The low FODMAP diet: recent advances in understanding its mechanisms and efficacy in IBS

Efficacy of a low FODMAP diet in irritable bowel syndrome: systematic review and network meta-analysis

OBJECTIVE

A diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) is recommended for irritable bowel syndrome (IBS), if general lifestyle and dietary advice fails. However, although the impact of a low FODMAP diet on individual IBS symptoms has been examined in some randomised controlled trials (RCTs), there has been no recent systematic assessment, and individual trials have studied numerous alternative or control interventions, meaning the best comparator is unclear. We performed a network meta-analysis addressing these uncertainties.

DESIGN

We searched the medical literature through to 2 April 2021 to identify RCTs of a low FODMAP diet in IBS. Efficacy was judged using dichotomous assessment of improvement in global IBS symptoms or improvement in individual IBS symptoms, including abdominal pain, abdominal bloating or distension, and bowel habit. Data were pooled using a random effects model, with efficacy reported as pooled relative risks (RRs) with 95% CIs, and interventions ranked according to their P-score.

RESULTS

We identified 13 eligible RCTs (944 patients). Based on failure to achieve an improvement in global IBS symptoms, a low FODMAP diet ranked first vs habitual diet (RR of symptoms not improving=0.67; 95% CI 0.48 to 0.91, P-score=0.99), and was superior to all other interventions. Low FODMAP diet ranked first for abdominal pain severity, abdominal bloating or distension severity and bowel habit, although for the latter it was not superior to any other intervention. A low FODMAP diet was superior to British Dietetic Association (BDA)/National Institute for Health and Care Excellence (NICE) dietary advice for abdominal bloating or distension (RR=0.72; 95% CI 0.55 to 0.94). BDA/NICE dietary advice was not superior to any other intervention in any analysis.

CONCLUSION

In a network analysis, low FODMAP diet ranked first for all endpoints studied. However, most trials were based in secondary or tertiary care and did not study effects of FODMAP reintroduction and personalisation on symptoms.

A Low-FODMAP Diet Provides Benefits for Functional Gastrointestinal Symptoms but Not for Improving Stool Consistency and Mucosal Inflammation in IBD: A Systematic Review and Meta-Analysis

Background: A low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols diet (LFD) is claimed to improve functional gastrointestinal symptoms (FGSs). However, the role of LFD in inflammatory bowel disease (IBD) patients with FGSs remains unclear. Objective: To systematically assess the efficacy of LFD in IBD patients with FGSs. Methods: Six databases were searched from inception to 1 January 2022. Data were synthesized as the relative risk of symptoms improvement and normal stool consistency, mean difference of Bristol Stool Form Scale (BSFS), Short IBD Questionnaire (SIBDQ), IBS Quality of Life (IBS-QoL), Harvey-Bradshaw index (HBi), Mayo score, and fecal calprotectin (FC). Risk of bias was assessed based on study types. A funnel plot and Egger’s test were used to analyze publication bias. Results: This review screened and included nine eligible studies, including four randomized controlled trials (RCTs) and five before–after studies, involving a total of 446 participants (351 patients with LFD vs. 95 controls). LFD alleviated overall FGSs (RR: 0.47, 95% CI: 0.33–0.66, p = 0.0000) and obtained higher SIBDQ scores (MD = 11.24, 95% CI 6.61 to 15.87, p = 0.0000) and lower HBi score of Crohn’s disease (MD = −1.09, 95% CI −1.77 to −0.42, p = 0.002). However, there were no statistically significant differences in normal stool consistency, BSFS, IBS-QoL, Mayo score of ulcerative colitis, and FC. No publication bias was found. Conclusions: LFD provides a benefit in FGSs and QoL but not for improving stool consistency and mucosal inflammation in IBD patients. Further well-designed RCTs are needed to develop the optimal LFD strategy for IBD.

Effect of Oral Intake of Lactiplantibacillus plantarum APsulloc 331261 (GTB1TM) on Diarrhea-Predominant Irritable Bowel Syndrome: A Randomized, Double-Blind, Placebo-Controlled Study

Irritable bowel syndrome (IBS) causes intestinal discomfort, gut dysfunction, and poor quality of life. This randomized, double-blind placebo-controlled trial evaluated the efficacy of Lactiplantibacillus (Lp., formerly Lactobacillus) plantarum APsulloc 331261 (GTB1^TM) from green tea leaves in participants with diarrhea-predominant irritable bowel syndrome (IBS-D). Twenty-seven participants meeting the Rome IV diagnostic criteria were randomized for GTB1 or placebo ingestion for four weeks and follow-up for two weeks. The efficacy endpoints included adequate global relief of symptoms, assessment of intestinal discomfort symptom severity and frequency, stool frequency, satisfaction, and fecal microbiome abundance. Of all participants, 94.4% and 62.5% reported global relief of symptoms in the GTB1 and placebo groups, respectively, with significant differences (p = 0.037). GTB1 significantly reduced the severity and frequency of abdominal pain, bloating, and feeling of incomplete evacuation. The frequencies of diarrhea were decreased −45.89% and −26.76% in the GTB1 and placebo groups, respectively (p = 0.045). Hence, GTB1 ingestion improved IBS-D patient quality of life. After four weeks treatment, the relative abundance of Lactobacillus was higher in the GTB1 than in the placebo group (p = 0.010). Our results showed that GTB1 enhanced intestinal discomfort symptoms, defecation consistency, quality of life, beneficial microbiota, and overall intestinal health.

Menstrual Cycle Variation in MRI-Based Quantification of Intraluminal Gas in Women With and Without Dysmenorrhea

Women frequently report increased bloating, flatulence, and pain during the perimenstrual period. However, it is unknown whether women have more intraluminal gas during menses. To evaluate whether pain-free women or women with dysmenorrhea have different amounts of intraluminal bowel gas during the menses, we utilized magnetic resonance imaging (MRI) to determine colonic gas volumes throughout the menstrual cycle. To avoid dietary influence, the participants were instructed to avoid gas-producing foods before their scheduled MRI. We verified the measurement repeatability across the reviewers and obtained an intraclass correlation coefficient of 0.92. There were no significant differences in intraluminal gas volume between menses and non-menses scans (p = 0.679). Even among the women with dysmenorrhea, there was no significant difference in the intraluminal gas volume between menses and non-menses (p = 0.753). During menstruation, the participants with dysmenorrhea had less intraluminal gas than participants without dysmenorrhea (p = 0.044). However, the correlation between the bowel gas volume and the pain symptoms were not significant (p > 0.05). Although increased bowel symptoms and bloating are reported in the women with dysmenorrhea during menses, our results do not support the hypothesis that increased intraluminal gas is a contributing factor. Although dietary treatment has been shown in other studies to improve menstrual pain, the mechanism responsible for abdominal symptoms requires further investigation. Our findings demonstrate that the intraluminal bowel gas volume measurements are feasible and are unaffected by menses under a controlled diet. The method described might prove helpful in future mechanistic studies in clarifying the role of intraluminal bowel gas in other conditions.

The Role of Diet and Gut Microbiota in Regulating Gastrointestinal and Inflammatory Disease

Diet is an important lifestyle factor that is known to contribute in the development of human disease. It is well established that poor diet plays an active role in exacerbating metabolic diseases, such as obesity, diabetes and hypertension. Our understanding of how the immune system drives chronic inflammation and disease pathogenesis has evolved in recent years. However, the contribution of dietary factors to inflammatory conditions such as inflammatory bowel disease, multiple sclerosis and arthritis remain poorly defined. A western diet has been associated as pro-inflammatory, in contrast to traditional dietary patterns that are associated as being anti-inflammatory. This may be due to direct effects of nutrients on immune cell function. Diet may also affect the composition and function of gut microbiota, which consequently affects immunity. In animal models of inflammatory disease, diet may modulate inflammation in the gastrointestinal tract and in other peripheral sites. Despite limitations of animal models, there is now emerging evidence to show that anti-inflammatory effects of diet may translate to human gastrointestinal and inflammatory diseases. However, appropriately designed, larger clinical studies must be conducted to confirm the therapeutic benefit of dietary therapy.

Biomolecules from Plant Wastes Potentially Relevant in the Management of Irritable Bowel Syndrome and Co-Occurring Symptomatology

During and following the processing of a plant’s raw material, considerable amounts are wasted, composted, or redistributed in non-alimentary sectors for further use (for example, some forms of plant waste contribute to biofuel, bioethanol, or biomass production). However, many of these forms of waste still consist of critical bioactive compounds used in the food industry or medicine. Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders. The primary treatment is based on symptomatology alleviation and controlled dietary management. Thus, this review aimed to describe the possible relevance of molecules residing in plant waste that can be used to manage IBS and co-occurring symptoms. Significant evidence was found that many forms of fruit, vegetable, and medicinal plant waste could be the source of some molecules that could be used to treat or prevent stool consistency and frequency impairments and abdominal pain, these being the main IBS symptoms. While many of these molecules could be recovered from plant waste during or following primary processing, the studies suggested that enriched food could offer efficient valorization and prevent further changes in properties or stability. In this way, root, stem, straw, leaf, fruit, and vegetable pomaces were found to consist of biomolecules that could modulate intestinal permeability, pain perception, and overall gastrointestinal digestive processes.

Atractylenolide-1 targets SPHK1 and B4GALT2 to regulate intestinal metabolism and flora composition to improve inflammation in mice with colitis

BACKGROUND

Atractylenolide-1, an active component of Atractylodes Lancea, which is widely used to improve the gastrointestinal function. However, the efficacy and mechanism remain unclear in treating ulcerative colitis (UC).

PURPOSE

This study aimed to investigate the efficacy and the underlying mechanism of atractylenolide-1in UC.

METHODS

A dextran sulfate sodium (DSS)-induced UC mouse model was used to investigate the efficacy of atractylenolide-1. 16S DNA sequencing, GC-MS technique and transcriptome sequencing were used to detect the composition of mouse intestinal flora, the changes of metabolites and gene expression in mouse intestine. Compound-reaction-enzyme-gene network was used to find drug targets. Recombinant plasmid overexpression was used to verify drug targets in DSS mouse models.

RESULTS

The results showed that Atractylenolide-1 could significantly improve weight loss, diarrhea, blood in the stool, shortening of the colon, the loss of colonic goblet cells, reduction in mucoprotein MUC2, and tight junction proteins (zo-1, occludin) in mice with colitis. It reduced the inflammatory factors TNF-α, IL-6, IL-1β as well. The 16S sequencing showed that Atractylenolide-1 regulated the diversity and abundance of the intestinal flora in mice with colitis, and the analysis of flora enrichment indicated that the regulation of intestinal flora by atractylenolide-1 may be related to the regulation of metabolism. Correlation analysis of metabolomics and transcriptome showed that two genes SPHK1 and B4GALT2 related to the metabolism of fructose and galactose were regulated by atractylenolide-1. Further verification showed that atractylenolide-1 significantly inhibited the aberrance of SPHK1 and B4GALT2 in the colon with colitis. Meanwhile, it inhibited the activation of the PI3K-AKT pathway. SPHK1 and B4GALT2 overexpressing reversed the therapeutic effect of atractylenolide-1 in mice with colitis.

CONCLUSION

Atractylenolide-1 is a potential drug for the treatment of colitis by suppressing inflammation via the SPHK1/PI3K/AKT axis and by targeting SPHK1 and B4GAT2 to regulate fructose/galactose-related metabolism, thereby regulating the composition of the intestinal flora.

Dietary interventions for functional abdominal pain disorders in children: a systematic review and meta-analysis

BACKGROUND

Functional abdominal pain disorders (FAPDs) are common among children and are associated with decreased quality of life and school attendance. Several dietary interventions have been suggested to improve symptoms of FAPDs. This systematic review assessed the efficacy and safety of dietary interventions for pediatric FAPDs.

DESIGN AND METHODS

Electronic databases were searched (inception-October 2021). Systematic reviews or RCTs were included if children (4-18 years) with FAPDs were treated with dietary interventions and compared to placebo, no diet or any other diet. Data extraction and assessment of quality of evidence based on GRADE system was independently performed by two review authors. Outcomes were treatment success, pain intensity and frequency, and withdrawal due to adverse events.

RESULTS

Twelve articles were included, representing data of 819 pediatric FAPD patients. Trials investigating fibers, FODMAP diet, fructans, fructose-restricted diet, prebiotic (inulin), serum-derived bovine immunoglobulin, and vitamin D supplementation were included. We found very low-certainty evidence that the use of fibers leads to higher treatment success (NNT = 5).

CONCLUSION

Based on current evidence, the use of fibers can be discussed in daily practice. High-quality intervention trials are highly needed to investigate if other dietary interventions are effective in the treatment of pediatric FAPD.

Long-term personalized low FODMAP diet improves symptoms and maintains luminal Bifidobacteria abundance in irritable bowel syndrome

BACKGROUND

Short-term trials demonstrate the low FODMAP diet improves symptoms of irritable bowel syndrome (IBS) but impacts nutrient intake and the gastrointestinal microbiota. The aim of this study was to investigate clinical symptoms, nutrient intake, and microbiota of patients with IBS 12 months after starting a low FODMAP diet.

METHODS

Participants enrolled in a previous short-term clinical trial and who had been through structured FODMAP restriction, reintroduction, and personalization were invited to participate in a follow-up study at one time point at 12 months. Gastrointestinal symptoms, stool output, dietary intake, and quality of life were recorded. Stool samples were collected and analyzed for microbiota (qPCR) and short-chain fatty acids (SCFA). Data were compared with baseline (prior to any intervention in the original clinical trial) using non-parametric statistics.

KEY RESULTS

Eighteen participants were included in the study. Adequate relief of symptoms occurred in 5/18 (28%) at baseline and increased to 12/18 (67%) following long-term personalized low FODMAP diet (p = 0.039). There was a reduction in IBS-SSS total score between baseline (median 227, IQR 99) and long term (154, 89; p < 0.001). Bifidobacteria abundance was not different between baseline (median 9.29 log10 rRNA genes/g, IQR 1.45) and long term (9.20 log10 rRNA genes/g, 1.41; p = 0.766, q = 0.906); however, there were lower concentrations of total SCFA, acetate, propionate, and butyrate.

CONCLUSIONS

In this long-term analysis, two thirds of patients reported adequate relief of symptoms after 12 months of personalized low FODMAP diet that did not result in differences from baseline in Bifidobacteria. FODMAP reintroduction and personalization may normalize some of the effects of short-term FODMAP restriction.

Irritable bowel syndrome and diet

PURPOSE OF REVIEW

Irritable bowel syndrome (IBS) is a highly prevalent functional gastrointestinal disorder (FGID) characterized by chronic abdominal pain and altered bowel habits. The diagnosis of IBS is based on the presence of defined clinical Rome IV criteria in the absence of alarm features. The majority of patients with IBS report of food triggers eliciting typical IBS symptoms and trying to modify their dietary intake.

RECENT FINDINGS

FGID including IBS are defined as disorders of the gut-brain interaction. A large proportion of individuals with IBS link their symptoms to dietary factors, and recent clinical studies have shown benefits of a diet low in FODMAPs (Fermentable Oligo-, Di-, and Monosaccharides and Polyols) on IBS symptoms and quality of life. Dietary interventions mediate directly changes of luminal gut contents affecting chemosensing-enteroendocrine cells in the modulation of the gut brain microbiome axis in IBS patients. Long-term assessment of clinical outcomes in patients on a low FODMAP diet is needed. Professional guidelines have incorporated the suggestion to offer IBS patients a diet low in FODMAPs.

SUMMARY

The FGIDs, including IBS, are defined as gut-brain disorders. Low FODMAP diet has been shown in clinical trials to reduce IBS symptoms but long-term efficacy and nutritional side-effects remain uncertain.

Genetic and phenotypic diversity of fecal Candida albicans strains in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common disorder characterized by chronic abdominal pain and changes in bowel movements. Visceral hypersensitivity is thought to be responsible for pain complaints in a subset of patients. In an IBS-like animal model, visceral hypersensitivity was triggered by intestinal fungi, and lower mycobiota α-diversity in IBS patients was accompanied by a shift toward increased presence of Candida albicans and Saccharomyces cerevisiae. Yet, this shift was observed in hypersensitive as well as normosensitive patients and diversity did not differ between IBS subgroups. The latter suggests that, when a patient changes from hyper- to normosensitivity, the relevance of intestinal fungi is not necessarily reflected in compositional mycobiota changes. We now confirmed this notion by performing ITS1 sequencing on an existing longitudinal set of fecal samples. Since ITS1 methodology does not recognize variations within species, we next focused on heterogeneity within cultured healthy volunteer and IBS-derived C. albicans strains. We observed inter- and intra-individual genomic variation and partial clustering of strains from hypersensitive patients. Phenotyping showed differences related to growth, yeast-to-hyphae morphogenesis and gene expression, specifically of the gene encoding fungal toxin candidalysin. Our investigations emphasize the need for strain-specific cause-and-effect studies within the realm of IBS research.

Immune activation in irritable bowel syndrome: what is the evidence?

Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder that is characterized by abdominal pain and an altered defecation pattern. It affects between 5 and 20% of the general population and can seriously impact quality of life. The pathophysiology of IBS is rather complex and multifactorial including, for example, altered signalling by the gut-brain axis, dysbiosis, abnormal visceral pain signalling and intestinal immune activation. The latter has gained particular interest in recent years, with growing insight into the bidirectional communication between the nervous system and the immune system. In this Review, we detail the current evidence suggesting that immune activation contributes to the pathology seen in patients with IBS and discuss the potential mechanisms involved. Moreover, we describe how immune mediators, particularly those released by mast cells, can directly activate or sensitize pain-transmitting nerves, leading to increased pain signalling and abdominal pain. Finally, we discuss the potential of interventions targeting immune activation as a new therapeutic strategy for patients suffering from IBS.

Dietary Intake Is Unlikely to Explain Symptom Severity and Syndrome-Specific Microbiome Alterations in a Cohort of Women with Fibromyalgia

BACKGROUND

Significant alterations were recently identified in the composition and putative function of the gut microbiome in women with fibromyalgia. As diet can influence the composition of the gut microbiome, differences in nutritional intake could, in theory, account for some of these specific fibromyalgia microbiome alterations. The current study aims to compare the diet of women with fibromyalgia to that of controls in order to explore possible associations between the intake of certain nutrients, symptom severity and gut microbiome composition.

METHODS

The study population was comprised of 56 women with fibromyalgia and 68 controls. Dietary intake was assessed using the NIH Automated Self-Administered 24 h recall, following dietitian's instructions and the completion of a three-day dietary recall. The gut microbiome was assessed by 16S ribosomal RNA gene sequencing of stool samples.

RESULTS

Most demographic and anthropometric characteristics were comparable between groups. The average energy and macronutrient intake (total and relative) and overall diet quality score were not different between patients and controls, nor were the main vitamins, minerals, fatty acids, alcohol, caffeine, sugar or fiber intakes. The daily intake of micronutrients and normalized macronutrients in women with fibromyalgia was largely not correlated with disease-specific measures, including pain intensity, fatigue, cognitive symptoms and quality of sleep, or with the relative quantity of almost any of the gut microbiome bacterial taxa differentially abundant in fibromyalgia.

CONCLUSION

These data demonstrate that dietary intakes, as evaluated by self-reported questionnaires, probably cannot explain the syndrome-specific differences in gut microbiome or the clinical phenotype of fibromyalgia.

A Food First Approach to Carbohydrate Supplementation in Endurance Exercise: A Systematic Review

This systematic review analyzed whether carbohydrate source (food vs. supplement) influenced performance and gastrointestinal (GI) symptoms during endurance exercise. Medline, SPORTDiscus, and citations were searched from inception to July 2021. Inclusion criteria were healthy, active males and females aged >18 years, investigating endurance performance, and GI symptoms after ingestion of carbohydrate from a food or supplement, <60 min before or during endurance exercise. The van Rosendale scale was used to determine risk of bias, with seven studies having low risk of bias. A total of 151 participants from 15 studies were included in the review. Three studies provided 0.6-1 g carbohydrate/kg body mass during 5-45 min precycling exercise (duration 60-70 min) while 12 studies provided 24-80 g/hr carbohydrate during exercise (60-330 min). Except one study that suggested a likely harmful effect (magnitude-based inferences) of a bar compared to a gel consumed during exercise on cycling performance, there were no differences in running (n = 1) or cycling (n = 13) performance/capacity between food and supplemental sources. Greater GI symptoms were reported with food compared with supplemental sources. Highly heterogenous study designs for carbohydrate dose and timing, as well as exercise protocol and duration, make it difficult to compare findings between studies. A further limitation results from only one study assessing running performance. Food choices of carbohydrate consumed immediately before and during endurance exercise result in similar exercise performance/capacity responses to supplemental carbohydrate sources, but may slightly increase GI symptoms in some athletes, particularly with exercise >2 hr.

Gut-brain axis dysfunction underlies FODMAP-induced symptom generation in irritable bowel syndrome

BACKGROUND

FODMAPs produce similar small bowel water and colonic gas in patients with irritable bowel syndrome (IBS) and healthy controls (HCs), despite IBS patients reporting increased gastrointestinal (GI) symptoms.

AIM

To unravel the mechanisms underlying FODMAP-induced symptom reporting, we investigated gut and brain responses to fructan administration in IBS patients and HC.

METHODS

This randomised, double-blind, cross-over study consisted of three visits where fructans (40 g/500 mL saline), glucose (40 g/500 mL saline) or saline (500 mL) were infused intragastrically during 1 h MR brain scanning; abdominal MRI was performed before, 1 h, and 2 h post-infusion. Symptoms were rated using validated scales.

RESULTS

In IBS (n = 13), fructans induced more cramps, pain, flatulence and nausea compared to glucose (P = 0.03, 0.001, 0.009 and <0.001 respectively), contrary to HC (n = 13) (all P > 0.14), with between-group differences for cramps and nausea (P = 0.004 and 0.023). Fructans increased small bowel motility and ascending colonic gas and volume equally in IBS and HC (between-group P > 0.25). The difference in colonic gas between fructans and saline covaried with differences in bloating and cramps in IBS (P = 0.008 and 0.035 respectively). Pain-related brain regions responded differentially to fructans in IBS compared to HC, including the cerebellum, supramarginal gyrus, anterior and midcingulate cortex, insula and thalamus (p_{FWE-corrected}  < 0.05); these brain responses covaried with symptom responses in IBS.

CONCLUSIONS

Fructans increase small bowel motility and colon gas and volume similarly in IBS patients and HC. Increased symptom responses to fructans in IBS covary with altered brain responses in pain-related regions, indicating that gut-brain axis dysregulation may drive FODMAP-induced symptom generation in IBS.

Lactose Malabsorption and Presumed Related Disorders: A Review of Current Evidence

Background. Lactose malabsorption (LM) is a frequent clinical problem associated with several digestive and extra-digestive diseases. The aim of this manuscript was to clarify the real clinical impact of LM on these disorders. Methods. A literature search for digestive and extra-digestive disorders related to LM was carried out using PubMed, Medline and Cochrane. Results. A transient lactase deficiency is present in celiac disease (CD) on a normal diet. The persistence of symptoms in CD on a gluten-free diet may be instead, in part, attributed to a primary LM. Similar circumstances are present in inflammatory bowel diseases (IBD), in which LM can be responsible for a part of persistent symptoms in IBD on clinical remission. LM and irritable bowel syndrome (IBS) are instead independent conditions. On the other hand, a lactose-restricted diet may be useful for some IBS patients. A reduced lactose intake can lead to low bone mass and limited risk of fragility fractures. Finally, the absorption of levothyroxine could be conditioned by LM. Conclusions. LM can be responsible for persistent symptoms in CD and IBD. The association with IBS seems to be casual. Bone mass and levothyroxine absorption can be affected by LM.

The Role of Carbohydrates in Irritable Bowel Syndrome: Protocol for a Randomized Controlled Trial Comparing Three Different Treatment Options

BACKGROUND

Although it is widely acknowledged that food intake can worsen symptoms in patients with irritable bowel syndrome (IBS), there is a lack of efficient treatments that can apply to all patients and subtypes of IBS. As IBS can manifest in different ways, it is likely that the most successful treatment option will differ among patients; therefore, this large, randomized controlled trial comparing 3 different treatment options for patients with IBS is highly warranted.

OBJECTIVE

This study aims to conduct a randomized controlled trial to evaluate the effectiveness of 3 different treatment options for patients with IBS.

METHODS

A total of 300 patients with IBS will be randomized (1:1:1) to receive one of the following three treatment options: a diet with low total carbohydrate content; a diet combining low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols and traditional dietary advice in IBS; and optimized medical treatment. The study will comprise a 10-day screening period, 28 days of intervention, and a 6-month follow-up for patients receiving dietary treatment. Questionnaires assessing both gastrointestinal and extraintestinal symptoms will be used as end points, as well as metabolomics, microbiota profiling, and immunological markers. Furthermore, qualitative methods will be used to evaluate the patients' experiences regarding diet treatments.

RESULTS

Recruitment for this study began in January 2017. By May 2021, of the proposed 300 participants, 270 (90%) had been randomized, and 244 (81.3%) participants had finished the 4-week intervention. The study is still in progress, and the results are expected to be published in 2022.

CONCLUSIONS

By collecting a wide range of data before, during, and after treatment in a large group of patients with IBS and diverse bowel habits, we will gain new insights into the predictors of response to treatment. That information can, in the future, be used to personalize treatment for the patient, based on the individual's phenotype and IBS symptoms. In addition, the long-term effects of 2 different dietary treatments will be evaluated regarding their impact on gut microbiota and clinical laboratory tests and to ensure that they are safe, effective, and applicable for patients with IBS.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02970591; https://clinicaltrials.gov/ct2/show/NCT02970591.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/31413.

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.

Fermentable Oligo-, Di-, and Mono-Saccharides and Polyols (FODMAPs) Consumption and Irritable Bowel Syndrome in the French NutriNet-Santé Cohort

(1) Background: Specific foods, and more particularly, fermentable oligo-, di-, and mono-saccharides and polyols (FODMAPs) are often considered as triggers of digestive symptoms in Irritable Bowel Syndrome (IBS). Our aim was to study FODMAP consumption in controls and IBS participants in a large French population-based cohort; (2) Methods: Participants from the NutriNet-Santé cohort study completed the Rome IV and IBS-SSS questionnaire in a cross sectional study. Among them, 27,949 eligible participants had previously completed three 24-h recalls as well as anthropometrics, socio-demographical and lifestyle data. Total FODMAP intake (in g/day) was computed using a specific composition table. The association between FODMAPs and IBS was estimated through multivariable logistic regression models; (3) Results: Included participants were mainly women (75.4%) and the mean age was 43.4 ± 14.1 years. FODMAPs accounted for a mean daily intake of 19.4 ± 9.5 g/day. Overall 1295 participants (4.6%) were identified with an IBS. After adjusting for confounding factors, IBS participants had lower intakes in FODMAPs than non-IBS ones (aOR: 0.88, 95% CI: 0.82–0.95, p-value: 0.001). IBS severity was associated with more frequent low FODMAP intakes (<9 g/day); (4) Conclusions: Participants tended to consume 19 g of FODMAPs per day, but slightly less for IBS participants than for controls. In IBS participants, higher severity was associated with lower intakes.

Better response to low FODMAP diet in disorders of gut-brain interaction patients with pronounced hydrogen response to a nutrient challenge test

BACKGROUND AND AIM

Previous studies have shown a reduction of gastrointestinal symptoms in irritable bowel syndrome (IBS) patients following a low FODMAP diet (LFD). It remains unknown which disorders of gut-brain interaction (DGBI) patients would benefit most from LFD. We aimed to analyze LFD response regarding a preceding nutrient challenge test (NCT).

METHODS

Data of 110 consecutive DGBI patients undergoing NCT and LFD between August 2015 and August 2018 were analyzed retrospectively. LFD response was assessed by changes in IBS Symptom Severity Score (IBS-SSS). In mixed-effects linear regression models, the impact of hydrogen values and abdominal symptoms during NCT, performed with 30-g lactulose and 400-mL liquid test meal, on IBS-SSS changes were analyzed.

RESULTS

Low FODMAP diet induced a significant IBS-SSS reduction of 78 points (95% confidence interval [CI] 50-96; P < 0.001). Patients with higher NCT-induced hydrogen increase during proximal intestinal transit had a significantly better LFD response (-66 IBS-SSS reduction per 10-ppm hydrogen increase, 95% CI -129 to -4, P = 0.045). Additionally, the higher the NCT-induced maximum hydrogen increase during mid-distal and distal intestinal transit, the better are the responses to LFD (-6 IBS-SSS per 10-ppm maximum delta hydrogen, 95% CI -11 to -1, P = 0.040). There was no association of LFD response with abdominal symptom generation during NCT.

CONCLUSIONS

Our study is the first one analyzing and demonstrating significant associations between NCT results and LFD response. These findings are of high clinical importance, as they identify a subgroup of DGBI patients that may profit most from a restrictive LFD as first-line therapy.

High FODMAP diet causes barrier loss via lipopolysaccharide-mediated mast cell activation

Fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) are carbohydrates thought to contribute to the symptoms of IBS. A diet in high in FODMAPs (HFM) induces gastrointestinal symptoms in patients with irritable bowel syndrome (IBS), and a diet low in FODMAPs (LFM) improves symptoms in up to 60% of patients with IBS. However, the mechanism by which FODMAPs affect IBS symptoms is unclear. We showed that mice fed on a HFM diet have mast cell activation and colonic barrier loss. Using mast cell-deficient mice with and without mast cell reconstitution, we showed that HFM-mediated colonic barrier loss is dependent on TLR4-dependent mast cell activation. In in vitro studies, we demonstrated that IBS fecal supernatant stimulates mast cells significantly more compared with fecal supernatant from healthy controls. This effect of IBS fecal supernatant on mast cell stimulation is ameliorated in the absence of the TLR4 receptor and after a LFM diet. We found that a LFM diet improves colonic barrier function and reduces mast cell activation while decreasing fecal LPS levels. Our findings indicate that a HFM diet causes mast cell activation via LPS, which in turn leads to colonic barrier loss, and a LFM diet reverses these pathophysiologic mucosal changes.

Epigastric symptom response to low FODMAP dietary advice compared with standard dietetic advice in individuals with functional dyspepsia

BACKGROUND

Certain dietary constituents may provoke symptoms of functional dyspepsia (FD); however, there is an absence of dietary trials testing specific dietary interventions. Empirically derived dietary strategies and the low FODMAP diet are frequently used in practice. This study aimed to compare the effectiveness of low FODMAP dietary advice with standard dietary advice for reducing epigastric and overall gastrointestinal symptoms in individuals with FD.

METHODS

Data were collected from 59 consecutive eligible individuals with FD attending an initial and review outpatient dietetic consultation at Princess Alexandra Hospital. Of these, 40 received low FODMAP advice and 19 received standard dietary advice. As part of usual care, the Structured Assessment of Gastrointestinal Symptom Scale (SAGIS) was used to assess epigastric (maximum score = 28) and overall gastrointestinal symptoms (maximum score = 88). Dietary adherence data were collected, and change in symptom score and proportion of responders (defined as a ≥30% reduction in score) for epigastric and total symptoms was calculated.

KEY RESULTS

Most individuals (48/59, 81%) had FD and coexisting irritable bowel syndrome. There was a greater reduction in epigastric score in those receiving low FODMAP dietary advice compared with those receiving standard advice (est. marginal mean [95% CI]: -3.6 [-4.9, -2.2] vs. -0.9 [-2.9, 1.1], p = 0.032) and total symptom score (-9.4 [-12.4, -6.4] vs. -3.3 [-7.7, 1.1] p = 0.026). A greater proportion receiving low FODMAP dietary advice were responders versus those receiving standard advice (50% vs. 16%, p = 0.012). Dietary adherence did not differ between groups (p = 0.497).

CONCLUSIONS & INFERENCES

The low FODMAP diet appears more effective for improving epigastric symptoms in people with FD compared with standard advice. A randomized controlled trial is required to substantiate these findings.

Group education on the low FODMAP diet improves gastrointestinal symptoms but neither anxiety or depression in irritable bowel syndrome

BACKGROUND

The low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet is an effective dietitian-led treatment for irritable bowel syndrome (IBS). An increasing demand of IBS patient referrals has warranted group FODMAP education led by specialist dietitians. Psychological co-morbidities are common in IBS, although how the low FODMAP diet influences psychological outcomes is not understood. The present study aimed to evaluate symptom related outcomes of the diet following group education and assess its effect on psychological profiles.

METHODS

An observational, prospective study was conducted in 55 IBS patients who attended FODMAP Restriction and FODMAP Reintroduction group sessions. Data were collected at baseline and follow-up after FODMAP Restriction and analysed using descriptive and McNemar's tests. Primary outcome was evaluated by IBS Symptom Severity Score (IBS-SSS). Secondary psychological outcomes included anxiety and depression using the Hospital Anxiety and Depression Scale (HADS) and risk of eating disorder questionnaire (SCOFF).

RESULTS

After FODMAP Restriction, 27 of 55 (54%) patients reported clinically relevant symptom improvement, as defined by a reduction in the IBS-SSS ≥50 points, whereas no differences were recorded in the proportion of patients identified with clinical anxiety (p = 1.000) or clinical depression (p = 0.375). Positively, no increased risk of an eating disorder was observed.

CONCLUSIONS

The present study provides data supporting the efficacy of the low FODMAP diet in IBS patients who attended dietitian led group education settings in tertiary care. Clinically significant improvements in gastrointestinal symptoms were observed, although with no impact on clinical levels of anxiety, depression or the risk of an eating disorder.

Role of microRNAs in Disorders of Gut-Brain Interactions: Clinical Insights and Therapeutic Alternatives

Disorders of gut-brain interactions (DGBIs) are heterogeneous in nature and intertwine with diverse pathophysiological mechanisms. Regular functioning of the gut requires complex coordinated interplay between a variety of gastrointestinal (GI) cell types and their functions are regulated by multiple mechanisms at the transcriptional, post-transcriptional, translational, and post-translational levels. MicroRNAs (miRNAs) are small non-coding RNA molecules that post-transcriptionally regulate gene expression by binding to specific mRNA targets to repress their translation and/or promote the target mRNA degradation. Dysregulation of miRNAs might impair gut physiological functions leading to DGBIs and gut motility disorders. Studies have shown miRNAs regulate gut functions such as visceral sensation, gut immune response, GI barrier function, enteric neuronal development, and GI motility. These biological processes are highly relevant to the gut where neuroimmune interactions are key contributors in controlling gut homeostasis and functional defects lead to DGBIs. Although extensive research has explored the pathophysiology of DGBIs, further research is warranted to bolster the molecular mechanisms behind these disorders. The therapeutic targeting of miRNAs represents an attractive approach for the treatment of DGBIs because they offer new insights into disease mechanisms and have great potential to be used in the clinic as diagnostic markers and therapeutic targets. Here, we review recent advances regarding the regulation of miRNAs in GI pacemaking cells, immune cells, and enteric neurons modulating pathophysiological mechanisms of DGBIs. This review aims to assess the impacts of miRNAs on the pathophysiological mechanisms of DGBIs, including GI dysmotility, impaired intestinal barrier function, gut immune dysfunction, and visceral hypersensitivity. We also summarize the therapeutic alternatives for gut microbial dysbiosis in DGBIs, highlighting the clinical insights and areas for further exploration. We further discuss the challenges in miRNA therapeutics and promising emerging approaches.

How can probiotic improve irritable bowel syndrome symptoms?

The onset and manifestations of irritable bowel syndrome (IBS) is associated with several factors, and the pathophysiology involves various central and peripheral mechanisms. Most studies indicate that the management of gut microbiota could significantly affect the improvement of subjective disorders in patients with IBS. Numerous clinical trials have assessed the efficacy of probiotics for IBS with controversial conclusions. Several clinical trials have suggested that probiotics can improve global IBS symptoms, while others only improve individual IBS symptoms, such as bloating scores and abdominal pain scores. Only a few clinical trials have found no apparent effect of probiotics on IBS symptoms. Generally, probiotics appear to be safe for patients with IBS. However, the question of which probiotics should be used for certain IBS subtypes remains unresolved. In everyday practice, the dose of the recommended probiotic remains questionable, as well as how long the probiotic should be used in therapy. The use of probiotics in the M subtype and non-classified IBS is particularly problematic, in which combination therapy should be recommended due to the change in symptoms. Therefore, new approaches are needed in the design of clinical studies that should address certain subtypes of IBS.

Ayurvedic vs. Conventional Nutritional Therapy Including Low-FODMAP Diet for Patients With Irritable Bowel Syndrome-A Randomized Controlled Trial

Aims: To compare the effects of Ayurvedic and conventional nutritional therapy in patients with irritable bowel syndrome (IBS).

Methods: Sixty-nine patients with IBS were randomized to Ayurvedic (n = 35) or conventional nutritional therapy according to the recommendations of the German Nutrition Society including the low-FODMAP diet (n = 34). Study visits took place at baseline and after 1, 3, and 6 months. The primary outcome was IBS symptom severity (IBS-SSS) after 3 months; secondary outcomes included stress (CPSS), anxiety and depression (HADS), well-being (WHO-5) and IBS-specific quality of life (IBS-QOL). A repeated measures general linear model (GLM) for intent-to-treat-analyses was applied in this explorative study.

Results: After 3 months, estimated marginal means for IBS-SSS reductions were 123.8 [95% confidence interval (95% CI) = 92.8–154.9; p < 0.001] in the Ayurvedic and 72.7 (95% CI = 38.8–106.7; p < 0.001) in the conventional group. The IBS-SSS reduction was significantly higher in the Ayurveda group compared to the conventional therapy group (estimated marginal mean = 51.1; 95% CI = 3.8–98.5; p = 0.035) and clinically meaningful. Sixty-eight percentage of the variance in IBS-SSS reduction after 3 months can be explained by treatment, 6.5% by patients' expectations for their therapies and 23.4% by IBS-SSS at pre-intervention. Both therapies are equivalent in their contribution to the outcome variance. The higher the IBS-SSS score at pre-intervention and the larger the patients' expectations, the greater the IBS-SSS reduction. There were no significant group differences in any secondary outcome measures. No serious adverse events occurred in either group.

Conclusion: Patients with IBS seem to benefit significantly from Ayurvedic or conventional nutritional therapy. The results warrant further studies with longer-term follow-ups and larger sample sizes.

Clinical Trial Registration:https://clinicaltrials.gov/ct2/show/NCT03019861, identifier: NCT03019861.

Dietary management for people with an ileostomy: a scoping review

OBJECTIVE

The objective of this review was to identify and map the evidence for oral dietary management of ileostomies.

INTRODUCTION

Dietary advice is commonly provided for ileostomy management but can be inconsistent, conflicting, and inadequate. There is a lack of high-quality research investigating dietary management of ileostomies. This scoping review highlights gaps in the literature that need addressing to inform practice, and identifies dietary strategies and outcomes to be investigated in future studies.

INCLUSION CRITERIA

Evidence relating to the use of oral dietary strategies to manage complications and nutritional consequences associated with having an ileostomy was included. Evidence included all types of original research (ie, quantitative and qualitative methodologies, expert opinion articles, and consensus guidelines).

METHODS

This review followed JBI methodology for scoping reviews. A pre-determined search of 13 databases, including MEDLINE, Embase, and Web of Science, was conducted in August 2019. The search was not limited by date, but during screening, expert opinion evidence was limited to 2008 onward. Data extraction was carried out by two reviewers for each study/article using a database tool designed specifically for this review. Results are presented using a combination of tabular summaries and narrative reports.

RESULTS

Thirty-one research studies were included: 11 experimental (including four crossover randomized controlled trials), three pre-post design, 13 observational (12 cross-sectional, one longitudinal), and four qualitative. Forty-four expert opinion articles/guidelines were also included. In experimental studies, nine nutrient modifications and 34 individual foods/drinks were investigated. In pre-post studies, 10 nutrient modifications, 80 foods/drinks, and 11 eating-related behaviors were investigated. In observational studies, eight nutrient modifications, 94 foods/drinks, and five eating-related behaviors were reported. In qualitative studies, two nutrient modifications, 17 foods/drinks, and one eating-related behavior were reported. In expert opinion articles/guidelines, recommendations relating to 51 nutrient modifications, 339 foods/drinks, and 23 eating-related behaviors were reported. Although large numbers of individual foods and drinks were suggested to be associated with outcomes relating to ileostomy management, findings from observational studies showed these were generally reported by <50% of people with an ileostomy. The most common nutrients reported in association with outcomes related to ileostomy management were fiber, fat, and alcohol. Across most outcomes and studies/expert opinion, low fiber and low fat were suggested to be beneficial, while alcohol was detrimental. Other nutrient associations frequently reported in expert opinion (but with minimal attention in research studies) included negative consequences of caffeinated drinks and positive effects of white starchy carbohydrates on stoma output. Output volume and consistency were the most commonly reported outcomes relating to ileostomy management across all study types. Flatulence and odor were also common outcomes in observational studies.

CONCLUSIONS

This review found an abundance of literature, particularly expert opinion, reporting on dietary management for people with an ileostomy. However, this literature was highly heterogeneous in terms of dietary strategies and outcomes reported. It is likely that most dietary advice provided in practice is based on expert opinion with some supported by limited research. High-quality research investigating the effect of the dietary strategies identified in this review on commonly associated outcomes relating to ileostomy management is needed to improve evidence-based advice.

A Low-FODMAP Diet Improves the Global Symptoms and Bowel Habits of Adult IBS Patients: A Systematic Review and Meta-Analysis

Background: A low-fermentable oligo-, di-, monosaccharides, and polyols (FODMAP) diet has been reported to be associated with improving the symptoms of irritable bowel syndrome (IBS); however, its efficacy as evaluated by different studies remains controversial. Objective: A systematic review and meta-analysis of randomized controlled trials (RCTs) were conducted to explore the efficacy of a low-FODMAP diet (LFD) in alleviating the symptoms of IBS. Methods: A search of the literature for RCTs that assessed the efficacy of an LFD in treating IBS patients was conducted using the electronic databases PubMed, Embase, Cochrane Central Register of Controlled Trials, and Web of Science. The searches in each database were conducted from the inception of the database to February 2021. Two independent reviewers screened citations and a third reviewer resolved disagreements. Two independent reviewers also performed eligibility assessments and data extraction. The RCTs that evaluated LFDs vs. a normal IBS or usual diet and assessed changes of IBS symptoms were included in the search. Data were synthesized as the relative risk of global symptoms improvement, mean difference of IBS Severity Scoring System (IBS-SSS) score, sub-items of IBS-SSS irritable bowel syndrome-related quality of life (IBS-QOL), hospital anxiety and depression scale (HADS), stool consistency/frequency, and body mass index (BMI) using a random effects model. The risk of bias was assessed using Risk of Bias Tool 2 (RoB 2). The bias of publication was assessed based on Egger's regression analysis. The quality of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology. Results: A total of 2,768 citations were identified. After full-text screening, a total of 10 studies were eligible for the systematic review and were subsequently used to compare an LFD with various control interventions in 511 participants. An LFD was associated with the improvement of global symptoms [n = 420; Risk Ratio (RR) = 1.54; 95% Confidence Interval (CI) 1.18 to 2; I 2 = 38%], improvement of stool consistency [n = 434; Mean difference (MD) = -0.25; 95% CI -0.44 to -0.06; I 2= 19%), and a reduction trend of stool frequency (n = 434; MD = -0.28; 95% CI -0.57 to 0.01; I 2 = 68%) compared with control interventions. There was no statistically significant change in IBS-QOL (n = 484; MD = 2.77; 95% CI -2 to 7.55; I 2 = 62%), anxiety score (n = 150; MD = -0.45; 95% CI -3.38 to 2.49; I 2 = 86%), depression score (n = 150; MD = -0.05; 95% CI -2.5 to 2.4; I 2 = 88%), and BMI (n = 110; MD = -0.22; 95% CI -1.89 to 1.45; I 2 = 14%). The overall quality of the data was "moderate" for "global improvement of IBS symptom," "stool consistency," "stool consistency for IBS with diarrhea (IBS-D)," and "stool frequency for IBS-D," and "low" or "very low" for other outcomes according to GRADE criteria. Conclusion: An LFD is effective in reducing the global symptoms and improving the bowel habits of adult IBS patients. The efficacy for IBS-D patients can also be more pronounced. Systematic Review Registration: CRD42021235843.

Dietary modulation of gut microbiota for the relief of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a frequently diagnosed gastrointestinal (GI) disorder characterized by recurrent abdominal pain, bloating, and changes in the stool form or frequency without any structural changes and overt inflammation. It is not a life-threatening condition but causes a considerable level of discomfort and distress. Among the many pathophysiologic factors, such as altered GI motility, visceral hypersensitivity, and low-grade mucosal inflammation, as well as other immunologic, psychologic, and genetic factors, gut microbiota imbalance (dysbiosis), which is frequently found in IBS, has been highlighted as an etiology of IBS. Dysbiosis may affect gut mucosal homeostasis, immune function, metabolic regulation, and even visceral motor function. As diet is shown to play a fundamental role in the gut microbiota profile, this review discusses the influence of diet on IBS occurring through the modulation of gut microbiota. Based on previous studies, it appears that dietary modulation of the gut microbiota may be effective for the alleviation of IBS symptoms and, also an effective IBS management strategy based on the underlying mechanism; especially because, IBS currently has no specific treatment owing to its uncertain etiology.

Comparative study of the laxative effects of konjac oligosaccharides and konjac glucomannan on loperamide-induced constipation in rats

Dietary fiber is the basic therapeutic method to relieve the symptoms of chronic constipation. The aim of this study was to compare the laxative effect of konjac glucomannan (KGM) and konjac oligosaccharides (KOS) on constipated rats. KGM and KOS were administered to loperamide-induced constipated rats at dosages of 100 mg per kg bw and 400 mg per kg bw for 15 days. Feces were collected to evaluate the defecation function. X-ray imaging and an electrophysiological system were used to determine gastrointestinal (GI) motility. Immunohistochemistry and western blotting were used to measure the protein levels. Magnetic resonance imaging (MRI) was performed to assess flatulence. Our results demonstrated that low-dose KOS (L-KOS) exerted the best laxative effect. Compared to the normal control (NC) group, the fecal number in the L-KOS group increased by 39.4%, and the fecal weight significantly increased by 31.9% which was higher than those in the low-dose KGM (L-KGM) and high-dose KGM (H-KGM) groups. The fecal moisture content and transit scores were significantly increased only in the L-KOS group. Meanwhile, less GI gas was produced by KOS. Additionally, further investigations suggested that KOS could upregulate the protein expression of stem cell factors (SCF)/c-kit, and significantly promoted the secretion of mucus. In conclusion, compared to KGM, KOS had a conspicuous laxative effect especially at a low dosage. The potential laxative mechanisms of KOS probably are regulating the SCF/c-kit signalling pathway and increasing mucus secretion. These findings indicated that as a kind of functional oligosaccharide, KOS is more conducive to alleviating constipation compared to polysaccharides.

Metabolic Profiling of Plasma in Patients with Irritable Bowel Syndrome after a 4-Week Starch- and Sucrose-Reduced Diet

A 4-week dietary intervention with a starch- and sucrose-restricted diet (SSRD) was conducted in patients with irritable bowel syndrome (IBS) to examine the metabolic profile in relation to nutrient intake and gastrointestinal symptoms. IBS patients were randomized to SSRD intervention (n = 69) or control continuing with their ordinary food habits (n = 22). Food intake was registered and the questionnaires IBS-symptoms severity scale (IBS-SSS) and visual analog scale for IBS (VAS-IBS) were completed. Metabolomics untargeted analysis was performed by gas chromatography mass spectrometry (GC-MS) and liquid chromatography mass spectrometry (LC-MS) in positive and negative ionization modes. SSRD led to marked changes in circulating metabolite concentrations at the group level, most prominent for reduced starch intake and increased polyunsaturated fat, with small changes in the control group. On an individual level, the correlations were weak. The marked reduction in gastrointestinal symptoms did not correlate with the metabolic changes. SSRD was observed by clear metabolic effects mainly related to linoleic acid metabolism, fatty acid biosynthesis, and beta-oxidation.

Nutritional Profiling and Preliminary Bioactivity Screening of Five Micro-Algae Strains Cultivated in Northwest Europe

This study aimed to map the nutritional profile and bioactivities of five microalgae that can be grown in Northwest Europe or areas with similar cultivation conditions. Next to the biochemical composition, the in vitro digestibility of carbohydrates, proteins, and lipids was studied for Chlamydomonas nivalis, Porphyridium purpureum, Chlorella vulgaris, Nannochloropsis gaditana, and Scenedesmus species biomass. These microalgae were also assessed for their ability to inhibit the angiotensin-1-converting enzyme (ACE-1, EC 3.4.15.1), which is known to play a role in the control of blood pressure in mammals. Large differences in organic matter solubility after digestion suggested that a cell disruption step is needed to unlock the majority of the nutrients from N. gaditana and Scenedesmus species biomass. Significant amounts of free glucose (16.4–25.5 g glucose/100 g dry algae) were detected after the digestion of C. nivalis, P. purpureum, and disrupted Scenedesmus. The fatty acid profiles showed major variations, with particularly high Ω-3 fatty acid levels found in N. gaditana (5.5 ± 0.5 g/100 g dry algae), while lipid digestibility ranged from 33.3 ± 6.5% (disrupted N. gaditana) to 67.1 ± 11.2% (P. purpureum). C. vulgaris and disrupted N. gaditana had the highest protein content (45–46% of dry matter), a nitrogen solubility after digestion of 65–71%, and the degree of protein hydrolysis was determined as 31% and 26%, respectively. Microalgae inhibited ACE-1 by 73.4–87.1% at physiologically relevant concentrations compared to a commercial control. These data can assist algae growers and processors in selecting the most suitable algae species for food or feed applications.

[Irritable bowel syndrome: Role of gut microbiota]

Irritable Bowel Syndrome (IBS) is a functional disorder of the gastrointestinal tract with high prevalence. IBS, in particular the diarrheic subtype, is associated with alterations in gut microbiota composition and functionality, called dysbiosis. However, the treatment of this disease mainly relies on the patient's symptoms without considering the gut microbiota perturbations. In this review, we present epidemiological data about IBS-D. Then, we describe the main pathophysiological mechanisms associated with this disease, by focusing on gut microbiota alterations. We end up discussing the current therapies now available.

Evidence from comparative genomic analyses indicating that Lactobacillus-mediated irritable bowel syndrome alleviation is mediated by conjugated linoleic acid synthesis

Irritable bowel syndrome (IBS) is a chronic intestinal disorder accompanied by low-grade inflammation, visceral hypersensitivity, and gut microbiota dysbiosis. Several studies have indicated that Lactobacillus supplementation can help to alleviate IBS symptoms and that these effects are strain-specific. Therefore, this study aimed to investigate the key physiological characteristics and functional genes contributing to the IBS-alleviating effects of Lactobacillus. An IBS model was established by subjecting C57BL/6 mice to Citrobacter rodentium ingestion and water avoidance stress. Lactobacillus strains with different physiological characteristics were administered to mice intragastrically for 4 weeks (5 × 109 CFU/0.2 mL per mouse per day). Indicators of colonic inflammation, visceral hypersensitivity, and gut microbiota were also evaluated. Finally, differences in functional genes between Lactobacillus strains were analyzed by a comparative genomic analysis, and the relationships between the physiological characteristics, functional genes, and IBS-alleviating effects of the strains were quantified using correlation analysis. Among the eight tested Lactobacillus strains, only Lactobacillus plantarum CCFM8610 significantly inhibited the expression of IL-1β, IL-6, PAR-2, and mast cell tryptase. L. plantarum CCFM8610 also significantly increased the intestinal barrier function, inhibited visceral hypersensitivity symptoms, and modulated the gut microbiota diversity and composition. The correlation analysis of factors associated with the IBS-alleviating effects of Lactobacillus revealed the ability to synthesize conjugated linoleic acid as the most strongly associated physiological characteristic and COG1028-related genes as the most strongly associated functional genes. In conclusion, these findings can facilitate the rapid screening of Lactobacillus strains with IBS-alleviating effects and lay a foundation for studies of the related mechanisms.

Higher intake of microbiota-accessible carbohydrates and improved cardiometabolic risk factors: a meta-analysis and umbrella review of dietary management in patients with type 2 diabetes

BACKGROUND

Microbiota-accessible carbohydrates (MACs) are critical substrates for intestinal microbes; the subsequent production of SCFAs may have some potential benefits for patients with type 2 diabetes mellitus (T2DM).

OBJECTIVES

We conducted a meta-analysis of randomized controlled trials (RCTs) to assess the effects of higher compared with lower MAC intakes on cardiovascular risk factors in T2DM patients and performed an umbrella review of RCTs to evaluate the evidence quality concerning existing dietary T2DM interventions.

METHODS

Publications were identified by searching MEDLINE, EMBASE, and CINAHL. In the meta-analysis, random-effects models were used to calculate pooled estimates, and sensitivity analyses, meta-regression, subgroup analyses, and Egger's test were performed. For the umbrella review, we summarized pooled estimates, 95% CIs, heterogeneity, and publication bias. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) and modified NutriGrade were used to assess the quality of evidence in the meta-analysis and umbrella review, respectively.

RESULTS

Forty-five RCTs with 1995 participants were included in the meta-analysis. High MAC intake significantly reduced glycated hemoglobin (HbA1c) (weighted mean difference [WMD] -0.436% [-0.556, -0.315]), fasting glucose (WMD -0.835 mmol/L [-1.048, -0.622]), total cholesterol (WMD -0.293 mmol/L [-0.397, -0.190]), triglycerides (WMD -0.118 mmol/L [-0.308, -0.058]), BMI (WMD -0.476 [-0.641, -0.312]), and systolic blood pressure (WMD -3.066 mmHg [-5.653, -0.478]), with a moderate-to-high quality of evidence, compared with low intake. Region, dose, and MAC type were key variables. The umbrella review of all dietary interventions for cardiovascular risk factors in patients with T2DM included 26 meta-analyses with 158 pooled estimates. The evidence quality of MACs, dietary fiber, high-protein diet, ω-3 (n-3), viscous fiber, vitamin D, and vitamin E intake was moderate to high.

CONCLUSIONS

When compared with lower intake, increased MAC intake improved glycemic control, blood lipid, body weight, and inflammatory markers for people with T2DM. This trial was registered at PROSPERO (https://www.crd.york.ac.uk/PROSPERO/#recordDetails) as CRD42019120531.

Impact of food-derived bioactive peptides on gut function and health

The gastrointestinal tract (GIT) is the largest interface between our body and the environment. It is an organ system extending from the mouth to the anus and functions for food intake, digestion, transport and absorption of nutrients, meanwhile providing protection from environmental factors, like toxins, antigens, and pathogens. Diet is one of the leading factors modulating the function of the GIT. Bioactive peptides presenting naturally in food or derived from food proteins during digestion or processing have been revealed multifunctional in diverse biological processes, including maintaining gut health and function. This review summarizes the available evidence regarding the effects of food-derived bioactive peptides on gut function and health. Findings and insights from studies based on in vitro and animal models are discussed. The gastrointestinal mucosa maintains a delicate balance between immune tolerance to nutrients and harmful components, which is crucial for the digestive system's normal functions. Dietary bioactive peptides positively impact gastrointestinal homeostasis by modulating the barrier function, immune responses, and gut microbiota. However, there is limited clinical evidence on the safety and efficacy of bioactive peptides, much less on the applications of dietary peptides for the treatment or prevention of diseases related to the GIT. Further study is warranted to establish the applications of bioactive peptides in regulating gut health and function.

Lactose Sensitivity and Lactose Malabsorption: The 2 Faces of Lactose Intolerance

Background/Aims

Self-reported lactose intolerance (LI) is frequent in patients with functional bowel disorders (FBD) that could be interpreted as irritable bowel syndrome (IBS). The present study aims to characterize the responses of patients with FBD, without small intestinal bacterial overgrowth (SIBO), and LI, in terms of lactose malabsorption (LM) and lactose sensitivity (LS) according to psychological and clinical features.

Methods

One hundred and fifty-eight consecutive FBD outpatients with LI, and no SIBO, were classified according to the Rome III questionnaire and filled Beck Depression Inventory, and State and Trait Anxiety questionnaires. They underwent a lactose tolerance test in which glycemia during 60 minutes and digestive symptoms for 3 hours were recorded.

Results

Abnormal lactose tolerance tests were found in 110 patients (70%), 44 (28%) with LM, 96 (61%) with LS, and 30 (19%) having both LM and LS. LM patients had a higher frequency of functional diarrhea (P = 0.040) and a lower frequency of dysphagia (P = 0.031). LS patients had a higher depression score (P = 0.007), higher frequency of globus (P = 0.042), irritable bowel syndrome (IBS) (P = 0.027) and mixed IBS (P = 0.049), and lower frequency of abdominal pain (P = 0.040). LS was significantly associated with a higher depression score (P = 0.002), and a higher frequency of globus (P = 0.046).

Conclusions

Thirty percent of LI patients have normal lactose absorption and normal LS. In the other 70% of patients, LI could be associated with LM and/or LS.

Intestinal microbiota fingerprint in subjects with irritable bowel syndrome responders to a low FODMAP diet

Irritable Bowel Syndrome (IBS) is a functional gastrointestinal disorder characterized by abdominal pain and altered bowel habit. IBS patients report that FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) diet induce or exacerbate their symptoms. It has been reported that low-FODMAP diet (LFD) improves the symptoms in 50%-80% of IBS patients. We aimed to identify IBS responders and non-responders' patients to LFD by determining baseline fecal microbial composition, sequencing the 16S rRNA gene V3-V4 region. Thirty-two participants with IBS were included, 29 women (90.62%) and three men (9.37%), and instructed to follow a four-week LFD, Visual Analogue Scale for IBS was used to assess intervention response. Twenty-two participants were responders (68.75%), and ten were non-responders (31.25%). Differential abundance analysis of Amplicon Sequence Variant (ASVs), before LFD, identified Prevotella 9 and Veillonella genus in responder group, and Barnesiella, Paraprevotella, Bifidobacterium and Ruminococcus 1 genus in non-responder group. After LFD, differentially abundant ASVs were only identified in R, belonging to Veilonella, Butyrivibrio, and 5 ASVs belonging to Ruminiclostridium 6 genus. Linear Discriminant Analysis (LDA), was used to classify patients by responsiveness, considering baseline abundance of 5 bacterial genera, LDA accuracy model was 96.87%, correctly classifying 95.45% of in responder group and 100% and non-responder group. In conclusion, bacterial biomarkers are useful to classify IBS individuals by responsiveness to LFD.

Long-term symptom severity in people with irritable bowel syndrome following dietetic treatment in primary care: A service evaluation

BACKGROUND

Evidence suggests that dietary interventions can improve symptoms in people with irritable bowel syndrome (IBS), although most data explore the short-term (immediate) impact. Data on long-term (>6 months) impact are limited, especially from primary care settings. The present study aimed to investigate the long-term effect of dietetic-led interventions for IBS delivered in primary care.

METHODS

A service evaluation of a dietetic-led IBS clinic was completed, analysing data on symptom severity, stool frequency and consistency, and healthcare input. Data were collected before and immediately after dietary intervention as part of patients' routine clinical appointments. Long-term data were collected via a postal questionnaire at least 11 months later.

RESULTS

In total, 211 patients responded to the long-term follow-up questionnaire at a median of 13 months (interquartile range 12-16 months) post follow-up appointment. Of these, 84% had been advised to follow a low FODMAP (i.e., fermentable oligosaccharides, disaccharides, monosaccharides and polyols carbohydrates) diet. All symptoms were reported significantly less frequently short term, and all except heartburn and acid regurgitation remained so over the long term. The four most commonly reported bowel symptoms reduced in frequency were abdominal pain (62%), bloating (50%), increased wind (48%) and urgency to open bowels (49%) (p < 0.001). The percentage of patients reporting satisfactory relief of gut symptoms was 10% at baseline and 55% at long-term follow-up (p < 0.001). Visits to a general practitioner were reduced (from 96% to 34%; p < 0.001), as were those to the gastroenterologist (from 37% to 12%; p = 0.002), during the year prior to long-term follow-up compared to the year prior to dietary intervention.

CONCLUSIONS

Patients with IBS who received dietetic-led interventions in primary care reported long-term symptoms improvements that may result in reduced healthcare usage.

Gastrointestinal Involvement in Anderson-Fabry Disease: A Narrative Review

Anderson-Fabry disease (FD) is an X-linked lysosomal storage disorder leading to a wide array of clinical manifestations. Among these, gastrointestinal (GI) symptoms such as abdominal pain, bloating, and diarrhea affect about half of the FD adults and more than half of FD children. GI symptoms could be the first manifestation of FD; however, being non-specific, they overlap with the clinical picture of other conditions, such as irritable bowel syndrome and inflammatory bowel disease. This common overlap is the main reason why FD patients are often unrecognized and diagnosis is delayed for many years. The present narrative review is aimed to promote awareness of the GI manifestations of FD amongst general practitioners and specialists and highlight the latest findings of this rare condition including diagnostic tools and therapies. Finally, we will discuss some preliminary data on a patient presenting with GI symptoms who turned to be affected by a variant of uncertain significance of alpha-galactosidase (GLA) gene.

Hydrogen Breath Tests: Are They Really Useful in the Nutritional Management of Digestive Disease?

Background: Carbohydrate malabsorption is a frequent digestive problem associated with abdominal pain, bloating and diarrhea. Hydrogen breath testing (BT) represents the most reliable and validated diagnostic technique. The aim of this manuscript was to clarify the usefulness of BTs in the nutritional management of these disorders. Methods: A literature search for BT related to carbohydrate malabsorption was carried out using the online databases of Pubmed, Medline and Cochrane. Results: Lactose BT showed good sensitivity and optimal specificity for lactose malabsorption. However, an accurate diagnosis of lactose intolerance should require blind lactose challenge although this method is difficult to utilize in clinical practice. Regarding dose-depending fructose and sorbitol malabsorption, BTs could not add diagnostic advantage compared with a direct dietary intervention. In addition, carbohydrates are fundamental components of fermentable oligo-, di- and monosaccharides and polyols (FODMAPs). Before starting a low FODMAP diet, lactose BT should be suggested in a population with low prevalence of hypolactasia. Conclusions: BTs represent a valid and noninvasive technique in many digestive conditions. Regarding the management of carbohydrate intolerance, lactose BT can be recommended with some limitations. No sufficient evidence is available about the usefulness of BTs for other sugars in clinical practice.

Therapeutic Implications of Diet in Inflammatory Bowel Disease and Related Immune-Mediated Inflammatory Diseases

Despite being a focal issue to patients, the effect of diet on adult inflammatory bowel disease (IBD) remains underexplored with limited guidance. While promising clinical trials are currently underway, there is a need for further evidence-based recommendations. As such, we summarize the current evidence on various diets used in the treatment of IBD and also explore the potential applications of dietary data from related immune-mediated inflammatory diseases (IMIDs), such as rheumatoid arthritis and psoriasis, to provide additional information to inform IBD providers. To date, there have been multiple diets investigated as adjunctive therapy in IBD, but many associated studies are small, non-randomized, and not controlled. Mediterranean, vegetarian/vegan, and reduced-calorie/fasting diets have been studied and have shown some positive results in other IMIDs, which may suggest potential applicability to those with IBD, but larger, well-designed clinical trials are needed for further guidance. Gluten-free and low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP)diets do not appear to have an impact on IBD disease activity, but low FODMAP may potentially be helpful for those with concurrent functional gastrointestinal symptoms. Specific carbohydrate diets have been mainly assessed in children but show some potential in small adult studies.

Nutrition in adult patients with selected lysosomal storage diseases

Lysosomal storage disorders (LSDs) are a group of clinically heterogeneous disorders affecting the function of lysosomes and are characterized by an accumulation of undigested substrates within several cell types. In recent years there have been substantial advances in supportive care and drug treatment for some LSDs, leading to improved patient survival, as seen in Gaucher, Pompe and Fabry disease and some Mucopolysaccharidoses; however, many symptoms still persist. Thus it is now even more important to improve patients' quality of life and reduce symptoms and comorbidities. One potential way of achieving this goal is through adjunct nutritional therapy, which is challenging as patients may be overweight with associated consequences, or malnourished, or underweight. Furthermore, drugs used to treat LSDs can modify the metabolic status and needs of patients. There are currently not enough data to make specific dietary recommendations for individual LSDs; however, suggestions can be made for managing clinical manifestations of the diseases, as well as treatment-associated adverse events. The metabolic and nutritional status of adult patients must be regularly assessed and individualized dietary plans may be created to cater to a patient's specific needs. Damage to the autophagic process is a common feature in LSDs that is potentially sensitive to dietary manipulation and needs to be assessed in clinical studies.

Efficacy of a low-FODMAP diet in adult irritable bowel syndrome: a systematic review and meta-analysis

Purpose

This review provides an updated overview of observational and intervention studies investigating the effect of a low-FODMAP (fermentable oligo-, di- and monosaccharides, and polyols) diet (LFD) on gastrointestinal (GI) symptoms, quality of life (QoL), nutritional adequacy, and gut microbiome in irritable bowel syndrome (IBS) patients.

Methods

We systematically searched available literature until October 2020 for studies that investigated the effect of LFDs on GI symptoms, QoL, nutritional adequacy, and the gut microbiome in IBS patients. The data were represented as standardized mean differences (SMD) for IBS severity, and as mean differences (MD) for IBS-QoL. Meta-analyses were performed for the quantitative analyses using random effects models with inverse variance weighing.

Results

Twelve papers (nine parallel trials, three crossover studies) were included for the meta-analysis. The LFD reduced IBS severity by a moderate-to-large extent as compared to a control diet (SMD − 0.66, 95% CI − 0.88, − 0.44, I² = 54%). When analyzing only studies that used the validated IBS-SSS questionnaire, a mean reduction of 45 points (95% CI − 77, − 14; I² = 89%) was observed. Subgroup analyses on adherence, age, intervention duration, IBS subtype, outcome measure, and risk of bias revealed no significantly different results. The LFD also increased IBS-QoL scores, when compared with a control diet (MD 4.93; 95% CI 1.77, 8.08; I² = 42%).

Conclusions

The low-FODMAP diet reduces GI symptoms and improves quality of life in IBS subjects as compared to control diets. Future work is required to obtain definitive answers regarding potential long-term effects of such diets on nutritional adequacy and the gut microbiome.

PROSPERO registration number

CRD42020175157.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-020-02473-0.

FODMAP intake in children with coeliac disease influences diet quality and health-related quality of life and has no impact on gastrointestinal symptoms

Children with coeliac disease (CD) following the gluten-free diet may experience ongoing gastrointestinal symptoms despite strict adherence. The study objective was to evaluate the association between foods high in fermentable oligo/di/monosaccharides, and polyols (FODMAP) and gastrointestinal symptoms, and the potential implications to diet quality and health-related quality of life in CD children. Dietary intake was studied in age-sex matched children 5-18 years (CD, n = 46; non-coeliac mild chronic gastrointestinal complaints [GIC], n = 46; healthy controls [HC], n = 46). CD children consumed fewer foods high in FODMAPs compared to GIC and HC (p < .0001). FODMAP intake was not related to gastrointestinal symptoms in CD children (p > 0.05) but was positively associated with child health-related quality of life (p < 0.05). FODMAP intake from fruits and vegetables was positively associated with diet adequacy and total diet quality in CD children (p < 0.05). FODMAP intake may influence diet quality and health-related quality of life but has no impact on gastrointestinal symptoms in CD children.

The Brain-Gut-Microbiotal Axis: A framework for understanding functional GI illness and their therapeutic interventions

Functional gastrointestinal disorders (FGIDs), characterized by chronic abdominal complaints without a structural or biochemical cause, are common diseases that are frequently encountered by specialists in internal medicine. Collectively, irritable bowel syndrome (IBS) and functional dyspepsia are estimated to affect up to 22% of the population, and are often associated with additional somatic and pain complaints, all without an obvious structural source [1,2]. An appreciation of the current understanding of the mechanistic basis for these disorders is key to developing treatment goals and optimization of patient management strategies. In recent years, the brain-gut axis increasingly has been recognized as a central factor in the experience of functional abdominal pain disorders, including the most recent Rome IV guidelines which identify FGIDs as disorders of gut-brain interaction [3]. The brain-gut axis (BGA), simply defined, is a complex network of bidirectional communication between the central and enteric nervous systems. This axis broadly includes all the systems involved with communication between the GI tract and central nervous system (CNS), with principle inputs into this network occurring between the CNS, enteric nervous system (ENS), and autonomic nervous systems (ANS), but also includes interfaces with numerous other factors, including endocrine hormones and immune effector cells as well as interactions with the gut microbiota. Perturbances to this system have been found to play a critical role in the development of visceral hypersensitivity, bowel dysregulation, and mood. This review will summarize the principle processes involved in the neurologic and biologic function of the brain-gut axis, our current understanding of its role in functional GI disorders, and potential targets for therapeutic intervention.