut microbiota metabolites with regard to their impact on the brain and gut function and associated diseases. Finally, we assess clinical applications of gut-microbiota-related substances and metabolites with their development pipelines. We hope this review can serve as a useful resource in understanding the current knowledge on this emerging field in an effort to further solving of the remaining challenges and fulfilling its potential.

Randomized controlled pilot study assessing fructose tolerance during fructose reintroduction in non-constipated irritable bowel syndrome patients successfully treated with a low FODMAP diet

BACKGROUND

Limited data exist to guide FODMAP (fermentable oligo-, di-, monosaccharides, and polyols) reintroduction to assess tolerance following a low FODMAP diet (LFD). Fructose reintroduction is often stepwise up to 7.5 g fructose (e.g., three tsp of honey). We aimed to determine the fructose tolerance threshold in non-constipated, LFD-responsive patients with irritable bowel syndrome (IBS) and assess whether stool microbiome predicted LFD response or fructose tolerance.

METHODS

Thirty-nine non-constipated IBS patients (51% women, mean age 33.7 years) completed a 4-week LFD. LFD responders were defined as those who reported adequate relief of IBS symptoms following the LFD. Responders were randomized to one of the three solution groups (100% fructose, 56% fructose/44% glucose, or 100% glucose) and received four doses (2.5, 5, 10, 15 g) for 3 days each. Patients reached their tolerance dose if their mean daily IBS symptom severity (visual analog scale [VAS], 0-100 mm) was >20 mm higher than post-LFD VAS. Stool samples before and after LFD were analyzed using shotgun metagenomics.

RESULTS

Seventy-nine percent of patients were LFD responders. Most responders tolerated the 15 g sugar dose. There was no significant difference in mean dose tolerated between solution groups (p = 0.56). Compared to baseline, microbiome composition (beta diversity) significantly shifted and six bacterial genes in fructose and mannose metabolism pathways decreased after LFD, irrespective of LFD response or the solution group.

CONCLUSIONS

Non-constipated, LFD-responsive IBS patients should be reintroduced to fructose in higher doses than 15 g to assess tolerance. LFD is associated with significant changes in microbial composition and bacterial genes involved in FODMAP metabolism.

Dietary contributors to fermentable carbohydrate intake in healthy American college students

OBJECTIVE

The study explored food items that contribute most toward increased fermentable carbohydrate (FC) intake and its association with diet quality in college students.

METHOD

This cross-sectional study included 571 consented college students (≥18 years) with reported energy intakes (500-3500 kcal/day for women; 800-4000 kcal/day for men). FC intake and healthy eating index-2015 (HEI-2015) scores were assessed by diet history questionnaire-II. Data were analyzed by unadjusted bivariate linear regression and Pearson correlation tests.

RESULTS

The mean intakes of total FC (β = 1.24; 95% Confidence Interval: 1.02, 1.47) significantly predicted HEI-2015 scores. Positive correlations were found between FC intake and red and orange vegetables (r = 0.62), whole fruits (r = 0.63), and dark green vegetables (r = 0.58). Conclusions: Higher FC intake was associated with higher diet quality; vegetables and fruits are primary contributors to FC content. Efforts are required to promote these food items to improve diet quality and FC intake to shape eating choices in college students.

Two microbiota subtypes identified in irritable bowel syndrome with distinct responses to the low FODMAP diet

OBJECTIVE

Reducing FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) can be clinically beneficial in IBS but the mechanism is incompletely understood. We aimed to detect microbial signatures that might predict response to the low FODMAP diet and assess whether microbiota compositional and functional shifts could provide insights into its mode of action.

DESIGN

We used metagenomics to determine high-resolution taxonomic and functional profiles of the stool microbiota from IBS cases and household controls (n=56 pairs) on their usual diet. Clinical response and microbiota changes were studied in 41 pairs after 4 weeks on a low FODMAP diet.

RESULTS

Unsupervised analysis of baseline IBS cases pre-diet identified two distinct microbiota profiles, which we refer to as IBSP (pathogenic-like) and IBSH (health-like) subtypes. IBSP microbiomes were enriched in Firmicutes and genes for amino acid and carbohydrate metabolism, but depleted in Bacteroidetes species. IBSH microbiomes were similar to controls. On the low FODMAP diet, IBSH and control microbiota were unaffected, but the IBSP signature shifted towards a health-associated microbiome with an increase in Bacteroidetes (p=0.009), a decrease in Firmicutes species (p=0.004) and normalisation of primary metabolic genes. The clinical response to the low FODMAP diet was greater in IBSP subjects compared with IBSH (p=0.02).

CONCLUSION

50% of IBS cases manifested a 'pathogenic' gut microbial signature. This shifted towards the healthy profile on the low FODMAP diet; and IBSP cases showed an enhanced clinical responsiveness to the dietary therapy. The effectiveness of FODMAP reduction in IBSP may result from the alterations in gut microbiota and metabolites produced. Microbiota signatures could be useful as biomarkers to guide IBS treatment; and investigating IBSP species and metabolic pathways might yield insights regarding IBS pathogenic mechanisms.

The Role of Food in the Treatment of Bowel Disorders: Focus on Irritable Bowel Syndrome and Functional Constipation

Irritable bowel syndrome (IBS) and functional constipation (FC) are among the most common disorders of gut-brain interaction, affecting millions of individuals worldwide. Most patients with disorders of gut-brain interaction perceive food as a trigger for their gastrointestinal symptoms, and specific dietary manipulations/advice have now been recognized as a cornerstone therapeutic option for IBS and FC. We discuss in detail the 2 most common dietary interventions used for the management of IBS-general dietary advice based on the National Institute for Health and Care Excellence guidelines and a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs). We summarize the literature around the possible mechanisms of FODMAP-mediated IBS pathophysiology, the current 3-step, top-down approach of administering a low FODMAP diet (LFD) (restriction phase, followed by reintroduction and personalization), the efficacy data of its restriction and personalization phases, and possible biomarkers for response to an LFD. We also summarize the limitations and challenges of an LFD along with the alternative approach to administering an LFD (e.g., bottom-up). Finally, we discuss the available efficacy data for fiber, other dietary interventions (e.g., Mediterranean diet, gluten-free diet, and holistic dietary interventions), and functional foods (e.g., kiwifruit, rhubarb, aloe, and prunes) in the management of IBS and FC.

Pediatric Aspects of Nutrition Interventions for Disorders of Gut-Brain Interaction

Dietary factors may play an important role in the generation of symptoms in children with disorders of gut-brain interaction (DGBIs). Although dietary modification may provide successful treatment, there is a relative paucity of controlled trials that have shown the effectiveness of dietary interventions. This study is a narrative review that explores the existing literature on food and pediatric DGBIs. The following have been shown to be beneficial: (i) in infants with colic, removing cow's milk from the infant's diet or from the maternal diet in those who are breastfed; (ii) in infants with regurgitation, adding thickeners to the formula or removing cow's milk protein from the infant's diet or the maternal diet in those who are breastfed; and (iii) in children with pain-predominant DGBIs, using soluble fiber supplementation or a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols diet. In children with functional constipation, there is no evidence that adding fiber is beneficial. Given that most dietary interventions include restriction of different foods in children, a thoughtful approach and close follow-up are needed.

How to manage irritable bowel syndrome in children

AIM

This paper discusses the risk factors and management of paediatric irritable bowel syndrome (IBS), with a focus on the role of the gastrointestinal microbiome.

METHODS

English articles of interest published in PubMed and Google Scholar were searched using subject heading and keywords of interest.

RESULTS

Only few randomised controlled trials on the management of IBS in children have been published. The vast majority of these intervention trials target to change the composition of the gastrointestinal microbiome. Most studies are underpowered. Major heterogeneities in study designs such as differences in inclusion criteria, including patients with different pain-related functional gastrointestinal disorders and differences in primary outcomes, make it impossible to formulate recommendations. Overall, few adverse events are reported what could indicate safety or point to suboptimal conduction of clinical trials and safety reporting. However, it can also not be excluded that some interventions such as the administration of selected probiotic products may result in benefit.

CONCLUSION

There is insufficient evidence to recommend any therapeutic intervention in paediatric IBS, including manipulation of the gastrointestinal tract microbiome, despite the evidence that dysbiosis seems an associated pathophysiologic factor. More designed prospective trials are needed since IBS is not a rare condition during childhood.

An Update on the Assessment and Management of Pediatric Abdominal Pain

Chronic abdominal pain is very common in children and adolescent and results in high personal and social costs. Most youth with chronic abdominal pain fulfill criteria for a functional abdominal pain disorder (FAPD) as defined by Rome criteria. These are complex conditions with a wide array of biological, psychological, and social factors contributing to the experience of pain. The purpose of the current review is to provide an overview of the pathophysiology of FAPDs and an up-to-date summary of the literature related to FAPDs in children and adolescents, with additional focus on several areas (eg, diet and probiotics) where patients and families frequently have questions or implement self-directed care. We also provide an approach to the assessment and treatment of pediatric FAPDs focusing on the robust literature regarding psychological interventions and much sparser literature regarding medication treatment.

Psychological comorbidity in gastrointestinal diseases: Update on the brain-gut-microbiome axis

The high comorbidity of psychological disorders in both functional and organic gastrointestinal diseases suggests the intimate and complex link between the brain and the gut. Termed the brain-gut axis, this bidirectional communication between the central nervous system and enteric nervous system relies on immune, endocrine, neural, and metabolic pathways. There is increasing evidence that the gut microbiome is a key part of this system, and dysregulation of the brain-gut-microbiome axis (BGMA) has been implicated in disorders of brain-gut interaction, including irritable bowel syndrome, and in neuropsychiatric disorders, including depression, Alzheimer's disease, and autism spectrum disorder. Further, alterations in the gut microbiome have been implicated in the pathogenesis of organic gastrointestinal diseases, including inflammatory bowel disease. The BGMA is an attractive therapeutic target, as using prebiotics, probiotics, or postbiotics to modify the gut microbiome or mimic gut microbial signals could provide novel treatment options to address these debilitating diseases. However, despite significant advancements in our understanding of the BGMA, clinical data is lacking. In this article, we will review current understanding of the comorbidity of gastrointestinal diseases and psychological disorders. We will also review the current evidence supporting the key role of the BGMA in this pathology. Finally, we will discuss the clinical implications of the BGMA in the evaluation and management of psychological and gastrointestinal disorders.

Fructan-sensitive children with irritable bowel syndrome have distinct gut microbiome signatures

BACKGROUND

Dietary fructans may worsen gastrointestinal symptoms in children with irritable bowel syndrome (IBS).

AIM

To determine whether gut microbiome composition and function are associated with childhood IBS fructan-induced symptoms.

METHODS

Faecal samples were collected from 38 children aged 7-17 years with paediatric Rome III IBS, who previously completied a double-blind, randomised, placebo-controlled crossover (fructan vs maltodextrin) trial. Fructan sensitivity was defined as an increase of ≥30% in abdominal pain frequency during the fructan diet. Gut microbial composition was determined via 16Sv4 rDNA sequencing. LEfSe evaluated taxonomic composition differences. Tax4Fun2 predicted microbial fructan metabolic pathways.

RESULTS

At baseline, 17 fructan-sensitive (vs 21 fructan-tolerant) subjects had lower alpha diversity (q < 0.05) and were enriched in the genus Holdermania. In contrast, fructan-tolerant subjects were enriched in 14 genera from the class Clostridia. During the fructan diet, fructan-sensitive (vs tolerant) subjects were enriched in both Agathobacter (P = 0.02) and Cyanobacteria (P = 0.0001). In contrast, fructan-tolerant subjects were enriched in three genera from the Clostridia class. Comparing the fructan vs maltodextrin diet, fructan-sensitive subjects had a significantly increased relative abundance of Bifidobacterium (P = 0.02) while fructan-tolerant subjects had increased Anaerostipes (P = 0.03) during the fructan diet. Only fructan-sensitive subjects had a trend towards increased predicted β-fructofuranosidase during the fructan vs maltodextrin diet.

CONCLUSIONS

Fructan-sensitive children with IBS have distinct gut microbiome signatures. These microbiome signatures differ both at baseline and in response to a fructan challenge.

Functional abdominal pain in adolescents: case-based management

Functional gastrointestinal disorders (FGIDs), including functional abdominal pain (FAP), account for a large portion of conditions seen by paediatric gastroenterologists. Despite the commonality of FGIDs, there remains significant stigma around these diagnoses among medical providers, patients and families. This is due to the absence of easily identifiable biological markers in FGIDs and the overlay with psychological and social factors contributing to symptom onset and maintenance. As such, the biopsychosocial model is essential in conceptualising, evaluating and treating FGIDs. The way in which medical providers explain FGIDs and the manner in which they collaborate with other specialists (eg, psychologists, dieticians, physical therapists, school nurses) is paramount to the patient and family acceptance of an FGID diagnosis and the success of subsequent treatment. The following review outlines paediatric FGIDs with a focus on FAP in adolescents, in particular within the context of the biopsychosocial approach to pathophysiology, diagnosis and treatment.