Breath Hydrogen Research Articles

Impact of 24-h high and low fermentable oligo-, di-, monosaccharide, and polyol diets on markers of exercise-induced gastrointestinal syndrome in response to exertional heat stress.

The study aimed to determine the effects of 24-h high (HFOD) and low (LFOD) fermentable oligo-, di-, monosaccharide, and polyol (FODMAP) diets before exertional heat stress on gastrointestinal integrity, function, and symptoms. Eighteen endurance runners consumed a HFOD and a LFOD (double-blind crossover design) before completing 2 h of running at 60% maximal oxygen uptake in 35 °C ambient temperature. Blood samples were collected before and after exercise to determine plasma cortisol and intestinal fatty acid binding protein (I-FABP) concentrations, and bacterial endotoxin and cytokine profiles. Breath hydrogen (H2) and gastrointestinal symptoms (GIS) were determined pre-exercise, every 15 min during, and in recovery. No differences were observed for plasma cortisol concentration between diets. Plasma I-FABP concentration was lower on HFOD compared with LFOD (p = 0.033). A trend for lower lipopolysaccharide binding protein (p = 0.088), but not plasma soluble CD14 (p = 0.478) and cytokine profile (p > 0.05), responses on HFOD was observed. A greater area under the curve breath H2 concentration (p = 0.031) was observed throughout HFOD (mean and 95% confidence interval: HFOD 2525 (1452-3597) ppm·4 h-1) compared with LFOD (1505 (1031-1978) ppm·4 h-1). HFOD resulted in greater severity of GIS compared with LFOD (pre-exercise, p = 0.017; during, p = 0.035; and total, p = 0.014). A 24-h HFOD before exertional heat stress ameliorates disturbances to epithelial integrity but exacerbates carbohydrate malabsorption and GIS severity in comparison with a LFOD. Novelty Twenty-four-hour high FODMAP diet ameliorated disturbances to gastrointestinal integrity. Twenty-four-hour high FODMAP diet results in greater carbohydrate malabsorption compared with low FODMAP diet. Incidence of GIS during exertional heat stress were pronounced on both low and high FODMAP diets, but greater GIS severity was observed with high FODMAP diet.

Hydrogel Carbohydrate-Electrolyte Beverage Does Not Improve Glucose Availability, Substrate Oxidation, Gastrointestinal Symptoms or Exercise Performance, Compared With a Concentration and Nutrient-Matched Placebo.

The impact of a carbohydrate-electrolyte solution with sodium alginate and pectin for hydrogel formation (CES-HGel), was compared to a standard CES with otherwise matched ingredients (CES-Std), for blood glucose, substrate oxidation, gastrointestinal symptoms (GIS; nausea, belching, bloating, pain, regurgitation, flatulence, urge to defecate, and diarrhea), and exercise performance. Nine trained male endurance runners completed 3hr of steady-state running (SS) at 60% V˙O2max, consuming 90g/hr of carbohydrate from CES-HGel or CES-Std (53g/hr maltodextrin, 37g/hr fructose, 16% w/v solution) in a randomized crossover design, followed by an incremental time to exhaustion (TTE) test. Blood glucose and substrate oxidation were measured every 30min during SS and oxidation throughout TTE. Breath hydrogen (H2) was measured every 30min during exercise and every 15min for 2 hr postexercise. GIS were recorded every 15min throughout SS, immediately after and every 15-min post-TTE. No differences in blood glucose (incremental area under the curve [mean ± SD]: CES-HGel 1,100 ± 96mmol·L-1·150min-1 and CES-Std 1,076 ± 58mmol·L-1·150min-1; p = .266) were observed during SS. There were no differences in substrate oxidation during SS (carbohydrate: p = .650; fat: p = .765) or TTE (carbohydrate: p = .466; fat: p = .633) and no effect of trial on GIS incidence (100% in both trials) or severity (summative rating score: CES-HGel 29.1 ± 32.6 and CES-Std 34.8 ± 34.8; p = .262). Breath hydrogen was not different between trials (p = .347), nor was TTE performance (CES-HGel 722 ± 182s and CES-Std: 756 ± 187s; p = .08). In conclusion, sodium alginate and pectin added to a CES consumed during endurance running does not alter the blood glucose responses, carbohydrate malabsorption, substrate oxidation, GIS, or TTE beyond those of a CES with otherwise matched ingredients.

A study protocol for a randomised crossover study evaluating the effect of diets differing in carbohydrate quality on ileal content and appetite regulation in healthy humans

Introduction: A major component of the digesta reaching the colon from the distal ileum is carbohydrate. This carbohydrate is subject to microbial fermentation and can radically change bacterial populations in the colon and the metabolites they produce, particularly short-chain fatty acids (SCFA). However, very little is currently known about the forms and levels of carbohydrate in the ileum and the composition of the ileal microbiota in humans. Most of our current understanding of carbohydrate that is not absorbed by the small intestine comes from ileostomy models, which may not reflect the physiology of an intact gastrointestinal tract. Methods: We will investigate how ileal content changes depending on diet using a randomised crossover study in healthy humans. Participants will be inpatients at the research facility for three separate 4-day visits. During each visit, participants will consume one of three diets, which differ in carbohydrate quality: 1) low-fibre refined diet; 2) high-fibre diet with intact cellular structures; 3) high-fibre diet where the cellular structures have been disrupted (e.g. milling, blending). On day 1, a nasoenteric tube will be placed into the distal ileum and its position confirmed under fluoroscopy. Ileal samples will be collected via the nasoenteric tube and metabolically profiled, which will determine the amount and type of carbohydrate present, and the composition of the ileal microbiota will be measured. Blood samples will be collected to assess circulating hormones and metabolites. Stool samples will be collected to assess faecal microbiota composition. Subjective appetite measures will be collected using visual analogue scales. Breath hydrogen will be measured in real-time as a marker of intestinal fermentation. Finally, an in vitro continuous fermentation model will be inoculated with ileal fluid in order to understand the shift in microbial composition and SCFA produced in the colon following the different diets. Registration: ISRCTN11327221.

Evaluation of lactulose, lactose, and fructose breath testing in clinical practice: A focus on methane.

Background and AimBreath testing (BT) is used to identify carbohydrate malabsorption and small intestine bacterial overgrowth. Measuring methane alongside hydrogen is advocated to reduce false‐negative studies, but the variability of methane production is unknown. The aim of this study is to examine the effect of high methane production on hydrogen excretion after ingesting lactulose, fructose, or lactose.MethodsA retrospective audit was performed of patients with gastrointestinal symptoms who underwent BT. Following a low fermentable carbohydrate diet for 24‐h, a fasting BT before consuming 35 ml lactulose, 35 g fructose, or lactose in 200 ml water, followed by BT every 10–15 min for up to 3‐h, was performed. A positive test was defined as a ≥20 ppm rise of hydrogen or methane from baseline. A high methane producer had an initial reading of ≥5 ppm. Breath hydrogen and methane production were measured as area under the curve. Chi‐squared tests were used to compare proportions of those meeting the cut‐off criteria.ResultsOf patients, 26% (28/106) were high methane producers at their initial lactulose test. The test–retest repeatability of methane production was high, with the same methane production status before ingesting lactose in all (70/70) and before ingesting fructose in most (71/73). Methane production was highly variable during testing, with 38% (10/26) having ≥1 reading lower than baseline. Hydrogen produced by high or low methane producers did not differ (1528 [960–3645] ppm min vs 2375 [1810–3195] ppm min [P = 0.11]). Symptoms and breath test results were not positively related.ConclusionThe validity of including an increase of ≥20 ppm methane to identify carbohydrate malabsorption or small intestine bacterial overgrowth should be questioned due to the variability of readings during testing.

Fructose malabsorption in asymptomatic children and in patients with functional chronic abdominal pain: a prospective comparative study

The objective of this prospective cohort study was to compare fructose malabsorption in patients with functional chronic abdominal pain and in healthy children. The sample was divided into two groups: asymptomatic children and pain-predominant functional gastrointestinal disorders according to the Rome IV criteria. All children were tested for fructose malabsorption by a standardized breath hydrogen test. Hydrogen and methane were measured and the test was presumed positive when it exceeded 20ppm above baseline. If positive, patients were given a low-fructose diet and the response was evaluated. One hundred five children were included (34 healthy children, 71 with functional chronic abdominal pain), with similar demographic characteristics in both groups (35.2% male, age 9.5 ± 2.8years). Hydrogen levels in breath were tested through a hydrogen test for fructose demonstrating malabsorption in 58.8% of healthy children (95%CI 40.8%-76.8%) and in 40.8% of children with chronic abdominal pain (95%CI 28.7%-53.0%), removing those who had bacterial overgrowth. Twenty-one of 31 patients with symptoms and a positive test (72.4%) reported an improvement on a low-fructose diet.Conclusion: Fructose malabsorption is more common in asymptomatic children than in patients with chronic abdominal pain. Better standardized test conditions are necessary to improve accuracy of diagnosis before using this test in clinical practice. What is Known: • Although fructose malabsorption is believed to be related with chronic abdominal pain, high-quality evidence is lacking. • Concerns have raised regarding the use of breath hydrogen test for fructose malabsorption in children with chronic abdominal pain. What is New: • Fructose malabsorption is not more common in children with pain-predominant functional gastrointestinal disorders than in asymptomatic children. • Improvement in symptoms with low-fructose diet may indicate that, although patients with pain-predominant functional gastrointestinal disorders did not have a higher percentage of malabsorption, they had greater fructose intolerance.

Validity of a Portable Breath Analyser (AIRE) for the Assessment of Lactose Malabsorption.

Hydrogen (H2) measurement in exhaled breath is a reliable and non-invasive method to diagnose carbohydrate malabsorption. Currently, breath H2 measurement is typically limited to clinic-based equipment. A portable breath analyser (AIRE, FoodMarble Digestive Health Limited, Dublin, Ireland) is a personalised device marketed for the detection and self-management of food intolerances, including lactose malabsorption (LM). Currently, the validity of this device for breath H2 analysis is unknown. Individuals self-reporting dairy intolerance (six males and six females) undertook a lactose challenge and a further seven individuals (all females) underwent a milk challenge. Breath samples were collected prior to and at frequent intervals post-challenge for up to 5 h with analysis using both the AIRE and a calibrated breath hydrogen analyser (BreathTracker, QuinTron Instrument Company Inc., Milwaukee, WI, USA). A significant positive correlation (p < 0.001, r > 0.8) was demonstrated between AIRE and BreathTracker H2 values, after both lactose and milk challenges, although 26% of the AIRE readings demonstrated the maximum score of 10.0 AU. Based on our data, the cut-off value for LM diagnosis (25 ppm H2) using AIRE is 3.0 AU and it is effective for the identification of a response to lactose-containing foods in individuals experiencing LM, although its upper limit is only 81 ppm.

Effect Modification by the Gut Microbiota on Metabolic Response to Resistant Starch (RS) Wheat Supplementation (FS11-03-19)

ObjectivesThe objective of the study is to determine whether features of individuals’ baseline gut microbiota modify the effect of a resistant starch (RS) intervention on post-prandial glycemic response and other metabolic markers that have been linked to gut microbial action (i.e., short-chain fatty acids (SCFA), bile acids, breath hydrogen/methane). MethodsMetabolic responses and 16S rRNA gene data generated from a double-blind, placebo controlled, crossover clinical trial of RS and regular wheat will be used to investigate whether baseline features of the microbiota are correlated with inter-individual differences in the effect of RS supplementation in individuals. Women and men consumed 3 or 4 rolls per day, respectively, made from RS (14–18 g total dietary fiber, TDF) or conventional wheat (4–5.5 g TDF) for 7 days during each arm of the trial duration. Linear mixed models of glycemic response and features of the gut microbiota hypothesized to modify the effect of the intervention as well as covariates (e.g., gender, habitual fiber intake) will be used to determine microbiota features associated with improvement in glycemic response as a result of RS supplementation. ResultsA total of 30 healthy adults ages 40–65 will be studied and 25 have completed the study thus far. Of the metabolic variables analyzed to date, a significant amount of inter-individual variability in the magnitude and direction of postprandial glycemia and breath hydrogen responses to RS wheat supplementation. For example, the intra-class correlations (ICC) of post-prandial glucose and insulin area under the curve (AUC) were high, 42.07% and 52.86%, respectively. However, there was a significant overall effect of RS wheat on glycemic response such that postprandial insulin during RS supplementation was lower than during regular wheat consumption (P = 0.004). ConclusionsThe results of this study show a high degree of inter-individual variability in metabolic response to fiber (RS) supplementation, suggesting the presence of individual factors that modify the effect of the intervention. Future studies should incorporate this analysis into their statistical plan to validate these findings and contribute to the current literature on personalized nutrition and the gut microbiota. This will enable us to predict and potentially modify metabolic response to dietary components. Funding SourcesInstitute for Innovation and Health (IIFH) and Arcadia Biosciences. Supporting Tables, Images and/or Graphs▪▪▪

A study protocol for a randomised crossover study evaluating the effect of diets differing in carbohydrate quality on ileal content and appetite regulation in healthy humans

Introduction:A major component of the digesta reaching the colon from the distal ileum is carbohydrate. This carbohydrate is subject to microbial fermentation and can radically change bacterial populations in the colon and the metabolites they produce, particularly short-chain fatty acids (SCFA). However, very little is currently known about the forms and levels of carbohydrate in the ileum and the composition of the ileal microbiota in humans. Most of our current understanding of carbohydrate that is not absorbed by the small intestine comes from ileostomy models, which may not reflect the physiology of an intact gastrointestinal tract.Methods:We will investigate how ileal content changes depending on diet using a randomised crossover study in healthy humans. Participants will be inpatients at the research facility for three separate 4-day visits. During each visit, participants will consume one of three diets, which differ in carbohydrate quality: 1) low-fibre refined diet; 2) high-fibre diet with intact cellular structures; 3) high-fibre diet where the cellular structures have been disrupted (e.g. milling, blending). On day 1, a nasoenteric tube will be placed into the distal ileum and its position confirmed under fluoroscopy. Ileal samples will be collected via the nasoenteric tube and metabolically profiled, which will determine the amount and type of carbohydrate present, and the composition of the ileal microbiota will be measured. Blood samples will be collected to assess circulating hormones and metabolites. Stool samples will be collected to assess faecal microbiota composition. Subjective appetite measures will be collected using visual analogue scales. Breath hydrogen will be measured in real-time as a marker of intestinal fermentation. Finally, anin vitrocontinuous fermentation model will be inoculated with ileal fluid in order to understand the shift in microbial composition and SCFA produced in the colon following the different diets.Registration:ISRCTN11327221.

Impact of Oral-Cecal Transit Time on the Interpretation of Lactulose Breath Tests After RYGB: a Personalized Approach to the Diagnosis of SIBO.

Traditionally, small intestinal bacterial overgrowth (SIBO) is diagnosed when there is an early peak in breath hydrogen or methane. Given unclear intestinal transit time in Roux-en-Y gastric bypass (RYGB) patients, it is unknown if the traditional approach at diagnosing SIBO is adequate in this patient population. To assess oral-cecal transit time (OCTT) and its impact on the interpretation of breath tests in the diagnosis of SIBO in patients with RYGB. This study was a retrospective review of prospectively collected data on RYGB patients who underwent testing for SIBO using lactulose breath test (LBT) with or without small bowel follow-through (SBFT) to assess OCTT. Outcomes of SIBO test based on LBT alone versus LBT with OCTT were compared using a chi-squared test. Sixty-two of the 151 RYGB patients who underwent LBT underwent an additional SBFT to assess OCTT. Median OCTT was 60min. Of these, 59.7% had OCTT shorter than 90min. Based on LBT alone, 36/62 patients (58.1%) were classified as positive SIBO. When LBT results were combined with OCTT, 26/36 patients (72.2%) had hydrogen or methane rise within OCTT, suggesting 27.8% false positive rate. Patients with true positive SIBO based on LBT and OCTT had a higher response rate to antibiotics compared to those with false positive SIBO (78.3% vs. 33.3%, p = 0.03). A personalized approach of combining LBT with SBFT to assess OCTT may improve the accuracy of SIBO testing and enhance clinical outcomes in patients with RYGB.

Chronic Physical Activity Does Not Impact Metabolic Responses to Low or High Doses of Resistant Starch: A Crossover Trial

Physical activity and resistant starch are known independently, to beneficially affect metabolic health especially in the gut. However, little is known about the combined effects of physical activity and resistant starch. Thus, the purpose of this study was to investigate the effects of physical activity at different dosages of resistant starch on gut and metabolic health, represented by breath hydrogen and blood glucose responses. Twenty young, healthy participants were stratified into two physical activity groups based on seven-day accelerometry data. Participants visited the lab twice in random order and consumed a meal with either 5 g or 25 g of resistant starch. Breath hydrogen and blood glucose were measured at baseline and serially for six and two hours after meal consumption respectively. Total area under the curve (AUC) for breath hydrogen and incremental AUC for blood glucose were not different between physical activity groups or resistant starch conditions. Thus, chronic physical activity status did not impact breath hydrogen or blood glucose responses to either low or high resistant starch meals.

Breathing hydrogen sulfide prevents delayed paraplegia in mice

Delayed paraplegia complicates the recovery from spinal cord ischemia or traumatic spinal cord injury. While delayed motor neuron apoptosis is implicated in the pathogenesis, no effective treatment or preventive measures is available for delayed paraplegia. Hydrogen sulfide exerts anti-apoptotic effects. Here, we examined effects of hydrogen sulfide breathing on the recovery from transient spinal cord ischemia. Breathing hydrogen sulfide starting 23 h after reperfusion for 5 h prevented delayed paraplegia after 5 min of spinal cord ischemia. Beneficial effects of hydrogen sulfide were mediated by upregulation of anti-apoptotic Bcl-XL and abolished by nitric oxide synthase 2 deficiency. S-nitrosylation of NFkB p65 subunit, which is induced by nitric oxide derived from nitric oxide synthase 2, facilitated subsequent sulfide-induced persulfidation of p65 and transcription of anti-apoptotic genes. These results uncover the molecular mechanism of the anti-apoptotic effects of sulfide based on the interaction between nitric oxide and sulfide. Exploitation of the anti-apoptotic effects of delayed hydrogen sulfide breathing may provide a new therapeutic approach for delayed paraplegia.

Hydrogen Sensing Properties of Co-Doped ZnO Nanoparticles

In this study, the gas sensing properties of Co-doped ZnO nanoparticles (Co-ZnO NPs) synthesized via a simple sol-gel method are reported. The microstructure and morphology of the synthesized Co-ZnO NPs were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. Co-ZnO NPs were then used for developing a conductometric gas sensor for the detection, at mild temperature, of low concentration of hydrogen (H2) in air. To evaluate the selectivity of the sensor, the sensing behavior toward some VOCs such as ethanol and acetone, which represent the most important interferents for breath hydrogen analysis, was also investigated in detail. Results reported demonstrated better selectivity toward hydrogen of the Co-ZnO NPs sensor when compared to pure ZnO. The main factors contributing to this behavior, i.e., the transition from n-type behavior of pristine ZnO to p-type behavior upon Co-doping, the modification of oxygen vacancies and acid-base characteristics have been considered. Hence, this study highlights the importance of Co doping of ZnO to realize a high performance breath hydrogen sensor.

A Pilot Study of the Effect of Green Kiwifruit on Human Intestinal Fermentation Measured by Hydrogen and Methane Breath Testing.

We investigated the impact of the ingestion of two green kiwifruit (Actinidia deliciosa var. Hayward) and one Royal Gala apple on breath hydrogen and methane production in humans. Consumption of two green kiwifruit led to no evidence of carbohydrate malabsorption (0/20), whereas consumption of one apple was associated with carbohydrate malabsorption in 6/20 participants (P = .008). There were no significant differences in the area under the curve for hydrogen or methane breath concentrations after consumption of the two fruits. Rates of lactose and fructose breath tests in this cohort were within expected parameters. Green kiwifruit are not associated with clinically significant carbohydrate malabsorption compared with apples in this pilot study.

Impact of Small Intestine Bacterial Overgrowth on Response to a Nutritional Intervention in Bangladeshi Children from an Urban Community.

.Small intestine bacterial overgrowth (SIBO) is prevalent among children living in low-income settings, leading to impaired growth and development. The aim of this study was to assess linear and ponderal growth parameters between malnourished SIBO-positive and SIBO-negative children aged 12–18 months who prospectively underwent a nutritional intervention. A glucose hydrogen breath test to detect SIBO was performed in 194 stunted (length-for-age Z score [LAZ] < −2 standard deviations) or at-risk of stunting (LAZ score between < −1 and −2 standard deviations) children. Participants received nutritional supplementation (egg and milk) in addition to their regular family meals 6 days per week for 90 days. Small intestine bacterial overgrowth was defined as a ≥ 12-ppm rise in breath hydrogen over the patient’s baseline during the 3-hour test. Small intestine bacterial overgrowth status before intervention was forced into a multivariable linear regression model to examine its effects on anthropometric changes in response to the intervention. Sociodemographic data at enrollment was analyzed through multivariable logistic regression in an attempt to predict SIBO positivity. Overall, 14.9% (29/194) children were diagnosed with SIBO before the nutritional intervention. No statistically significant difference was observed among SIBO-positive and SIBO-negative groups in terms of their response to the nutritional intervention (SIBO-positive coefficient [95% confidence interval (CI)], P-value for ∆length-for-age Z score −0.003 [−0.14, 0.13], 0.96; ∆weight-for-age Z score −0.05 [−0.20, 0.09], 0.46; and ∆weight-for-length Z score −0.10 [−0.31, 0.10], 0.33). This study demonstrated that a noteworthy proportion of malnourished children living in a disadvantaged urban community were SIBO positive; however, it failed to reveal an association between SIBO status and response to nutritional intervention.

Digestive Responses to Fortified Cow or Goat Dairy Drinks: A Randomised Controlled Trial.

Fortified milk drinks are predominantly manufactured from bovine (cow) sources. Alternative formulations include those prepared with hydrolysed bovine milk proteins or from alternate bovidae species, such as caprine (goat) milk. Currently, there is little data on protein digestive and metabolic responses following ingestion of fortified milk drinks. To examine the digestive and metabolic responses to commercially-available fortified milks, young adults (n = 15 males: 15 females), in a randomised sequence, ingested isonitrogenous quantities of whole cow-protein (WC), whole goat-protein (WG), or partially-hydrolysed whey cow-protein (HC), commercial fortified milks. Plasma amino acid (AA) and hormonal responses were measured at baseline and again at 5 h after ingestion. Paracetamol recovery, breath hydrogen, and subjective digestive responses were also measured. Postprandial plasma AA was similar between WC and WG, while AA appearance was suppressed with HC. Following HC, there was a negative incremental AUC in plasma branched-chain AAs. Further, HC had delayed gastric emptying, increased transit time, and led to exaggerated insulin and GLP-1 responses, in comparison to whole protein formulas. Overall, WC and WG had similar protein and digestive responses with no differences in digestive comfort. Contrastingly, HC led to delayed gastric emptying, attenuated AA appearance, and a heightened circulating insulin response.

Breath Hydrogen Test in Lactose Malabsorption

Lactose is the most important source in mammalian milk. In normal children, Lactose is hydrolyzed by lactase, and directly absorbed into bloodstream by an active transport mechanism. The term of lactose malabsorption is reserved to patients in whom impaired intestinal lactose hydrolysis and uptake has been proven by an appropriate test. The severity of lactose malabsorption and the extent of symptoms vary widely and are the results of several factors such as the amount of ingested lactose, gastric emptying time, intestinal transit time, and colonic flora. The diagnosis of lactose malabsorption is based on clinical findings and the results of appropriate tests. The breath hydrogen test has obvious advantages for pediatric population because it is painless, non-invasive, sensitive and specific. In the absence of bacterial colonization in the small intestine, the elevation of the concentration of hydrogen in the expired air implies the arrival of lactose in the colon. The increasing respiratory excretion of hydrogen is indicative of a deficit of lactase in enterocyte brush border. This test can also be used to show the existence of bacterial growth. Dietary fiber, some drugs, preparation for colonoscopy, colonic pH, and diarrhea can influence the result of breath hydrogen test.

Impact of Agaricus bisporus Mushroom Consumption on Gut Health Markers in Healthy Adults.

Eating Agaricus bisporus mushrooms may impact gut health, because they contain known prebiotics. This study assessed mushroom consumption compared to meat on gastrointestinal tolerance, short chain fatty acid (SCFA) production, laxation, and fecal microbiota. A randomized open-label crossover study was conducted in healthy adults (n = 32) consuming protein-matched amounts of mushrooms or meat twice daily for ten days. Breath hydrogen measures were taken on day one, and gastrointestinal tolerance was evaluated throughout treatments. Fecal sample collection was completed days 6–10, and samples were assessed for bacterial composition, SCFA concentrations, weight, pH, and consistency. There were no differences in breath hydrogen, stool frequency, consistency, fecal pH, or SCFA concentrations between the two diets. The mushroom diet led to greater overall gastrointestinal symptoms than the meat diet on days one and two. The mushroom-rich diet resulted in higher average stool weight (p = 0.002) and a different fecal microbiota composition compared to the meat diet, with greater abundance of Bacteroidetes (p = 0.0002) and lower abundance of Firmicutes (p = 0.0009). The increase in stool weight and presence of undigested mushrooms in stool suggests that mushroom consumption may impact laxation in healthy adults. Additional research is needed to interpret the health implications of fecal microbiota shifts with mushroom feeding.

The physiologic and phenotypic significance of variation in human amylase gene copy number

Salivary α-amylase gene (AMY1) copy number (CN) correlates with the amount of salivary α-amylase, but beyond this, the physiologic significance is uncertain. We hypothesized that individuals with higher AMY1 CN would digest starchy foods faster and show higher postprandial responses and lower breath hydrogen excretion compared with those with low CN. Four linked studies were conducted. In Study 1, we genotyped 201 healthy subjects with the use of real-time quantitative polymerase chain reaction and determined glucose tolerance, insulin sensitivity, salivary α-amylase activity, body mass index (BMI), and macronutrient intake. In Study 2, a pool of 114 subjects tested 6 starchy foods, 3 sugary foods, 1 mixed meal, and 2 reference glucose solutions, containing either 50 or 25 g of available carbohydrate. In Study 3, we compared glycemic and insulin responses to starchy foods with responses to glucose in 40 individuals at extremes of high and low CN. In Study 4, we compared breath hydrogen and methane responses over 8 h in 30 individuals at extremes of CN. AMY1 CN correlated positively with salivary α-amylase activity (r=0.62, P<0.0001, n=201) but not with BMI, glucose tolerance, or insulin sensitivity. However, CN was strongly correlated with normalized glycemic responses to all starchy foods (explaining 26-61% of interindividual variation), but not to sucrose or fruit. Individuals in the highest compared with the lowest decile of CN produced modestly higher glycemia (+15%, P=0.018), but not insulinemia, after consuming 2 starchy foods. Low-CN individuals displayed >6-fold higher breath methane levels in the fasting state and after starch ingestion than high-CN individuals (P=0.001), whereas hydrogen excretion was similar. Starchy foods are digested faster and produce higher postprandial glycemia in individuals with high AMY1 CN. In contrast, having low CN is associated with colonic methane production. This trial was registered at www.anzctr.org.au as ACTRN12617000670370.

Impact of Oral-Cecal Transit Time on the Interpretation of Breath Tests After RYGB: A Personalized Approach to the Diagnosis of SIBO

Introduction: Traditionally, small intestinal bacterial overgrowth (SIBO) is diagnosed when there is an early peak in breath hydrogen or methane. Given unclear intestinal transit time in Roux-en-Y gastric bypass (RYGB) patients, it is unknown if the traditional approach at diagnosing SIBO is adequate in this patient population. This study aims to assess oral-cecal transit time (OCTT) and its impact on the interpretation of breath tests in the diagnosis of SIBO in patients with RYGB. Methods: This study consisted of prospectively collected cohort of RYGB patients who underwent testing for SIBO using lactulose breath test (LBT) with or without small bowel follow-through (SBFT) to assess OCTT. Outcomes of SIBO test based on LBT alone versus LBT with OCTT were compared using a Chi-squared test. Results: 151 RYGB patients underwent LBT to assess for SIBO. Sixty-two of the 151 patients (41.1%) underwent SBFT to assess OCTT in addition to LBT. Median OCTT was 60 minutes. Of these, 59.7% had OCTT shorter than 90 minutes. Based on LBT alone, 36/62 patients (58.1%) were classified as positive SIBO. When LBT results were combined with OCTT, 26/36 patients (72.2%) had hydrogen or methane rise within OCTT, suggesting 27.8 % false positive rate. Patients with true positive SIBO based on LBT and OCTT had a higher response rate to antibiotics compared to those with false positive SIBO (78.3% vs 33.3%, p=0.03). Conclusion: A personalized approach of combining LBT with SBFT to assess OCTT may improve the accuracy of SIBO testing and enhance clinical outcomes in patients with RYGB.

The Effect of White Rice and White Bread as Staple Foods on Gut Microbiota and Host Metabolism.

The purpose of this study was to examine the influence of two kinds of major Japanese staple foods, white rice and white bread, on gut microbiota against the background in which participants eat common side dishes. Seven healthy subjects completed the dietary intervention with two 1-week test periods with a 1-week wash-out period in cross-over design (UMIN registration UMIN000023142). White bread or white rice and 21 frozen prepared side dishes were consumed during the test periods. At baseline and at the end of each period, fasting blood samples, breath samples, and fecal samples were collected. For fecal samples, 16S rRNA gene sequencing was used to analyze the gut microbiota. After the bread period, the abundance of fecal Bifidobacterium genus (19.2 ± 14.5 vs. 6.2 ± 6.6 (%), p = 0.03), fasting glucagon-like peptide 1 (GLP-1) (13.6 ± 2.0 vs. 10.5 ± 2.9 (pg/mL), p = 0.03), and breath hydrogen (23.4 ± 9.9 vs. 8.2 ± 5.5 (ppm), p = 0.02) were significantly higher than those of after the rice period. Plasma SCFAs also tended to be higher after the bread period. White bread contains more dietary fiber than refined short grain rice. These findings suggest that indigestible carbohydrate intake from short grain rice as a staple food may be smaller than that of white bread.