Carbohydrate intake in the etiology of Crohn's disease and ulcerative colitis

Disentangling the nutrition-microbiota liaison in inflammatory bowel disease

Inflammatory Bowel Disease (IBD) is a set of chronic intestinal inflammatory disorders affecting the gastrointestinal (GI) tract. Beside compromised intestinal barrier function and immune hyperactivation, a common IBD feature is dysbiosis, characterized by a reduction of some strains of Firmicutes, Bacteroidetes, Actinobacteria and an increase in Proteobacteria and pathobionts. Emerging evidence points to diet and nutrition-dependent gut microbiota (GM) modulation, as etiopathogenetic factors and adjuvant therapies in IBD. Currently, no nutritional regimen shows universal efficacy, and advice are controversial, especially those involving restrictive diets potentially resulting in malnutrition. This review provides an overview of the role of macronutrients, dietary protocols and GM modulation in IBD patients. A Western-like diet contributes to an aberrant mucosal immune response to commensal bacteria and impairment of the intestinal barrier integrity, thereby triggering intestinal inflammation. Conversely, a Mediterranean nutritional pattern appears to be one of the most beneficial dietetic regimens able to restore the host intestinal physiology, by promoting eubiosis and preserving the intestinal barrier and immune function, which in turn create a virtuous cycle improving patient adherence to the pattern. Further clinical studies are warranted, to corroborate current IBD nutritional guidelines, and develop more accurate models to move forward precision nutrition and ameliorate patients' quality of life.

Dietary content and eating behavior in ulcerative colitis: a narrative review and future perspective

Ulcerative colitis (UC) has experienced a steady increase in global incidence and prevalence recently. Current research into UC pathogenesis focuses on the complex interplay of genetic and environmental factors with the immune system and gut microbiome, leading to disruption of the intestinal barrier. Normally, the microbiome, intestinal epithelium, and immune system interact to maintain intestinal homeostasis. However, when this equilibrium is disturbed, a harmful cycle of dysbiosis, immune dysregulation, and inflammation emerges, resulting in intestinal barrier dysfunction and UC progression. Among various risk factors, diet significantly influences epithelial barrier integrity and architectural stability through both direct and indirect mechanisms, shaping the entire UC continuum from pre-clinical prevention to active phase treatment and remission maintenance. This review provides insights into the impact of dietary content and eating behaviors on UC, focusing on specific food, food groups, nutrients, and intermittent fasting, while providing a detailed explanation of why the gut microbiota may mediate the sustained effects of diet across all stages of UC. Additionally, it addresses the limitations of current studies, explores underexamined areas in UC dietary research and proposes potential directions for future research and expansion.

The Role of Environmental and Nutritional Factors in the Development of Inflammatory Bowel Diseases: A Case-Control Study

BACKGROUND

The incidence and prevalence of inflammatory bowel diseases (IBD) are increasing around the world, especially in Western countries. The objective of this study was to evaluate the health habits of healthy controls and individuals with IBDs to identify possible risk factors for IBD development.

METHODS

A case-control study was conducted among Spanish participants over 18 years of age. A self-administered questionnaire was completed by subjects to collect information on several sociodemographic variables and habits, such as the consumption of tobacco, alcohol, antibiotics, nonsteroidal anti-inflammatory agents and macronutrients; anxiety and depression; and quality of life.

RESULTS

The main risk factors identified were age; living in an urban environment; anxiety; and excessive consumption of proteins, carbohydrates and fats. In addition, the consumption of fibre had a preventive effect against IBD development.

CONCLUSIONS

Age, anxiety and living in urban areas pose a risk of suffering from IBD, as does the excessive consumption of certain macronutrients. However, the consumption of fibre has a protective effect on the development of some IBD types.

No causal relationship between glucose and inflammatory bowel disease: a bidirectional two-sample mendelian randomization study

BACKGROUND

Association between glucose and inflammatory bowel disease (IBD) was found in previous observational studies and in cohort studies. However, it is not clear whether these associations reflect causality. Thus, this study investigated whether there is such a causal relation between elevated glucose and IBD, Crohn's disease (CD) and ulcerative colitis (UC).

METHODS

We performed a two-sample Mendelian Randomization (MR) with the independent genetic instruments identified from the largest available genome-wide association study (GWAS) for IBD (5,673 cases; 213,119 controls) and its main subtypes, CD and UC. Summarized data for glucose which included 200,622 cases and glycemic traits including HbA1c and type 2 diabetes(T2DM) were obtained from different GWAS studies. Primary and secondary analyses were conducted by preferentially using the radial inverse-variance weighted (IVW) approach. A number of other meta-analysis approach and sensitivity analyses were carried out to assess the robustness of the results.

RESULTS

We did not find a causal effect of genetically predicted glucose on IBD as a whole (OR 0.858; 95% CI 0.649-1.135; P = 0.286). In subtype analyses glucose was also suggestively not associated with Crohn's disease (OR 0.22; 95% CI 0.04-1.00; P = 0.05) and ulcerative colitis (OR 0.940; 95% CI 0.628-1.407; P = 0.762). In the other direction, IBD and its subtypes were not related to glucose and glycemic traits.

CONCLUSIONS

This MR study is not providing any evidence for a causal relationship between genetically predicted elevated glucose and IBD as well as it's subtypes UC and CD. Regarding the other direction, no causal associations could be found. Future studies with robust genetic instruments are needed to confirm this conclusion.

Challenges in IBD Research 2024: Environmental Triggers

Environmental factors play an important role in inflammatory bowel diseases (IBD; Crohn's disease, [CD], ulcerative colitis [UC]). As part of the Crohn's & Colitis Challenges 2024 agenda, the Environmental Triggers workgroup summarized the progress made in the field of environmental impact on IBD since the last Challenges cycle in this document. The workgroup identified 4 unmet gaps in this content area pertaining to 4 broad categories: (1) Epidemiology; (2) Exposomics and environmental measurement; (3) Biologic mechanisms; and (4) Interventions and Implementation. Within epidemiology, the biggest unmet gaps were in the study of environmental factors in understudied populations including racial and ethnic minority groups and in populations witnessing rapid rise in disease incidence globally. The workgroup also identified a lack of robust knowledge of how environmental factors may impact difference stages of the disease and for different disease-related end points. Leveraging existing cohorts and targeted new prospective studies were felt to be an important need for the field. The workgroup identified the limitations of traditional questionnaire-based assessment of environmental exposure and placed high priority on the identification of measurable biomarkers that can quantify cross-sectional and longitudinal environmental exposure. This would, in turn, allow for identifying the biologic mechanisms of influence of environmental factors on IBD and understand the heterogeneity in effect of such influences. Finally, the working group emphasized the importance of generating high-quality data on effective environmental modification on an individual and societal level, and the importance of scalable and sustainable methods to deliver such changes.

Role of diet in prevention versus treatment of Crohn's disease and ulcerative colitis

Diet is a modifiable risk factor for disease course and data over the past decade have emerged to indicate its role in Crohn's disease (CD) and ulcerative colitis (UC). However, literature is riddled with misinterpretation of data, often leading to unexpected or conflicting results. The key understanding is that causative factors in disease development do not always proceed to an opportunity to change disease course, once established. Here, we discuss the data on dietary influences in three distinct disease states for CD and UC-predisease, active disease and quiescent disease. We appraise the literature for how our dietary recommendations should be shaped to prevent disease development and if or how that differs for CD and UC induction therapy and maintenance therapy. In UC, principles of healthy eating are likely to play a role in all states of disease. Conversely, data linking dietary factors to CD prevention and treatment are paradoxical with the highest quality evidence for CD treatment being exclusive enteral nutrition, a lactose, gluten and fibre-free diet comprising solely of ultraprocessed food-all dietary factors that are not associated or inversely associated with CD prevention. High-quality evidence from dietary trials is much awaited to expand our understanding and ultimately lead our dietary recommendations for targeted patient populations.

Preventative and therapeutic potential of nutrition for inflammatory bowel diseases: A narrative review

Diet strongly shapes the gut microbiome and metabolome, which in turn influence intestinal inflammation in patients with inflammatory bowel disease (IBD). Separate from inflammation and malnutrition, diet's direct interactions with the gastrointestinal system can also provoke or attenuate a host of nonspecific gastrointestinal symptoms. Given these multifaceted effects of diet on inflammation and symptoms, nutrition has been investigated for its potential roles in the prevention and treatment of IBD. This review presents epidemiological, observational cohort, and clinical trial evidence that underlie our current understanding of nutrition for prevention and treatment of IBD.

Factors influencing the quality of life in inflammatory bowel disease: A comprehensive review

Inflammatory bowel disease (IBD) is a group of chronic relapsing disorders, including Crohn's disease (CD) and ulcerative colitis (UC), which affects an increasing number of people worldwide. In the last few decades, the scientific world has witnessed many developments in IBD management by controlling debilitating symptoms and remaining in remission for more protracted periods. Even so, we still have a large population suffering from active IBD. An individual's quality of life (QoL) can be severely affected by IBD, like any other chronic illness. In this article, we have reviewed factors influencing the QoL in IBD patients, including chronic pain, diet, physical activity, and psychological factors like depression, anxiety, and stress symptoms. We also discussed the mechanisms of diet-microbial-immune system interaction, currently available dietary therapies for active CD and UC, and early psycho-social interventions that can reduce the disease burden and improve QoL in IBD patients.

Perinatal foodborne titanium dioxide exposure-mediated dysbiosis predisposes mice to develop colitis through life

BACKGROUND

Perinatal exposure to titanium dioxide (TiO2), as a foodborne particle, may influence the intestinal barrier function and the susceptibility to develop inflammatory bowel disease (IBD) later in life. Here, we investigate the impact of perinatal foodborne TiO2 exposure on the intestinal mucosal function and the susceptibility to develop IBD-associated colitis. Pregnant and lactating mother mice were exposed to TiO2 until pups weaning and the gut microbiota and intestinal barrier function of their offspring was assessed at day 30 post-birth (weaning) and at adult age (50 days). Epigenetic marks was studied by DNA methylation profile measuring the level of 5-methyl-2'-deoxycytosine (5-Me-dC) in DNA from colic epithelial cells. The susceptibility to develop IBD has been monitored using dextran-sulfate sodium (DSS)-induced colitis model. Germ-free mice were used to define whether microbial transfer influence the mucosal homeostasis and subsequent exacerbation of DSS-induced colitis.

RESULTS

In pregnant and lactating mice, foodborne TiO2 was able to translocate across the host barriers including gut, placenta and mammary gland to reach embryos and pups, respectively. This passage modified the chemical element composition of foetus, and spleen and liver of mothers and their offspring. We showed that perinatal exposure to TiO2 early in life alters the gut microbiota composition, increases the intestinal epithelial permeability and enhances the colonic cytokines and myosin light chain kinase expression. Moreover, perinatal exposure to TiO2 also modifies the abilities of intestinal stem cells to survive, grow and generate a functional epithelium. Maternal TiO2 exposure increases the susceptibility of offspring mice to develop severe DSS-induced colitis later in life. Finally, transfer of TiO2-induced microbiota dysbiosis to pregnant germ-free mice affects the homeostasis of the intestinal mucosal barrier early in life and confers an increased susceptibility to develop colitis in adult offspring.

CONCLUSIONS

Our findings indicate that foodborne TiO2 consumption during the perinatal period has negative long-lasting consequences on the development of the intestinal mucosal barrier toward higher colitis susceptibility. This demonstrates to which extent environmental factors influence the microbial-host interplay and impact the long-term mucosal homeostasis.

Pre-illness dietary risk factors in dogs with chronic enteropathy

BACKGROUND

Dietary factors have been extensively studied as potential triggers of inflammatory bowel disease in humans. Scant literature exists regarding diet as a pre-illness risk factor in dogs with chronic enteropathy (CE).

HYPOTHESIS

To evaluate possible pre-illness dietary risk factors in dogs with CE.

ANIMALS

Ninety-five client-owned dogs; 48 with CE (25 presumptive and 23 confirmed) and 47 without a history of signs of gastrointestinal disease.

METHODS

Retrospective case-control questionnaire-based study at a veterinary referral teaching hospital in the United Kingdom. Diet history was obtained relating to the onset of initial presenting signs for all dogs. The main diet consumed underwent ingredient analysis and caloric distribution calculation using a guaranteed analysis convertor software. Length of time the main diet was fed and adherence to the World Small Animal Veterinary Association Global Nutrition Committee guidelines was also recorded.

RESULTS

The frequency of the main diet containing no carbohydrate was greater for controls (5/47 dogs, 11%) vs the combined presumptive and confirmed CE dogs (0/48 dogs, 0%; P = .05). Fewer dogs with confirmed CE were fed a main diet containing red meat as the primary protein source (2/23 dogs, 9%) vs controls (15/47 dogs, 32%; P = .03). A main diet moisture percentage of ≤14% as fed was significantly associated with confirmed CE in logistic regression analysis (OR 5.71 [95% CI: 1.18-27.69]; P = .03).

CONCLUSIONS AND CLINICAL IMPORTANCE

The presence of dietary carbohydrate, protein source, and dietary moisture content, or factors related to moisture content such as preservatives, might play a role as potential pre-illness dietary risk factors in dogs with CE.

Dietary Interventions for the Treatment of Inflammatory Bowel Diseases: An Updated Systematic Review and Meta-analysis

BACKGROUND & AIMS

This study aimed (1) to systematically review controlled trials of solid food diets for the treatment of inflammatory bowel disease (IBD); and (2) to grade the overall quality of evidence.

METHODS

Systematic review of prospective controlled trials of solid food diets for the induction or maintenance of remission in IBD. Two authors independently performed study selection, data extraction, and assessment of certainty of evidence. Meta-analyses were performed on studies with quantitative data on response, remission, and relapse.

RESULTS

There were 27 studies for meta-analysis. For induction of remission in Crohn's disease (CD), low refined carbohydrate diet and symptoms-guided diet outperformed controls, but studies had serious imprecision and very low certainty of evidence. The Mediterranean diet was similar to the Specific Carbohydrate Diet (low certainty of evidence), and partial enteral nutrition (PEN) was similar to exclusive enteral nutrition (very low certainty of evidence). PEN reduced risk of relapse (very low certainty of evidence), whereas reduction of red meat or refined carbohydrates did not (low certainty of evidence). For ulcerative colitis, diets were similar to controls (very low and low certainty of evidence).

CONCLUSIONS

Among the most robust dietary trials in IBD currently available, certainty of evidence remains very low or low. Nonetheless, emerging data suggest potential benefit with PEN for induction and maintenance of remission in CD. Reduction of red meat and refined carbohydrates might not reduce risk of CD relapse. As more dietary studies become available, the certainty of evidence could improve, thus allowing for more meaningful recommendations for patients.

Lifestyle factors associated with inflammatory bowel disease: data from the Swiss IBD cohort study

BACKGROUND

Various environmental risk factors have been associated with the pathogenesis of inflammatory bowel disease. In this study we aimed to identify lifestyle factors that affect the onset of Crohn's disease and ulcerative colitis.

METHODS

2294 patients from the Swiss IBD Cohort Study received a questionnaire regarding physical activity, nutritional habits and status of weight. In addition, a control group was formed comprising patients' childhood friends, who grew up in a similar environment.

RESULTS

Overall, 1111 questionnaires were returned (response rate: 48.4%). Significantly more patients with inflammatory bowel disease reported no regular practice of sport during childhood and beginning of adulthood compared to the control group (p = 0.0001). No association between intake of refined sugar and onset of inflammatory bowel disease was observed. More patients with Crohn's disease compared to ulcerative colitis and controls suffered from overweight during childhood (12.8% vs. 7.7% and 9.7%, respectively; p = 0.027).

CONCLUSIONS

Our study underlines the relevance of environmental factors in the development of inflammatory bowel disease. Our results imply a protective effect of physical activity regarding the onset of inflammatory bowel disease.

A Mendelian Randomization Analysis Investigates Causal Associations between Inflammatory Bowel Diseases and Variable Risk Factors

The question of whether variable risk factors and various nutrients are causally related to inflammatory bowel diseases (IBDs) has remained unanswered so far. Thus, this study investigated whether genetically predicted risk factors and nutrients play a function in the occurrence of inflammatory bowel diseases, including ulcerative colitis (UC), non-infective colitis (NIC), and Crohn's disease (CD), using Mendelian randomization (MR) analysis. Utilizing the data of genome-wide association studies (GWASs) with 37 exposure factors, we ran Mendelian randomization analyses based on up to 458,109 participants. Univariable and multivariable MR analyses were conducted to determine causal risk factors for IBD diseases. Genetic predisposition to smoking and appendectomy as well as vegetable and fruit intake, breastfeeding, n-3 PUFAs, n-6 PUFAs, vitamin D, total cholesterol, whole-body fat mass, and physical activity were related to the risk of UC (p < 0.05). The effect of lifestyle behaviors on UC was attenuated after correcting for appendectomy. Genetically driven smoking, alcohol consumption, appendectomy, tonsillectomy, blood calcium, tea intake, autoimmune diseases, type 2 diabetes, cesarean delivery, vitamin D deficiency, and antibiotic exposure increased the risk of CD (p < 0.05), while vegetable and fruit intake, breastfeeding, physical activity, blood zinc, and n-3 PUFAs decreased the risk of CD (p < 0.05). Appendectomy, antibiotics, physical activity, blood zinc, n-3 PUFAs, and vegetable fruit intake remained significant predictors in multivariable MR (p < 0.05). Besides smoking, breastfeeding, alcoholic drinks, vegetable and fruit intake, vitamin D, appendectomy, and n-3 PUFAs were associated with NIC (p < 0.05). Smoking, alcoholic drinks, vegetable and fruit intake, vitamin D, appendectomy, and n-3 PUFAs remained significant predictors in multivariable MR (p < 0.05). Our results provide new and comprehensive evidence demonstrating that there are approving causal effects of various risk factors on IBDs. These findings also supply some suggestions for the treatment and prevention of these diseases.

Fructose Stimulated Colonic Arginine and Proline Metabolism Dysbiosis, Altered Microbiota and Aggravated Intestinal Barrier Dysfunction in DSS-Induced Colitis Rats

The dysbiosis of intestinal microbiota and their metabolites is linked to the occurrence and development of metabolic syndrome. Although fructose has been proven to be associated with worsened mucus in the colon, its mechanism remains unclear. In this study, we evaluated the relatively low intake of sucrose and fructose in the experimental colitis of Sprague Dawley rats by investigating the microbiome and metabolome. Results showed that sucrose and fructose significantly reduced body weight, colon length and increased inflammation infiltration in colon. Sucrose and fructose worsen colon functions by inhibiting the expression of tight junction (TJ) protein ZO-1 and increasing the level of lipopolysaccharide neoandrographolide (LPS) in plasma, while fructose was more significant. Furthermore, sucrose and fructose significantly changed the composition of gut microbiota characterized by decreasing Adlercreutzia, Leuconostoc, Lactococcus and Oscillospira and increasing Allobaculum and Holdemania along with reducing histidine, phenylalanine, arginine, glycine, aspartic acid, serine, methionine valine, alanine, lysine, isoleucine, leucine, threonine, tryptophan, tyrosine, proline, citrulline, 4-hydroxyproline and gamma amino butyric acid (GABA). Metabolome results showed that fructose may aggravate experimental colitis symptoms by inducing amino metabolism dysbiosis in the colon. These findings suggested that fructose worsened colitis by manipulating the crosstalk between gut microbiota and their metabolites.

Ultra-processed foods as a possible culprit for the rising prevalence of inflammatory bowel diseases

Inflammatory bowel diseases (IBD) are chronic inflammatory disorders of the gastrointestinal tract, and the exact pathogenesis is still unclear. It is believed that IBD develops in response to a complex interaction between the microbiota, environmental factors, and the immune system, in genetically predisposed individuals. Identifying these environmental factors will offer more insight in the development of the disease, and reveal new therapeutic targets for IBD patients. One of the environmental factors that has gained more interest over the last years is our diet. The prevalence of IBD has increased significantly and this increase is thought to be associated with a ‘Western diet', characterized by high intake of fats, added sugar, meat, and ultra-processed foods (UPFs). The UPFs now account for almost 50% of the energy intake in Westernized countries and are therefore an important characteristic of this Western diet. UPFs are characterized by higher amounts of salt, fat, sugar and the presence of different food additives. Epidemiological studies have found associations between UPF intake and a range of non-communicable diseases, including inflammatory bowel disease (IBD). Preclinical and clinical evidence suggest that non-nutritive ingredients and additives, present in UPFs, can negatively affect different components of the intestinal barrier, such as the microbiota, the mucus layer, the epithelium, and the immune cells in the lamina propria. Disruption of this barrier can cause the immune system to encounter an increased bacterial exposure, leading to an aberrant immune response. In this article, the available evidence on the possible role of UPFs and their components in the increasing incidence and prevalence of IBD is reviewed. These findings can be translated to the clinic and may be helpful to consider when giving dietary advice to IBD patients. A better understanding of the role of UPFs may lead to less restrictive diets for patients with IBD, hence increasing the dietary compliance and efficacy of exclusion diets.

Reconstruction and Differential Expression Profiling Core Target Analyses of the circRNA-miRNA-mRNA Network Based on Competitive Endogenous RNAs in Ulcerative Colitis

Ulcerative colitis (UC) is a common autoimmune disease worldwide. Circular RNA (circRNA) is a type of noncoding ribonucleic acids (ncRNAs). In addition to their roles in numerous biological processes, circRNAs are also linked to a vast range of diseases including UC. Although previous studies have examined many circRNAs, the physiological and pathological roles of the circRNA-associated competing endogenous RNA (ceRNA) network in UC remain unclear. Thus, we constructed a circRNA-miRNA-mRNA network based on the ceRNA hypothesis by analyzing data from the National Center for Biotechnology Information Gene Expression Omnibus (NCBI-GEO) database. Genes with higher degree values than others in the ceRNA network were selected as central nodes when constructing the corresponding core subnetworks. To fully understand the biological function of the ceRNA network, we entered all differentially expressed mRNAs (DEmRNAs) from the ceRNA network into the Database for Annotation and Integrated Discovery (DAVID), which was used to perform Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. We further entered DEmRNAs into the STRING database for protein-protein interaction (PPI) network analysis. The results elucidated that the ceRNA network comprised 403 circRNA nodes, 5 miRNA nodes, 138 mRNA nodes, and 559 edges. Three core ceRNA subnetworks centered on hsa-miR-342-3p, hsa-miR-199a-5p, and hsa-miR-142-3p were reconstructed in this study. GO and KEGG enrichment analyses identified 167 enriched GO categories and 14 enriched KEGG pathway terms. The core PPI network was composed of 15 core targets, of which CD44, HIF1A, and MMP2 were the most significant. In summary, 3 hub miRNAs (hsa-miR-342-3p, hsa-miR-199a-5p, hsa-miR-142-3p) and 3 hub genes (CD44, HIF1A, and MMP2) might play an important role in the development of UC. These hub nodes, first proposed here, might also be used as potential diagnostic markers and therapeutic targets.

Exploration of Potential Gut Microbiota-Derived Biomarkers to Predict the Success of Fecal Microbiota Transplantation in Ulcerative Colitis: A Prospective Cohort in Korea

Background/Aims

Although fecal microbiota transplantation (FMT) has been proven as one of the promising treatments for patients with ulcerative colitis (UC), potential prognostic markers regarding the clinical outcomes of FMT remain elusive.

Methods

We collected fecal samples of 10 participants undergoing FMT to treat UC and those from the corresponding donors. We categorized them into two groups: responders and nonresponders. Sequencing of the bacterial 16S rRNA gene was conducted on the samples to explore bacterial composition.

Results

Analyzing the gut microbiota of patients who showed different outcomes in FMT presented a distinct microbial niche. Source tracking analysis showed the nonresponder group had a higher rate of preservation of donor microbiota, underscoring that engraftment degrees are not one of the major drivers for the success of FMT. At the phylum level, Bacteroidetes bacteria were significantly depleted (p<0.003), and three genera, including Enterococcus, Rothia, and Pediococcus, were enriched in the responder group before FMT (p=0.003, p=0.025, and p=0.048, respectively). Furthermore, we applied a machine learning algorithm to build a prediction model that might allow the prediction of FMT outcomes, which yielded an area under the receiver operating characteristic (ROC) curve of 0.844. Notably, the microbiota-based model was much better at predicting outcomes than the clinical features model (area under the ROC curve=0.531).

Conclusions

This study is the first to suggest the significance of indigenous microbiota of recipients as a critical factor. The result highlights that bacterial composition should be evaluated before FMT to select suitable patients and achieve better efficiency.

The potential role of Bifidobacterium spp. as a preventive and therapeutic agent in controlling inflammation via affecting inflammatory signalling pathways

Inflammatory bowel disease (IBD) is a chronic inflammatory disease with relapses and periods of remission. Forasmuch as, dysregulation of the immune system is one of the triggers of IBD, taking probiotics as one of the immunomodulators in the gut, could help to control inflammation and IBD via influencing signalling pathways. Here, we aimed to investigate the efficacy of five selected Bifidobacterium strains in modulating JAK/STAT and NF-kB inflammatory signalling pathways via using the in vitro assay. A quantitative real-time polymerase chain reaction assay was used to analyse the expression of JAK/STAT and inflammatory genes followed by potential probiotic treatments before, after and simultaneously with the inflammation induction (sonicated pathogen). The production of IL-6 and IL-1β after probiotic treatment was evaluated. Probiotic treatment resulted in the downregulation of TIRAP, IRAK4, NEMO and RIP genes in the NF-kB pathway, as well as JAK genes compared to sonicate-treated cells. The expression of STAT genes was different after our selected Bifidobacterium strains treatment. The production of IL-6 and IL-1β decreased after probiotic treatment. These strains of Bifidobacterium spp. showed anti-inflammatory effects on HT-29 cells via modulation of JAK/STAT and NF-kB signalling pathways. The use of Bifidobacterium spp. could be considered as a suitable preventive and complementary treatment for patients with inflammatory bowel disease.

Different Dose of Sucrose Consumption Divergently Influences Gut Microbiota and PPAR-γ/MAPK/NF-κB Pathway in DSS-Induced Colitis Mice

Sugar reduction and sugar control are advocated and gaining popularity around the world. Sucrose, as the widely consumed ingredient in our daily diet, has been reported a relation to gastrointestinal diseases. However, the role of sucrose in inflammatory bowel disease remains controversial. Hence, our study aimed to elucidate the potential role of three doses of sucrose on DSS-induced colitis in C57BL/6 mice and the underlying mechanisms. The results showed that low-dose sucrose intervention alleviated colitis in mice, reducing the expression of inflammatory cytokines and repairing mucosal damages. In contrast, high-dose sucrose intervention exacerbated colitis. Furthermore, three doses of sucrose administration markedly altered gut microbiota composition. Notably, the low-dose sucrose restored microbial dysfunction and enhanced the production of short chain fatty acids (SCFAs). Specifically, the abundance of SCFAs-producing bacteria Faecalibaculum, Bacteroides, and Romboutsia were increased significantly in the LOW group. Consistently, PPAR-γ, activated by SCFAs, was elevated in the LOW group, thereby inhibiting the MAPK/NF-κB pathway. Together, our study demonstrates the differential effects of sucrose on colitis at different doses, providing a scientific basis for measuring and modifying the safe intake level of sugar and providing favorable evidence for implementing sugar reduction policies.

Spermidine Ameliorates Nonalcoholic Steatohepatitis through Thyroid Hormone-Responsive Protein Signaling and the Gut Microbiota-Mediated Metabolism of Bile Acids

Spermidine, a natural polyamine and physiological autophagy inducer, is involved in various physiological processes. However, the impact and mechanism of spermidine on nonalcoholic steatohepatitis (NASH) remains unclarified. We found that daily spermidine intake was significantly lower in volunteers with liver dysfunction than the healthy controls, and the serum and fecal spermidine levels were negatively correlated with the NASH phenotypes. Spermidine supplementation significantly attenuated hepatic lipid accumulation, insulin resistance, hepatic inflammation, and fibrosis in NASH mice induced by a western diet. The ameliorating effect of spermidine on lipid accumulation might be partly regulated by thyroid hormone-responsive protein (THRSP) signaling and autophagy. Moreover, spermidine altered the profile of hepatic bile acids (BAs) and microbial composition and function. Furthermore, spermidine reversed the progression of hepatic steatosis, inflammation, and fibrosis in mice with preexisting NASH. Therefore, spermidine ameliorates NASH partly through the THRSP signaling and the gut microbiota-mediated metabolism of BAs, suggesting that spermidine might be a viable therapy for NASH.

Nutrition in Patients with Inflammatory Bowel Diseases: A Narrative Review

Inflammatory bowel diseases (IBD) affect the gastrointestinal tract: they include Crohn's disease (CD) and ulcerative colitis (UC). Each has a different phenotypic spectrum, characterized by gastrointestinal and extra-intestinal manifestations. People living with IBD are very interested in diet, but little is known about the impact of diet on these patients; no guidelines are available yet. In this review, we analyze the dietary patterns of patients with IBD and the approach to the choices of foods both in adults and pediatric patients. Very often, IBD patients report an intentional avoidance of gluten to manage the disease; furthermore, a proportion of IBD patients believe that dairy products worsen their symptoms and that avoidance may help the disease. They have a low compliance with the Mediterranean Diet, which is considered to have potential benefits but is little used in practice. In conclusion, the review underscores the pivotal role of nutritional counselling in IBD patients, and the importance of future clinical studies to evaluate the beneficial effects of dietary recommendations in the management of IBD.

Long-Term Overconsumption of Fat and Sugar Causes a Partially Reversible Pre-inflammatory Bowel Disease State

Nutrition appears to be an important environmental factor involved in the onset of inflammatory bowel diseases (IBD) through yet poorly understood biological mechanisms. Most studies focused on fat content in high caloric diets, while refined sugars represent up to 40% of caloric intake within industrialized countries and contribute to the growing epidemics of inflammatory diseases. Herein we aim to better understand the impact of a high-fat-high-sucrose diet on intestinal homeostasis in healthy conditions and the subsequent colitis risk. We investigated the early events and the potential reversibility of high caloric diet-induced damage in mice before experimental colitis. C57BL/6 mice were fed with a high-fat or high-fat high-sucrose or control diet before experimental colitis. In healthy mice, a high-fat high-sucrose diet induces a pre-IBD state characterized by gut microbiota dysbiosis with a total depletion of bacteria belonging to Barnesiella that is associated with subclinical endoscopic lesions. An overall down-regulation of the colonic transcriptome converged with broadly decreased immune cell populations in the mesenteric lymph nodes leading to the inability to respond to tissue injury. Such in-vivo effects on microbiome and transcriptome were partially restored when returning to normal chow. Long-term consumption of diet enriched in sucrose and fat predisposes mice to colitis. This enhanced risk is preceded by gut microbiota dysbiosis and transcriptional reprogramming of colonic genes related to IBD. Importantly, diet-induced transcriptome and microbiome disturbances are partially reversible after switching back to normal chow with persistent sequelae that may contribute to IBD predisposition in the general population.

Dietary Intake of Total Carbohydrates, Sugar and Sugar-Sweetened Beverages, and Risk of Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis of Prospective Cohort Studies

Objectives: No earlier study has summarized findings from prospective cohort studies on the association of dietary carbohydrates, sugar, and sugar-sweetened beverages (SSBs) consumption and risk of inflammatory bowel disease (IBD). The current study was done to quantitatively summarize earlier information from prospective cohort studies on the link between dietary carbohydrates, sugar, and SSBs intake with risk of IBD.

Methods: Relevant studies published up to June 2021 were searched through PubMed, Medline, SCOPUS, EMBASE, and Google Scholar with the use of relevant keywords. All prospective cohort studies investigating the association of dietary carbohydrates, sugar, and SSBs consumption with risk of IBD were included.

Results: Combining 5 effect sizes from 4 cohort studies, no significant association was found between dietary intake of carbohydrates and risk of ulcerative colitis (UC) (RR: 1.22; 95% CI: 0.70–2.14). The same findings were obtained for risk of Crohn's disease (CD) (RR: 1.06; 95% CI: 0.64–1.75) based on 4 studies with 5 effect sizes. A significant positive association was observed between sugar intake and risk of UC (RR: 1.59; 95% CI: 1.15–2.20), as well as CD (RR: 1.90; 95% CI: 1.06–3.41) when 5 effect sizes from 4 cohort studies were combined. The overall effect size, based on 4 estimates, revealed no significant association between SSBs consumption and risk of UC (RR: 1.02; 95% CI: 0.92–1.12) and CD (RR: 1.22; 95% CI: 0.91–1.64).

Conclusions: Summarizing earlier studies, sugar intake was found to be associated with increased risk of IBD and its subtypes. Any significant association between dietary intake of carbohydrates and SSBs and risk of IBD and its subtypes was not found.

Titanium dioxide particles from the diet: involvement in the genesis of inflammatory bowel diseases and colorectal cancer

The gastrointestinal tract is a complex interface between the external environment and the immune system. Its ability to control uptake across the mucosa and to protect the body from damage of harmful substances from the lumen is defined as the intestinal barrier function (IBF). The IBF involves four elements: the intestinal microbiota, the mucus layer, the epithelium and the immune system. Its dysfunction is linked with human diseases including inflammatory, metabolic, infectious, autoimmune and neurologic disorders. Most of these diseases are complex and involve genetic, psychological and environmental factors. Over the past 10 years, many genetic polymorphisms predisposing to inflammatory bowel disease (IBD) have been identified. Yet, it is now clear that they are insufficient to explain the onset of these chronic diseases. Although it has been evidenced that some environmental factors such as cigarette smoking or carbohydrate intake are associated with IBD, other environmental factors also present potential health risks such as ingestion of food additives introduced in the human diet, including those composed of mineral particles, by altering the four elements of the intestinal barrier function. The aim of this review is to provide a critical opinion on the potential of TiO₂ particles, especially when used as a food additive, to alter the four elements of the intestinal barrier function, and consequently to evaluate if this additive would likely play a role in the development and/or exacerbation of IBD.

Dietary simple sugars alter microbial ecology in the gut and promote colitis in mice

The higher prevalence of inflammatory bowel disease (IBD) in Western countries points to Western diet as a possible IBD risk factor. High sugar, which is linked to many noncommunicable diseases, is a hallmark of the Western diet, but its role in IBD remains unknown. Here, we studied the effects of simple sugars such as glucose and fructose on colitis pathogenesis in wild-type and Il10^-/- mice. Wild-type mice fed 10% glucose in drinking water or high-glucose diet developed severe colitis induced by dextran sulfate sodium. High-glucose-fed Il10^-/- mice also developed a worsened colitis compared to glucose-untreated Il10^-/- mice. Short-term intake of high glucose or fructose did not trigger inflammatory responses in healthy gut but markedly altered gut microbiota composition. In particular, the abundance of the mucus-degrading bacteria Akkermansia muciniphila and Bacteroides fragilis was increased. Consistently, bacteria-derived mucolytic enzymes were enriched leading to erosion of the colonic mucus layer of sugar-fed wild-type and Il10^-/- mice. Sugar-induced exacerbation of colitis was not observed when mice were treated with antibiotics or maintained in a germ-free environment, suggesting that altered microbiota played a critical role in sugar-induced colitis pathogenesis. Furthermore, germ-free mice colonized with microbiota from sugar-treated mice showed increased colitis susceptibility. Together, these data suggest that intake of simple sugars predisposes to colitis and enhances its pathogenesis via modulation of gut microbiota in mice.

Diet Rich in Simple Sugars Promotes Pro-Inflammatory Response via Gut Microbiota Alteration and TLR4 Signaling

Diet is a strong modifier of microbiome and mucosal microenvironment in the gut. Recently, components of western-type diets have been associated with metabolic and immune diseases. Here, we studied how high-sugar diet (HSD) consumption influences gut mucosal barrier and immune response under steady state conditions and in a mouse model of acute colitis. We found that HSD significantly increased gut permeability, spleen weight, and neutrophil levels in spleens of healthy mice. Subsequent dextran sodium sulfate administration led to severe colitis. In colon, HSD significantly promoted neutrophil infiltration and increased the levels of IL-6, IL-1β, and TNF-α. Moreover, HSD-fed mice had significantly higher abundance of pathobionts, such as Escherichia coli and Candida, in fecal samples. Although germ-free mice colonized with microbiota of conventionally reared mice that consumed different diets had equally severe colitis, mice colonized with HSD microbiota showed markedly increased infiltration of neutrophils to the gut. The induction of colitis in Toll-like receptor 4 (TLR4)-deficient HSD-fed mice led to significantly milder colitis than in wild-type mice. In conclusion, our results suggested a significant role of HSD in disruption of barrier integrity and balanced mucosal and systemic immune response. In addition, these processes seemed to be highly influenced by resident potentially pathogenic microbiota or metabolites via the TLR4 signaling pathway.

The Role of Epidemiological Evidence from Prospective Population Studies in Shaping Dietary Approaches to Therapy in Crohn's Disease

SCOPE

The concept that dietary factors are key risk and preventive agents in the development of Crohn's disease (CD), while widely believed and supported by epidemiological evidence, has yet to lead to clear identification of those factors through clinical trials. The aims are to examine the strength of the epidemiological evidence of diet and its association with CD, examine how interpretation of mostly epidemiological data has shaped ideas for potential dietary therapies, and to explore other factors that have driven the design of dietary clinical trials in CD.

METHODS

A literature search is performed in PubMed, Medline, EMBASE, and Google Scholar for prospective cohort studies and randomized clinical trials (RCTs) using search terms-"Crohn's disease," "diet," "risk," "remission," "treat," "cohort," "randomised."

RESULTS

Only four prospective cohort studies examine the relationship of diet and CD development, but these trials have been largely ignored by dietary RCTs in CD, which have used predominantly exclusion diets in small populations without objective endpoint assessment. Only one demonstrated clinical benefit to intestinal inflammation.

CONCLUSION

Investment in large multicenter dietary clinical trials that focus on dietary inclusions with objective endpoint assessment are needed to provide safe, sustainable dietary therapy to patients with CD.

A food pyramid, based on a review of the emerging literature, for subjects with inflammatory bowel disease

Emerging literature suggests that diet plays an important modulatory role in inflammatory bowel disease (IBD) through the management of inflammation and oxidative stress. The aim of this narrative review is to evaluate the evidence collected up till now regarding optimum diet therapy for IBD and to design a food pyramid for these patients. The pyramid shows that carbohydrates should be consumed every day (3 portions), together with tolerated fruits and vegetables (5 portions), yogurt (125ml), and extra virgin olive oil; weekly, fish (4 portions), white meat (3 portions), eggs (3 portions), pureed legumes (2 portions), seasoned cheeses (2 portions), and red or processed meats (once a week). At the top of the pyramid, there are two pennants: the red one means that subjects with IBD need some personalized supplementation and the black one means that there are some foods that are banned. The food pyramid makes it easier for patients to decide what they should eat.

Role of Diet in the Development and Management of Crohn's Disease

PURPOSE OF REVIEW

This article provides an updated review on the role of diet in the risk of developing Crohn's disease (CD) and CD management, areas of ongoing study.

RECENT FINDINGS

Higher intake of dietary fiber (fruit fiber) has been associated with a reduced risk for CD. The exclusive enteral nutrition (EEN) diet remains the most validated nutritional recommendation for inducing remission in CD. The specific carbohydrate diet (SCD) has demonstrated reductions in CD severity scores in conjunction with medical therapies, and larger trials on its efficacy are ongoing. Several new exclusion diets modeled after EEN and SCD have shown potential efficacy in smaller studies that warrant replication. There is a paucity of clear dietary recommendations for the reduction in risk of CD clinical relapse. There are various components of diet that likely impact risk for CD development and contribute to its disease course; however, studies are often limited in their size or ability to demonstrate mechanistic causation. Further studies including diets that aim to expand on the restrictive nature of EEN may lead to stronger evidence for a diet-based approach to CD management.

A meta-analysis of dietary carbohydrate intake and inflammatory bowel disease risk: evidence from 15 epidemiology studies

BACKGROUND AND PURPOSE

epidemiological studies that assess the association of dietary total carbohydrate intake and inflammatory bowel disease risk (IBD) have yielded controversial results. Therefore, this study of various epidemiological studies was conducted in order to explore this relationship.

METHODS

a systematic literature search of the PubMed, Embase, Web of Science and Medline databases was performed up to September 2017. Cohort, case-control or cross-sectional design studies were included that reported the association of dietary carbohydrate intake and IBD risk. Summary odds ratio (OR) and the corresponding 95% CI were calculated using the random effects model.

RESULTS

a total of eight articles with 15 individual studies that included 1,361 cases were eligible according to the inclusion criteria. Dietary carbohydrate intake had a non-significant relationship with the risk of IBD (OR = 1.091, 95% CI = 0.817-1.455, I2 = 31.6%, pfor heterogeneity = 0.116). The pooled OR and 95% CI for ulcerative colitis (UC) and Crohn's disease (CD) with regard to dietary carbohydrate intake was 1.167 (0.777-1.752) and 1.010 (0.630-1.618), respectively. These associations were also non-significant in both European and Asia populations.

CONCLUSIONS

a higher dietary total carbohydrate intake had a non-significant relationship with IBD risk. Further studies with large populations are needed to verify this relationship.

Diet in the etiology of inflammatory bowel disease

The two predominant forms of inflammatory bowel disease (IBD) namely Crohn's disease (CD) and ulcerative colitis (UC) can have a significant impact on patients' quality of life and incur major costs in terms of time off work and for therapies. The precise aetiology of IBD is unknown, but is probably due to a combination of: genetic, immunological and environmental factors. The role for the latter is strongly supported by rises in the incidence of IBD in the 20th century, and emergence of both CD and UC in countries in the East. Dietary changes over time and according to region may be the environmental factor explaining these incidence patterns.

Importance of nutritional therapy in the management of intestinal diseases: beyond energy and nutrient supply

The gut is an immune-microbiome-epithelial complex. Gut microbiome-host interactions have widespread biological implications, and the role of this complex system extends beyond the digestion of food and nutrient absorption. Dietary nutrients can affect this complex and play a key role in determining gut homeostasis to maintain host health. In this article, we review various dietary nutrients and their contribution to the pathogenesis and treatment of various intestinal diseases including inflammatory bowel disease, irritable bowel syndrome, colorectal cancer, and diverticulitis, among other such disorders. A better understanding of diet-host-gut microbiome interactions is essential to provide beneficial nutrients for gut health and to limit nutritional hazards to ensure successful nutritional management of gastrointestinal conditions in clinical practice.

Inflammatory Bowel Diseases and Food Additives: To Add Fuel on the Flames!

Inflammatory bowel diseases (IBDs) develop in genetically predisposed individuals in response to environmental factors. IBDs are concomitant conditions of industrialized societies, and diet is a potential culprit. Consumption of ultra-processed food has increased over the last decade in industrialized countries, and epidemiological studies have found associations between ultra-processed food consumption and chronic diseases. Further studies are now required to identify the potential culprit in ultra-processed food, such as a poor nutritional composition or the presence of food additives. In our review, we will focus on food additives, i.e., substances from packaging in contact with food, and compounds formed during production, processing, and storage. A literature search using PubMed from inception to January 2019 was performed to identify relevant studies on diet and/or food additive and their role in IBDs. Manuscripts published in English from basic science, epidemiological studies, or clinical trials were selected and reviewed. We found numerous experimental studies highlighting the key role of food additives in IBD exacerbation but epidemiological studies on food additives on IBD risk are still limited. As diet is a modifiable environmental risk factor, this may offer a scientific rationale for providing dietary advice for IBD patients.

Bases for the Adequate Development of Nutritional Recommendations for Patients with Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic and relapsing inflammatory condition of the gastrointestinal tract; it is a heterogeneous and multifactorial disorder resulting from a complex interplay between genetic variation, intestinal microbiota, the host immune system and environmental factors such as diet, drugs, breastfeeding and smoking. The interactions between dietary nutrients and intestinal immunity are complex. There is a compelling argument for environmental factors such as diet playing a role in the cause and course of IBD, given that three important factors in the pathogenesis of IBD can be modulated and controlled by diet: intestinal microbiota, the immune system and epithelial barrier function. The aim of this review is to summarize the epidemiological findings regarding diet and to focus on the effects that nutrients exert on the intestinal mucosa-microbiota-permeability interaction. The nature of these interactions in IBD is influenced by alterations in the nutritional metabolism of the gut microbiota and host cells that can influence the outcome of nutritional intervention. A better understanding of diet-host-microbiota interactions is essential for unravelling the complex molecular basis of epigenetic, genetic and environmental interactions underlying IBD pathogenesis as well as for offering new therapeutic approaches for the treatment of IBD.

Impact of red meat, processed meat and fibre intake on risk of late-onset chronic inflammatory diseases: prospective cohort study on lifestyle factors using the Danish 'Diet, Cancer and Health' cohort (PROCID-DCH): protocol

INTRODUCTION

Chronic inflammatory diseases (CIDs) (Crohn's disease, ulcerative colitis, psoriasis, psoriatic arthritis, rheumatoid arthritis and multiple sclerosis) are diseases of the immune system that have some shared genetic and environmental predisposing factors, but still few studies have investigated the effects of lifestyle on disease risk of several CIDs. The primary aim of this prospective cohort study is to investigate the impact of fibre, red meat and processed meat on risk of late-onset CID, with the perspective that results of this study can contribute in supporting future diet recommendations for effective personalised prevention.

METHODS AND ANALYSIS

The study will use data from 57 053 persons from the prospective Danish cohort study 'Diet, Cancer and Health' together with National Health Registry data. The follow-up period is from December 1993 to December 2018. Questionnaire data on diet and lifestyle were collected at entry to the Diet, Cancer and Health study. The outcome CID is defined as having a diagnosis of one of the CIDs registered in the National Patient Registry or, for multiple sclerosis, in the Danish Multiple Sclerosis Registry during follow-up and being treated with a drug used for the specific disease. The major outcome of the analyses will be to detect variability in risk of late onset of any CID and, if power allows, disease risk of late onset of each CID diagnosis between persons with different fibre and red meat, and processed meat intake. The outcome will be adjusted for age, sex, body mass index, physical activity, energy, alcohol, fermented dairy products, education, smoking status, hormone replacement therapy and comorbidity.

ETHICS AND DISSEMINATION

The study is approved by the Danish Data Protection Agency (2012-58-0018). The core study is an open register-based cohort study. The study does not need approval from the Ethics committee or Institutional Review Board by Danish law. Study findings will be disseminated through peer-reviewed journals, patient associations and presentations at international conferences.

TRIAL REGISTRATION NUMBER

NCT03456206; Post-results.

Starch Consumption May Modify Antiglycan Antibodies and Fecal Fungal Composition in Patients With Ileo-Anal Pouch

BACKGROUND

Inflammatory bowel diseases (IBDs) are characterized by serologic responses to glycans. Patients with ulcerative colitis (UC) after proctocolectomy with ileo-anal anastomosis (pouch surgery) may develop inflammation (pouchitis) that resembles Crohn's disease (CD). We hypothesized that patients' serologic responses were affected by their consumption of dietary sugars. This study analyzed the correlations between antiglycan antibody expression and dietary sugar consumption in patients with UC pouch and the evolution in antibody levels over time.

METHODS

Patients were followed prospectively for 2 consecutive visits. The following antiglycan carbohydrate antibodies were detected by enzyme-linked immunosorbent assay: antichitobioside (ACCA), antilaminaribioside (ALCA), antimannobioside (AMCA), and anti-Saccharomyces cerevisiae (ASCA) antibodies. Patients completed a food frequency questionnaire. The fungal community in patients' fecal samples was analyzed by sequencing the internal transcribed spacer 2 (ITS2) region of nuclear ribosomal DNA.

RESULTS

We included 75 UC pouch patients aged 45.2 ± 14 years who underwent pouch surgery 9.8 ± 6.7 years previously. Of these patients, 34.7% (n = 26) showed seropositivity for antiglycan antibodies. Starch consumption was significantly higher in patients with positive serologic responses (P = 0.05). Higher starch consumption was associated with higher AMCA and ACCA titers, which increased by 4.08% (0.8%-7.4%; P = 0.014) and 4.8% (0.7%-9.1%; P = 0.007), respectively, for each 10-g increase of dietary starch. The per-patient change in the relative abundance of Candida albicans in fecal samples correlated positively with changes in starch consumption (Spearman's r = 0.72; P = 0.012).

CONCLUSIONS

Starch consumption correlated with positive antiglycan serology (ACCA and AMCA), suggesting that increased dietary starch intake may promote a specific immune response in patients with IBD.

Evolving role of diet in the pathogenesis and treatment of inflammatory bowel diseases

Recent advances in basic and clinical science over the last 3 years have dramatically altered our appreciation of the role of diet in inflammatory bowel diseases (IBD). The marked increase in incidence of these diseases along with the important role of non-genetic susceptibility among patients with IBD has highlighted that these diseases have a strong environmental component. Progress in the field of microbiome and IBD has demonstrated that microbiome appears to play an important role in pathogenesis, and that diet may in turn impact the composition and functionality of the microbiome. Uncontrolled clinical studies have demonstrated that various dietary therapies such as exclusive enteral nutrition and newly developed exclusion diets might be potent tools for induction of remission at disease onset, for patients failing biologic therapy, as a treatment for disease complications and in reducing the need for surgery. We review these advances from bench to bedside, along with the need for better clinical trials to support these interventions.

The role of diet in the aetiopathogenesis of inflammatory bowel disease

Crohn's disease and ulcerative colitis, collectively known as IBD, are chronic inflammatory disorders of the gastrointestinal tract. Although the aetiopathogenesis of IBD is largely unknown, it is widely thought that diet has a crucial role in the development and progression of IBD. Indeed, epidemiological and genetic association studies have identified a number of promising dietary and genetic risk factors for IBD. These preliminary studies have led to major interest in investigating the complex interaction between diet, host genetics, the gut microbiota and immune function in the pathogenesis of IBD. In this Review, we discuss the recent epidemiological, gene-environment interaction, microbiome and animal studies that have explored the relationship between diet and the risk of IBD. In addition, we highlight the limitations of these prior studies, in part by explaining their contradictory findings, and review future directions.

Differences in dietary habits between patients with inflammatory bowel disease in clinical remission and a healthy population

BACKGROUND

Although patients with active inflammatory bowel disease (IBD) change their dietary habits according to suggestions from their healthcare team, no restriction is required in the remission phase. Accordingly, we compared eating patterns in IBD patients with drug-induced clinical remission with those in healthy subjects.

METHODS

A total of 150 IBD patients, 84 with Crohn's disease (CD) and 66 with ulcerative colitis (UC), in clinical remission, receiving immunomodulator/biologic therapy, and 100 healthy volunteers (controls) were enrolled. The IBD diagnosis had previously been established by a combined assessment of symptoms, endoscopy, histology and abdominal imaging. Clinical remission was defined as a Harvey Bradshaw index <5 for CD and a partial Mayo score <2 for UC. An experienced nutritionist guided the compilation of a food diary for 7 days according to current guidelines. Macronutrient and fiber intake was evaluated using dedicated software. Comparison between continuous variables was performed using Student's t-test or analysis of variance plus Bonferroni post-hoc analysis. Categorical variables were tested with the χ2 test.

RESULTS

No difference in protein and carbohydrate intake was observed. IBD patients ate more calories (1970.7±348.4 vs. 1882.1±280.2 kcal/day, P=0.03), more lipids (68.9±15.2 vs. 59.4±19.0 g/day, P<0.001) and less fibers (11.9±4.7 vs. 15.5±8.3 g/day, P<0.001) than controls. No significant difference in total calories, proteins, lipids, carbohydrates or fibers was seen between CD and UC patients.

CONCLUSION

IBD patients have a different macronutrient and fiber intake compared to healthy subjects, even when clinical remission and no symptoms do not dictate dietary restrictions. Therefore, psychological issues may be involved.

Prediagnostic Serum Vitamin D Levels and the Risk of Crohn's Disease and Ulcerative Colitis in European Populations: A Nested Case-Control Study

Background

A low vitamin D status has been put forward as a potential risk factor for the development of inflammatory bowel disease (IBD). This study investigated the association between prediagnostic circulating vitamin D concentrations and dietary intakes of vitamin D, and the risk of Crohn's disease (CD) and ulcerative colitis (UC).

Methods

Among 359,728 participants of the European Prospective Investigation into Cancer and Nutrition cohort, individuals who developed CD or UC after enrollment were identified. Each case was matched with2 controls by center, gender, age, date of recruitment, and follow-up time. At cohort entry, blood samples were collected and dietary vitamin D intakes were obtained from validated food frequency questionnaires. Serum 25-hydroxyvitamin D levels were measured using liquid chromatography-tandem mass spectrometry. Conditional logistic regression was performed to determine the odds of CD and UC.

Results

Seventy-two participants developed CD and 169 participants developed UC after a median follow-up of 4.7 and 4.1 years, respectively. Compared with the lowest quartile, no associations with the 3 higher quartiles of vitamin D concentrations were observed for CD (p trend = 0.34) or UC (p trend = 0.66). Similarly, no associations were detected when serum vitamin D levels were analyzed as a continuous variable. Dietary vitamin D intakes were not associated with CD (p trend = 0.39) or UC (p trend = 0.83).

Conclusions

Vitamin D status was not associated with the development of CD or UC. This does not suggest a major role for vitamin D deficiency in the etiology of IBD, although larger studies are needed to confirm these findings.

Impact of red and processed meat and fibre intake on treatment outcomes among patients with chronic inflammatory diseases: protocol for a prospective cohort study of prognostic factors and personalised medicine

INTRODUCTION

Chronic inflammatory diseases (CIDs) are frequently treated with biological medications, specifically tumour necrosis factor inhibitors (TNFi)). These medications inhibit the pro-inflammatory molecule TNF alpha, which has been strongly implicated in the aetiology of these diseases. Up to one-third of patients do not, however, respond to biologics, and lifestyle factors are assumed to affect treatment outcomes. Little is known about the effects of dietary lifestyle as a prognostic factor that may enable personalised medicine. The primary outcome of this multidisciplinary collaborative study will be to identify dietary lifestyle factors that support optimal treatment outcomes.

METHODS AND ANALYSIS

This prospective cohort study will enrol 320 patients with CID who are prescribed a TNFi between June 2017 and March 2019. Included among the patients with CID will be patients with inflammatory bowel disease (Crohn's disease and ulcerative colitis), rheumatic disorders (rheumatoid arthritis, axial spondyloarthritis, psoriatic arthritis), inflammatory skin diseases (psoriasis, hidradenitis suppurativa) and non-infectious uveitis. At baseline (pretreatment), patient characteristics will be assessed using patient-reported outcome measures, clinical assessments of disease activity, quality of life and lifestyle, in addition to registry data on comorbidity and concomitant medication(s). In accordance with current Danish standards, follow-up will be conducted 14-16 weeks after treatment initiation. For each disease, evaluation of successful treatment response will be based on established primary and secondary endpoints, including disease-specific core outcome sets. The major outcome of the analyses will be to detect variability in treatment effectiveness between patients with different lifestyle characteristics.

ETHICS AND DISSEMINATION

The principle goal of this project is to improve the quality of life of patients suffering from CID by providing evidence to support dietary and other lifestyle recommendations that may improve clinical outcomes. The study is approved by the Ethics Committee (S-20160124) and the Danish Data Protecting Agency (2008-58-035). Study findings will be disseminated through peer-reviewed journals, patient associations and presentations at international conferences.

TRIAL REGISTRATION NUMBER

NCT03173144; Pre-results.

Environmental triggers in IBD: a review of progress and evidence

A number of environmental factors have been associated with the development of IBD. Alteration of the gut microbiota, or dysbiosis, is closely linked to initiation or progression of IBD, but whether dysbiosis is a primary or secondary event is unclear. Nevertheless, early-life events such as birth, breastfeeding and exposure to antibiotics, as well as later childhood events, are considered potential risk factors for IBD. Air pollution, a consequence of the progressive contamination of the environment by countless compounds, is another factor associated with IBD, as particulate matter or other components can alter the host's mucosal defences and trigger immune responses. Hypoxia associated with high altitude is also a factor under investigation as a potential new trigger of IBD flares. A key issue is how to translate environmental factors into mechanisms of IBD, and systems biology is increasingly recognized as a strategic tool to unravel the molecular alterations leading to IBD. Environmental factors add a substantial level of complexity to the understanding of IBD pathogenesis but also promote the fundamental notion that complex diseases such as IBD require complex therapies that go well beyond the current single-agent treatment approach. This Review describes the current conceptualization, evidence, progress and direction surrounding the association of environmental factors with IBD.

Dietary practices and inflammatory bowel disease

The etiology of inflammatory bowel disease (IBD) remains elusive but it is believed to result from incompletely understood interactions between environmental triggers in a potentially genetically susceptible host and a subsequent aberrant immune response. Its incidence is increasing worldwide at an unprecedented rate, outpacing what genetic influences alone could instigate. The increasingly integral role played by eating in social life has led patients to gravitate to diet and food in their consultations with physicians and other health care professionals, in an attempt to improve, control, or even "cure" IBD through diet. Diet is a modifiable factor, and both patients and healthcare professionals have fuelled resurgent interest in the role of diet in maintaining IBD remission. Despite significant and increasing interest, there is a lack of credible evidence to support dietary modification or restrictions to prevent relapse of IBD. However, recent studies have shown that more than half of the patients believe that diet plays an important role in triggering relapse, leading to self-imposed dietary restrictions, some of which can have adverse consequences. This underpins the need for physicians and health care professionals to have a better understanding of dietary practices, in triggering, perpetuating, and improving IBD. This review examines and discusses the evidence behind this.

Research Gaps in Diet and Nutrition in Inflammatory Bowel Disease. A Topical Review by D-ECCO Working Group [Dietitians of ECCO]

Although the current doctrine of IBD pathogenesis proposes an interaction between environmental factors and gut microbiota in genetically susceptible individuals, dietary exposures have attracted recent interest and are, at least in part, likely to explain the rapid rise in disease incidence and prevalence. The D-ECCO working group along with other ECCO experts with expertise in nutrition, microbiology, physiology, and medicine reviewed the evidence investigating the role of diet and nutritional therapy in the onset, perpetuation, and management of IBD. A narrative topical review is presented where evidence pertinent to the topic is summarised collectively under three main thematic domains: i] the role of diet as an environmental factor in IBD aetiology; ii] the role of diet as induction and maintenance therapy in IBD; and iii] assessment of nutritional status and supportive nutritional therapy in IBD. A summary of research gaps for each of these thematic domains is proposed, which is anticipated to be agenda-setting for future research in the area of diet and nutrition in IBD.

Diet as a Therapeutic Option for Adult Inflammatory Bowel Disease

There are many mechanisms to explain how food may drive and ameliorate inflammation. Although there are no consistent macronutrient associations inflammatory bowel disease (IBD) development, many exclusion diets have been described: IgG-4 guided exclusion diet; semivegetarian diet; low-fat, fiber-limited exclusion diet; Paleolithic diet; Maker's diet; vegan diet; Life without Bread diet; exclusive enteral nutrition (EEN), the Specific Carbohydrate Diet (SCD) and the low FODMAP diet. The literature on diet and IBD is reviewed with a particular focus on EEN, SCD, and low FODMAP diets. Lessons learned from the existing observations and strengths and shortcomings of existing data are presented.

The Impact of Western Diet and Nutrients on the Microbiota and Immune Response at Mucosal Interfaces

Recent findings point toward diet having a major impact on human health. Diets can either affect the gut microbiota resulting in alterations in the host’s physiological responses or by directly targeting the host response. The microbial community in the mammalian gut is a complex and dynamic system crucial for the development and maturation of both systemic and mucosal immune responses. Therefore, the complex interaction between available nutrients, the microbiota, and the immune system are central regulators in maintaining homeostasis and fighting against invading pathogens at mucosal sites. Westernized diet, defined as high dietary intake of saturated fats and sucrose and low intake of fiber, represent a growing health risk contributing to the increased occurrence of metabolic diseases, e.g., diabetes and obesity in countries adapting a westernized lifestyle. Inflammatory bowel diseases (IBD) and asthma are chronic mucosal inflammatory conditions of unknown etiology with increasing prevalence worldwide. These conditions have a multifactorial etiology including genetic factors, environmental factors, and dysregulated immune responses. Their increased prevalence cannot solely be attributed to genetic considerations implying that other factors such as diet can be a major contributor. Recent reports indicate that the gut microbiota and modifications thereof, due to a consumption of a diet high in saturated fats and low in fibers, can trigger factors regulating the development and/or progression of both conditions. While asthma is a disease of the airways, increasing evidence indicates a link between the gut and airways in disease development. Herein, we provide a comprehensive review on the impact of westernized diet and associated nutrients on immune cell responses and the microbiota and how these can influence the pathology of IBD and asthma.

Macronutrient Intake and Risk of Crohn's Disease: Systematic Review and Dose-Response Meta-Analysis of Epidemiological Studies

Dietary intake is potentially associated with the onset of Crohn’s disease (CD), but evidence from epidemiological studies has remained unclear. This study aimed to evaluate the role of macronutrient intake in the development of CD. A systematic search was conducted in PubMed and Web of Science to identify all relevant studies, and the role of macronutrients in the development of CD was quantitatively assessed by dose–response meta-analysis. Four case-control studies (a total of 311 CD cases and 660 controls) and five prospective cohort studies (238,887 participants and 482 cases) were identified. The pooled relative risks (RR) for per 10 g increment/day were 0.991 (95% confidence interval (CI): 0.978–1.004) for total carbohydrate intake, 1.018 (95% CI: 0.969–1.069) for total fat intake, and 1.029 (95% CI: 0.955–1.109) for total protein intake. Fiber intake was inversely associated with CD risk (RR for per 10 g increment/day: 0.853, 95% CI: 0.762–0.955), but the association was influenced by study design and smoking adjustment. In subtypes, sucrose intake was positively related with CD risk (RR for per 10 g increment/day: 1.088, 95% CI: 1.020–1.160). Non-linear dose–response association was also found between fiber and sucrose intake and CD risk. In conclusion, this meta-analysis suggested a lack of association between total carbohydrate, fat or protein intake and the risk of CD, while high fiber intake might decrease the risk. In subtypes, high sucrose intake might increase the risk of CD.