Multiomics analyses reveal a critical role of selenium in controlling T cell differentiation in Crohn's disease.

Inflammatory bowel disease (IBD) mainly includes Crohn's disease (CD) and ulcerative colitis (UC). Immune disorders play an essential role in the pathogenesis of these two IBDs, but the differences in the immune microenvironment of the colon and their underlying mechanisms remain poorly investigated. Here we examined the immunological features and metabolic microenvironment of untreated individuals with IBD by multiomics analyses. Modulation of CD-specific metabolites, particularly reduced selenium, can obviously shape type 1 T helper (Th1) cell differentiation, which is specifically enriched in CD. Selenium supplementation suppressed the symptoms and onset of CD and Th1 cell differentiation via selenoprotein W (SELW)-mediated cellular reactive oxygen species scavenging. SELW promoted purine salvage pathways and inhibited one-carbon metabolism by recruiting an E3 ubiquitin ligase, tripartite motif-containing protein 21, which controlled the stability of serine hydroxymethyltransferase 2. Our work highlights selenium as an essential regulator of T cell responses and potential therapeutic targets in CD.

Management of Crohn's disease in an immunosuppressed COVID-19-positive patient: safety-driven prioritisation of nutritional therapy as a bridge to restarting immunosuppression.

Active inflammatory bowel disease (IBD), combined immunosuppression and corticosteroid therapy have all been identified as risk factors for a poor outcome in COVID-19 infection. The management of patients with both COVID-19 infection and active IBD is therefore complex. We present the case of a 31-year-old patient with Crohn's disease, on dual immunosuppression with infliximab and mercaptopurine presenting with inflammatory small bowel obstruction and COVID-19 infection. The case highlights the use of nutritional therapy, which remains underused in the management of adults with IBD, to manage his flare acutely. Following negative SARS-CoV-2 PCR testing and SARS-CoV-2 IgG testing confirming an antibody response, ustekinumab (anti-interleukin 12/23) was prescribed for long-term maintenance.

Treatment Adherence and Clinical Outcomes of Patients with Inflammatory Bowel Disease on Biological Agents During the SARS-CoV-2 Pandemic.

BACKGROUND: The outbreak of COVID19 evolved rapidly into a global pandemic, forcing hospitals, including inflammatory bowel disease (IBD) referral units, to change their practices to ensure quality of care. AIMS: To describe the clinical outcomes and the fulfilment of the treatment schedule of patients with IBD treated with biological agents in a single-center of a red-zone of the pandemic, and to report the patients' perceptions about COVID-19 and the measures adopted at our center. METHODS: Therapeutic adherence and clinical outcomes were collected for all patients undergoing treatment with intravenous biologicals and subcutaneous biologicals at our center. A telephone survey was also performed to assess these patients' perceptions of the COVID pandemic and the related measures adopted at their IBD unit. RESULTS: A total of 234 patients were included (117 on intravenous and 117 on subcutaneous biologicals). Only 10% of patients postponed intravenous infusions intentionally and 5% postponed the collection of subcutaneous biologicals at the hospital pharmacy. Only five confirmed COVID-19 cases were registered (2.1%), all of them of mild severity. One hundred and fifty-five patients participated in the survey (77 on intravenous and 78 on subcutaneous drugs). Fear of going to the hospital was the most common reason for postponing biological administrations. Among those on combination therapy, only 7% admitted to have withdrawn immunosuppressants. CONCLUSIONS: Adherence to intravenous and subcutaneous biological therapies during the pandemic was high in a single-center cohort of IBD patients even though the cumulative incidence of confirmed COVID-19 was low.

Endocannabinoid System as a Promising Therapeutic Target in Inflammatory Bowel Disease - A Systematic Review.

Inflammatory bowel disease (IBD) is a general term used to describe a group of chronic inflammatory conditions of the gastrointestinal tract of unknown etiology, including two primary forms: Crohn's disease (CD) and ulcerative colitis (UC). The endocannabinoid system (ECS) plays an important role in modulating many physiological processes including intestinal homeostasis, modulation of gastrointestinal motility, visceral sensation, or immunomodulation of inflammation in IBD. It consists of cannabinoid receptors (CB1 and CB2), transporters for cellular uptake of endocannabinoid ligands, endogenous bioactive lipids (Anandamide and 2-arachidonoylglycerol), and the enzymes responsible for their synthesis and degradation (fatty acid amide hydrolase and monoacylglycerol lipase), the manipulation of which through agonists and antagonists of the system, shows a potential therapeutic role for ECS in inflammatory bowel disease. This review summarizes the role of ECS components on intestinal inflammation, suggesting the advantages of cannabinoid-based therapies in inflammatory bowel disease.

Wound healing of metastatic perineal Crohn's disease using hyperbaric oxygen therapy: A case series.

BACKGROUND: Metastatic Crohn's disease (CD) is a rare manifestation of CD. It involves inflammatory skin lesions with histopathological findings (granulomas) similar to CD, without connection to the gastrointestinal tract. Hyperbaric oxygen therapy (HBO) has been suggested as a possible treatment option. OBJECTIVE: This study aimed to identify and treat a consecutive series of patients with biopsy-proven metastatic CD and monitor wound healing using prospectively acquired outcomes. METHODS: Pathology results of all patients with ongoing perineal wound-healing problems after proctectomy between 2005 and 2018 at the Amsterdam University Medical Centre were assessed for metastatic CD. Patients with a biopsy-proven diagnosis of perineal metastatic CD were offered HBO (40 daily sessions of 100% oxygen at 2.4 atmosphere absolute). Wound healing was monitored using photographs and standardised questionnaires (the Inflammatory Bowel Disease Questionnaire, EuroQol Visual Analogue Scale and the Female Sexual Function Index) at baseline and 1 and 3 months after HBO. RESULTS: Out of 13 patients in the cohort with persisting perineal wounds after proctectomy, six (46%) had biopsy results consistent with metastatic CD. Of these, three accepted treatment with HBO. All three patients were female. One patient had complete healing of her perineal wound; another patient showed initial improvement but had a flare of luminal and perineal disease at the 3-month follow-up. The third patient showed improvement solely in the questionnaires, with higher scores on all three questionnaires. CONCLUSION: A high rate of metastatic CD was found in patients with ongoing wound-healing problems after proctectomy, implying that the disease might not be as rare in these selected patients as previously thought. HBO might be beneficial in the treatment of metastatic CD.

Treatment Pathways Leading to Biologic Therapies for Ulcerative Colitis and Crohn's Disease in the United States.

OBJECTIVES: Biologic therapies have been available for inflammatory bowel disease for >20 years, but patient outcomes have not changed appreciably over this time period. To better understand medication utilization for this disease, we evaluated a novel technique for visualizing treatment pathways, including initial treatment, switching, and combination therapies. METHODS: This retrospective, observational study used administrative claims data from the Truven Health MarketScan Commercial and Medicare Database. Adult patients with ≥2 consecutive health claims and newly diagnosed with ulcerative colitis (UC) or Crohn's disease (CD) were evaluated. Treatment pathways were visualized using Sankey diagrams representing the number of patients receiving treatment and duration of each treatment. RESULTS: In all, 28,119 patients with UC and 16,260 patients with CD were identified. The most common initial treatment for UC was 5-aminosalicylic acid monotherapy (61% of the patients), followed by corticosteroid monotherapy (25%); <1% of patients were initially treated with biologics. The most common initial treatment for CD was corticosteroid monotherapy (42%), followed by 5-aminosalicylic acid monotherapy (35%); <5% of the patients were initially treated with biologics. Significantly fewer patients followed biologic vs nonbiologic treatment pathways (UC: 6% vs 94%, CD: 19% vs 81%, both P < 0.05). DISCUSSION: Significantly fewer patients with inflammatory bowel disease followed treatment pathways that included biologic therapies compared with nonbiologic therapies, and very few patients were ever initiated on biologic therapy. Although we have made significant progress in treatment, our most effective medications are only being used in a small proportion of patients, suggesting barriers prevent optimized patient management.

A Double-Blind, Placebo-Controlled Trial to Assess Safety and Tolerability of (Thetanix) Bacteroides thetaiotaomicron in Adolescent Crohn's Disease.

INTRODUCTION: Thetanix (gastroresistant capsules containing lyophilized Bacteroides thetaiotaomicron) is a live biotherapeutic, under development for Crohn's disease, that antagonizes transcription factor nuclear factor kappa B, reducing proinflammatory cytokines, particularly tumor necrosis factor alpha. We aimed to assess safety and tolerability in adolescents with Crohn's disease in remission. METHODS: Subjects who were 16-18 years with Crohn's in remission (weighted pediatric Crohn's disease activity index <12.5) were recruited. Each active dose comprised ∼108.2±1.4 colony forming units of B. thetaiotaomicron (randomized 4:1 active:placebo). Part A was single dose. Part B involved 7.5 days twice daily dosing. Serial stools were analyzed for calprotectin, 16S rRNA sequencing, and B. thetaiotaomicron real-time polymerase chain reaction. Bloods were taken serially. Subjects reported adverse events and recorded temperature twice daily. RESULTS: Fifteen subjects were treated-8 in part A (75% men, median 17.1 years) and 10 in part B, including 3 from part A (80% men, median 17.1 years); all 18 completed. Seventy percent took concurrent immunosuppression. Reported compliance was >99% in part B. Two subjects reported adverse events deemed related-one in part A with eructation, flatulence, and reflux; one in part B with dizziness, abdominal pain, and headache. No serious adverse events were reported. There was no significant change in median calprotectin across part B (87.8 [4.4-447] to 50.5 [5.3-572], P = 0.44 by the Fisher exact test in the active group). No significant differences were found in microbiota profiles, but diversity seemed to increase in treated subjects. DISCUSSION: Thetanix, after single and multiple doses, was well tolerated. Although the numbers in this study were small, the safety profile seems good. Future studies should explore efficacy.

Nutritional regulators of intestinal inflammation.

PURPOSE OF REVIEW: Recent knowledge teaches us that food is one of the most important environmental factors affecting our health from disease prevention to cause. Food is one of the key players in the normal gut microenvironment, affecting microbial composition, function, gut barrier and host immunity. This review aims to summarize the current data on food components as regulators of intestinal inflammation, with particular focus on the inflammatory bowel diseases (IBDs). RECENT FINDINGS: We summarize our current understanding on nutrition as possible cause and treatment for IBD and concentrate on several food components that have an anti-inflammatory role on the intestine (vitamin D, butyrate, resveratrol, curcumin). SUMMARY: The proven efficacy of exclusive enteral nutrition to induce remission in children (and recently adults) with Crohn's disease has totally changed the clinical practice. Food components that have an anti-inflammatory role on the intestine (vitamin D, butyrate, resveratrol, curcumin) may now serve as an adjuvant to treatment. While our understanding has expanded in recent years, there remain many aspects of the interactions between nutrition and the gut that remain to be elucidated. Further focused research may lead to advances in understanding of disease pathogenesis and also result in new improved therapeutic interventions.

[Crohn's Disease - New Therapies]. / Chronisch entzündliche Darmerkrankungen: Neue Therapieformen.

New promising treatment options for chronic inflammatory bowel diseases, confirm the expanded pathophysiological understanding in terms of the interactions of the gastrointestinal microbiome with the adaptive and innate immune response and barrier protection. Therefore, these interrelations are focus of research and therapeutic strategies. The following review will give insights into the pathomechanisms, current treatment options and future developments.

Inflammatory bowel disease: new therapies from antisense oligonucleotides.

Inflammatory bowel diseases (IBD) are chronic inflammatory conditions of the gastrointestinal tract encompassing two main clinical entities: Crohn's disease (CD) and ulcerative colitis (UC). These disorders are characterized by various grades of tissue damage and development of local complications and extra-intestinal manifestations. The cause of IBD remains unknown but accumulating evidence indicates that both CD and UC arise in genetically predisposed individuals as a result of the action of multiple environmental factors, which ultimately trigger excessive and poorly controlled immune response against antigens of the luminal flora. Despite this realization, a full understanding of IBD pathogenesis is still out of reach and, consequently, treatment is far from optimal. However, in recent years, several pathways of intestinal damage have been delineated and the improved knowledge has contributed to the development of new therapies. Various approaches have been used to either inhibit the expression and/or function of inflammatory molecules or enhance counter-regulatory mechanisms. This review summarizes the available pre-clinical and clinical data for antisense oligonucleotides and oligonucleotide-based therapy to provide a comprehensive understanding of the rationale and mechanism of action of these compounds in IBD. Key messages Preclinical studies and clinical trials show that antisense oligonucleotide (ASO)-based therapy could be of benefit in inflammatory bowel diseases. ASOs have an excellent safety profile. Technical issues emerged from clinical trials suggest that changes in drug formulation and/or route of administration could improve ASO efficacy.

Immunopathogenesis of inflammatory bowel disease and mechanisms of biological therapies.

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract with a multifactorial pathophysiology. Full comprehension of IBD pathology is still out of reach and, therefore, treatment is far from ideal. Nevertheless, components involved in IBD pathogenesis including environmental, genetic, microbial, and immunological factors are continuously being investigated and the improved knowledge contributes to the development of new therapies. In this article we review the aspects of the immunopathogenesis of IBD, with focus on mucosal immunity, and discuss mechanisms of action for current and emerging biological therapies.

Vitamin D deficiency and the pathogenesis of Crohn's disease.

Vitamin D has emerged as a key regulator of innate immune responses to pathogen threat. The hormonal form of vitamin D signals through a nuclear receptor transcription factor and regulates gene transcription. Several papers have shown that vitamin D signaling is active both upstream and downstream of pattern recognition receptors, vanguards of innate immune responses. Crohn's disease (CD) is a relapsing-recurring inflammatory bowel disease (IBD) that arises from dysregulated intestinal innate immunity. Indeed, genetic studies have identified several CD susceptibility markers linked to mechanisms of innate immune responses to infection. Interest in links between vitamin D deficiency and CD has grown substantially, particularly in the last five years. While a number of studies have consistently revealed an association between CD and vitamin D deficiency, recent experimental work has uncovered a compelling mechanistic basis for the contribution of vitamin D deficiency to the pathogenesis of the disease. Moreover, a number of intervention trials have provided generally solid evidence that robust vitamin D supplementation may be of therapeutic benefit to patients with CD. This review summarizes these laboratory and clinical findings.

Adalimumab efficacy in enteropathic spondyloarthritis: A 12-mo observational multidisciplinary study.

AIM: To report adalimumab (Ada) efficacy on articular-gastrointestinal disease and health-related quality of life (HRQoL) in patients with enteropathic spondyloarthritis (ES). METHODS: A cohort of 52 patients with ES was evaluated in the departments of gastroenterology and internal medicine. At baseline, all patients underwent assessment by an integrated gastro-rheumatologic evaluation of articular and gastrointestinal activity, as well patient reported outcomes (PROs) of the HRQoL questionnaires. After this integrated evaluation and following a specific working flowchart, the Ada anti-tumor necrosis factor (TNF)-inhibitor was assigned to a cohort of 30 patients and its clinical efficacy was evaluated at baseline and after 6-mo and 12-mo treatment by the following tests: (1) Ankylosing Spondylitis Disease Activity Score-C-Reactive Protein (ASDAS-CRP); Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI) and Bath Ankylosing Spondylitis Metrology Index (BASMI) for articular activity; (2) Inflammatory Bowel Disease Questionnaire (IBDQ), Crohn's Disease Activity Index (CDAI) and partial Mayo (pMayo) score for gastrointestinal symptoms and activity; and (3) Health Assessment Questionnaire (HAQ), Patient Global Assessment (PGA) and Short Form-36 health survey (SF-36) questionnaires for PROs of the HRQoL. RESULTS: Integrated evaluation and management of the patients affected by ES, carried out simultaneously by a gastroenterologist and a rheumatologist, allowed clinicians to choose the optimal therapeutic strategy. In a cohort of 30 ES patients affected by active articular and gastrointestinal disease, or axial active articular inflammation, Ada led to fast and sustained improvement of both articular and gastrointestinal disease activities. In fact, all the clinimetric evaluation tests exploring articular or gastrointestinal activity, as well as all the HRQoL scores, showed a significant improvement having been achieved at the earliest (6-mo) assessment. This important clinical improvement was maintained at the 12-mo follow-up. Importantly, global and gastrointestinal quality of life significantly correlated with articular disease activity, providing evidence to support that the integrated evaluation is the best option to manage patients with ES. CONCLUSION: Ada treatment, upon multidisciplinary (gastro-rheumatologic) evaluation, significantly improves both articular and gastrointestinal inflammation, thereby improving the HRQoL in patients affected by ES.

Dietary n­3 polyunsaturated fatty acids ameliorate Crohn's disease in rats by modulating the expression of PPAR­Î³/NFAT.

Dietary n­3 polyunsaturated fatty acid (PUFA) exerts anti­inflammatory and immunoregulatory effects via downregulation of the innate and adaptive immune responses. However, the effect of dietary n­3 PUFA on experimental Crohn's Disease (CD) in rats and the underlying mechanisms are unclear. The present study aimed to investigate the effects of n­3 PUFA on CD induced by 2,4,6­trinitrobenzene sulfonic acid (TNBS) in rats, and to determine the underlying mechanisms, including the peroxisome proliferator­activated receptor (PPAR)­Î³ and nuclear factor of activated T­cells (NFAT) pathway. Sprague­Dawley rats (n=90) were randomly assigned to the following groups: Control (intragastric distilled water); PUFA control (intragastric n­3 PUFA, 20 mg/kg/day); trans­fatty acid (TFA) control (intragastric TFA, 13 mg/kg/day); model (intragastric distilled water + TNBS); PUFA model (intragastric n­3 PUFA, 20 mg/kg/day + TNBS); and TFA model (intragastric TFA, 13 mg/kg/day + TNBS). The disease activity index (DAI), colon macroscopic damage index (CMDI) and tissue damage index (TDI) were evaluated. The expression of PPAR­Î³, NFAT, interleukin (IL)­4 and IL­2 mRNA in colonic tissues was determined by reverse transcription­quantitative polymerase chain reaction (RT­qPCR), and the serum levels of IL­6, IL­12, tumor necrosis factor­α and interferon­Î³ were measured by ELISA. The results demonstrated that dietary n­3 PUFA markedly attenuated colonic inflammation compared with the model group, as indicated by reduced DAI, CMDI and TDI scores, amelioration in pathological evaluation and improvements in localized mucosal inflammation, as indicated by the levels of cytokines associated with local mucosal immunity. Treatment with n­3 PUFA increased the gene expression of PPAR­Î³ in TNBS­treated rats, and reduced the expression of NFAT, which ultimately reduced the release of IL­4 and IL­2 detected by RT­qPCR. A TFA­enriched diet was observed to increase DAI and TDI scores, aggravate pathological inflammation with epithelioid granulomas and enhance the release of proinflammatory cytokines, compared with the model group. In conclusion, the present study demonstrated that dietary n­3 PUFA may attenuate experimental CD induced by TNBS in rats by regulating the expression and activity of the PPAR­Î³/NFAT signaling pathway. These results provide a promising potential therapeutic method for the treatment of CD.

The influence of vitamin D on M1 and M2 macrophages in patients with Crohn's disease.

Defective bacterial clearance by macrophages plays an important role in Crohn's disease (CD). Phenotypes and functions of inflammatory M1 and anti-inflammatory M2 have not been studied in CD. Vitamin D supplementation reduces the severity of CD by unclear mechanisms. We studied macrophage characteristics in CD and controls and the effects of 1,25 vitamin D (1,25D). PBMC were isolated from CD patients and controls. M1 and M2 were generated by culturing of monocytes with GM-CSF and M-CSF, respectively. CD M1 and M2 showed normal phagocytosis and chemotaxis to CCL2 and fMLP. LPS-induced production of TNF-α, IL-12p40 and IL-10 was comparable between groups. Phagocytosis was unaltered with 1,25D; migration only increased marginally. M1 produced more IL-12p40 and TNF-α; IL-10 was greater in M2. 1,25D markedly decreased IL-12p40 by M1 and M2. 1,25D decreased TNF-α in CD M1; IL-10 levels were unaffected. M2 express F13A1, PTGS2, CD163, CXCL10, CD14 and MMP2, whereas TGF-ß, CCL1 and CYP27B1 expression was higher in M1. Marker expression was similar between CD and controls. M1 and M2 markers were not differentially modulated by 1,25D. CD macrophages are not functionally or phenotypically different vs. CONTROLS: 1,25D markedly decreased pro-inflammatory M1 cytokines but did not modulate polarization to anti-inflammatory M2 phenotype.

Therapeutic Potential of Amino Acids in Inflammatory Bowel Disease.

Inflammatory bowel disease (IBD), which includes both ulcerative colitis and Crohn's disease, is a chronic relapsing inflammation of the gastrointestinal tract, and is difficult to treat. The pathophysiology of IBD is multifactorial and not completely understood, but genetic components, dysregulated immune responses, oxidative stress, and inflammatory mediators are known to be involved. Animal models of IBD can be chemically induced, and are used to study etiology and to evaluate potential treatments of IBD. Currently available IBD treatments can decrease the duration of active disease but because of their adverse effects, the search for novel therapeutic strategies that can restore intestinal homeostasis continues. This review summarizes and discusses what is currently known of the effects of amino acids on the reduction of inflammation, oxidative stress, and cell death in the gut when IBD is present. Recent studies in animal models have identified dietary amino acids that improve IBD, but amino acid supplementation may not be adequate to replace conventional therapy. The animal models used in dietary amino acid research in IBD are described.

Treatment options for children and adolescents with inflammatory bowel disease: is granulomonocytapheresis an effective alternative to drug therapy?

INTRODUCTION: Patients with inflammatory bowel diseases (IBD) require life-long medications, which even if effective have the potential to cause adverse effects as additional morbidity factors. In pediatric patients, drug therapy has more serious limitations, including impaired physical and mental development. A non-drug therapeutic option is believed to be depletion of elevated and activated granulocytes and monocytes known to release inflammatory cytokines, like the CD14+CD16+ monocyte phenotype known to release tumor necrosis factor-α. Areas covered: Granulomonocyteapheresis (GMA) with an Adacolumn as a treatment option for IBD patients has been applied for the past 15 years. This article reviews the argument that GMA is a relevant and effective non-pharmacologic intervention in pediatric IBD setting. Expert commentary: GMA with an Adacolumn has shown promise in adult, pediatric, and adolescent patients with active IBD. There is evidence of post-GMA immunomodulation in terms of increased regulatory T-cell and B-cell activities. Additionally, patients who respond to GMA may attain a favorable long-term clinical course by avoiding pharmacologicals during an early phase of their active IBD. GMA has a good safety profile, especially in difficult-to-treat and pediatric settings. An additional trial is warranted to assess the efficacy of GMA in the early phase of pediatric IBD to optimize patient selection.

Associations between Folate and Vitamin B12 Levels and Inflammatory Bowel Disease: A Meta-Analysis.

BACKGROUND: Inflammatory bowel disease (IBD) patients may be at risk of vitamin B12 and folate insufficiencies, as these micronutrients are absorbed in the small intestine, which is affected by IBD. However, a consensus has not been reached on the association between IBD and serum folate and vitamin B12 concentrations. METHODS: In this study, a comprehensive search of multiple databases was performed to identify studies focused on the association between IBD and serum folate and vitamin B12 concentrations. Studies that compared serum folate and vitamin B12 concentrations between IBD and control patients were selected for inclusion in the meta-analysis. RESULTS: The main outcome was the mean difference in serum folate and vitamin B12 concentrations between IBD and control patients. Our findings indicated that the average serum folate concentration in IBD patients was significantly lower than that in control patients, whereas the mean serum vitamin B12 concentration did not differ between IBD patients and controls. In addition, the average serum folate concentration in patients with ulcerative colitis (UC) but not Crohn's disease (CD) was significantly lower than that in controls. This meta-analysis identified a significant relationship between low serum folate concentration and IBD. CONCLUSIONS: Our findings suggest IBD may be linked with folate deficiency, although the results do not indicate causation. Thus, providing supplements of folate and vitamin B12 to IBD patients may improve their nutritional status and prevent other diseases.

Prebiotic inulin-type fructans and galacto-oligosaccharides: definition, specificity, function, and application in gastrointestinal disorders.

Prebiotics are non-digestible selectively fermented dietary fibers that specifically promote the growth of one or more bacterial genera in the gastrointestinal tract and thus provide health benefit to the host. The two most investigated prebiotics being the inulin-type fructans and galacto-oligosaccharides. Prebiotic specificity is mediated through species-specific gene clusters within saccharolytic bacteria controlled by signaling sensors for various substrates. Prebiotic health benefits are attributed to immune regulation and bacterial metabolite production. In humans, prebiotic supplementation leads to increased growth of specific gut microbiota (e.g., bifidobacteria), immune modulation, and depending on the bacterial augmentation, short-chain fatty acid production. Irritable bowel syndrome and Crohn's disease are gastrointestinal disorders associated with reductions in some gut bacteria and greater mucosal inflammation. Prebiotic supplementation studies have shown some promise at low doses for modulation of the gut bacteria and reduction of symptoms in IBS; however, larger doses may have neutral or negative impact on symptoms. Studies in Crohn's disease have not shown benefit to bacterial modulation or inflammatory response with prebiotic supplementation. Dietary restriction of fermentable carbohydrates (low FODMAP diet), which restricts some naturally occurring prebiotics from the diet, has shown efficacy in improving symptoms in irritable bowel syndrome, but it lowers the numbers of some key gut microbiota. Further research is required on the effect of prebiotics in gastrointestinal disorders and, in particular, on their use in conjunction with the low FODMAP diet.