Bariatric Surgery Does Not Appear to Affect Women's Breast-Milk Composition.

Background: The breast-milk composition in the first 6 wk postpartum of women who have undergone bariatric surgery (BS) is unknown. Objective: The aim of this study was to examine 1) the breast-milk macronutrient and vitamin A composition in women who had and who had not undergone BS and 2) the impact of maternal diet on the breast-milk composition. We hypothesized that the milk of women who had undergone BS would be less energy dense and have a lower vitamin A concentration than that of other women. Methods: A multicenter prospective substudy was conducted at 2 university hospitals. Breast-milk samples were collected from 24 normal-weight [NW; mean ± SD body mass index (BMI; kg/m2): 21.5 ± 1.7; mean ± SD age: 29 ± 6 y], 39 overweight (OW; BMI: 26.9 ± 1.5; aged 29 ± 5 y), and 12 obese women (BMI: 35.0 ± 5.7; aged 29 ± 5 y) as well as from 11 women who had undergone BS (BMI: 28.0 ± 4.4; aged 30 ± 4 y) from day 3 until week 6 of lactation. Milk energy and macronutrients (Human Milk Analyzer; Miris) and vitamin A concentrations (iCheck Fluoro; BioAnalyt) were determined at the end of each week. Maternal diet (food-frequency questionnaire) and physical activity (Kaiser Physical Activity Survey) were measured during the third trimester of pregnancy and on day 3 or 4 and during week 6 of lactation. Statistical analyses include 1-factor ANOVA, Spearman and Pearson correlations, and multiple linear regression. Results: In all women, a weekly increase in milk energy, total fat, and total carbohydrates was seen, whereas a weekly decrease in proteins and vitamin A was found during the first 2 wk of lactation, followed by a stable concentration of all nutrients. At week 4, milk protein concentrations were higher in women who had undergone BS (14 g/L) compared with NW (8 g/L; P = 0.005) and OW (9 g/L; P = 0.019) women. At week 5, milk carbohydrate concentrations were higher in women who had undergone BS (74 g/L) compared with NW women (68 g/L; P = 0.042). Conclusions: Breast milk of women who have undergone BS appears to be adequate in energy, macronutrients, and vitamin A during the first 6 wk of lactation. This supports the conclusion that breast feeding should not be discouraged in this group of women. This trial was registered at http://www.clinicaltrials.gov as NCT02515214.

Systemic availability and metabolism of colonic-derived short-chain fatty acids in healthy subjects: a stable isotope study.

KEY POINTS: The short-chain fatty acids (SCFAs) are bacterial metabolites produced during the colonic fermentation of undigested carbohydrates, such as dietary fibre and prebiotics, and can mediate the interaction between the diet, the microbiota and the host. We quantified the fraction of colonic administered SCFAs that could be recovered in the systemic circulation, the fraction that was excreted via the breath and urine, and the fraction that was used as a precursor for glucose, cholesterol and fatty acids. This information is essential for understanding the molecular mechanisms by which SCFAs beneficially affect physiological functions such as glucose and lipid metabolism and immune function. ABSTRACT: The short-chain fatty acids (SCFAs), acetate, propionate and butyrate, are bacterial metabolites that mediate the interaction between the diet, the microbiota and the host. In the present study, the systemic availability of SCFAs and their incorporation into biologically relevant molecules was quantified. Known amounts of 13 C-labelled acetate, propionate and butyrate were introduced in the colon of 12 healthy subjects using colon delivery capsules and plasma levels of 13 C-SCFAs 13 C-glucose, 13 C-cholesterol and 13 C-fatty acids were measured. The butyrate-producing capacity of the intestinal microbiota was also quantified. Systemic availability of colonic-administered acetate, propionate and butyrate was 36%, 9% and 2%, respectively. Conversion of acetate into butyrate (24%) was the most prevalent interconversion by the colonic microbiota and was not related to the butyrate-producing capacity in the faecal samples. Less than 1% of administered acetate was incorporated into cholesterol and <15% in fatty acids. On average, 6% of colonic propionate was incorporated into glucose. The SCFAs were mainly excreted via the lungs after oxidation to 13 CO2 , whereas less than 0.05% of the SCFAs were excreted into urine. These results will allow future evaluation and quantification of SCFA production from 13 C-labelled fibres in the human colon by measurement of 13 C-labelled SCFA concentrations in blood.

The Influence of CKD on Colonic Microbial Metabolism.

There is increasing interest in the colonic microbiota as a relevant source of uremic retention solutes accumulating in CKD. Renal disease can also profoundly affect the colonic microenvironment and has been associated with a distinct colonic microbial composition. However, the influence of CKD on the colonic microbial metabolism is largely unknown. Therefore, we studied fecal metabolite profiles of hemodialysis patients and healthy controls using a gas chromatography-mass spectrometry method. We observed a clear discrimination between both groups, with 81 fecal volatile organic compounds detected at significantly different levels in hemodialysis patients and healthy controls. To further explore the differential impact of renal function loss per se versus the effect of dietary and other CKD-related factors, we also compared fecal metabolite profiles between patients on hemodialysis and household contacts on the same diet, which revealed a close resemblance. In contrast, significant differences were noted between the fecal samples of rats 6 weeks after 5/6th nephrectomy and those of sham-operated rats, still suggesting an independent influence of renal function loss. Thus, CKD associates with a distinct colonic microbial metabolism, although the effect of renal function loss per se in humans may be inferior to the effects of dietary and other CKD-related factors. The potential beneficial effect of therapeutics targeting colonic microbiota in patients with CKD remains to be examined.

Faecal metabolite profiling identifies medium-chain fatty acids as discriminating compounds in IBD.

BACKGROUND: Bacteria play a role in the onset and perpetuation of intestinal inflammation in IBD. Compositional alterations may also change the metabolic capacities of the gut bacteria. OBJECTIVE: To examine the metabolic activity of the microbiota of patients with Crohn's disease (CD), UC or pouchitis compared with healthy controls (HC) and determine whether eventual differences might be related to the pathogenesis of the disease. METHODS: Faecal samples were obtained from 40 HC, 83 patients with CD, 68 with UC and 13 with pouchitis. Disease activity was assessed in CD using the Harvey-Bradshaw Index, in UC using the UC Disease Activity Index and in pouchitis using the Pouchitis Disease Activity Index. Metabolite profiles were analysed using gas chromatography-mass spectrometry. RESULTS: The number of metabolites identified in HC (54) was significantly higher than in patients with CD (44, p<0.001), UC (47, p=0.042) and pouchitis (43, p=0.036). Multivariate discriminant analysis predicted HC, CD, UC and pouchitis group membership with high sensitivity and specificity. The levels of medium-chain fatty acids (MCFAs: pentanoate, hexanoate, heptanoate, octanoate and nonanoate), and of some protein fermentation metabolites, were significantly decreased in patients with CD, UC and pouchitis. Hexanoate levels were inversely correlated to disease activity in CD (correlation coefficient=-0.157, p=0.046), whereas a significant positive correlation was found between styrene levels and disease activity in UC (correlation coefficient=0.338, p=0.001). CONCLUSIONS: Faecal metabolic profiling in patients with IBD relative to healthy controls identified MCFAs as important metabolic biomarkers of disease-related changes. TRIAL REGISTRATION NO: NCT 01666717.

Inflammation-Induced Downregulation of Butyrate Uptake and Oxidation Is Not Caused by a Reduced Gene Expression.

In ulcerative colitis (UC) the butyrate metabolism is impaired, leading to energy-deficiency in the colonic cells. The effect of inflammation on the butyrate metabolism was investigated. HT-29 cells were incubated with pro-inflammatory cytokines (TNF-α and/or IFN-γ) for 1 and 24 h. Cells were additionally stimulated with butyrate to investigate its anti-inflammatory potential. Butyrate uptake and oxidation were measured using (14)C-labeled butyrate. Gene expression of the butyrate metabolism enzymes, interleukin 8 (IL-8; inflammatory marker) and villin-1 (VIL-1; epithelial cell damage marker) was measured via quantitative RT-PCR. Significantly increased IL-8 expression and decreased VIL-1 expression after 24 h incubation with TNF-α and/or IFN-γ confirmed the presence of inflammation. These conditions induced a decrease of both butyrate uptake and oxidation, whereas the gene expression was not reduced. Simultaneous incubation with butyrate counteracted the reduced butyrate oxidation. In contrast, 1 h incubation with TNF-α induced a significant increased IL-8 expression and decreased butyrate uptake. Incubation with TNF-α and/or IFN-γ for 1 h did not induce cell damage nor influence butyrate oxidation. The inflammation-induced downregulation of the butyrate metabolism was not caused by a reduced gene expression, but appeared consequential to a decreased butyrate uptake. Increasing the luminal butyrate levels might have therapeutic potential in UC.

Wheat bran extract alters colonic fermentation and microbial composition, but does not affect faecal water toxicity: a randomised controlled trial in healthy subjects.

Wheat bran extract (WBE), containing arabinoxylan-oligosaccharides that are potential prebiotic substrates, has been shown to modify bacterial colonic fermentation in human subjects and to beneficially affect the development of colorectal cancer (CRC) in rats. However, it is unclear whether these changes in fermentation are able to reduce the risk of developing CRC in humans. The aim of the present study was to evaluate the effects of WBE on the markers of CRC risk in healthy volunteers, and to correlate these effects with colonic fermentation. A total of twenty healthy subjects were enrolled in a double-blind, cross-over, randomised, controlled trial in which the subjects ingested WBE (10 g/d) or placebo (maltodextrin, 10 g/d) for 3 weeks, separated by a 3-week washout period. At the end of each study period, colonic handling of NH3 was evaluated using the biomarker lactose[15N, 15N']ureide, colonic fermentation was characterised through a metabolomics approach, and the predominant microbial composition was analysed using denaturing gradient gel electrophoresis. As markers of CRC risk, faecal water genotoxicity was determined using the comet assay and faecal water cytotoxicity using a colorimetric cell viability assay. Intake of WBE induced a shift from urinary to faecal 15N excretion, indicating a stimulation of colonic bacterial activity and/or growth. Microbial analysis revealed a selective stimulation of Bifidobacterium adolescentis. In addition, WBE altered the colonic fermentation pattern and significantly reduced colonic protein fermentation compared with the run-in period. However, faecal water cytotoxicity and genotoxicity were not affected. Although intake of WBE clearly affected colonic fermentation and changed the composition of the microbiota, these changes were not associated with the changes in the markers of CRC risk.

Metabolomics in the Clinical Diagnosis of Inflammatory Bowel Disease.

BACKGROUND: Crohn's disease and ulcerative colitis represent the 2 major phenotypes of inflammatory bowel disease (IBD) that are characterized by chronic inflammation of all or parts of the gastrointestinal tract. The pathogenesis of both diseases is influenced by genetic predispositions as well as microbial and environmental factors. Currently, there is an emerging consensus hypothesis that a microbial dysbiosis is involved in initiating the disease or in maintaining it. These compositional alterations may be reflected in altered metabolic activities of the gut microbiota and has led to the use of 'omic' profiling to improve the understanding of the pathophysiology of IBD. Key Messages: In the past few years, a metabolic approach has increasingly been applied in a number of studies of experimental and human IBD which were mostly focused on exploring disease-related metabolites to gain more insight into metabolic pathways. Metabolomics involves the high throughput identification, characterization and quantification of small molecule metabolites by different analytical techniques and has been performed in different biofluids such as serum/plasma, urine or fecal samples. The application of such a metabolite profiling technique has revealed different metabolites that allow the discrimination of IBD patients from healthy controls. In addition, separate IBD subtypes could be differentiated. Some of these metabolic changes were directly associated to alterations of specific gut microbial populations, implying a perturbation in the gut microbiome in the development of IBD. CONCLUSIONS: This review covers the emerging contribution of metabolomics for the discovery of an IBD signature and to identify biomarkers linked with a metabolic imbalance. For the implementation of metabolomics as a diagnostic tool in IBD, large prospective cohort studies are necessary.

A decrease of the butyrate-producing species Roseburia hominis and Faecalibacterium prausnitzii defines dysbiosis in patients with ulcerative colitis.

OBJECTIVE: Bacteria play an important role in the onset and perpetuation of intestinal inflammation in inflammatory bowel disease (IBD). Unlike in Crohn's disease (CD), in which dysbiosis has been better characterised, in ulcerative colitis (UC), only small cohorts have been studied and showed conflicting data. Therefore, we evaluated in a large cohort if the microbial signature described in CD is also present in UC, and if we could characterise predominant dysbiosis in UC. To assess the functional impact of dysbiosis, we quantified the bacterial metabolites. DESIGN: The predominant microbiota from 127 UC patients and 87 age and sex-matched controls was analysed using denaturing gradient gel electrophoresis (DGGE) analysis. Differences were quantitatively validated using real-time PCR. Metabolites were quantified using gas chromatography-mass spectrometry. RESULTS: Based on DGGE analysis, the microbial signature previously described in CD was not present in UC. Real-time PCR analysis revealed a lower abundance of Roseburia hominis (p<0.0001) and Faecalibacterium prausnitzii (p<0.0001) in UC patients compared to controls. Both species showed an inverse correlation with disease activity. Short-chain fatty acids (SCFA) were reduced in UC patients (p=0.014), but no direct correlation between SCFA and the identified bacteria was found. CONCLUSIONS: The composition of the fecal microbiota of UC patients differs from that of healthy individuals: we found a reduction in R hominis and F prausnitzii, both well-known butyrate-producing bacteria of the Firmicutes phylum. These results underscore the importance of dysbiosis in IBD but suggest that different bacterial species contribute to the pathogenesis of UC and CD.

Functional analysis of colonic bacterial metabolism: relevant to health?

With the use of molecular techniques, numerous studies have evaluated the composition of the intestinal microbiota in health and disease. However, it is of major interest to supplement this with a functional analysis of the microbiota. In this review, the different approaches that have been used to characterize microbial metabolites, yielding information on the functional end products of microbial metabolism, have been summarized. To analyze colonic microbial metabolites, the most conventional way is by application of a hypothesis-driven targeted approach, through quantification of selected metabolites from carbohydrate (e.g., short-chain fatty acids) and protein fermentation (e.g., p-cresol, phenol, ammonia, or H(2)S), secondary bile acids, or colonic enzymes. The application of stable isotope-labeled substrates can provide an elegant solution to study these metabolic pathways in vivo. On the other hand, a top-down approach can be followed by applying metabolite fingerprinting techniques based on (1)H-NMR or mass spectrometric analysis. Quantification of known metabolites and characterization of metabolite patterns in urine, breath, plasma, and fecal samples can reveal new pathways and give insight into physiological regulatory processes of the colonic microbiota. In addition, specific metabolic profiles can function as a diagnostic tool for the identification of several gastrointestinal diseases, such as ulcerative colitis and Crohn's disease. Nevertheless, future research will have to evaluate the relevance of associations between metabolites and different disease states.

Dysbiosis of the faecal microbiota in patients with Crohn's disease and their unaffected relatives.

BACKGROUND AND AIMS: A general dysbiosis of the intestinal microbiota has been established in patients with Crohn's disease (CD), but a systematic characterisation of this dysbiosis is lacking. Therefore the composition of the predominant faecal microbiota of patients with CD was studied in comparison with the predominant composition in unaffected controls. Whether dysbiosis is present in relatives of patients CD was also examined. METHODS: Focusing on families with at least three members affected with CD, faecal samples of 68 patients with CD, 84 of their unaffected relatives and 55 matched controls were subjected to community fingerprinting of the predominant microbiota using denaturing gradient gel electrophoresis (DGGE). To analyse the DGGE profiles, BioNumerics software and non-parametric statistical analyses (SPSS V.17.0) were used. Observed differences in the predominant microbiota were subsequently confirmed and quantified with real-time PCR. RESULTS: Five bacterial species characterised dysbiosis in CD, namely a decrease in Dialister invisus (p=0.04), an uncharacterised species of Clostridium cluster XIVa (p = 0.03), Faecalibacterium prausnitzii (p < 1.3 × 10⁻5) and Bifidobacterium adolescentis (p = 5.4 × 10⁻6), and an increase in Ruminococcus gnavus (p = 2.1 × 10⁻7). Unaffected relatives of patients with CD had less Collinsella aerofaciens (p = 0.004) and a member of the Escherichia coli-Shigella group (p = 0.01) and more Ruminococcus torques (p = 0.02) in their predominant microbiota as compared with healthy subjects. CONCLUSION: Unaffected relatives of patients with CD have a different composition of their microbiota compared with healthy controls. This dysbiosis is not characterised by lack of butyrate producing-bacteria as observed in CD but suggests a role for microorganisms with mucin degradation capacity.

Antimicrobial sensitivity patterns of Staphylococcus species isolated from mobile phones and implications in the health sector.

OBJECTIVES: The aim of this research was to determine drug sensitivity profiles of Staphylococcus species isolated from mobile phones of students in Microbiology and Biomedical Laboratory Sciences from UZIMA University, Kisumu (Kenya) and the University Colleges Leuven-Limburg, Leuven (Belgium), respectively. RESULTS: All mobile phones (16/16, 100%) had gram-positive bacteria. 3/8 (37.5%) mobile devices had Staphylococcus aureus. 2/3 (67%) Staphylococcus aureus strains were resistant to ampicillin, oxacillin, ceftazidime, vancomycin and amoxicillin. Guidelines for disinfection of mobile phones need to be developed urgently to stop transmission of resistant bacteria.

Quantification of (15)N-nitrate in urine with gas chromatography combustion isotope ratio mass spectrometry to estimate endogenous NO production.

The use of stable isotope labeled substrates and subsequent analysis of urinary nitrate, forms a noninvasive test for evaluation of the in vivo NO metabolism. The present paper describes a new method for simultaneous quantification of (15)N-nitrate and total nitrate with gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS). Nitrate, isolated from urine with a nitrate selective resin, was reduced to nitrite using copperized cadmium. Subsequently, Sudan I was formed by diazotation. Sudan II was added as internal standard, and both molecules were analyzed with GC-C-IRMS as tert-butyldimethylsilyl derivatives. The accuracy was determined during a recovery study of two different known nitrate concentrations and two (15)N-enrichments. A recovery of 101.6% and 103.9% for total nitrate and 107.6% and 91.2% for (15)N-nitrate was obtained, respectively. The validated method was applied on complete 72 h urine collections after intravenous administration of (15)N-nitrate and (15)N-arginine in humans. On average, 51.8% (47.0-71.0%) of administered (15)N-nitrate was excreted, while 0.68% (0.44-1.17%) of (15)N-arginine was metabolized to nitrate. In conclusion, this method can be used for accurate simultaneous determination of (15)N-nitrate and total nitrate concentrations in urine and can be applied in clinical studies for noninvasive evaluation of NO metabolism in vivo.

p-Cresyl sulfate serum concentrations in haemodialysis patients are reduced by the prebiotic oligofructose-enriched inulin.

INTRODUCTION: Protein-bound uraemic retention solutes, including p-cresyl sulfate and indoxyl sulfate, contribute substantially to the uraemic syndrome. These and several other uraemic retention solutes originate from intestinal bacterial protein fermentation. We investigated whether the prebiotic oligofructose-enriched inulin reduced serum concentration of p-cresyl sulfate and indoxyl sulfate, through interference with intestinal generation. METHODS: We performed a single centre, non-randomized, open-label phase I/II study in maintenance HD patients with a 4-week, escalating dose regimen of oligofructose-enriched inulin (ORAFTI Synergy 1, Tienen, Belgium) (www.clinicaltrials.gov NCT00695513). Changes in p-cresyl sulfate and indoxyl sulfate serum concentrations as well as changes in p-cresyl sulfate and indoxyl sulfate generation rates were analysed. RESULTS: Compliance with therapy was excellent. p-Cresyl sulfate serum concentrations at 4 weeks were significantly reduced by 20% (intention to treat, P = 0.01; per protocol, P = 0.03). Also p-cresyl sulfate generation rates were reduced (P = 0.007). In contrast, neither indoxyl sulfate generation rates (P = 0.9) nor serum concentrations (P = 0.4) were significantly changed. CONCLUSION: The prebiotic oligofructose-inulin significantly reduced p-cresyl sulfate generation rates and serum concentrations in haemodialysis patients. Whether reduction of p-cresyl sulfate serum concentrations, an independent predictor of cardiovascular disease in HD patients, will result in improved cardiovascular outcomes remains to be proven.

In vitro kinetics of prebiotic inulin-type fructan fermentation by butyrate-producing colon bacteria: implementation of online gas chromatography for quantitative analysis of carbon dioxide and hydrogen gas production.

Kinetic analyses of bacterial growth, carbohydrate consumption, and metabolite production of five butyrate-producing clostridial cluster XIVa colon bacteria grown on acetate plus fructose, oligofructose, inulin, or lactate were performed. A gas chromatography method was set up to assess H2 and CO2 production online and to ensure complete coverage of all metabolites produced. Method accuracy was confirmed through the calculation of electron and carbon recoveries. Fermentations with Anaerostipes caccae DSM 14662(T), Roseburia faecis DSM 16840(T), Roseburia hominis DSM 16839(T), and Roseburia intestinalis DSM 14610(T) revealed similar patterns of metabolite production with butyrate, CO2, and H2 as the main metabolites. R. faecis DSM 16840(T) and R. intestinalis DSM 14610(T) were able to degrade oligofructose, displaying a nonpreferential breakdown mechanism. Lactate consumption was only observed with A. caccae DSM 14662(T). Roseburia inulinivorans DSM 16841(T) was the only strain included in the present study that was able to grow on fructose, oligofructose, and inulin. The metabolites produced were lactate, butyrate, and CO2, without H2 production, indicating an energy metabolism distinct from that of other Roseburia species. Oligofructose degradation was nonpreferential. In a coculture of R. inulinivorans DSM 16841(T) with the highly competitive strain Bifidobacterium longum subsp. longum LMG 11047 on inulin, hardly any production of butyrate and CO2 was detected, indicating a lack of competitiveness of the butyrate producer. Complete recovery of metabolites during fermentations of clostridial cluster XIVa butyrate-producing colon bacteria allowed stoichiometric balancing of the metabolic pathway for butyrate production, including H2 formation.

Dose-response effect of arabinoxylooligosaccharides on gastrointestinal motility and on colonic bacterial metabolism in healthy volunteers.

OBJECTIVE: Arabinoxylooligosaccharides (AXOS) are non-digestible in the upper gastrointestinal tract and have been shown to exert prebiotic effects in animals. The aim of this study was to characterize the influence of AXOS with an average degree of polymerization of 15 and an average degree of arabinose substitution of 0.26 (AXOS-15-0.26) on gastrointestinal motility and colonic bacterial metabolism in healthy human volunteers. METHODS: Twelve healthy volunteers received five test meals, containing different amounts of AXOS-15-0.26, with one week intervals between each test meal. Breath tests were used to measure gastric emptying rate, oro-cecal transit time (OCTT) and hydrogen excretion. Colonic bacterial metabolism was estimated using the biomarkers lactose-[(15)N, (15)N']-ureide ((15)N-LU) and p-cresol. RESULTS: Gastric emptying and OCTT were not influenced by addition of varying amounts of AXOS-15-0.26. Administration of 2.2g or 4.9 g AXOS-15-0.26 significantly decreased the urinary (15)N-excretion (respectively p = 0.008 and p = 0.035) as compared to the baseline, whereas fecal (15)N-excretion was significantly increased (respectively p = 0.034 and p = 0.019). This shift from urinary to fecal (15)N-excretion suggests a higher uptake or incorporation by bacteria due to the stimulation of colonic bacterial growth and/or metabolic activity. Furthermore, a significant increase in hydrogen excretion after administration of 2.2g (p = 0.002) and 4.9 g (p = 0.004) AXOS-15-0.26 was observed. No influence on urinary p-cresol excretion was observed. CONCLUSION: These findings suggest that a minimal dose of 2.2g AXOS-15-0.26 favorably modulates the colonic bacterial metabolism in healthy humans. However, long term studies are required to confirm a possible prebiotic effect.

Metabonomics and systems biology.

Systems biology represents an integrative research strategy that studies the interactions between DNA, mRNA, protein, and metabolite level in an organism, thereby including the interactions with the physical environment and other organisms. The application of metabonomics, or the quantitative study of metabolites in biological systems, in systems biology is currently an emerging area of research, which can contribute to the discovery of (disease) signatures, drug targeting and design, and the further elucidation of basic and more complex biochemical principles. This chapter covers the contribution of metabonomics in advancing our understanding in systems biology.

Low-residue and low-fiber diets in gastrointestinal disease management.

Recently, low-residue diets were removed from the American Academy of Nutrition and Dietetics' Nutrition Care Manual due to the lack of a scientifically accepted quantitative definition and the unavailability of a method to estimate the amount of food residue produced. This narrative review focuses on defining the similarities and/or discrepancies between low-residue and low-fiber diets and on the diagnostic and therapeutic values of these diets in gastrointestinal disease management. Diagnostically, a low-fiber/low-residue diet is used in bowel preparation. A bowel preparation is a cleansing of the intestines of fecal matter and secretions conducted before a diagnostic procedure. Therapeutically, a low-fiber/low-residue diet is part of the treatment of acute relapses in different bowel diseases. The available evidence on low-residue and low-fiber diets is summarized. The main findings showed that within human disease research, the terms "low residue" and "low fiber" are used interchangeably, and information related to the quantity of residue in the diet usually refers to the amount of fiber. Low-fiber/low-residue diets are further explored in both diagnostic and therapeutic situations. On the basis of this literature review, the authors suggest redefining a low-residue diet as a low-fiber diet and to quantitatively define a low-fiber diet as a diet with a maximum of 10 g fiber/d. A low-fiber diet instead of a low-residue diet is recommended as a diagnostic value or as specific therapy for gastrointestinal conditions.

Additional Value of CH4 Measurement in a Combined (13)C/H2 Lactose Malabsorption Breath Test: A Retrospective Analysis.

The lactose hydrogen breath test is a commonly used, non-invasive method for the detection of lactose malabsorption and is based on an abnormal increase in breath hydrogen (H2) excretion after an oral dose of lactose. We use a combined (13)C/H2 lactose breath test that measures breath (13)CO2 as a measure of lactose digestion in addition to H2 and that has a better sensitivity and specificity than the standard test. The present retrospective study evaluated the results of 1051 (13)C/H2 lactose breath tests to assess the impact on the diagnostic accuracy of measuring breath CH4 in addition to H2 and (13)CO2. Based on the (13)C/H2 breath test, 314 patients were diagnosed with lactase deficiency, 138 with lactose malabsorption or small bowel bacterial overgrowth (SIBO), and 599 with normal lactose digestion. Additional measurement of CH4 further improved the accuracy of the test as 16% subjects with normal lactose digestion and no H2-excretion were found to excrete CH4. These subjects should have been classified as subjects with lactose malabsorption or SIBO. In conclusion, measuring CH4-concentrations has an added value to the (13)C/H2 breath test to identify methanogenic subjects with lactose malabsorption or SIBO.

High dose of prebiotics reduces fecal water cytotoxicity in healthy subjects.

SCOPE: In vitro and animal studies have shown differential colonic fermentation of structurally different prebiotics. We evaluated the impact of two structurally different prebiotics (wheat bran extract (WBE, containing arabinoxylan-oligosaccharides) and oligofructose) on colonic fermentation and markers of bowel health in healthy volunteers. METHODS AND RESULTS: Nineteen healthy subjects completed a double-blind, cross-over randomized controlled trial. Interventions with WBE, oligofructose or placebo for 2 wk (week 1: 15 g/day; week 2: 30 g/day) were separated by 2-wk wash-out periods. At the end of each study period, colonic fermentation was characterized through a metabolomics approach. Fecal water genotoxicity and cytotoxicity were determined using the comet and WST-1 assay, respectively, as parameters of gut health. Cluster analysis revealed differences in effects of WBE and oligofructose on colonic fermentation. WBE, but not oligofructose, reduced fecal p-cresol (p = 0.009) and isovaleric acid concentrations (p = 0.022), markers of protein fermentation. Fecal water cytotoxicity was significantly lower after intake of WBE (p = 0.015). Both WBE- and oligofructose-intake tended to reduce fecal water genotoxicity compared to placebo (WBE: p = 0.060; oligofructose: p = 0.057). Changes in fermentation were not related to changes in fecal water toxicity. CONCLUSION: Structurally different prebiotics affect colonic fermentation and gut health in a different way.