Effects of chili on postprandial gastrointestinal symptoms in diarrhoea predominant irritable bowel syndrome: evidence for capsaicin-sensitive visceral nociception hypersensitivity

Nonallergic Diseases Associated With Foods

Clinicians are faced with evaluating real and alleged reactions to foods that may be allergic or nonallergic. Pathogenesis, diagnosis, and treatment of various non-IgE-mediated diseases are discussed in this review. These food-related conditions range from mild to severe. Referral for an allergy workup may be pursued despite the lack of IgE-mediated symptoms. Diagnostic testing is available for defined non-IgE-mediated food diseases that are either immunologic or nonimmunologic. These include celiac disease and related disorders, carbohydrate maldigestion, pancreatic insufficiency, and histamine intolerance. In contrast, there is a paucity of definitive studies to prove food intolerance diseases. There are no definitive diagnostic criteria or testing for nonceliac gluten sensitivity. Functional gastrointestinal disorders, such as irritable bowel syndrome, are better stratified diagnostically but still lack reliable testing. Both nonceliac gluten sensitivity and irritable bowel syndrome are linked to dietary triggers including fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. Therefore, dietary alteration alone may be diagnostic and therapeutic when all other conditions are ruled out. These conditions are important considerations when evaluating a patient with history of a food reaction. There is little evidence that foods are causative in other ailments such as acne, migraines, and nasal congestion and hypersecretion.

Food intolerance related to gastrointestinal symptoms amongst adults living with bile acid diarrhoea: A cross-sectional study

BACKGROUND

The role of food in managing bile acid diarrhoea (BAD) is poorly understood. The present study explored the prevalence of food intolerance amongst adults with BAD.

METHODS

The study comprised a cross-sectional survey of adults with BAD determined by the 75 selenium homotaurocholic acid test (SeHCAT) living in the UK. Participants anonymously completed an online questionnaire on 39 food items. Frequency of food in general affecting BAD symptoms, as well as frequencies of diarrhoea, abdominal pain, bloating, flatulence and consequential food avoidance after food item ingestion, were assessed. Food group avoidance was also assessed.

RESULTS

There were 434 participants who completed the questionnaire between April and May 2021 of whom 80% reported moderate to severe chronic diarrhoea. Food intolerances were reported by 88.0% (95% confidence interval [CI] = 84.6-90.9) of participants. Diarrhoea was reported most frequently after take-away food, fish and chips, creamy sauces, cream and large quantities of fruit (range 41.0%-33.6%). Lowest frequencies were for potato, avocado, mango, watermelon and pear (range 3.7%-7.4%) for the foods listed in the questionnaire. Similar trends were found for abdominal pain, bloating, flatulence and consequential food avoidance. Symptom-triggering within 30 min of ingestion was more prevalence than after 30 min for almost all foods. Food group avoidance was highest for fatty foods (81.2%; 95% CI = 77.8-85.3) followed by dairy (53.9%; 95% CI = 49.1-58.7).

CONCLUSIONS

Perceived food intolerance amongst adults with BAD and persisting diarrhoeal symptoms is high. Important triggers were meals with a higher fat content and higher-fat dairy products. Diets amongst those with persisting diarrhoeal symptoms may be overly restrictive.

Food Intolerances, Food Allergies and IBS: Lights and Shadows

This narrative review delves into the intricate relationship between irritable bowel syndrome (IBS) and food intolerances. IBS, a chronic functional gastrointestinal disorder, is characterized by symptoms like abdominal pain and altered bowel habits. The prevalence of IBS has increased globally, especially among young adults. Food and dietary habits play a crucial role in IBS management. About 85-90% of IBS patients report symptom exacerbation linked to specific food consumption, highlighting the strong connection between food intolerances and IBS. Food intolerances often exhibit a dose-dependent pattern, posing a challenge in identifying trigger foods. This issue is further complicated by the complex nature of gastrointestinal physiology and varying food compositions. This review discusses various dietary patterns and their impact on IBS, including the low-FODMAP diet, gluten-free diet, and Mediterranean diet. It highlights the importance of a personalized approach in dietary management, considering individual symptom variability and dietary history. In conclusion, this review emphasizes the need for accurate diagnosis and holistic management of IBS, considering the complex interplay between dietary factors and gastrointestinal pathophysiology. It underlines the importance of patient education and adherence to treatment plans, acknowledging the challenges posed by the variability in dietary triggers and the psychological impact of dietary restrictions.

Significant Differences in Gut Microbiota Between Irritable Bowel Syndrome with Diarrhea and Healthy Controls in Southwest China

BACKGROUND

Irritable bowel syndrome (IBS) is a heterogeneous disease, which is closely related to environmental factors and gut microbiota.

OBJECTIVE

To study gut microbiota in IBS-D of Han nationality in Southwest China and explore its relationship with environmental factors.

METHODS

One hundred and twenty cases of IBS-D and 63 cases of HCs were recruited; baseline data such as age, height, and weight were collected. HAMA, HAMD, IBS-SSS, IBS-QOL, and laboratory tests were performed. Feces were collected for 16S rDNA sequencing. Then, the differences of gut microbiota were analyzed and looked for biomarkers of each. FAPROTAX was used to predict the functional differences of gut microbiota. Spearman analysis was conducted between the phylum level and environmental factor.

RESULTS

There were significant differences in daily life between IBS-D and HCs, especially in the spicy taste. The scores of HAMA and HAMD, urea, and transaminase in IBS-D were significantly higher than those of HCs. The richness of gut microbiota in IBS-D was significantly lower than that of HCs, as well as the beta diversity, but not diversity. The biomarkers of IBS-D were Prevotella, Clostridiales, and Roseburia, and the biomarkers of HCs were Veillonellaceae, Bacteroides coprocola, and Bifidobacteriales. The functions of gut microbiota in IBS-D were significantly different from HCs. Correlation analysis showed that multiple gut microbiota were closely related to HAMA, IBS-SSS, IBS-QOL, inflammatory indexes, and liver enzymes.

CONCLUSION

There are significant differences in richness of gut microbiota, flora structure, and flora function between IBS-D and HCs in Southwest China. These differences may be closely related to environmental factors such as eating habits, living habits, and mental and psychological factors.

CLINICAL TRIAL REGISTRATION

The trial was registered and approved in China Clinical Trial Registry (Registration No. ChiCTR2100045751).

Capsaicin as an amphipathic modulator of NaV1.5 mechanosensitivity

SCN5A-encoded Na_V1.5 is a voltage-gated Na⁺ channel that drives the electrical excitability of cardiac myocytes and contributes to slow waves of the human gastrointestinal smooth muscle cells. Na_V1.5 is mechanosensitive: mechanical force modulates several facets of Na_V1.5’s voltage-gated function, and some Na_V1.5 channelopathies are associated with abnormal Na_V1.5 mechanosensitivity (MS). A class of membrane-active drugs, known as amphiphiles, therapeutically target Na_V1.5’s voltage-gated function and produce off-target effects including alteration of MS. Amphiphiles may provide a novel option for therapeutic modulation of Na_V1.5’s mechanosensitive operation. To more selectively target Na_V1.5 MS, we searched for a membrane-partitioning amphipathic agent that would inhibit MS with minimal closed-state inhibition of voltage-gated currents. Among the amphiphiles tested, we selected capsaicin for further study. We used two methods to assess the effects of capsaicin on Na_V1.5 MS: (1) membrane suction in cell-attached macroscopic patches and (2) fluid shear stress on whole cells. We tested the effect of capsaicin on Na_V1.5 MS by examining macro-patch and whole-cell Na⁺ current parameters with and without force. Capsaicin abolished the pressure- and shear-mediated peak current increase and acceleration; and the mechanosensitive shifts in the voltage-dependence of activation (shear) and inactivation (pressure and shear). Exploring the recovery from inactivation and use-dependent entry into inactivation, we found divergent stimulus-dependent effects that could potentiate or mitigate the effect of capsaicin, suggesting that mechanical stimuli may differentially modulate Na_V1.5 MS. We conclude that selective modulation of Na_V1.5 MS makes capsaicin a promising candidate for therapeutic interventions targeting MS.

Lactobacillus rhamnosus attenuates Thai chili extracts induced gut inflammation and dysbiosis despite capsaicin bactericidal effect against the probiotics, a possible toxicity of high dose capsaicin

Because of a possible impact of capsaicin in the high concentrations on enterocyte injury (cytotoxicity) and bactericidal activity on probiotics, Lactobacillus rhamnosus L34 (L34) and Lactobacillus rhamnosus GG (LGG), the probiotics derived from Thai and Caucasian population, respectively, were tested in the chili-extract administered C57BL/6 mice and in vitro experiments. In comparison with placebo, 2 weeks administration of the extract from Thai chili in mice caused loose feces and induced intestinal permeability defect as indicated by FITC-dextran assay and the reduction in tight junction molecules (occludin and zona occludens-1) using fluorescent staining and gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, the chili extracts also induced the translocation of gut pathogen molecules; lipopolysaccharide (LPS) and (1→3)-β-d-glucan (BG) and fecal dysbiosis (microbiome analysis), including reduced Firmicutes, increased Bacteroides, and enhanced total Gram-negative bacteria in feces. Both L34 and LGG attenuated gut barrier defect (FITC-dextran, the fluorescent staining and gene expression of tight junction molecules) but not improved fecal consistency. Additionally, high concentrations of capsaicin (0.02-2 mM) damage enterocytes (Caco-2 and HT-29) as indicated by cell viability test, supernatant cytokine (IL-8), transepithelial electrical resistance (TEER) and transepithelial FITC-dextran (4.4 kDa) but were attenuated by Lactobacillus condition media (LCM) from both probiotic-strains. The 24 h incubation with 2 mM capsaicin (but not the lower concentrations) reduced the abundance of LGG (but not L34) implying a higher capsaicin tolerance of L34. However, Lactobacillus rhamnosus fecal abundance, using qRT-PCR, of L34 or LGG after 3, 7, and 20 days of the administration in the Thai healthy volunteers demonstrated the similarity between both strains. In conclusion, high dose chili extracts impaired gut permeability and induced gut dysbiosis but were attenuated by probiotics. Despite a better capsaicin tolerance of L34 compared with LGG in vitro, L34 abundance in feces was not different to LGG in the healthy volunteers. More studies on probiotics with a higher intake of chili in human are interesting.

Intestinal chemosensitivity in irritable bowel syndrome associates with small intestinal TRPV channel expression

BACKGROUND

Irritable bowel syndrome (IBS) patients often experience meal-associated symptoms. However, the underlying mechanisms are unclear.

AIM

To determine small intestinal mechanisms of lipid-induced symptoms and rectal hypersensitivity in IBS METHODS: We recruited 26 IBS patients (12 IBS-C, 14 IBS-D) and 15 healthy volunteers (HV). In vivo permeability was assessed using saccharide excretion assay. Rectal sensitivity was assessed using a barostat before and after small bowel lipid infusion; symptoms were assessed throughout. Next, an extended upper endoscopy with probe-based confocal laser endomicroscopy (pCLE) was performed with changes induced by lipids. Duodenal and jejunal mucosal biopsies were obtained for transcriptomics.

RESULTS

Following lipid infusion, a higher proportion of HV than IBS patients reported no pain, no nausea, no fullness and no urgency (P < 0.05 for all). In a model adjusted for sex and anxiety, IBS-C and IBS-D patients had lower thresholds for first rectal sensation (P = 0.0007) and pain (P = 0.004) than HV. In vivo small intestinal permeability and mean pCLE scores were similar between IBS patients and HV. Post-lipid, pCLE scores were higher than pre-lipid but were not different between groups. Baseline duodenal transient receptor potential vanilloid (TRPV) 1 and 3 expression was increased in IBS-D, and TRPV3 in IBS-C. Duodenal TRPV1 expression correlated with abdominal pain (r = 0.51, FDR = 0.01), and inversely with first rectal sensation (r = -0.48, FDR = 0.01) and pain (r = -0.41, FDR = 0.02) thresholds.

CONCLUSION

Lipid infusion elicits a greater symptom response in IBS patients than HV, which is associated with small intestinal expression of TRPV channels. TRPV-mediated small intestinal chemosensitivity may mediate post-meal symptoms in IBS.

An Update on the Assessment and Management of Pediatric Abdominal Pain

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

Low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols diet compared with traditional dietary advice for diarrhea-predominant irritable bowel syndrome: a parallel-group, randomized controlled trial with analysis of clinical and microbiological factors associated with patient outcomes

BACKGROUND

The efficacy and factors associated with patient outcomes for a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (LFD) compared with traditional dietary advice (TDA) based on modified National Institute for Clinical Excellence guidelines for irritable bowel syndrome with diarrhea (IBS-D) in regions consuming a non-Western diet are unclear.

OBJECTIVES

We aimed to determine the efficacy of an LFD compared with TDA for the treatment of IBS-D in Chinese patients and to investigate the factors associated with favorable outcomes.

METHODS

One hundred and eight Chinese IBS-D patients (Rome III criteria) were randomly assigned to an LFD or TDA. The primary endpoint was a ≥50-point reduction in the IBS Severity Scoring System at 3 wk. Fecal samples collected before and after the dietary intervention were assessed for changes in SCFAs and microbiota profiles. A logistic regression model was used to identify predictors of outcomes.

RESULTS

Among the 100 patients who completed the study, the primary endpoint was met in a similar number of LFD (30 of 51, 59%) and TDA (26 of 49, 53%) patients (∆6%; 95% CI: -13%, 24%). Patients in the LFD group achieved earlier symptomatic improvement in stool frequency and excessive wind than those following TDA. LFD reduced carbohydrate-fermenting bacteria such as Bifidobacterium and Bacteroides, and decreased saccharolytic fermentation activity. This was associated with symptomatic improvement in the responders. High saccharolytic fermentation activity at baseline was associated with a higher symptom burden (P = 0.01) and a favorable therapeutic response to the LFD (log OR: 4.9; 95% CI: -0.1, 9.9; P = 0.05).

CONCLUSIONS

An LFD and TDA each reduced symptoms in Chinese IBS-D patients; however, the LFD achieved earlier symptomatic improvements in stool frequency and excessive wind. The therapeutic effect of the LFD was associated with changes in the fecal microbiota and the fecal fermentation index. At baseline, the presence of severe symptoms and microbial metabolic dysbiosis characterized by high saccharolytic capability predicted favorable outcomes to LFD intervention.This trial was registered at clinicaltrials.gov as NCT03304041.

Differences in dietary habits of people with vs without irritable bowel syndrome and their association with symptom and psychological status: A pilot study

BACKGROUND

Previous studies have demonstrated that dietary factors are involved in irritable bowel syndrome (IBS), but the role of diet was evaluated mostly based on food frequency questionnaire. Whether food categories, quantity per time, and intake frequency are different between IBS patients and non-IBS individuals has not been clearly clarified.

AIM

To explore differences in dietary habits of people with vs without IBS and their correlation with symptom and psychological status.

METHODS

A total of 220 questionnaires were administered in a community population and the Rome IV criteria was applied to diagnose IBS. The dietary questionnaire used in this study was multidimensional from food categories, quantity per time, and intake frequency, in contrast to "yes or no" classification used in previous studies. Questionnaires including IBS symptom severity scale (IBS-SSS), IBS quality of life, visceral sensitivity index, hospital anxiety and depression score (HADS), and gastrointestinal symptom rating scale were used to assess the participants. Rank sum test was used to compare the quantity per time and intake frequency between IBS patients and non-IBS participants. The correlation between psychological factors and diet was evaluated by Spearman correlation analysis. Logistic regression analysis was used to assess the possible dietary risk factors for IBS.

RESULTS

In total, 203 valid questionnaires were collected (response rate 92.3%). Twenty-five participants met the Rome IV criteria for IBS, including 15 (60.0%) women and 10 (40.0%) men. Compared with the non-IBS group, the quantity per time and intake frequency of soybean and its products, spicy food, and dry-fried nuts were statistically significant in IBS participants (P < 0.05). They were positively associated with IBS-SSS and HADS anxiety and depression scores (P < 0.05). Besides, seafood, soft drinks, vegetables, and fruits differed only in quantity per time. The intake frequencies of egg, barbecue, and coarse grain were statistically significant in IBS patients (P < 0.05). We also found that the frequency of soybean and its products (≥ 7 times/week, odds ratio = 11.613, 95% confidence interval: 2.145-62.855, P = 0.004) was an independent risk factor for IBS.

CONCLUSION

Both quantity per time and intake frequency, especially soybean, differ between IBS patients and non-IBS participants. Dietary habits might play potential roles in the pathophysiology of IBS.

The role of diet in the pathophysiology and management of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic gastrointestinal (GI) disorder that reportedly affects 5% to 20% of the world population. The etiology of IBS is not completely understood, but diet appears to play an important role in its pathophysiology. Asian diets differ considerably from those in Western countries, which might explain differences in the prevalence, sex, and clinical presentation seen between patients with IBS in Asian and Western countries. Dietary regimes such as a low-fermentable oligo-, di-, monosaccharides, and polyols (FODMAP) diet and the modified National Institute for Health and Care Excellence (NICE) diet improve both symptoms and the quality of life in a considerable proportion of IBS patients. It has been speculated that diet is a prebiotic for the intestinal microbiota and favors the growth of certain bacteria. These bacteria ferment the dietary components, and the products of fermentation act upon intestinal stem cells to influence their differentiation into enteroendocrine cells. The resulting low density of enteroendocrine cells accompanied by low levels of certain hormones gives rise to intestinal dysmotility, visceral hypersensitivity, and abnormal secretion. This hypothesis is supported by the finding that changing to a low-FODMAP diet restores the density of GI cells to the levels in healthy subjects. These changes in gut endocrine cells caused by low-FODMAP diet are also accompanied by improvements in symptoms and the quality of life.

Diet therapy for irritable bowel syndrome

The review provides present information on the pathogenesis of irritable bowel syndrome (IBS), the relationship of endogenous and exogenous factors with the development of IBS-symptoms, questions of diet therapy are discussed, diets traditionally prescribed in IBS treatment and diets, such as FODMAP and gluten-free diet, which are the most promising and have a positive effect on the symptoms of IBS.

Diet and functional dyspepsia: Clinical correlates and therapeutic perspectives

Hypervigilance and symptoms anticipation, visceral hypersensitivity and gastroduodenal sensorimotor abnormalities account for the varied clinical presentation of functional dyspepsia (FD) patients. Many patients recognize meals as the main triggering factor; thus, dietary manipulations often represent the first-line management strategy in this cohort of patients. Nonetheless, scarce quality evidence has been produced regarding the relationship between specific foods and/or macronutrients and the onset of FD symptoms, resulting in non-standardized nutritional approaches. Most dietary advises are indeed empirical and often lead to exclusion diets, reinforcing in patients the perception of “being intolerant” to food and self-perpetuating some of the very mechanisms underlying dyspepsia physiopathology (i.e., hypervigilance and symptom anticipation). Clinicians are often uncertain regarding the contribution of specific foods to dyspepsia physiopathology and dedicated professionals (i.e., dietitians) are only available in tertiary referral settings. This in turn, can result in nutritionally unbalanced diets and could even encourage restrictive eating behaviors in severe dyspepsia. In this review, we aim at evaluating the relationship between dietary habits, macronutrients and specific foods in determining FD symptoms. We will provide an overview of the evidence-based nutritional approach that should be pursued in these patients, providing clinicians with a valuable tool in standardizing nutritional advises and discouraging patients from engaging into indiscriminate food exclusions.

Fruits

Fruits come in a wide variety of colors, shapes, and flavors. This chapter will cover selected fruits that are known to be healthy and highly nutritious. These fruits were chosen due to their common usage and availability. Since it is not possible to cover all health benefits or essential nutrients and important phytochemicals of the fruit composition, this chapter will focus on the key valuable constituents and their potential health effects.

Desensitization of transient receptor potential vanilloid type-1 (TRPV1) channel as promising therapy of irritable bowel syndrome: characterization of the action of palvanil in the mouse gastrointestinal tract

TRPV1 are involved in the control of the gastrointestinal (GI) functions and pain sensation. Their activation induces pain but it is followed by desensitization, which in turn causes analgesia. The studies from the last two decades indicate that TRPV1 are involved in visceral hypersensitivity in the GI tract and pathogenesis of irritable bowel syndrome (IBS). Therefore, the aim of this study is to assess the action of fast desensitizing agonist of TRPV1, palvanil (N-palmitoyl-vanillamine), in the murine GI tract and on nociception to evaluate its potential application in the therapy of IBS. The effect of palvanil on smooth muscle contractility was evaluated using organ baths. The impact of palvanil on intestinal secretion was assessed in Ussing chambers. In vivo, the action of palvanil (0.1–1 mg/kg) was assessed in whole GI transit, fecal pellet output, and colonic bead expulsion tests. The antinociceptive potency of palvanil was tested in the mustard oil-induced pain test. Palvanil inhibited colonic contractions (evoked by electrical field stimulation, EFS) and decreased the ion transport in the colon stimulated with forskolin. It did not affect secretion in experiments with veratridine. In vivo, palvanil prolonged whole GI transit at all doses tested. At the lower dose tested, it accelerated colonic motility during first 60 min following injection. By contrast, at the dose of 1 mg/kg, colonic motility was inhibited. Palvanil induced antinociceptive action at all tested doses in mustard oil-induced pain test. TRPV1 fast-desensitizing compounds, i.e., palvanil, may be promising agents in the therapy of IBS since it modulates intestinal motility and reduces visceral pain.

Empirically derived dietary patterns and constipation among a middle-aged population from China, 2016-2018

Background

The association of dietary patterns with constipation is not well established, particularly in Chinese population. Therefore, the present study aimed to determine the relationship between dietary patterns and the risk of constipation in a middle-aged Chinese population.

Methods

A total of 2267 participants aged 45–59 years were recruited in Hangzhou city, the capital of Zhejiang Province, east China from August 2016 to October 2018. Dietary intake was estimated using a semi-quantitative food frequency questionnaire (FFQ) containing 138 food items. Constipation was defined using the Rome II criteria. Multivariate logistic regression was used to examine the association between dietary patterns and the risk of constipation.

Results

Three major dietary patterns were extracted by factor analysis and labeled as the traditional southern Chinese, Western and grains-vegetables patterns. The prevalence of constipation in our study population was 13.28%. Compared with the participants in the lowest quartile, the participants in the highest quartile of the traditional southern Chinese pattern were associated with reduced odds of constipation (odd ratios (OR) = 0.79; 95%confidence interval (CI): 0.626–0.981; P < 0.05), after adjusting for confounding variables. In contrast, we found no significant associations between the Western and grains-vegetables patterns and the risk of constipation (P > 0.05).

Conclusions

Our study demonstrated that the traditional southern Chinese pattern was associated with a reduced risk of constipation. Further longitudinal studies are needed to confirm our findings.

The role of diet in irritable bowel syndrome: implications for dietary advice

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder that affects approximately 10% of the population. Diet triggers symptoms in the vast majority of individuals with IBS. In view of this, there has been a focus on the role of diet in IBS. The diets currently being headlined for IBS include (i) traditional dietary advice, (ii) the low fermentable oligo-, di-, mono- saccharides and polyols (FODMAPs) diet and (iii) the gluten-free diet (GFD). Although traditional dietary advice is considered as the first-line dietary therapy, its evidence base is variable, with a few randomized controlled trials (RCTs) exploring the efficacy of this approach, other than for fibre. There are now a growing number of RCTs demonstrating the efficacy of the low FODMAP diet in the short-term, with some emerging data on the long-term 'adapted' low FODMAP diet. There are also several RCTs showing the benefits of a GFD in IBS; however, this concept is hampered with uncertainty as to the mechanism of action. Nevertheless, all of these dietary therapies are viable options for individuals with IBS, with the dietitian and patient engagement at the forefront of achieving success. However, future pragmatic studies are needed to clarify the comparative efficacy and convenience of implementing these various diets into routine life. Moreover, it is imperative to better delineate the concern that restrictive diets - such as the low FODMAP and GFD - may promote nutritional inadequacies, disordered eating behaviours, and lead to detrimental alterations to the gut microbiota.

Diet in Irritable Bowel Syndrome (IBS): Interaction with Gut Microbiota and Gut Hormones

Diet plays an important role not only in the pathophysiology of irritable bowel syndrome (IBS), but also as a tool that improves symptoms and quality of life. The effects of diet seem to be a result of an interaction with the gut bacteria and the gut endocrine cells. The density of gut endocrine cells is low in IBS patients, and it is believed that this abnormality is the direct cause of the symptoms seen in IBS patients. The low density of gut endocrine cells is probably caused by a low number of stem cells and low differentiation progeny toward endocrine cells. A low fermentable oligo-, di-, monosaccharide, and polyol (FODMAP) diet and fecal microbiota transplantation (FMT) restore the gut endocrine cells to the level of healthy subjects. It has been suggested that our diet acts as a prebiotic that favors the growth of a certain types of bacteria. Diet also acts as a substrate for gut bacteria fermentation, which results in several by-products. These by-products might act on the stem cells in such a way that the gut stem cells decrease, and consequently, endocrine cell numbers decrease. Changing to a low-FODMAP diet or changing the gut bacteria through FMT improves IBS symptoms and restores the density of endocrine cells.

Second Asian Consensus on Irritable Bowel Syndrome

BACKGROUND/AIMS

There has been major progress in our understanding of the irritable bowel syndrome (IBS), and novel treatment classes have emerged. The Rome IV guidelines were published in 2016 and together with the growing body of Asian data on IBS, we felt it is timely to update the Asian IBS Consensus.

METHODS

Key opinion leaders from Asian countries were organized into 4 teams to review 4 themes: symptoms and epidemiology, pathophysiology, diagnosis and investigations, and lifestyle modifications and treatments. The consensus development process was carried out by using a modified Delphi method.

RESULTS

Thirty-seven statements were developed. Asian data substantiate the current global viewpoint that IBS is a disorder of gut-brain interaction. Socio-cultural and environmental factors in Asia appear to influence the greater overlap between IBS and upper gastrointestinal symptoms. New classes of treatments comprising low fermentable oligo-, di-, monosacharides, and polyols diet, probiotics, non-absorbable antibiotics, and secretagogues have good evidence base for their efficacy.

CONCLUSIONS

Our consensus is that all patients with functional gastrointestinal disorders should be evaluated comprehensively with a view to holistic management. Physicians should be encouraged to take a positive attitude to the treatment outcomes for IBS patients.

Self-reported Food Intolerance in Korean Patients With Irritable Bowel Syndrome

Background/Aims

Various foods trigger and/or worsen the symptoms of irritable bowel syndrome (IBS). However, Korean food-related gastrointestinal (GI) symptoms in IBS patients have not yet been investigated. This study aims to evaluate the prevalence of self-reported food intolerance in Korean IBS patients and determine the Korean food items and food groups perceived by patients to worsen their GI symptoms.

Methods

We recruited 393 study subjects, comprising 101 IBS patients, 167 symptomatic non-IBS subjects, and 125 control subjects. All participants completed a questionnaire to identify the most problematic foods and assess the occurrence of GI symptoms caused by 119 Korean food items. They also completed the validated Rome III questionnaire for IBS.

Results

The prevalence of self-reported food intolerance in Korean IBS patients was 79.2%, which was significantly higher than that in control subjects (44.8%, P < 0.001). The most problematic foods reported by IBS patients who experienced food intolerance were high-fat foods (25.0%), gluten foods (23.8%), spicy foods (15.0%), and dairy products (15.0%). A total of 63.4% of IBS patients reported GI symptoms related to the consumption of foods high in fermentable oligo-, di-, mono-saccharides, and polyols (FODMAP), while 48.5% of IBS patients reported symptoms associated with high-fat foods. Gas problems and loose stools were the most frequently reported symptoms.

Conclusions

A large proportion of Korean IBS patients complained of intolerance to certain food items, with high-fat and high-FODMAP foods being the main triggers. This study provides a basis for planning food intervention studies for Korean IBS patients.

Descending monoaminergic pathways projecting to the spinal defecation center enhance colorectal motility in rats

The central regulating mechanisms of defecation, especially roles of the spinal defecation center, are still unclear. We have shown that monoamines including norepinephrine, dopamine, and serotonin injected into the spinal defecation center cause propulsive contractions of the colorectum. These monoamines are the main neurotransmitters of descending pain inhibitory pathways. Therefore, we hypothesized that noxious stimuli in the colorectum would activate the descending monoaminergic pathways projecting to the spinal defecation center and that subsequently released endogenous monoamine neurotransmitters would enhance colorectal motility. Colorectal motility was measured in rats anesthetized with α-chloralose and ketamine. As a noxious stimulus, capsaicin was administered into the colorectal lumen. To interrupt neuronal transmission in the spinal defecation center, antagonists of norepinephrine, dopamine, and/or serotonin receptors were injected intrathecally at the L6-S1 spinal level, where the spinal defecation center is located. Intraluminal administration of capsaicin, acting on the transient receptor potential vanilloid 1 channel, caused transient propulsive contractions. The effect of capsaicin was abolished by surgical severing of the pelvic nerves or thoracic spinal transection at the T4 level. Capsaicin-induced contractions were blocked by preinjection of D2-like dopamine receptor and 5-hydroxytryptamine subtype 2 and 3 receptor antagonists into the spinal defecation center. We demonstrated that intraluminally administered capsaicin causes propulsive colorectal motility through reflex pathways involving the spinal and supraspinal defecation centers. Our results provide evidence that descending monoaminergic neurons are activated by noxious stimulation to the colorectum, leading to facilitation of colorectal motility. NEW & NOTEWORTHY The present study demonstrates that noxious stimuli in the colorectum activates the descending monoaminergic pathways projecting to the spinal defecation center and that subsequently released endogenous monoamine neurotransmitters, serotonin and dopamine, enhance colorectal motility. Our findings provide a possible explanation of the concurrent appearance of abdominal pain and bowel disorder in irritable bowel syndrome patients. Thus the present study may provide new insights into understanding of mechanisms of colorectal dysfunction involving the central nervous system.

The Role of Diet in the Treatment of Irritable Bowel Syndrome: A Systematic Review

Irritable bowel syndrome (IBS) is a multifaceted illness involving maladaptive shifts in the gut microbiota that affect the enteric nervous and immune systems, mucosal barrier function, the balance of neurotransmitters and hormones, and emotional well-being. There is abundant evidence indicating that certain foods elicit symptoms in IBS. Numerous elimination-type diets have been shown to alleviate symptoms. However, among these, the most controversial is a group of foods called fructo, oligo-, di-, and monosaccharides and polyols (FODMAPs). This paper reviews the role of diet and systematically analyze the literature for the role of FODMAPs in IBS.

Food Therapy in Sinosphere Asia

Traditional Chinese Food Therapy has long been an integral part of dietary practices in Sinosphere Asia. This therapy is defined by the classification of foods into cooling (Yin) and heaty (Yang) and the manipulation of dietary intake of these foods as a therapeutic strategy for chronic diseases. Both functional dyspepsia (FD) and irritable bowel syndrome (IBS) are chronic, functional gut disorders widely prevalent in Sinosphere Asia. Diet is increasingly recognized as a symptom trigger in FD and IBS, and the evidence suggesting the utility of diet therapies as front-line management is growing, particularly in the West. Specifically, a diet low in Fermentable, Oligosaccharides, Disaccharides, Monosaccharides, and Polyols is an efficacious therapy for patients with IBS. In contrast, a proportion of patients with IBS in Sinosphere Asia utilize Chinese Food Therapy for symptom management. Chinese Food Therapy provides an attractive target for integration with evidence-based Western dietary therapies as a management strategy in FD and IBS. However, significant gaps in research exist with the utility of Chinese Food Therapy that first need to be addressed. This includes a lack of standardization for heaty and cooling classification, limited mechanistic rationale or clinical studies supporting its efficacy in FD and IBS, and the lack of an ideal practitioner for implementation of Chinese Food Therapy. Hence, the review provides a summary of the role of diet and nutrition in Sinosphere Asia with an emphasis on FD and IBS, and an examination of how modern dietary practices may be able to be integrated into practices in this region.

Dietary behaviors in relation to prevalence of irritable bowel syndrome in adolescent girls

BACKGROUNDS AND AIMS

There is limited evidence regarding the relationship between dietary behaviors and irritable bowel syndrome (IBS). This study aimed to explore the association between diet-related practices and prevalence of IBS.

METHODS

The study was conducted among 988 adolescent girls living in Iran. Dietary behaviors were pre-defined and assessed in nine domains using a pre-tested questionnaire. To investigate the association between diet-related practices and the presence of IBS, this study used logistic regression analysis in crude and adjusted models.

RESULTS

The prevalence of IBS was 16.9% in this population. Compared with individuals who did not consume fluid with their meal, those who always consumed fluid with meals had a greater chance of IBS (odds ratio [OR]: 2.91; P: 0.01). This study found a direct relationship between a greater intake of spicy food and IBS prevalence (OR: 5.28; P: 0.02). The individuals who ate fried foods every day also had a greater risk of IBS compared with those who did not consume fried foods (OR: 1.65; P: 0.01). The subjects who had lost ≥ 5 teeth had 2.23 times greater odds for IBS than the individual who had lost ≤ 1 tooth (OR: 2.23; P: 0.01) was a significant inverse relationship between the chewing sufficiency and the risk of IBS (OR: 4.04; P: 0.02). These associations remained significant after controlling for potential confounder.

CONCLUSIONS

Intra-meal fluid intake, chewing insufficiency, higher tooth loss, and the consumption of spicy and fried food were associated with increased risk of IBS. Prospective studies are needed to confirm these findings.

Dietary therapies for functional bowel symptoms: Recent advances, challenges, and future directions

BACKGROUND

Functional gastrointestinal symptoms in irritable bowel syndrome (IBS) and quiescent inflammatory bowel disease (IBD) cause significant morbidity and a reduction in quality of life. Multiple dietary therapies are now available to treat these symptoms, but supporting evidence for many is limited. In addition to a further need for studies demonstrating efficacy and mechanism of action of dietary therapies, the risk of nutritional inadequacy, alterations to the microbiome and changes in quality of life are key concerns requiring elucidation. Identifying predictors of response to dietary therapy is an important goal as management could be tailored to the individual to target specific dietary components, and thereby reduce the level of dietary restriction necessary.

PURPOSE

This review discusses the available dietary therapies to treat symptoms in patients with IBS and patients with quiescent IBD suffering from IBS symptoms, with the aim to understand where current dietary evidence lies and how to move forward in dietary research in this field.

Lack of an Effect of Gastric Capsaicin on the Rectal Component of the Gastrocolonic Response

Luminal capsaicin induces local and distant reflexes in the upper gastrointestinal tract and stimulates lower gastrointestinal symptoms in susceptible persons. We aimed to evaluate the effect of gastric capsaicin on rectal motor function and sensation.

METHODS

Eighteen healthy volunteers participated twice, at least 1 week apart, in this double-blind, placebo-controlled crossover study. Participants swallowed a gastric tube for capsaicin or saline infusion. A barostat tube was placed in the rectum to measure rectal tone before and during gastric capsaicin (40 µg/ml, 2.5 ml/min) or placebo infusion and to conduct distension experiments before and after gastric infusions. Gastric infusions were terminated after 60 min or when epigastric discomfort occurred. Differences in rectal tone, compliance, and sensitivity between gastric placebo and gastric capsaicin were determined.

RESULTS

On both study days, basal rectal volumes, compliance, and sensitivity parameters were comparable (NS) before gastric infusions. Gastric capsaicin infusion induced epigastric discomfort that necessitated termination of infusion after 29.6 ± 12.3 min (saline: 54.7 ± 8.9 min; p < 0.01). Rectal tone, aggregate perception scores, and rectal compliance did not differ between placebo and capsaicin trials (p > 0.05). Rectal tone increased significantly only when capsaicin induced epigastric discomfort (p < 0.05). The reproducibility of the barostat trial was acceptable with significant correlations of volumes, pressures (< 0.05; r ² from 0.41 to 0.55), rectal compliance (p < 0.01; r ² = 0.44), and aggregate perception scores (p values all < 0.05; r ² from 0.44 to 0.0.65) between the two barostat trials.

CONCLUSION

Gastric perfusion with capsaicin does not directly influence rectal physiology through a reflex arc.

Review article: transient receptor potential channels as possible therapeutic targets in irritable bowel syndrome

BACKGROUND

Abdominal pain in irritable bowel syndrome (IBS) remains challenging to treat effectively. Researchers have attempted to elucidate visceral nociceptive processes in order to guide treatment development. Transient receptor potential (TRP) channels have been implied in the generation (TRPV1, TRPV4, TRPA1) and inhibition (TRPM8) of visceral pain signals. Pathological changes in their functioning have been demonstrated in inflammatory conditions, and appear to be present in IBS as well.

AIM

To provide a comprehensive review of the current literature on TRP channels involved in visceral nociception. In particular, we emphasise the clinical implications of these nociceptors in the treatment of IBS.

METHODS

Evidence to support this review was obtained from an electronic database search via PubMed using the search terms "visceral nociception," "visceral hypersensitivity," "irritable bowel syndrome" and "transient receptor potential channels." After screening the abstracts the articles deemed relevant were cross-referenced for additional manuscripts.

RESULTS

Recent studies have resulted in significant advances in our understanding of TRP channel mediated visceral nociception. The diversity of TRP channel sensitization pathways is increasingly recognised. Endogenous TRP agonists, including poly-unsaturated fatty acid metabolites and hydrogen sulphide, have been implied in augmented visceral pain generation in IBS. New potential targets for treatment development have been identified (TRPA1 and TRPV4,) and alternative means of affecting TRP channel signalling (partial antagonists, downstream targeting and RNA-based therapy) are currently being explored.

CONCLUSIONS

The improved understanding of mechanisms involved in visceral nociception provides a solid basis for the development of new treatment strategies for abdominal pain in IBS.

Epidemiological and clinical perspectives on irritable bowel syndrome in India, Bangladesh and Malaysia: A review

Irritable bowel syndrome (IBS) is a chronic gastrointestinal disorder, common in clinic and in the community. It has a significant impact on both society and patients' quality of life. The epidemiology, clinical presentation, and management of IBS may vary in different geographical regions due to differences in diet, gastrointestinal infection, socio-cultural and psycho-social factors, religious and illness beliefs, symptom perception and reporting. Although previous reviews and consensus reports on IBS in Asia have been published, Asia is quite diverse socio-demographically. In this context, India, Bangladesh and Malaysia share some similarities, including: (1) large proportion of the population living in rural areas; (2) rapid development and associated lifestyle changes in urban areas; and (3) dietary, cultural and religious practices. The present review explores the clinical and epidemiological data on IBS from these three major nations in South and South-East Asia. In-depth review of the literature revealed important differences between IBS in the East, as revealed by studies from these three countries, and the West; these include a predominantly rural profile, differences in bowel habit and symptom profile, raising concern with regards to diagnostic criteria and subtyping of IBS, higher dietary fiber consumption, frequent lactose malabsorption, parasitosis, and possible overlap between post-infectious IBS and tropical sprue. Moreover, the current perception on difference in prevalence of the disorder in these countries, as compared to the West, might be related to variation in survey methods.

Diet in irritable bowel syndrome: What to recommend, not what to forbid to patients!

A substantial proportion of patients with irritable bowel syndrome (IBS) associate their symptoms with the ingestion of specific foods. Therefore, in recent years, scientific research has increasingly focused on the role of diet in IBS and dietary management is now considered an important tool in IBS treatment. This article reviews the main dietary approaches in IBS emphasizing evidence from experimental and observational studies and summarizing the main diet and lifestyle recommendations provided by dietary guidelines and scientific literature. Despite the limited evidence for a beneficial role, general advice on healthy eating and lifestyle is recommended as the first-line approach in the dietary management of IBS. Standard recommendations include adhering to a regular meal pattern, reducing intake of insoluble fibers, alcohol, caffeine, spicy foods, and fat, as well as performing regular physical activity and ensuring a good hydration. Second-line dietary approach should be considered where IBS symptoms persist and recommendations include following a low FODMAP diet, to be delivered only by a healthcare professional with expertise in dietary management. The efficacy of this diet is supported by a growing body of evidence. In contrast, the role of lactose or gluten dietary restriction in the treatment of IBS remains subject to ongoing research with a lack of high-quality evidence. Likewise, further clinical trials are needed to conclude the efficacy of probiotics on IBS symptoms.

Transient receptor potential ion channel function in sensory transduction and cellular signaling cascades underlying visceral hypersensitivity

Visceral hypersensitivity is an important mechanism underlying increased abdominal pain perception in functional gastrointestinal disorders including functional dyspepsia, irritable bowel syndrome, and inflammatory bowel disease in remission. Although the exact pathophysiological mechanisms are poorly understood, recent studies described upregulation and altered functions of nociceptors and their signaling pathways in aberrant visceral nociception, in particular the transient receptor potential (TRP) channel family. A variety of TRP channels are present in the gastrointestinal tract (TRPV1, TRPV3, TRPV4, TRPA1, TRPM2, TRPM5, and TRPM8), and modulation of their function by increased activation or sensitization (decreased activation threshold) or altered expression in visceral afferents have been reported in visceral hypersensitivity. TRP channels directly detect or transduce osmotic, mechanical, thermal, and chemosensory stimuli. In addition, pro-inflammatory mediators released in tissue damage or inflammation can activate receptors of the G protein-coupled receptor superfamily leading to TRP channel sensitization and activation, which amplify pain and neurogenic inflammation. In this review, we highlight the present knowledge on the functional roles of neuronal TRP channels in visceral hypersensitivity and discuss the signaling pathways that underlie TRP channel modulation. We propose that a better understanding of TRP channels and their modulators may facilitate the development of more selective and effective therapies to treat visceral hypersensitivity.

How do FODMAPs work?

Many patients report symptoms come on after eating, and experience with exclusion diets suggests that certainly poorly absorbed but rapidly fermentable carbohydrates may be responsible. While monomeric and short chain carbohydrate polymers exert osmotic forces and trap water in the small bowel with acceleration of transit, the longer polymer polymers such as inulin pass through the small bowel unaltered but are fermented in the colon where they may cause distension and symptoms. Recent developments in magnetic resonance imaging confirm the importance of fructose in stimulating small bowel water secretion and its negation by the presence of glucose. Fructans have no impact on the small intestine but cause colonic distension and symptoms including bloating.

Chili Peppers, Curcumins, and Prebiotics in Gastrointestinal Health and Disease

There is growing evidence for the role of several natural products as either useful agents or adjuncts in the management of functional GI disorders (FGIDs). In this review, we examine the medical evidence for three such compounds: chili, a culinary spice; curcumin, another spice and active derivative of a root bark; and prebiotics, which are nondigestible food products. Chili may affect the pathogenesis of abdominal pain especially in functional dyspepsia and cause other symptoms. It may have a therapeutic role in FGIDs through desensitization of transient receptor potential vanilloid-1 receptor. Curcumin, the active ingredient of turmeric rhizome, has been shown in several preclinical studies and uncontrolled clinical trials as having effects on gut inflammation, gut permeability and the brain-gut axis, especially in FGIDs. Prebiotics, the non-digestible food ingredients in dietary fiber, may serve as nutrients and selectively stimulate the growth and/or activity of certain colonic bacteria. The net effect of this change on colonic microbiota may lead to the production of acidic metabolites and other compounds that help to reduce the production of toxins and suppress the growth of harmful or disease-causing enteric pathogens. Although some clinical benefit in IBS has been shown, high dose intake of prebiotics may cause more bloating from bacterial fermentation.

A prospective study on symptom generation according to spicy food intake and TRPV1 genotypes in functional dyspepsia patients

BACKGROUND

Capsaicin is an ingredient of red peppers that binds to transient receptor potential vanilloid subtype 1 (TRPV1), and Koreans eat more capsaicin-rich food than do Japanese. This study aimed to compare symptom generation according to TRPV1 genotypes and the intake of spicy foods.

METHODS

Consecutive functional dyspepsia (FD) patients who were evaluated at Konkuk University Medical Centre (Korea) and Keio University Hospital (Japan) were included. Questionnaires on spicy food intake, patient assessment of gastrointestinal symptoms (PAGI-SYM), patient assessment of quality of life, and hospital anxiety and depression scale were provided. Blood was sampled for the detection of TRPV1 polymorphisms, and upper gastrointestinal endoscopy was performed with biopsies.

KEY RESULTS

Of 121 included subjects, 35 and 28 carried the TRPV1 CC and GG genotypes, respectively, with the prevalence rates not differing between Japan and Korea. The prevalence of FD subtypes did not differ with the spicy food intake, TRPV1 genotypes, or Helicobacter pylori infection. Neither TRPV1 polymorphisms nor H. pylori infections were related to scores on the PAGI-SYM questionnaires, but spicy food intake was positively correlated with the scores for stomach fullness (p = 0.001) and retching (p = 0.001). Using the linear regression analysis, stomach fullness was associated with spicy food intake (p = 0.007), whereas retching was related to younger age (p < 0.001) and female gender (p = 0.014).

CONCLUSIONS & INFERENCES

Upper gastrointestinal symptoms are more common in subjects with a higher consumption of spicy foods, younger age and female gender, regardless of TRPV1 genotypes and the H. pylori infection status. Capsaicin-rich foods may induce stomach fullness.

British Dietetic Association systematic review and evidence-based practice guidelines for the dietary management of irritable bowel syndrome in adults (2016 update)

BACKGROUND

The first British Dietetic Association (BDA) guidelines for the dietary management of irritable bowel syndrome (IBS) in adults were published in 2012. Subsequently, there has been a wealth of new research. The aim of this work was to systematically review the evidence for the role of diet in the management of IBS and to update the guidelines.

METHODS

Twelve questions relating to diet and IBS were defined based on review of the previous guideline questions, current evidence and clinical practice. Chosen topics were on healthy eating and lifestyle (alcohol, caffeine, spicy food, elimination diets, fat and fluid intakes and dietary habits), milk and dairy, dietary fibre, fermentable carbohydrates, gluten, probiotics and elimination diets/food hypersensitivity. Data sources were CINAHL, Cochrane Register of Controlled Trials, Embase, Medline, Scopus and Web of Science up to October 2015. Studies were assessed independently in duplicate using risk of bias tools specific to each included study based on inclusion and exclusion criteria for each question. National Health and Medical Research Council grading evidence levels were used to develop evidence statements and recommendations, in accordance with Practice-based Evidence in Nutrition Global protocol used by the BDA.

RESULTS

Eighty-six studies were critically appraised to generate 46 evidence statements, 15 clinical recommendations and four research recommendations. The IBS dietary algorithm was simplified to first-line (healthy eating, provided by any healthcare professional) and second-line [low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) to be provided by dietitian] dietary advice.

CONCLUSIONS

These guidelines provide updated comprehensive evidence-based details to achieve the successful dietary management of IBS in adults.

Capsaicin and Its Role in Chronic Diseases

A significant number of experimental and clinical studies published in peer-reviewed journals have demonstrated promising pharmacological properties of capsaicin in relieving signs and symptoms of non-communicable diseases (chronic diseases). This chapter provides an overview made from basic and clinical research studies of the potential therapeutic effects of capsaicin, loaded in different application forms, such as solution and cream, on chronic diseases (e.g. arthritis, chronic pain, functional gastrointestinal disorders and cancer). In addition to the anti-inflammatory and analgesic properties of capsaicin largely recognized via, mainly, interaction with the TRPV1, the effects of capsaicin on different cell signalling pathways will be further discussed here. The analgesic, anti-inflammatory or apoptotic effects of capsaicin show promising results in arthritis, neuropathic pain, gastrointestinal disorders or cancer, since evidence demonstrates that the oral or local application of capsaicin reduce inflammation and pain in rheumatoid arthritis, promotes gastric protection against ulcer and induces apoptosis of the tumour cells. Sadly, these results have been paralleled by conflicting studies, which indicate that high concentrations of capsaicin are likely to evoke deleterious effects, thus suggesting that capsaicin activates different pathways at different concentrations in both human and rodent tissues. Thus, to establish effective capsaicin doses for chronic conditions, which can be benefited from capsaicin therapeutic effects, is a real challenge that must be pursued.

The Science, Evidence, and Practice of Dietary Interventions in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a highly prevalent disorder that is characterized by symptoms of abdominal pain, bloating, constipation, and/or diarrhea. The diagnosis can be made using Rome III criteria or published guidelines after taking a thoughtful history, excluding warning signs, and performing a careful physical examination. Limited testing (ie, complete blood count and C-reactive protein level) may be useful in appropriate patients. A number of pharmacologic options are available, although many patients fail to respond to pharmacologic therapy. Although several IBS diets frequently are recommended, data supporting their use are limited. This article provides a rationale as to why specific diets might improve IBS symptoms and evaluates published trials.

Systematic review: instruments to assess abdominal pain in irritable bowel syndrome

BACKGROUND

Consensus on standard methods to assess chronic abdominal pain in patients with irritable bowel syndrome (IBS) is currently lacking.

AIM

To systematically review the literature with respect to instruments of measurement of chronic abdominal pain in IBS patients.

METHODS

Systematic literature search was performed in PubMed/Medline databases for studies using pain measurement instruments in patients with IBS.

RESULTS

One hundred and ten publications were reviewed. A multitude of different instruments is currently used to assess chronic abdominal pain in IBS patients. The single-item methods, e.g. the validated 10-point numeric rating scale (NRS), and questionnaires assessing gastrointestinal symptoms severity, focus mostly on the assessment of only the intensity of abdominal pain. Of these questionnaires, the validated IBS-Symptom Severity Scale includes the broadest measurement of pain-related aspects. General pain questionnaires and electronic momentary symptom assessment tools have been used to study abdominal pain in IBS patients, but have not yet been validated for this purpose. The evidence for the use of provocation tests, e.g. the rectal barostat with balloon distention, for measurement of abdominal pain in IBS is weak, due to the poor correlation between visceral pain thresholds assessed by provocation tests and abdominal pain as assessed by retrospective questionnaires.

CONCLUSIONS

The multitude of different instruments to measure chronic abdominal pain in IBS makes it difficult to compare endpoints of published studies. There is need for validated instruments to assess chronic abdominal pain in IBS patients, that overcome the limitations of the currently available methods.

Differential Contribution of TRPA1, TRPV4 and TRPM8 to Colonic Nociception in Mice

Background

Various transient receptor potential (TRP) channels in sensory neurons contribute to the transduction of mechanical stimuli in the colon. Recently, even the cold-sensing menthol receptor TRPM(melastatin)8 was suggested to be involved in murine colonic mechano-nociception.

Methods

To analyze the roles of TRPM8, TRPA1 and TRPV4 in distension-induced colonic nociception and pain, TRP-deficient mice and selective pharmacological blockers in wild-type mice (WT) were used. Visceromotor responses (VMR) to colorectal distension (CRD) in vivo were recorded and distension/pressure-induced CGRP release from the isolated murine colon ex vivo was measured by EIA.

Results

Distension-induced colonic CGRP release was markedly reduced in TRPA1^-/- and TRPV4^-/- mice at 90/150 mmHg compared to WT. In TRPM8-deficient mice the reduction was only distinct at 150 mmHg. Exposure to selective pharmacological antagonists (HC030031, 100 μM; RN1734, 10 μM; AMTB, 10 μM) showed corresponding effects. The unselective TRP blocker ruthenium red (RR, 10 μM) was as efficient in inhibiting distension-induced CGRP release as the unselective antagonists of mechanogated DEG/ENaC (amiloride, 100 μM) and stretch-activated channels (gadolinium, 50 μM). VMR to CRD revealed prominent deficits over the whole pressure range (up to 90 mmHg) in TRPA1^-/- and TRPV4^-/- but not TRPM8^-/- mice; the drug effects of the TRP antagonists were again highly consistent with the results from mice lacking the respective TRP receptor gene.

Conclusions

TRPA1 and TRPV4 mediate colonic distension pain and CGRP release and appear to govern a wide and congruent dynamic range of distensions. The role of TRPM8 seems to be confined to signaling extreme noxious distension, at least in the healthy colon.

Effects of Chili Treatment on Gastrointestinal and Rectal Sensation in Diarrhea-predominant Irritable Bowel Syndrome: A Randomized, Double-blinded, Crossover Study

Background/Aims

Whether, chronic chili ingestion can desensitize transient receptor potential vanilloid type 1 receptors in gastrointestinal (GI) tract leading to decrease GI symptoms and sensation in diarrhea-predominant irritable bowel syndrome (IBS-D) patients has not been well explored. The aim of this study was to determine the effects of 6-week chili treatment on postprandial GI symptoms and rectal sensation in response to balloon distention in IBS-D patients.

Methods

Sixteen IBS-D patients received placebo or chili capsules before meals 3 times/day for 6 weeks in a randomized, double-blinded, crossover fashion with 4-week washout period. Postprandial GI symptoms were evaluated. All patients underwent a rectal barostat study to evaluate rectal sensory threshold at the end of each treatment.

Results

The maximum postprandial abdominal burning scores were similar between both treatments at baseline (1.4 [0.0–2.0] vs. 1.1 [0.0–2.8], P > 0.05) but were significantly decreased after chili (0.0 [0.0–0.5] vs. 0.3 [0.0–1.6], P < 0.05) at the end of treatment. The chili treatment significantly increased sensory threshold for the first rectal sensation (median [interquartile range]:16 [12–16] mmHg vs. 8 [8–16] mmHg, P < 0.05) however, there was no significant effect on rectal compliance (7.3 ± 1.0 vs. 7.1 ± 1.8 mL/mmHg). Other postprandial GI symptoms did not vary significantly between both treatments at baseline and the end of treatment.

Conclusions

In IBS-D patients, 6-week chili ingestion significantly decreased postprandial abdominal burning and increased the rectal sensory threshold. These findings suggest a desensitization effect of chili ingestion on transient receptor potential vanilloid type 1 receptors in the proximal gut and rectum.