Inhibitory actions of a high fibre diet on intestinal gas transit in healthy volunteers

Bacterial, short-chain fatty acid and gas profiles of partially hydrolyzed guar gum in vitro fermentation by human fecal microbiota

Carbohydrates with different structures have metabolic differences in the human body, as well as individual differences. The present study aimed to investigate the effects of bacterial, short-chain fatty acids (SCFAs) and gas profiles of partially hydrolyzed guar gum (PHGG) on the fecal microbiota of 41 Chinese individuals by simulated fermentation in vitro. Results showed that PHGG stimulated the growth of Bifidobacterium and Faecalibacterium, inhibited the growth of Escherichia-Shigella, Klebsiella, and Dorea, and induced the production of fermentation gases (CO2, and H2) and SCFAs (acetic acid, butyric acid). Furthermore, Bifidobacterium was significantly increased in the young female and the old male-originated samples, while Klebsiella was significantly decreased in the old female ones after PHGG intervention, and there were also certain differences in gases and SCFAs among different population samples. These findings indicate that PHGG can modulate gut microbiota and metabolism well, whereas its use varies in different populations.

Effects of Four Different Dietary Fibre Supplements on Weight Loss and Lipid and Glucose Serum Profiles during Energy Restriction in Patients with Traits of Metabolic Syndrome: A Comparative, Randomized, Placebo-Controlled Study

Obesity and its associated complications require various lifestyle changes and treatment options. Dietary supplements are considered an attractive alternative to traditional therapy, mainly because they are accessible to the general population. The aim of this study was to investigate the additive effects of a combination of energy restriction (ER) and four dietary supplements on changes in the anthropometric and biochemical parameters in 100 overweight or obese participants who were randomly assigned one of the dietary fibre supplements containing different dietary fibres or a placebo for 8 weeks. The results confirmed that fibre supplements plus ER significantly (p < 0.01) reduced the body weight, body mass index (BMI), fat mass, and visceral fat and ameliorated the lipid profile and inflammation at 4 and 8 weeks after the start of the study, while in the placebo group, significant differences in some parameters were observed only after 8 weeks of ER. A fibre supplement containing glucomannan, inulin, psyllium, and apple fibre was the most effective at reducing the BMI, body weight, and CRP (p = 0.018 for BMI and body weight and p = 0.034 for CRP compared to placebo at the end of the intervention). Overall, the results suggest that dietary fibre supplements in combination with ER may have additional effects on weight loss and the metabolic profile. Therefore, taking dietary fibre supplements may be a feasible approach to improve weight and metabolic health in obese and overweight individuals.

Microbial inulinase promotes fructan hydrolysis under simulated gastric conditions

Fermentable oligo-, di-, monosaccharides and polyols (FODMAPs) have emerged as key contributors to digestive discomfort and intolerance to certain vegetables, fruits, and plant-based foods. Although strategies exist to minimize FODMAP consumption and exposure, exogenous enzyme supplementation targeting the fructan-type FODMAPs has been underexploited. The objective of this study was to test the hydrolytic efficacy of a food-grade, non-genetically engineered microbial inulinase preparation toward inulin-type fructans in the INFOGEST in vitro static simulation of gastrointestinal (GI) digestion. Purified inulin was shown to undergo acid-mediated hydrolysis at high gastric acidity as well as predominantly inulinase-mediated hydrolysis at lower gastric acidity. Inulinase dose-response simulations of inulin, garlic, and high-fructan meal digestion in the gastric phase suggest that as little as 50 inulinase units (INU) and up to 800 INU per serving promote fructan hydrolysis better than the control simulations without inulinase. Liquid chromatography-mass spectrometry (LC-MS) profiling of fructo-oligosaccharides (FOS) in the gastric digestas following inulinase treatment confirms the fructolytic activity of inulinase under simulated digestive conditions. Altogether, these in vitro digestion data support the use of microbial inulinase as an exogenous enzyme supplement for reducing dietary fructan-type FODMAP exposure.

The Polyunsaturated Fatty Acids Eicosapentaenoic Acid and Docosahexaenoic Acid, and Vitamin K1 Modulate the Gut Microbiome: A Study Using an In Vitro Shime Model

Omega-3 polyunsaturated fatty acids (PUFAs) and vitamins exert multiple beneficial effects on host health, some of which may be mediated through the gut microbiome. We investigated the prebiotic potential of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and lipid-soluble phylloquinone (vitamin K1), each at 0.2x, 1x and 5x using the simulator of the human intestinal microbial ecosystem (SHIME®) to exclude in vivo systemic effects and host-microbe interactions.Microbial community composition and, diversity [shotgun metagenomic sequencing] and microbial activity [pH, gas pressure, and production of short-chain fatty acids (SCFAs)] were measured over a period of 48 h. Fermentations supernatants were used to investigate the effect on gut barrier integrity using a Caco-2/goblet cell co-culture model.We found that EPA, DHA and vitamin K1 increased alpha-diversity at 24 h when compared with control. Moreover, there was an effect on beta-diversity with changes in gut microbial composition, such as an increase in the Firmicutes/Bacteroidetes (F/B) ratio and a consistent increase in Veillonella and Dialister abundances with all treatments. DHA, EPA, and vitamin K1 also modulated metabolic activity of the gut microbiome by increasing total SCFAs which was related mainly to an increase in propionate (highest with EPA and vitamin K1 at 0.2x). Finally, we found that EPA and DHA increased gut barrier integrity with DHA at 1x and EPA at 5x (p < 0.05, respectively). In conclusion, our in vitro data further establish a role of PUFAs and vitamin K to modulate the gut microbiome with effects on the production of SCFAs and barrier integrity.

The Role of Dietary Fibers in the Management of IBD Symptoms

Inflammatory bowel diseases (IBDs) are chronic, progressive, immune-mediated diseases of the intestinal tract. The main subtypes of IBDs are Chron's disease (CD) and ulcerative colitis (UC). The etiology is still unclear, but there are genetic, environmental and host-related factors that contribute to the development of these diseases. Recent literature has shown that dietary therapy is the cornerstone of IBD treatment in terms of management of symptoms, relapse and care of the pathology. IBD patients show that microbiota dysbiosis and diet, especially dietary fiber, can modulate its composition. These patients are more at risk of energy protein malnutrition than the general population and are deficient in micronutrients. So far, no dietary component is considered responsible for IBD and there is not a specific therapeutic diet for it. The aim of this review is to evaluate the role of dietary fibers in CD and UC and help health professionals in the nutritional management of these pathologies. Further studies are necessary to determine the appropriate amount and type of fiber to suggest in the case of IBD to ameliorate psychosocial conditions and patients' quality of life.

Short-Term Effect of Additional Daily Dietary Fibre Intake on Appetite, Satiety, Gastrointestinal Comfort, Acceptability, and Feasibility

Background: There is evidence that high-fibre diets have significant health benefits, although the effect of increasing fibre on individuals’ appetite, satiety, and gastrointestinal comfort is not well established, nor is its acceptability and feasibility. Methods: This mixed-methods feasibility randomised control trial included 38 participants allocated to one of three conditions: FibreMAX (two daily servings of 25 g of BARLEYmax^®), FibreGRAD (two daily servings with the amount of fibre gradually increased), and Control (two daily servings totalling 25 g of placebo product). Participants completed a food diary at baseline. The Hunger and Fullness Questionnaire and questions regarding gastrointestinal response were completed at baseline and at the end of each week. Participants completed the acceptability of intervention measure and engaged in a semi-structured interview, following trial completion. Results: The qualitative data suggested that increased fibre influenced appetite and fullness perceptions. Baseline fibre consumption and the method of increased fibre increase did not influence our findings. The qualitative results also indicated that the fibre intake was perceived as beneficial to well-being; it influenced feelings of hunger and caused some minor acute gastrointestinal symptoms that dissipated after a short adaption period. Conclusion: This study suggests that increasing fibre intake through BARLEYmax^® is a safe intervention that is acceptable to participants.

Associations of the Paleolithic Diet Pattern Scores and the Risk of Breast Cancer among Adults: A Case-Control Study

Evidence suggests the role of changing traditional lifestyle patterns such as Paleolithic to modern lifestyle in the incidence and epidemic of chronic diseases. Thus, this study aimed to investigate the association between Paleolithic diet (PD) and risk of Breast Cancer (BC) in adult Iranian women. This matched case-control study included 253 women with BC and 267 healthy women aged >18 years. PD score was evaluated using a validated 168-item quantitative food frequency questionnaire. Conditional logistic regression model was used to estimate odds ratios (ORs) and 95% confidence intervals (95%CIs), and dose-response was investigated. Mean of PD score was 39.00 ± 6.39. Among the food groups of the PD components, BC patients significantly had lower consumption of healthy food groups as vegetables, fruits, fish, and nuts, higher intakes of sugar-sweetened beverages as well as grains and starches. After adjustment for potential confounders, comparing the highest quartile of PD scores with the lowest quartile, a decrease in the risk of BC was observed for all women (OR: 0.26; 95% CI: 0.13-0.53), as well as those premenopausal (OR: 0.29; 95% CI: 0.11), and postmenopausal (OR: 0.17; 95% CI: 0.05 - 0.56). Our findings show that adherence to the PD pattern significantly reduces the risk of BC in the population studied. However, prospective studies are needed to further investigate this association.

Validation of a novel quality of life questionnaire: the Digestion-associated Quality of Life Questionnaire (DQLQ)

Background

Few health-related quality of life (QOL) questionnaires are designed specifically for healthy populations and are specific to gastrointestinal (GI) symptoms even though healthy individuals may frequently experience gas, bloating, constipation, diarrhea, and abdominal pain. The purpose of this study was to develop and validate a tool that could assess the impact of GI symptoms on digestion-associated QOL in otherwise healthy individuals.

Methods

After a review of current literature and with input from experienced GI researchers, a 24-item questionnaire was created. The questionnaire was reduced to 9 items with input from focus groups comprised of healthy adults experiencing GI-related symptoms and through variability analysis. The Digestion-associated QOL Questionnaire (DQLQ) was designed to be sensitive to the physical and mental well-being changes that may occur due to GI symptoms. The DQLQ was assessed for internal consistency reliability (Cronbach’s alpha; McDonald’s omega), test–retest reliability (intraclass correlation coefficient, ICC), and construct validity (Pearson correlations) in a study with healthy, academically stressed, undergraduate students. Convergent validity was evaluated by correlating the DQLQ with gastrointestinal symptom rating scale (GSRS) scores. Divergent validity was assessed by correlating DQLQ scores with stress scores, and bowel satisfaction scores.

Results

A total of 594 students (age 18–30 years) completed the DQLQ. Internal consistency reliability was favorable (n = 594; α = 0.84, ω = 0.84). A high level of agreement and correlation between DQLQ scores was found with the test–retest reliability analysis (n = 273; ICC = 0.89). The questionnaire was shown to have good convergent validity through correlation with the GSRS (n = 594; r = 0.54). Divergent validity was also shown to be appropriate by correlating DQLQ scores with stress (n = 592; r = 0.13, p < 0.005), and bowel satisfaction (n = 592; r = 0.18, p < 0.001) scores.

Conclusion

The DQLQ is a reliable and valid questionnaire for assessing digestion-associated QOL in healthy individuals.

Re-examining chemically defined liquid diets through the lens of the microbiome

Trends in nutritional science are rapidly shifting as information regarding the value of eating unprocessed foods and its salutary effect on the human microbiome emerge. Unravelling the evolution and ecology by which humans have harboured a microbiome that participates in every facet of health and disease is daunting. Most strikingly, the host habitat has sought out naturally occurring foodstuff that can fulfil its own metabolic needs and also the needs of its microbiota, each of which remain inexorably connected to one another. With the introduction of modern medicine and complexities of critical care, came the assumption that the best way to feed a critically ill patient is by delivering fibre-free chemically defined sterile liquid foods (that is, total enteral nutrition). In this Perspective, we uncover the potential flaws in this assumption and discuss how emerging technology in microbiome sciences might inform the best method of feeding malnourished and critically ill patients.

Impact of Plant-Based Meat Alternatives on the Gut Microbiota of Consumers: A Real-World Study

Eating less meat is increasingly seen as a healthier, more ethical option. This is leading to growing numbers of flexitarian consumers looking for plant-based meat alternatives (PBMAs) to replace at least some of the animal meat they consume. Popular PBMA products amongst flexitarians, including plant-based mince, burgers, sausages and meatballs, are often perceived as low-quality, ultra-processed foods. However, we argue that the mere industrial processing of ingredients of plant origin does not make a PBMA product ultra-processed by default. To test our hypothesis, we conducted a randomised controlled trial to assess the changes to the gut microbiota of a group of 20 participants who replaced several meat-containing meals per week with meals cooked with PBMA products and compared these changes to those experienced by a size-matched control. Stool samples were subjected to 16S rRNA sequencing. The resulting raw data was analysed in a compositionality-aware manner, using a range of innovative bioinformatic methods. Noteworthy changes included an increase in butyrate metabolising potential-chiefly in the 4-aminobutyrate/succinate and glutarate pathways-and in the joint abundance of butyrate-producing taxa in the intervention group compared to control. We also observed a decrease in the Tenericutes phylum in the intervention group and an increase in the control group. Based on our findings, we concluded that the occasional replacement of animal meat with PBMA products seen in flexitarian dietary patterns can promote positive changes in the gut microbiome of consumers.

Dietary Fiber Is Essential to Maintain Intestinal Size, L-Cell Secretion, and Intestinal Integrity in Mice

Dietary fiber has been linked to improved gut health, yet the mechanisms behind this association remain poorly understood. One proposed mechanism is through its influence on the secretion of gut hormones, including glucagon-like peptide-1 (GLP-1) and glucagon-like peptide-2 (GLP-2). We aimed to: 1) investigate the impact of a fiber deficient diet on the intestinal morphological homeostasis; 2) evaluate L-cell secretion; and 3) to ascertain the role of GLP-1, GLP-2 and Takeda G protein-receptor-5 (TGR5) signaling in the response using GLP-1 receptor, GLP-2 receptor and TGR5 knockout mice. Female C57BL/6JRj mice (n = 8) either received a standard chow diet or were switched to a crude fiber-deficient diet for a short (21 days) and long (112 days) study period. Subsequent identical experiments were performed in GLP-1 receptor, GLP-2 receptor and TGR5 knockout mice. The removal of fiber from the diet for 21 days resulted in a decrease in small intestinal weight (p < 0.01) and a corresponding decrease in intestinal crypt depth in the duodenum, jejunum and ileum (p < 0.001, p < 0.05, and p < 0.01, respectively). Additionally, colon weight was decreased (p < 0.01). These changes were associated with a decrease in extractable GLP-1, GLP-2 and PYY in the colon (p < 0.05, p < 0.01, and p < 0.01). However, we could not show that the fiber-dependent size decrease was dependent on GLP-1 receptor, GLP-2 receptor or TGR5 signaling. Intestinal permeability was increased following the removal of fiber for 112 days. In conclusion, our study highlights the importance of dietary fiber to maintain intestinal weight, colonic L-cell secretion and intestinal integrity.

Constipation and the Quality of Life in Conservatively Treated Chronic Kidney Disease Patients: A Cross-sectional Study

Background: Constipation is a common gastrointestinal disorder that in general population is associated with worse health-related quality of life (HRQoL). The epidemiology of constipation has not been reliably determined in conservatively-treated CKD patients. We aimed to determine the prevalence of constipation and constipation-related symptoms in conservatively-treated CKD patients, to find factors associated with their altered prevalence ratio (PR), and to verify the associations between constipation and HRQoL. Methods: In this cross-sectional study, 111 conservatively-treated CKD outpatients fulfilled questionnaires that included questions addressing HRQoL (SF-36v2®), constipation-related symptoms (The Patient Assessment of Constipation-Symptoms questionnaire), the Bristol stool form scale (BSFS), Rome III criteria of functional constipation (FC), and frequency of bowel movement (BM). Results: Depending on the used definition, the prevalence of constipation was 6.6-28.9%. Diuretics and paracetamol were independently associated with increased PR of BSFS-diagnosed constipation (PR 2.86, 95% CI 1.28-6.37, P = 0.01) and FC (PR 2.67, 95% CI 1.07-6.64, P = 0.035), respectively. The most commonly reported symptoms were bloating (50.9%) and straining to pass a BM (42.7%). Abdominal discomfort (37.3%) was independently associated with worse scores in all analyzed HRQoL domains. In multiple regressions, FC and having <7 BM/week, but not BSFS-diagnosed constipation, were associated with lower scores in several HRQoL domains. Conclusions: Constipation and related symptoms are prevalent in CKD patients. FC and decreased frequency of defecation, but not BSFS-diagnosed constipation, are associated with worse assessment of HRQoL in conservatively-treated CKD patients.

The effect of green kiwifruit on gas transit and tolerance in healthy humans

BACKGROUND

Green kiwifruit is a fiber-rich fruit that has been shown effective for treatment of constipation. However, fermentation of fibers by colonic bacteria may worsen commonly associated gas-related abdominal symptoms.

AIM

To determine the effect of green kiwifruit on transit and tolerance to intestinal gas in humans.

METHODS

In 11 healthy individuals, two gas challenge tests were performed (a) after 2 weeks on a low-flatulogenic diet and daily intake of 2 green kiwifruits and (b) after 2 weeks on a similar diet without intake of kiwifruits. The gas challenge test consisted in continuous infusion of a mixture of gases into the jejunum at 12 mL/min for 2 hours while measuring rectal gas evacuation, abdominal symptoms, and abdominal distension. During the 2 weeks prior to each gas challenge test (on-kiwifruit and off-kiwifruit), the number and consistency of stools, and abdominal symptoms were registered.

KEY RESULTS

Intake of kiwifruits was associated with more bowel movements per day (1.8 ± 0.1 vs 1.5 ± 0.1 off-kiwifruit; P = .001) and somewhat looser stools (Bristol score 3.3 ± 0.2 vs 2.8 ± 0.1 off-kiwifruit; P = .072) without relevant abdominal symptoms. Gas infusion produced similar gas evacuation (1238 ± 254 mL and 1172 ± 290 mL; P = .4355), perception of symptoms (score 1.2 ± 0.2 and 1.3 ± 0.3; P = .2367), and abdominal distension (17 ± 7 mm and 17 ± 6 mm; P = .4704) while on-kiwifruit or off-kiwifruit.

CONCLUSIONS AND INFERENCES

In healthy subjects, green kiwifruit increases stool frequency without relevant effects on intestinal gas transit and tolerance. If confirmed in patients, these fruits may provide a natural and well-tolerated treatment alternative for constipation.

Effects of High-Fiber Diets and Macronutrient Substitution on Bloating: Findings From the OmniHeart Trial

OBJECTIVES:

To examine the effects of high-fiber, isocaloric, macronutrient substitutions on bloating.

METHODS:

The OmniHeart study is a randomized 3-period crossover feeding trial conducted from April 2003 to June 2005. Participants were provided 3 isocaloric versions of high-fiber (∼30 g per 2,100 kcal) diet, each different in carbohydrate, protein, and unsaturated fat composition. Each feeding period lasted for 6 weeks with a 2- to 4-week washout period between diets. Participants reported the presence and severity of bloating at baseline (participants were eating their own diet) and at the end of each feeding period.

RESULTS:

One hundred sixty-four participants were included in the analysis (mean age: 53.1 years; 45% women; 55% black). The prevalence of bloating at baseline and at the end of the carbohydrate-rich, protein-rich, and unsaturated fat-rich diet period was 18%, 24%, 33%, and 30%, respectively. Compared with baseline, the relative risk of bloating for the carbohydrate-rich, protein-rich, and unsaturated fat-rich high-fiber diet was 1.34 (95% confidence interval [CI]: 0.93, 1.92), 1.78 (95% CI: 1.32, 2.40), and 1.63 (95% CI: 1.17, 2.26), respectively. The protein-rich diet increased the risk of bloating more than the carbohydrate-rich diet (relative risk = 1.40; 95% CI: 1.03, 1.88). Bloating did not significantly vary between protein-rich vs unsaturated fat-rich or unsaturated fat-rich vs carbohydrate-rich diets. Black participants compared with non-black participants had a higher risk of bloating after all 3 versions of the high-fiber OmniHeart diet (P-value for interaction = 0.012).

DISCUSSION:

Substitution of protein with carbohydrate may be an effective strategy to decrease bloating among individuals experiencing gastrointestinal bloating from a high-fiber diet.

Effects of the DASH Diet and Sodium Intake on Bloating: Results From the DASH-Sodium Trial

INTRODUCTION

Bloating is one of the most common gastrointestinal complaints. Evidence has linked fiber and sodium to bloating; however, randomized trials examining these diet components are lacking. Here, we used a randomized trial to examine the effects of the high-fiber DASH diet and dietary sodium intake on abdominal bloating. We hypothesized that both the high-fiber DASH diet and higher sodium intake would increase bloating.

METHODS

The DASH-Sodium trial (1998-1999) randomized healthy adults to a high-fiber (32 g/d) DASH or low-fiber (11 g/d) Western diet (control). On their assigned diet, participants ate 3 sodium levels (50, 100, and 150 mmol/d at 2100 kcal) in 30-day periods in random order, with 5-day breaks between each period. The participants reported the presence of bloating at baseline and after each feeding period. Statistical analyses included log-binomial models to evaluate the risk of bloating.

RESULTS

Of 412 participants (mean age 48 years; 57% women; 57% black), 36.7% reported bloating at baseline. Regardless of the diet, high sodium intake increased the risk of bloating (risk ratio = 1.27; 95% confidence interval: 1.06-1.52; P = 0.01). The high-fiber DASH diet also increased the risk of bloating over all sodium levels (risk ratio = 1.41; 95% confidence interval: 1.22-1.64; P < 0.001). The effect of high-fiber DASH on bloating was greater in men than in women (P for interaction = 0.001).

DISCUSSION

Higher dietary sodium increased bloating, as did the high-fiber DASH diet. Although healthful high-fiber diets may increase bloating, these effects may be partially mitigated by decreasing dietary sodium intake. Future research is needed to explore mechanisms by which sodium intake and diet can influence bloating.

Clinical and symptom scores are significantly correlated with fecal microbiota features in patients with symptomatic uncomplicated diverticular disease: a pilot study

BACKGROUND

There is growing consensus that symptomatic uncomplicated diverticular disease is a chronic inflammatory condition, and that alterations in the fecal microbiota may contribute to its pathogenesis.

OBJECTIVE

The aim of this study was to relate the fecal microbiota composition in symptomatic uncomplicated diverticular disease to measures of inflammation, symptoms, and history of previous acute diverticulitis.

PARTICIPANTS AND METHODS

Fecal microbiota composition in 28 individuals with symptomatic uncomplicated diverticular disease was characterized by 16S RNA gene amplicon sequencing. Microbiota composition was related to clinical history, symptom and inflammation measures, and demographic variables.

RESULTS

Previous acute diverticulitis was associated with higher relative abundance of Pseudobutyrivibrio, Bifidobacterium, Christensenellaceae family, and Mollicutes RF9 order (P=0.004, 0.006, 0.010, and 0.019, respectively), but not microbiota alpha or beta diversity. A higher bloating severity score was significantly correlated with a higher relative abundance of Ruminococcus (P=0.032), and significantly inversely correlated with the relative abundance of the Roseburia (P=0.002). Fecal calprotectin levels were positively correlated with alpha diversity (Shannon index, P=0.005) and the relative abundance of Lactobacillus (P=0.004). Pain score was positively correlated with the relative abundance of Cyanobacterium (adjusted P=0.032).

CONCLUSION

Patient symptoms in symptomatic diverticular disease are significantly correlated with features of the fecal microbiota. Our findings suggest the potential utility of therapies that target intestinal microbiology, such as dietary prebiotic supplements.

Dietary fiber in irritable bowel syndrome (Review)

Irritable bowel syndrome (IBS) is a common chronic gastrointestinal disorder. It is widely believed that IBS is caused by a deficient intake of dietary fiber, and most physicians recommend that patients with IBS increase their intake of dietary fiber in order to relieve their symptoms. However, different types of dietary fiber exhibit marked differences in physical and chemical properties, and the associated health benefits are specific for each fiber type. Short-chain soluble and highly fermentable dietary fiber, such as oligosaccharides results in rapid gas production that can cause abdominal pain/discomfort, abdominal bloating/distension and flatulence in patients with IBS. By contrast, long-chain, intermediate viscous, soluble and moderately fermentable dietary fiber, such as psyllium results in a low gas production and the absence of the symptoms related to excessive gas production. The effects of type of fiber have been documented in the management of IBS, and it is known to improve the overall symptoms in patients with IBS. Dietary fiber acts on the gastrointestinal tract through several mechanisms, including increased fecal mass with mechanical stimulation/irritation of the colonic mucosa with increasing secretion and peristalsis, and the actions of fermentation byproducts, particularly short-chain fatty acids, on the intestinal microbiota, immune system and the neuroendocrine system of the gastrointestinal tract. Fiber supplementation, particularly psyllium, is both safe and effective in improving IBS symptoms globally. Dietary fiber also has other health benefits, such as lowering blood cholesterol levels, improving glycemic control and body weight management.

A Systematic Review and Meta-analysis of the Effect of Gastric Bypass Surgery on Plasma Lipid Levels

BACKGROUND

Obesity-related dyslipidaemia comprises hypercholesterolaemia, hypertriglyceridaemia, low HDL-cholesterol and normal to raised LDL-cholesterol levels. 40% of morbidly obese surgical patients have dyslipidaemia. Roux-en-Y gastric bypass (RYGB) surgery has many beneficial metabolic effects, but the full impact on plasma lipids has not been clearly defined.

METHODS

A systematic review of electronic databases (Ovid; Medline; PubMed; Embase) between 1960 and March 2012 was performed using search terms including the following: obesity surgery, bariatric surgery, gastric bypass, cholesterol, lipids, triglycerides and non-esterified fatty acids. A total of 2442 manuscripts were screened. Papers with paired plasma lipid levels around RYGB surgery were included. Exclusions included the following: editorials, dual publications, n < 10, resulting in 75 papers of relevance. A meta-analysis was performed of the effect of RYGB surgery upon plasma lipids at different time points up to 4 years following surgery, using a random effects model.

RESULTS

Paired data were available for 7815 subjects around RYGB surgery for morbid obesity with a baseline BMI 48 kg/m(2) (n = 2331). There was a reduction in plasma total cholesterol and LDL-C from 1 month up to 4 years post-RYGB (p < 0.00001, p < 0.00001). Following RYGB, HDL-C increased from 1 year onwards (p < 0.00001), and triglyceride levels were reduced postoperatively from 3 months up to 4 years (p < 0.00001). NEFA levels were increased at 1 month postoperatively (p = 0.003), but from 3 months onwards did not differ from preoperative levels (p = 0.07).

CONCLUSIONS

RYGB surgery reverses the dyslipidaemia of obesity. These findings support the use of RYGB in the management of high cardiovascular risk lipid profiles in morbid obesity.

The use of probiotics versus psyllium husk as a bowel preparation for prostate radiotherapy: a retrospective analysis

Introduction

The use of bowel preparation strategies to reduce the degree of rectal distension during prostate radiotherapy is well documented. This retrospective pilot study analysed and compared a probiotic agent against a psyllium-supplemented diet to establish the feasibility of probiotics as a bowel preparation for patients receiving radical radiotherapy for prostate cancer.

Method

A retrospective chart review of five patients taking probiotics and five taking psyllium husk (psyllium) during their course of radiotherapy treatment was conducted. On treatment, cone beam computed tomography (CBCT) scans were compared with planning CTs to quantify inter-fractional variation in rectal volume and distension.

Results

Forty-five CBCT scans were available in both the psyllium and probiotics groups for analysis. Variation in mean difference in rectal volume from planning (ΔRV), mean rectal cross-section area (CSA) and mean relative cross-section area (CSArel) was significantly increased for the probiotics group compared with the psyllium group (p=0·001, 0·008 and 0·007, respectively). No statistically significant differences in mean ΔRV, CSA and CSArel were detected between the two groups.

Conclusion

This retrospective analysis suggests that a probiotics-based bowel preparation that utilises Lactobacillus acidophilus and Bifidobacterium lactis may result in increased rectal volume and CSA variation throughout treatment in comparison with a psyllium-supplemented diet.

The effect of bariatric surgery on intestinal absorption and transit time

BACKGROUND

Bariatric surgical procedures are classified by their presumed mechanisms of action: restrictive, malabsorptive or a combination of both. However, this dogma is questionable and remains unproven. We investigated post-operative changes in nutrient absorption and transit time following bariatric surgery.

METHODS

Participants were recruited into four groups: obese controls (body mass index (BMI) >30 kg/m2, n = 7), adjustable gastric banding (n = 6), Roux-en-Y gastric bypass (RYGB, n = 7) and biliopancreatic diversion with duodenal switch (DS, n = 5). Participants underwent sulphasalazine/sulphapyridine tests (oro-caecal transit time); fasting plasma citrulline (functional enterocyte mass); 3 days faecal collection for faecal elastase 1 (FE-1); calprotectin (FCp); faecal fatty acids (pancreatic exocrine function, gut inflammation and fat excretion, respectively); and 5 h D-xylose, L-rhamnose and lactulose test (intestinal absorption and permeability).

RESULTS

Age and gender were not different but BMI differed between groups (p = 0.001). No difference in oro-caecal transit time (p = 0.935) or functional enterocyte mass (p = 0.819) was detected. FCp was elevated post-RYGB vs. obese (p = 0.016) and FE-1 was reduced post-RYGB vs. obese (p = 0.002). Faecal fat concentrations were increased post-DS vs. obese (p = 0.038) and RYGB (p = 0.024) and were also higher post-RYGB vs. obese (p = 0.033). Urinary excretion of D-xylose and L-rhamnose was not different between the groups; however, lactulose/rhamnose ratio was elevated post-DS vs. other groups (all p < 0.02), suggesting increased intestinal permeability.

CONCLUSIONS

Following RYGB, there are surprisingly few abnormalities or indications of severe malabsorption of fats or sugars. Small bowel adaptation after bariatric surgery may be key to understanding the mechanisms responsible for the beneficial metabolic effects of these operations.

Colorectal carcinogenesis-update and perspectives

Colorectal cancer (CRC) is a very common malignancy in the Western World and despite advances in surgery, chemotherapy and screening, it is still the second leading cause of cancer deaths in this part of the world. Numerous factors are found important in the development of CRC including colonocyte metbolism, high risk luminal environment, inflammation, as well as lifestyle factors such as diet, tobacco, and alchohol consumption. In recent years focus has turned towards the genetics and molecular biology of CRC and several interesting and promising correlations and pathways have been discovered. The major genetic pathways of CRC are the Chromosome Instability Pathway representing the pathway of sporadic CRC through the K-ras, APC, and P53 mutations, and the Microsatellite Instability Pathway representing the pathway of hereditary non-polyposis colon cancer through mutations in mismatch repair genes. To identify early cancers, screening programs have been initiated, and the leading strategy has been the use of faecal occult blood testing followed by colonoscopy in positive cases. Regarding the treatment of colorectal cancer, significant advances have been made in the recent decade. The molecular targets of CRC include at least two important cell surface receptors: the epidermal growth factor receptor and the vascular endothelial growth factor receptor. The genetic and molecular knowledge of CRC has widen the scientific and clinical perspectives of diagnosing and treatment. However, despite significant advances in the understanding and treatment of CRC, results from targeted therapy are still not convincing. Future studies will determine the role for this new treatment modality.

Review article: Linaclotide for the management of irritable bowel syndrome with constipation

BACKGROUND

Irritable bowel syndrome with constipation (IBS-C) represents a significant burden to patients and healthcare systems due to its prevalence and lack of successful symptomatic resolution with established treatment options. Linaclotide 290 μg has recently been approved by the European Medicines Agency (EMA) for moderate-to-severe IBS-C and by the US Food and Drug Administration for IBS-C (290 μg dose) and for chronic constipation (145 μg dose).

AIM

To summarise data leading to the approval of linaclotide for IBS-C, with focus on EMA-pre-specified outcome measures.

METHODS

Literature search of a peer-review database (PubMed) and review of congress abstracts on linaclotide preclinical and clinical trial data in IBS-C.

RESULTS

Preclinical studies suggest that the guanylate cyclase C agonist (GCCA) linaclotide acts through elevation of cyclic guanosine monophosphate (cGMP) levels, leading to accelerated gastrointestinal (GI) transit through increased fluid secretion and reduced visceral hypersensitivity. Clinical trial data demonstrate that linaclotide improves abdominal symptoms (pain, bloating) and bowel symptoms (constipation) compared with placebo in patients with IBS-C. The most frequent side effect, diarrhoea, results from the therapeutic action of linaclotide. Linaclotide acts locally in the GI tract with minimal systemic exposure, resulting in low oral bioavailability and thus a low risk of relevant systemic adverse effects.

CONCLUSION

Linaclotide, a first-in-class GCCA, is a promising new drug with a novel, dual mechanism of action that, unlike more well-established agents, can relieve the abdominal pain, bloating and constipation associated with IBS-C and has a low propensity for systemic side effects.

A common cause of irritable bowel syndrome and diverticulitis: chronic distal colon distention from sedentary behavior and excessive dietary fiber

A multidisciplinary analysis restricted to validated reports was applied to the cause and management of irritable bowel syndrome and diverticular formation and subsequent diverticulitis. There is evidence that they are linked - both caused by attenuation of gravitational aid to distal intestinal motility, resulting in damaging chronic intestinal distention. Both irritable bowel syndrome and diverticular formation and subsequent diverticulitis have worsened in recent years owing to excessive dietary fiber intake. Potential solutions include augmenting weight-bearing time, moderating dietary fiber consumption, stimulating distal colon evacuation through chemical means and developing pharmaceuticals to block the reflexive distal colon distention associated with fiber consumption. Amplified intestinal distention commenced when all classes of Renaissance Europeans became the first group in human history to wear shoes, which led to a sedentary lifestyle that moderates gravitational aid to colon motility and evacuation.

Management of irritable bowel syndrome with constipation: a flexible approach to treating a complex condition with multiple symptoms

Irritable bowel syndrome is a heterogeneous disease with a complex underlying pathophysiology and multiple symptoms - that is, clinical manifestation patterns. As such, management of irritable bowel syndrome requires a flexible approach tailored to the individual patient. This article reviews rational, evidence-based management strategy and treatment options for this variable condition.

Fiber and functional gastrointestinal disorders

Despite years of advising patients to alter their dietary and supplementary fiber intake, the evidence surrounding the use of fiber for functional bowel disease is limited. This paper outlines the organization of fiber types and highlights the importance of assessing the fermentation characteristics of each fiber type when choosing a suitable strategy for patients. Fiber undergoes partial or total fermentation in the distal small bowel and colon leading to the production of short-chain fatty acids and gas, thereby affecting gastrointestinal function and sensation. When fiber is recommended for functional bowel disease, use of a soluble supplement such as ispaghula/psyllium is best supported by the available evidence. Even when used judiciously, fiber can exacerbate abdominal distension, flatulence, constipation, and diarrhea.

An investigation of fecal volatile organic metabolites in irritable bowel syndrome

Diagnosing irritable bowel syndrome (IBS) can be a challenge; many clinicians resort to invasive investigations in order to rule out other diseases and reassure their patients. Volatile organic metabolites (VOMs) are emitted from feces; understanding changes in the patterns of these VOMs could aid our understanding of the etiology of the disease and the development of biomarkers, which can assist in the diagnosis of IBS. We report the first comprehensive study of the fecal VOMs patterns in patients with diarrhea-predominant IBS (IBS-D), active Crohn's disease (CD), ulcerative colitis (UC) and healthy controls. 30 patients with IBS-D, 62 with CD, 48 with UC and 109 healthy controls were studied. Diagnosis of IBS-D was made using the Manning criteria and all patients with CD and UC met endoscopic, histologic and/or radiologic criteria. Fecal VOMs were extracted by solid phase microextraction (SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS). 240 VOMs were identified. Univariate analysis showed that esters of short chain fatty acids, cyclohexanecarboxylic acid and its ester derivatives were associated with IBS-D (p<0.05), while aldehydes were more abundant in IBD (p<0.05). A predictive model, developed by multivariate analysis, separated IBS-D from active CD, UC and healthy controls with a sensitivity of 94%, 96% and 90%; and a specificity of 82%, 80% and 80% respectively (p<0.05). The understanding of the derivation of these VOMs may cast light on the etiology of IBS-D and IBD. These data show that fecal VOMs analyses could contribute to the diagnosis of IBS-D, for which there is no laboratory test, as well as IBD.

Stopping or reducing dietary fiber intake reduces constipation and its associated symptoms

AIM: To investigate the effect of reducing dietary fiber on patients with idiopathic constipation.

METHODS: Sixty-three cases of idiopathic constipation presenting between May 2008 and May 2010 were enrolled into the study after colonoscopy excluded an organic cause of the constipation. Patients with previous colon surgery or a medical cause of their constipation were excluded. All patients were given an explanation on the role of fiber in the gastrointestinal tract. They were then asked to go on a no fiber diet for 2 wk. Thereafter, they were asked to reduce the amount of dietary fiber intake to a level that they found acceptable. Dietary fiber intake, symptoms of constipation, difficulty in evacuation of stools, anal bleeding, abdominal bloating or abdominal pain were recorded at 1 and 6 mo.

RESULTS: The median age of the patients (16 male, 47 female) was 47 years (range, 20-80 years). At 6 mo, 41 patients remained on a no fiber diet, 16 on a reduced fiber diet, and 6 resumed their high fiber diet for religious or personal reasons. Patients who stopped or reduced dietary fiber had significant improvement in their symptoms while those who continued on a high fiber diet had no change. Of those who stopped fiber completely, the bowel frequency increased from one motion in 3.75 d (± 1.59 d) to one motion in 1.0 d (± 0.0 d) (P < 0.001); those with reduced fiber intake had increased bowel frequency from a mean of one motion per 4.19 d (± 2.09 d) to one motion per 1.9 d (± 1.21 d) on a reduced fiber diet (P < 0.001); those who remained on a high fiber diet continued to have a mean of one motion per 6.83 d (± 1.03 d) before and after consultation. For no fiber, reduced fiber and high fiber groups, respectively, symptoms of bloating were present in 0%, 31.3% and 100% (P < 0.001) and straining to pass stools occurred in 0%, 43.8% and 100% (P < 0.001).

CONCLUSION: Idiopathic constipation and its associated symptoms can be effectively reduced by stopping or even lowering the intake of dietary fiber.

Are rice and spicy diet good for functional gastrointestinal disorders?

Rice- and chili-containing foods are common in Asia. Studies suggest that rice is completely absorbed in the small bowel, produces little intestinal gas and has a low allergenicity. Several clinical studies have demonstrated that rice-based meals are well tolerated and may improve gastrointestinal symptoms in functional gastrointestinal disorders (FGID). Chili is a spicy ingredient commonly use throughout Asia. The active component of chili is capsaicin. Capsaicin can mediate a painful, burning sensation in the human gut via the transient receptor potential vanilloid-1 (TRPV1). Recently, the TRPV1 expressing sensory fibers have been reported to increase in the gastrointestinal tract of patients with FGID and visceral hypersensitivity. Acute exposure to capsaicin or chili can aggravate abdominal pain and burning in dyspepsia and IBS patients. Whereas, chronic ingestion of natural capsaicin agonist or chili has been shown to decrease dyspeptic and gastroesophageal reflux disease (GERD) symptoms. The high prevalence of spicy food in Asia may modify gastrointestinal burning symptoms in patients with FGID. Studies in Asia demonstrated a low prevalence of heartburn symptoms in GERD patients in several Asian countries. In conclusion rice is well tolerated and should be advocated as the carbohydrate source of choice for patients with FGID. Although, acute chili ingestion can aggravate abdominal pain and burning symptoms in FGID, chronic ingestion of chili was found to improve functional dyspepsia and GERD symptoms in small randomized, controlled studies.

Aerophagia: excessive air swallowing demonstrated by esophageal impedance monitoring

BACKGROUND & AIMS

Patients with aerophagia suffer from the presence of an excessive volume of intestinal gas, which is thought to result from excessive air ingestion. However, this has not been shown thus far. The aim of this study was therefore to assess swallowing and air swallowing frequencies in patients with suspected aerophagia.

METHODS

Ambulatory 24-hour pH-impedance monitoring was performed in patients in whom excessive amounts of intestinal gas were visualized on plain abdominal radiograms. All patients had symptoms of bloating, abdominal distention, flatulence, or excessive belching. Reflux parameters and the number of swallows and air swallows were assessed.

RESULTS

The most common symptoms were bloating, abdominal distention, and constipation. Only 3 patients reported excessive belching and 1 patient reported flatulence as their predominant symptom. During the 24-hour measurement, patients showed high incidences of air swallows (521 +/- 63) and gastric belches (126 +/- 37). Patients had normal swallowing frequency (741 +/- 71).

CONCLUSIONS

This study presents objective parameters that confirm the existence of excessive air swallowing or aerophagia using esophageal impedance monitoring.

[Abdominal bloating: an up-to-date]

Bloating is a common symptom, especially in women. In the clinical practice, it remains a therapeutic challenge. Since recently, its pathophysiology is better understood: an impaired transit of gas (particularly in the small bowel) or a visceral hypersensitivity leading to the induction of an abdominal discomfort despite a normal volume of gas are two of the main causes, far more frequent than an excessive production of gas. Moreover, bloating can be related to abnormal viscera-somatic reflexes promoting both an abdomino-phrenic dyssynergia and the relaxation of the muscles of the abdominal wall. From a therapeutic point of view, the efficacy of the gas absorbants remains to be more documented. Besides the treatment of a constipation and the avoidance of nutrients either highly fermentable or rich in fructose, other therapeutic options include prokinetics and drugs acting on visceral sensitivity. Probiotics are another promising option. In some centers, a non pharmacological therapeutic approach, mainly based on hypnosis, is discussed.

Beneficial health properties of psyllium and approaches to improve its functionalities

Psyllium is an excellent dietary source for both soluble and insoluble fibers and has been used in supplemental and food products for its beneficial health effects. The strong water-absorbing and gelling capacities have made it a great challenge to incorporate psyllium in foods at the level needed to claim health benefits on the label. This review is focused on the approaches to improve the functionality, sensory property, and bioactivity of psyllium. Also included is a brief summary of the health beneficial effects of psyllium, along with its possible adverse effects. The information may be useful for those in psyllium research and functional food development.

Irritable bowel syndrome and bloating

Gaseous symptoms in irritable bowel syndrome (IBS) including eructation, flatulence, and bloating occur as a consequence of excess gas production, altered gas transit, abnormal perception of normal amounts of gas within the gastrointestinal tract, or dysfunctional somatic muscle activity in the abdominal wall. Because of the prominence of gaseous complaints in IBS, recent investigations have focussed on new insights into pathogenesis and novel therapies of bloating. The evaluation of the IBS patient with unexplained gas and bloating relies on careful exclusion of organic disease with further characterisation of the underlying condition with directed functional testing. Treatment of gaseous symptomatology in IBS should be targeted to pathophysiologic defects whenever possible. Available therapies include lifestyle alterations, dietary modifications, enzyme preparations, adsorbents and agents which reduce surface tension, treatments that alter gut flora, and drugs that modulate gut transit.

Gas and Bloating

Gaseous symptoms including eructation, flatulence, and bloating occur as a consequence of excess gas production, altered gas transit, or abnormal perception of normal amounts of gas within the gastrointestinal tract. There are many causes of gas and bloating including aerophagia, luminal obstructive processes, carbohydrate intolerance syndromes, small intestinal bacterial overgrowth, diseases of gut motor activity, and functional bowel disorders including irritable bowel syndrome (IBS). Because of the prominence of gaseous complaints in IBS, recent investigations have focused on new insights into pathogenesis and novel therapies of bloating. The evaluation of the patient with unexplained gas and bloating relies on careful exclusion of organic disease with further characterization of the underlying condition with directed functional testing. Treatment of gaseous symptomatology should be targeted to pathophysiologic defects whenever possible. Available therapies include lifestyle alterations, dietary modifications, enzyme preparations, adsorbents and agents which reduce surface tension, treatments that alter gut flora, and drugs that modulate gut transit.

Nutrient modulation of intestinal gas dynamics in healthy humans: dependence on caloric content and meal consistency

The actions of nutrients on gut transit of liquids and solids have been extensively studied, but the effects of meal ingestion on intestinal gas flow are unexplored. We hypothesized that meals of varying caloric content and consistency modulate gas transit to different degrees. Nine healthy volunteers underwent jejunal perfusion of physiological gas mixtures at 12 ml.min(-1).3 h, with ingestion of nothing (control), water (240 ml), 240-kcal liquid meals, and 240-kcal solid meals at the end of the second hour in separate studies. Gas was quantified from an intrarectal catheter. After an initial lag phase, gas evacuation approached steady state by the end of the fasting period. Solid and liquid caloric meals increased total gas volumes evacuated from 5-40 min after ingestion vs. control studies (P < 0.05). These increases resulted from increased numbers of bolus gas evacuations (P < 0.05), whereas bolus volumes, pressures, and flow rates were similar for all test conditions. Solid and liquid caloric meals elicited similar effects on bolus gas dynamic parameters, whereas water did not affect these measures vs. control (NS, not significant). Both caloric meals and the noncaloric liquid meal increased continuous gas flow, which represented <2% of total gas expulsion. In conclusion, caloric meals promote bolus gas transit in healthy humans, whereas noncaloric liquids have no effect. Solids stimulate early postprandial gas dynamics to the same extent as liquid meals of similar caloric content. Thus modulatory effects of meals on intestinal gas transit depend on their caloric content but not their consistency.

Modulation of intestinal gas dynamics in healthy human volunteers by the 5-HT receptor agonist tegaserod

OBJECTIVES

Bloating in irritable bowel syndrome (IBS) may result from impaired intestinal gas transit and is reduced by the 5-HT4 agonist tegaserod. Abnormal serotonergic function underlies many IBS symptoms, but the role of 5-HT4 pathways in regulating gas dynamics under healthy conditions is unexplored. We hypothesized that 5-HT4 activation by tegaserod stimulates gas transit in healthy individuals.

METHODS

Sixteen normal volunteers underwent jejunal perfusion of gas mixtures (88% N2, 5.5% O2, 6.5% CO2) at 11.2 mL/min x 3 h under control conditions and 3 h after oral tegaserod 6 mg on separate days. Gas collected from an intrarectal catheter was quantified using a barostat.

RESULTS

Under control conditions, gas evacuation after a lag period (1,959 +/- 428 s) was predominantly pulsatile with expulsion of 1,984 +/- 90 mL. A mean of 29 +/- 2 boluses with volumes of 72 +/- 5 mL were expelled. In 10 subjects with physiologic degrees of gas retention in control studies (248 +/- 73 mL), tegaserod increased expulsion from 1,768 +/- 73 to 1,973 +/- 37 mL and decreased retention to 43 +/- 37 mL (p < 0.05). Total volumes expelled as boluses were greater after tegaserod (1,708 +/- 73 vs 1,846 +/- 59 mL, p < 0.05) from increased bolus numbers in four subjects and increased bolus volumes in seven. Nonpulsatile continuous flow tended to increase with tegaserod (43 +/- 7 vs 126 +/- 43 mL, p= 0.10). Tegaserod did not increase evacuation in individuals without physiologic gas retention.

CONCLUSIONS

The 5-HT4 agonist tegaserod promotes evacuation of jejunally perfused gas mixtures in healthy humans. These findings provide the foundation for future investigations into use of 5-HT4 agonists in conditions of pathologic gas retention.

The role of fiber in the treatment of irritable bowel syndrome: therapeutic recommendations

Irritable bowel syndrome is a common clinical condition that often presents a therapeutic challenge. There is no standard therapy and a multilevel approach is recommended. A high-fiber diet is often one of these components. Many investigators have studied the effectiveness of either fiber supplementation or bulking agents in patients with irritable bowel syndrome. The purpose of this review is to summarize the current literature on the use of fiber in irritable bowel syndrome and to provide some specific recommendations. Systematic reviews of these trials have generally not found fiber to be significantly more effective than placebo at relieving global irritable bowel syndrome symptoms. There may be differences between results obtained with soluble and insoluble fiber. Adverse effects of fiber use may include abdominal discomfort and bloating. Although dietary fiber or bulking agents do not appear to be useful as sole treatment of irritable bowel syndrome, they may have a limited role in empiric therapy depending upon the patient's symptom complex, especially if constipation is the most significant symptom. The basic principles for using fiber therapy are to start with a low dose and increase slowly, to give an adequate trial and to evaluate the results early and periodically.

Bloating and intestinal gas

The most common symptoms associated with intestinal gas are eructation, flatulence, abdominal bloating, and distention. Aerophagia is an uncommon cause of eructation in which repetitive air swallowing results in belching, abdominal distention, and increased flatus. Few therapies have been shown to be effective in treating these symptoms. Eructation can be treated by decreasing excessive air swallowing. Occasionally, behavioral therapy and psychotherapy are employed. Bloating, distention, and other gas-related symptoms are common in functional gastrointestinal disorders; however, their pathophysiology is poorly understood. Additionally, evidence supporting the use of various available therapies in treating gas-related symptoms is either absent or poor. Dietary therapy may be effective in patients with excessive gas production. Excessive gas production, identified by increased flatus, may benefit from a low-carbohydrate diet. Many patients with gas-related symptoms have normal gas production but may have either impaired gas transport or transit through the gut or visceral hypersensitivity. Few studies have addressed the treatment of impaired gas transport.