Resistant starch in the diet increases breath hydrogen and serum acetate in human subjects

Interactive Effects of Dietary Fiber and Lipid Types Modulate the Predicted Production and Absorption of Cecal and Colorectal Short-Chain Fatty Acids in Growing Pigs

BACKGROUND

High-fiber diets are supplemented with lipids to meet the required energy content, but data on the interactions between dietary fiber (DF) and lipid types on gastrointestinal fermentation in pigs are scant.

OBJECTIVES

This study aimed to use a combination of in vivo and in vitro fermentation methodologies to determine the interactive effects of DF and lipid types on short-chain fatty acid (SCFA) production and absorption and organic matter (OM) fermentability in the cecum and colorectal tract of pigs.

METHODS

Eight ileal- and cecal-cannulated Yorkshire barrows were fed either pectin- or cellulose-containing diets that were supplemented with either corn oil or beef tallow in 2 independent Youden squares with a 2 × 2 factorial arrangement of treatments (n = 6). Ileal and cecal digesta were collected, freeze-dried, and fermented using inoculum from fresh cecal digesta and feces, respectively, to determine individual SCFA production and absorption and fermentability of OM.

RESULTS

Interactions (P < 0.001) between DF and lipid types were observed in which the addition of beef tallow decreased the quantity of cecal and colorectal acetic acid production and cecal acetic absorption, cecal butyric production, predicted cecal OM fermentability, and predicted colorectal propionic acid in pectin diets, but the effects were not observed for cellulose diets. The addition of beef tallow increased (P < 0.001) the production of cecal butyric and propionic acids during in vitro fermentation in cellulose diets and apparent total tract digestibility (ATTD) of OM in pectin diets.

CONCLUSIONS

The interactions between DF and lipids on gastrointestinal fermentation largely depend on the degree of saturation of fatty acids in dietary lipids. The addition of beef tallow selectively decreased the production and absorption of individual SCFAs in pectin and cellulose diets but increased cecal butyric and propionic acid production in cellulose diets and the ATTD of OM in pectin diets.

Detection of changes in regional colonic fermentation in response to supplementing a low FODMAP diet with dietary fibres by hydrogen concentrations, but not by luminal pH

BACKGROUND

Carbohydrate fermentation plays a pivotal role in maintaining colonic health with excessive proximal and deficient distal fermentation being detrimental.

AIMS

To utilise telemetric gas- and pH-sensing capsule technologies for defining patterns of regional fermentation following dietary manipulations, alongside conventional techniques of measuring fermentation.

METHODS

In a double-blind crossover trial, 20 patients with irritable bowel syndrome were fed low FODMAP diets that included no extra fibre (total fibre content 24 g/day), or additional poorly fermented fibre, alone (33 g/day) or with fermentable fibre (45 g/day) for 2 weeks. Plasma and faecal biochemistry, luminal profiles defined by tandem gas- and pH-sensing capsules, and faecal microbiota were assessed.

RESULTS

Plasma short-chain fatty acid (SCFA) concentrations (μmol/L) were median (IQR) 121 (100-222) with fibre combination compared with 66 (44-120) with poorly fermented fibre alone (p = 0.028) and 74 (55-125) control (p = 0.069), but no differences in faecal content were observed. Luminal hydrogen concentrations (%), but not pH, were higher in distal colon (mean 4.9 [95% CI: 2.2-7.5]) with fibre combination compared with 1.8 (0.8-2.8) with poorly fermented fibre alone (p = 0.003) and 1.9 (0.7-3.1) control (p = 0.003). Relative abundances of saccharolytic fermentative bacteria were generally higher in association with supplementation with the fibre combination.

CONCLUSIONS

A modest increase in fermentable plus poorly fermented fibres had minor effects on faecal measures of fermentation, despite increases in plasma SCFA and abundance of fermentative bacteria, but the gas-sensing capsule, not pH-sensing capsule, detected the anticipated propagation of fermentation distally in the colon. The gas-sensing capsule technology provides unique insights into localisation of colonic fermentation.

TRIAL REGISTRATION

ACTRN12619000691145.

H2 generated by fermentation in the human gut microbiome influences metabolism and competitive fitness of gut butyrate producers

BACKGROUND

Hydrogen gas (H2) is a common product of carbohydrate fermentation in the human gut microbiome and its accumulation can modulate fermentation. Concentrations of colonic H2 vary between individuals, raising the possibility that H2 concentration may be an important factor differentiating individual microbiomes and their metabolites. Butyrate-producing bacteria (butyrogens) in the human gut usually produce some combination of butyrate, lactate, formate, acetate, and H2 in branched fermentation pathways to manage reducing power generated during the oxidation of glucose to acetate and carbon dioxide. We predicted that a high concentration of intestinal H2 would favor the production of butyrate, lactate, and formate by the butyrogens at the expense of acetate, H2, and CO2. Regulation of butyrate production in the human gut is of particular interest due to its role as a mediator of colonic health through anti-inflammatory and anti-carcinogenic properties.

RESULTS

For butyrogens that contained a hydrogenase, growth under a high H2 atmosphere or in the presence of the hydrogenase inhibitor CO stimulated production of organic fermentation products that accommodate reducing power generated during glycolysis, specifically butyrate, lactate, and formate. Also as expected, production of fermentation products in cultures of Faecalibacterium prausnitzii strain A2-165, which does not contain a hydrogenase, was unaffected by H2 or CO. In a synthetic gut microbial community, addition of the H2-consuming human gut methanogen Methanobrevibacter smithii decreased butyrate production alongside H2 concentration. Consistent with this observation, M. smithii metabolic activity in a large human cohort was associated with decreased fecal butyrate, but only during consumption of a resistant starch dietary supplement, suggesting the effect may be most prominent when H2 production in the gut is especially high. Addition of M. smithii to the synthetic communities also facilitated the growth of E. rectale, resulting in decreased relative competitive fitness of F. prausnitzii.

CONCLUSIONS

H2 is a regulator of fermentation in the human gut microbiome. In particular, high H2 concentration stimulates production of the anti-inflammatory metabolite butyrate. By consuming H2, gut methanogenesis can decrease butyrate production. These shifts in butyrate production may also impact the competitive fitness of butyrate producers in the gut microbiome. Video Abstract.

Global Impacts of Western Diet and Its Effects on Metabolism and Health: A Narrative Review

The Western diet is a modern dietary pattern characterized by high intakes of pre-packaged foods, refined grains, red meat, processed meat, high-sugar drinks, candy, sweets, fried foods, conventionally raised animal products, high-fat dairy products, and high-fructose products. The present review aims to describe the effect of the Western pattern diet on the metabolism, inflammation, and antioxidant status; the impact on gut microbiota and mitochondrial fitness; the effect of on cardiovascular health, mental health, and cancer; and the sanitary cost of the Western diet. To achieve this goal, a consensus critical review was conducted using primary sources, such as scientific articles, and secondary sources, including bibliographic indexes, databases, and web pages. Scopus, Embase, Science Direct, Sports Discuss, ResearchGate, and the Web of Science were used to complete the assignment. MeSH-compliant keywords such "Western diet", "inflammation", "metabolic health", "metabolic fitness", "heart disease", "cancer", "oxidative stress", "mental health", and "metabolism" were used. The following exclusion criteria were applied: (i) studies with inappropriate or irrelevant topics, not germane to the review's primary focus; (ii) Ph.D. dissertations, proceedings of conferences, and unpublished studies. This information will allow for a better comprehension of this nutritional behavior and its effect on an individual's metabolism and health, as well as the impact on national sanitary systems. Finally, practical applications derived from this information are made.

The gastrointestinal and microbiome impact of a resistant starch blend from potato, banana, and apple fibers: A randomized clinical trial using smart caps

The gastrointestinal (GI) impact of fibers including resistant starch (RS) consumption depends on various types and amounts of fibers, the initial microbiome states, and accurate intake measurements. A randomized clinical trial evaluated the GI impact of varying doses of a novel resistant starch blend (RSB) with smart cap monitoring. RSB contained at least 50% RS and was a proprietary mixture of a potato starch, green banana flour, and apple fiber powder (a source of apple pectin, not resistant starch). The study design randomized participants to one of four arms: 10 g/day of potato starch (0 RSB), 10 g/day of RSB, 10 to 20 to 20 g/day of RSB or 10 to 20 to 30 g/day RSB for two-week intervals over 6 weeks. Results confirmed that while resistant starch of approximately 5 g per day improves GI symptoms at 2, 4, and 6 weeks, it did not demonstrate a detectable effect on short chain fatty acids. Increasing doses of the blend (RSB) led to a decrease in the diarrhea score. Using an estimate of total consumption of RSB based on smart cap recordings of container openings and protocol-specified doses of RSB, a reduction in the sleep disturbance score was associated with higher RSB dose. The exploratory microbiome evaluation demonstrated that among the 16S rRNA gene sequences most associated with the consumption of the novel blend RSB, two belong to taxa of notable interest to human health: Faecalibacterium and Akkermansia.

A Randomized Dietary Intervention to Increase Colonic and Peripheral Blood Short-Chain Fatty Acids Modulates the Blood B- and T-cell Compartments in Healthy Humans

BACKGROUND

Short-chain fatty acids (SCFA) have immune-modulating effects in animal models of disease. However, there is limited evidence that this may occur in humans.

OBJECTIVES

This study aimed to determine the effects of increased exposure to SCFA via dietary manipulation on colonic fermentation and adaptive immune cells.

METHODS

Twenty healthy, young adults (18-45 years of age) underwent a blinded, randomized, cross-over dietary intervention, consuming a high-SCFA producing diet and matched low-SCFA diet for 21 days with 21-day wash-out in between. SCFA were provided through resistant starch, inulin and apple cider vinegar. Blood and 3-day total fecal output were collected at baseline and at the end of each diet. Gas chromatography was used to measure fecal and plasma SCFA. Flow cytometry was used for peripheral blood immuno-phenotyping.

RESULTS

High-SCFA diet was associated with significantly (paired samples Wilcoxon test) higher median [IQR] fecal SCFA concentrations (86.6 [59.0] vs 75.4 [56.2] µmol/g, P = 0.02) and significantly lower median fecal ammonia concentrations (26.2 [14.7] vs 33.4 [18.5] µmol/g, P = 0.04) than the low-SCFA diet. Plasma propionate (9.87 [12.3] vs 4.72 [7.6] µmol/L, P = 0.049) and butyrate (2.85 [1.35] vs 2.02 [1.29] µmol/L, P = 0.03) were significantly higher after high-SCFA diet than after low-SCFA diet. Blood total B cells (184 [112] vs 199 [143] cells/µL, P = 0.04), naive B cells (83 [66] vs 95 [89] cells/µL, P = 0.02), Th1 cells (22 [19] vs 29 [16] cells/µL, P = 0.03) and mucosal-associated invariant T (MAIT) cells (62 [83] vs 69 [114] cells/µL, P = 0.02) were significantly lower after high-SCFA diet than low-SCFA diet.

CONCLUSION

Increasing colonic and peripheral blood SCFA has discrete effects on circulating immune cells in healthy humans following 3-week intervention. Further studies, e.g., in patients with inflammatory disease, are necessary to determine if these changes have immunomodulatory effects, whether these are therapeutically beneficial, and whether prolonged intake might be required. Clinical trial registry: Australian New Zealand Clinical trials registry: ACTRN12618001054202. <https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=375342&isReview=true>.

Guidelines for Transparency on Gut Microbiome Studies in Essential and Experimental Hypertension

Hypertension is a complex and modifiable condition in which environmental factors contribute to both onset and progression. Recent evidence has accumulated for roles of diet and the gut microbiome as environmental factors in blood pressure regulation. However, this is complex because gut microbiomes are a unique feature of each individual reflecting that individual’s developmental and environmental history creating caveats for both experimental models and human studies. Here, we describe guidelines for conducting gut microbiome studies in experimental and clinical hypertension. We provide a complete guide for authors on proper design, analyses, and reporting of gut microbiota/microbiome and metabolite studies and checklists that can be used by reviewers and editors to support robust reporting and interpretation. We discuss factors that modulate the gut microbiota in animal (eg, cohort, controls, diet, developmental age, housing, sex, and models used) and human studies (eg, blood pressure measurement and medication, body mass index, demographic characteristics including age, cultural identification, living structure, sex and socioeconomic environment, and exclusion criteria). We also provide best practice advice on sampling, storage of fecal/cecal samples, DNA extraction, sequencing methods (including metagenomics and 16S rRNA), and computational analyses. Finally, we discuss the measurement of short-chain fatty acids, metabolites produced by the gut microbiota, and interpretation of data. These guidelines should support better transparency, reproducibility, and translation of findings in the field of gut microbiota/microbiome in hypertension and cardiovascular disease.

Successful elevation of circulating acetate and propionate by dietary modulation does not alter T-regulatory cell or cytokine profiles in healthy humans: a pilot study

PURPOSE

Increased circulating concentrations of short-chain fatty acids (SCFA) achieved by ingestion of high-fibre diets is associated with anti-inflammatory effects through promotion of FoxP3+ regulatory T(reg) cells in mouse models. This study aimed to determine whether similar increments in blood SCFA levels can be achieved in humans and whether these are associated with similar immune modulatory effects.

METHODS

In a pilot single-blinded, randomised, controlled cross-over study in ten healthy subjects, the effects were determined of high- (39 g/day) and low-fibre (18 g/day) intake (all food provided) on SCFA (gas chromatography), proportions of Treg cells (flow cytometry) and a panel of cytokines (multiplex methodology) measured in peripheral blood at day 5 of each diet.

RESULTS

Actual fibre intake differed between the diets by 19 [16-21] g/day (P< 0.001). Median [range] total plasma SCFA levels with high-fibre intake were 174.5 [104.8-249.5] µmol/L, which were greater than those associated with low-fibre intake at 59.0 [26.5-79.9] (P < 0.001). Differences were significantly different for both acetate and propionate. The frequencies of total CD4 T cells and T-regulatory cells, and concentrations of inflammatory and anti-inflammatory cytokines were not significantly different between the dietary interventions.

CONCLUSIONS

Plasma SCFA levels can be modulated by altering dietary fibre consumption in healthy individuals with increments similar to those achieved in murine studies. Five days of diet intervention did not result in changes in regulatory T-cell proportions and cytokine concentrations in peripheral blood, and may require longer duration of dietary change.

Decreased maternal serum acetate and impaired fetal thymic and regulatory T cell development in preeclampsia

Maternal immune dysregulation seems to affect fetal or postnatal immune development. Preeclampsia is a pregnancy-associated disorder with an immune basis and is linked to atopic disorders in offspring. Here we show reduction of fetal thymic size, altered thymic architecture and reduced fetal thymic regulatory T (Treg) cell output in preeclamptic pregnancies, which persists up to 4 years of age in human offspring. In germ-free mice, fetal thymic CD4+ T cell and Treg cell development are compromised, but rescued by maternal supplementation with the intestinal bacterial metabolite short chain fatty acid (SCFA) acetate, which induces upregulation of the autoimmune regulator (AIRE), known to contribute to Treg cell generation. In our human cohorts, low maternal serum acetate is associated with subsequent preeclampsia, and correlates with serum acetate in the fetus. These findings suggest a potential role of acetate in the pathogenesis of preeclampsia and immune development in offspring.

Comparison of a sports-hydration drink containing high amylose starch with usual hydration practice in Australian rules footballers during intense summer training

BACKGROUND

Fluid deficits exceeding 1.6% can lead to physical and cognitive impairment in athletes. Sport drinks used by athletes are often hyper-osmolar but this is known to be suboptimal for rehydration in medical settings and does not utilize colonic absorptive capacity. Colonic absorption can be enhanced by fermentative production of short chain fatty acids (SCFA) from substrates such as high amylose maize starch (HAMS). This study therefore compared, in elite Australian Football League (AFL) players at the height of outdoor summer training, a novel dual-action sports oral rehydration strategy that contained HAMS as well as glucose, to their usual rehydration practices (Control). The primary outcome markers of hydration were hematocrit and body weight.

METHODS

A randomized single-blind crossover study was undertaken in thirty-one AFL players; twenty-seven completed the study which was conducted on four days (two days in the Intervention arm and two in Control arm). The Intervention arm was comprised a 50-100 g evening preload of an acetylated HAMS (Ingredion Pty Ltd) followed by consumption of a specially formulated sports oral rehydration solution (SpORS) drink during intense training and recovery. Players followed their usual hydration routine in the Control arm. Quantitative assessments of body weight, hematocrit and urine specific gravity were made at three time-points on each day of training: pre-training, post-training (90 min), and at end of recovery (30-60 min later). GPS tracking monitored player exertion.

RESULTS

Across the three time-points, hematocrit was significantly lower and body weight significantly higher in Intervention compared to Control arms (p < 0.02 and p = 0.001 respectively, mixed effects model). Weights were significantly heavier at all three assessment points for Intervention compared to Control arms (Δ = 0.30 ± 0.13, p = 0.02 pre-training; Δ = 0.43 ± 0.14, p = 0.002 post training; and Δ = 0.68 ± 0.14, p < 0.001 for recovery). Between the pre-training and end-of-recovery assessments, the Control arm lost 0.80 kg overall compared with 0.12 kg in the Intervention arm, an 85% lower reduction of bodyweight across the assessment period.

CONCLUSION

The combination of the significantly lower hematocrit and increased body weight in the Intervention arm represents better hydration not only at the end of training as well as following a recovery period but also at its commencement. The magnitude of the benefit seems sufficient to have an impact on performance and further studies to test this possibility are now indicated.

TRIAL REGISTRATION

Trial is listed on the Australian New Zealand Clinical Trials Registry ( ACTRN 12613001373763 ).

Impact of Altered Intestinal Microbiota on Chronic Kidney Disease Progression

In chronic kidney disease (CKD), accumulation of uremic toxins is associated with an increased risk of CKD progression. Some uremic toxins result from nutrient processing by gut microbiota, yielding precursors of uremic toxins or uremic toxins themselves, such as trimethylamine N-Oxide (TMAO), p-cresyl sulphate, indoxyl sulphate and indole-3 acetic acid. Increased intake of some nutrients may modify the gut microbiota, increasing the number of bacteria that process them to yield uremic toxins. Circulating levels of nutrient-derived uremic toxins are associated to increased risk of CKD progression. This offers the opportunity for therapeutic intervention by either modifying the diet, modifying the microbiota, decreasing uremic toxin production by microbiota, increasing toxin excretion or targeting specific uremic toxins. We now review the link between nutrients, microbiota and uremic toxin with CKD progression. Specific focus will be placed on the generation specific uremic toxins with nephrotoxic potential, the decreased availability of bacteria-derived metabolites with nephroprotective potential, such as vitamin K and butyrate and the cellular and molecular mechanisms linking these toxins and protective factors to kidney diseases. This information provides a conceptual framework that allows the development of novel therapeutic approaches.

Review article: short chain fatty acids as potential therapeutic agents in human gastrointestinal and inflammatory disorders

BACKGROUND

Butyrate, propionate and acetate are short chain fatty acids (SCFA), important for maintaining a healthy colon and are considered as protective in colorectal carcinogenesis. However, they may also regulate immune responses and the composition of the intestinal microbiota. Consequently, their importance in a variety of chronic inflammatory diseases is emerging.

AIMS

To review the physiology and metabolism of SCFA in humans, cellular and molecular mechanisms by which SCFA may act in health and disease, and approaches for therapeutic delivery of SCFA.

METHODS

A PubMed literature search was conducted for clinical and pre-clinical studies using search terms: 'dietary fibre', short-chain fatty acids', 'acetate', 'propionate', 'butyrate', 'inflammation', 'immune', 'gastrointestinal', 'metabolism'.

RESULTS

A wide range of pre-clinical evidence supports roles for SCFA as modulators of not only colonic function, but also multiple inflammatory and metabolic processes. SCFA are implicated in many autoimmune, allergic and metabolic diseases. However, translating effects of SCFA from animal studies to human disease is limited by physiological and dietary differences and by the challenge of delivering sufficient amounts of SCFA to the target sites that include the colon and the systemic circulation. Development of novel targeted approaches for colonic delivery, combined with postbiotic supplementation, may represent desirable strategies to achieve adequate targeted SCFA delivery.

CONCLUSIONS

There is a large array of potential disease-modulating effects of SCFA. Adequate targeted delivery to the sites of action is the main limitation of such application. The ongoing development and evaluation of novel delivery techniques offer potential for translating promise to therapeutic benefit.

Sufficient intake of high amylose cornstarch maintains high colonic hydrogen production for 24 h in rats

Colonic hydrogen (H2) can suppress oxidative stress and damage in the body. We examined the minimum requirement of high amylose cornstarch (HAS) to maintain high colonic H2 production for 24 h. Ileorectostomized and sham-operated rats were fed a control diet supplemented with or without 20% HAS for 7 days. Colonic starch utilization was determined. Next, rats were fed the control diet with or without 10% or 20% HAS for 14 or 28 days, respectively. Breath and flatus H2 excretion for 24 h was measured. 1.04 g of resistant fraction in HAS was utilized for 24 h by colonic bacteria. High H2 excretion was not maintained for 24 h in rats fed the 10% HAS diet, from which only 0.89 g of resistant starch was estimated to be delivered. High colonic H2 production for 24 h would be maintained by delivering more HAS to the large intestine than is utilized.

Ghrelin, CCK, GLP-1, and PYY(3-36): Secretory Controls and Physiological Roles in Eating and Glycemia in Health, Obesity, and After RYGB

The efficacy of Roux-en-Y gastric-bypass (RYGB) and other bariatric surgeries in the management of obesity and type 2 diabetes mellitus and novel developments in gastrointestinal (GI) endocrinology have renewed interest in the roles of GI hormones in the control of eating, meal-related glycemia, and obesity. Here we review the nutrient-sensing mechanisms that control the secretion of four of these hormones, ghrelin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), and peptide tyrosine tyrosine [PYY(3-36)], and their contributions to the controls of GI motor function, food intake, and meal-related increases in glycemia in healthy-weight and obese persons, as well as in RYGB patients. Their physiological roles as classical endocrine and as locally acting signals are discussed. Gastric emptying, the detection of specific digestive products by small intestinal enteroendocrine cells, and synergistic interactions among different GI loci all contribute to the secretion of ghrelin, CCK, GLP-1, and PYY(3-36). While CCK has been fully established as an endogenous endocrine control of eating in healthy-weight persons, the roles of all four hormones in eating in obese persons and following RYGB are uncertain. Similarly, only GLP-1 clearly contributes to the endocrine control of meal-related glycemia. It is likely that local signaling is involved in these hormones' actions, but methods to determine the physiological status of local signaling effects are lacking. Further research and fresh approaches are required to better understand ghrelin, CCK, GLP-1, and PYY(3-36) physiology; their roles in obesity and bariatric surgery; and their therapeutic potentials.

The metabolic fate of acetate in cancer

Recent high-profile reports have reignited an interest in acetate metabolism in cancer. Acetyl-CoA synthetases that catalyse the conversion of acetate to acetyl-CoA have now been implicated in the growth of hepatocellular carcinoma, glioblastoma, breast cancer and prostate cancer. In this Review, we discuss how acetate functions as a nutritional source for tumours and as a regulator of cancer cell stress, and how preventing its (re)capture by cancer cells may provide an opportunity for therapeutic intervention.

High wholegrain barley β-glucan lowers food intake but does not alter small intestinal macronutrient digestibility in ileorectostomised rats

Using barley cultivars differing widely in β-glucan content, we aimed to determine their effects on small intestinal macronutrient digestion in 24 ileorectostomised rats. The rats were fed 1 of 4 experimental diets, each containing a different barley variety, for 11 d. The diets had a content of 0, 2.1, 2.6 and 4.3 g of β-glucan/100 g. Feed intake and faecal excretion of fat, protein, starch, and non-starch polysaccharides were determined in the final 5 d of the study and apparent macronutrient digestibility calculated. Higher dietary levels of β-glucan (2.6% and 4.3%) lowered feed intake (by 15 and 19%, respectively) but final body weight was only lowered by the 4.3% β-glucan diet relative to rats fed the 0% β-glucan diet (all ps < 0.05). Protein, lipid and starch digestibility was unrelated to the dietary β-glucan content. Higher dietary levels of barley β-glucan lower feed intake of ileorectostomised rats, which is independent of intestinal fermentation and unrelated to macronutrient digestibility.

Review article: insights into colonic protein fermentation, its modulation and potential health implications

BACKGROUND

Beneficial effects of carbohydrate fermentation on gastrointestinal health are well established. Conversely, protein fermentation generates harmful metabolites but their relevance to gastrointestinal health is poorly understood.

AIM

To review the effects of increased protein fermentation on biomarkers of colonic health, factors influencing fermentative activity and potential for dietary modulation to minimise detrimental effects.

METHODS

A literature search was performed in PubMed, Medline, EMBASE and Google scholar for clinical and pre-clinical studies using search terms - 'dietary protein', 'fermentation', 'putrefaction', 'phenols', 'sulphide', 'branched-chain fatty acid', 'carbohydrate fermentation', 'gastrointestinal'.

RESULTS

High protein, reduced carbohydrate diets alter the colonic microbiome, favouring a potentially pathogenic and pro-inflammatory microbiota profile, decreased short-chain fatty acid production and increased ammonia, phenols and hydrogen sulphide concentrations. These metabolites largely compromise the colonic epithelium structure, causing mucosal inflammation but may also directly modulate the enteric nervous system and intestinal motility. Increased protein fermentation as a result of a high-protein intake can be attenuated by addition of oligosaccharides, resistant starch and nonstarch polysaccharides and a reduction in total protein or specifically, aromatic and sulphur-containing amino acids. These factors may have clinical importance as novel therapeutic approaches to problems, in which protein fermentation may be implicated, such as malodorous flatus, irritable bowel syndrome, ulcerative colitis and prevention of colorectal cancer.

CONCLUSIONS

The direct clinical relevance of excessive protein fermentation in the pathogenesis of irritable bowel syndrome, malodorous flatus and ulcerative colitis are underexplored. Manipulating dietary carbohydrate and protein intake have potential therapeutic applications in such settings and warrant further clinical studies.

Kiwifruit fibre level influences the predicted production and absorption of SCFA in the hindgut of growing pigs using a combined in vivo-in vitro digestion methodology

Combined in vivo (ileal cannulated pig) and in vitro (faecal inoculum-based fermentation) digestion methodologies were used to predict the production and absorption of SCFA in the hindgut of growing pigs. Ileal and faecal samples were collected from animals (n 7) fed diets containing either 25 or 50 g/kg DM of kiwifruit fibre from added kiwifruit for 14 d. Ileal and faecal SCFA concentrations normalised for food DM intake (DMI) and nutrient digestibility were determined. Ileal digesta were collected and fermented for 38 h using a fresh pig faecal inoculum to predict SCFA production. The predicted hindgut SCFA production along with the determined ileal and faecal SCFA were then used to predict SCFA absorption in the hindgut and total tract organic matter digestibility. The determined ileal and faecal SCFA concentrations (e.g. 8·5 and 4·4 mmol/kg DMI, respectively, for acetic acid for the low-fibre diet) represented only 0·2-3·2 % of the predicted hindgut SCFA production (e.g. 270 mmol/kg DMI for acetic acid). Predicted production and absorption of acetic, butyric and propionic acids were the highest for the high-fibre diet (P0·05). In conclusion, determined ileal and faecal SCFA concentrations represent only a small fraction of total SCFA production, and may therefore be misleading in relation to the effect of diets on SCFA production and absorption. Considerable quantities of SCFA are produced and absorbed in the hindgut of the pig by the fermentation of kiwifruit.

Pasting, textural and thermal properties of resistant starch prepared from potato (Solanum tuberosum) starch using pullulanase enzyme

Pullulanase enzyme (40 U/g, 10 h) was used for enzymatic hydrolysis of potato starch which was autoclaved (121 °C/30 min), stored under refrigeration (4 °C/24 h) and lyophilized. Comparison of morphological, pasting, textural and thermal properties among native hydrolysed starch (V2) and gelatinized hydrolysed starch (V3) prepared using pullulanase enzyme on potato starch (V1) were studied. The round, elliptical, irregular and oval shape with smooth surface of V1 was replaced with amorphous mass of cohesive structure leading to loss of granular appearance in V2 and V3. The percentage of amylose and resistant starch content of V2 (27.16 %) and (24.16 %); V3 (51.44 %) and (29.35 %) was higher when compared to V1 (22.17 %) and (3.62 %). The swelling power of V1 observed at 60 °C (0.85 %) and 95 °C (8.64 %) were significantly different from V2 at 60 °C (4.97 %) and 95 °C (7.66 %) and that of V3 at 60 °C (5.82 %) and 95 °C (7.5 %). Significance difference in water solubility (7.62 %) and absorption capacity (6.11 %) was noted in V3 when compared with V1 and V2 owing to amylose/amylopectin content. Increase in water solubility and absorption capacity along with decrease in swelling power of V2 and V3 was noted due to hydrolytic and thermal process. RS obtained from hydrolysis showed a reduction in viscosity, indicating the rupture of starch molecules. The viscosity was found to be inversely proportional to the RS content in the sample. The thermal properties of RS increased due to the retrogradation and recrystallization (P < 0.05).

Colonic hydrogen generated from fructan diffuses into the abdominal cavity and reduces adipose mRNA abundance of cytokines in rats

Hydrogen (H2) protects against inflammation-induced oxidative stress. Nondigestible saccharides (NDSs) enhance colonic H2 production. We examined whether colonic H2 transfers to tissues in the abdominal cavity and whether it affects expression of proinflammatory cytokines. In Expts. 1 and 2, rats were fed diets containing fructooligosaccharides [FOSs; 25 (Expt. 1) and 50 g/kg (Expts. 1 and 2)] for 7 and 14 d, respectively. The no-FOS diet was used as the control diet. At the end of the experiment, H2 excretion and the portal H2 concentration were significantly greater in the FOS group than in the control group. In the FOS group, the arterial H2 concentration was no more than 1.5% of the portal H2 concentration (P = 0.03). The H2 concentration in abdominal cavity tissues, especially adipose tissue, in the FOS group was 5.6- to 43-fold of that in the control group (P < 0.05). The H2 content in the abdominal cavity in the FOS group was 11-fold of that in the control group (P < 0.05). In Expt. 3, rats were fed a high-fat diet containing FOS and inulin (50 g/kg) for 28 d. The area under the curve for H2 excretion between 0 and 28 d and portal and adipose H2 concentrations were significantly higher in the FOS and inulin groups than in the high-fat control group. Adipose mRNA abundance of nuclear factor kappa-light-chain-enhancer of activated B cells 1 was lower in the FOS group than in the control group (P = 0.02) and those of interleukin-6 and chemokine (C-C motif) ligand 2 tended to be lower (P < 0.11). Colonic H2 generated from NDS diffuses to the abdominal cavity before transferring to abdominal tissues. Reduced cytokine expression by FOS feeding might be dependent on increased colonic H2. Colonic H2 may have important implications in the suppressive effect on metabolic syndrome via oxidative stress.

Role of the gut microbiota in human nutrition and metabolism

The human gastrointestinal tract harbors trillions of bacteria, most of which are commensal and have adapted over time to the milieu of the human colon. Their many metabolic interactions with each other, and with the human host, influence human nutrition and metabolism in diverse ways. Our understanding of these influences has come through breakthroughs in the molecular profiling of the phylogeny and the metabolic capacities of the microbiota. The gut microbiota produce a variety of nutrients including short-chain fatty acids, B vitamins, and vitamin K. Because of their ability to interact with receptors on epithelial cells and subepithelial cells, the microbiota also release a number of cellular factors that influence human metabolism. Thus, they have potential roles in the pathogenesis of metabolic syndrome, diabetes, non-alcoholic fatty liver disease, and cognition, which extend well beyond their traditional contribution to nutrition. This review explores the roles of the gut microbiota in human nutrition and metabolism, and the putative mechanisms underlying these effects.

Seven transmembrane G protein-coupled receptor repertoire of gastric ghrelin cells

The molecular mechanisms regulating secretion of the orexigenic-glucoregulatory hormone ghrelin remain unclear. Based on qPCR analysis of FACS-purified gastric ghrelin cells, highly expressed and enriched 7TM receptors were comprehensively identified and functionally characterized using in vitro, ex vivo and in vivo methods. Five Gαs-coupled receptors efficiently stimulated ghrelin secretion: as expected the β1-adrenergic, the GIP and the secretin receptors but surprisingly also the composite receptor for the sensory neuropeptide CGRP and the melanocortin 4 receptor. A number of Gαi/o-coupled receptors inhibited ghrelin secretion including somatostatin receptors SSTR1, SSTR2 and SSTR3 and unexpectedly the highly enriched lactate receptor, GPR81. Three other metabolite receptors known to be both Gαi/o- and Gαq/11-coupled all inhibited ghrelin secretion through a pertussis toxin-sensitive Gαi/o pathway: FFAR2 (short chain fatty acid receptor; GPR43), FFAR4 (long chain fatty acid receptor; GPR120) and CasR (calcium sensing receptor). In addition to the common Gα subunits three non-common Gαi/o subunits were highly enriched in ghrelin cells: GαoA, GαoB and Gαz. Inhibition of Gαi/o signaling via ghrelin cell-selective pertussis toxin expression markedly enhanced circulating ghrelin. These 7TM receptors and associated Gα subunits constitute a major part of the molecular machinery directly mediating neuronal and endocrine stimulation versus metabolite and somatostatin inhibition of ghrelin secretion including a series of novel receptor targets not previously identified on the ghrelin cell.

Dietary resistant starch dose-dependently reduces adiposity in obesity-prone and obesity-resistant male rats

BACKGROUND

Animal studies show that diets containing resistant starch (RS) at levels not achievable in the human diet result in lower body weight and/or adiposity in rodents. We aimed to determine whether RS dose-dependently reduces adiposity in obesity-prone (OP) and obesity-resistant (OR) rats.

METHODS

Male Sprague-Dawley rats (n=120) were fed a moderate-fat, high-energy diet for 4 wk. Rats that gained the most weight (40%) were classified as obesity-prone (OP) and obesity-resistant (OR) rats were the 40% that gained the least weight. OP and OR rats were randomly allocated to one of six groups (n=8 for each phenotype). One group was killed for baseline measurements, the other five groups were allocated to AIN-93 based diets that contained 0, 4, 8, 12 and 16% RS (as high amylose maize starch) for 4 wk. These diets were matched for total carbohydrate content. At 0, 4 and 7 wk from the start of the study insulin sensitivity was calculated by homeostasis model assessment of insulin resistance (HOMA-IR) and adiposity was determined by dual-energy X-ray absorptiometry (DXA). At 8 wk, rats were euthanized and fat pad weights, intestinal digesta short chain fatty acid (SCFA) pools and plasma gut hormone levels were determined.

RESULTS

Obesity prone rats gained less weight with 4, 12 and 16% RS compared to 0% RS, but the effect in OR animals was significant only at 16% RS. Irrespective of phenotype, diets containing ≥8% RS reduced adiposity compared to 0% RS. Energy intake decreased by 9.8 kJ/d for every 4% increase in RS. All diets containing RS increased total SCFA pools in the caecum and lowered plasma GIP concentrations compared to the 0% RS, whereas plasma GLP-1 and PYY were increased when the diet contained at least 8% RS. Insulin sensitivity was not affected by RS.

CONCLUSION

RS in amounts that could be potentially consumed by humans were effective in reducing adiposity and weight gain in OP and OR rats, due in part to a reduction in energy intake, and changes in gut hormones and large bowel carbohydrate fermentation.

Pectin and high-amylose maize starch increase caecal hydrogen production and relieve hepatic ischaemia-reperfusion injury in rats

We investigated whether the feeding of high H2-generating dietary fibre and resistant starch (RS) could suppress hepatic ischaemia-reperfusion (IR) injury, which results from oxidative stress, in rats fed a pectin (Pec) or high-amylose maize starch (HAS) diet. Male Sprague-Dawley rats were fed a control (C) diet, with or without Pec (0-5 % Pec) or HAS (0-30 % HAS) supplementation for 7 d. Portal H2 concentration showed a significant dose-dependent increase with the amount of Pec or HAS supplementation. Plasma alanine and aspartate aminotransferase activities remarkably increased in the C rats (5 % cellulose) due to IR treatment, while it decreased significantly or showed tendencies to decrease in 5 % Pec and 20 % HAS diet-fed rats. The hepatic oxidised glutathione (GSSG):total glutathione ratio increased significantly in IR rats maintained on the C diet compared with sham-operated rats. On the other hand, reduced glutathione (GSH):total glutathione and GSH:GSSG ratios decreased significantly. The GSSG:total glutathione ratio that increased due to IR treatment decreased significantly on HAS and Pec intake, while GSH:total glutathione and GSH:GSSG ratios increased significantly. Hepatic sinusoids of IR rats fed the C diet were occluded, but those of IR rats fed the Pec diet were similar to those in the sham-operated rats. In conclusion, we found that Pec or HAS, which enhance H2 generation in the large intestine, alleviated hepatic IR injury. The present study demonstrates another physiological significance of dietary fibre and RS.

African americans may have to consume more than 12 grams a day of resistant starch to lower their risk for type 2 diabetes

African Americans have a high prevalence rate of type 2 diabetes mellitus (DM). High-maize 260 (National Starch and Chemical Co., Bridgewater, NJ, USA) resistant starch (RS) is a promising food ingredient to reduce risk factors for type 2 DM. A 14-week, double-blind, crossover design study was conducted with African American male (n = 8) and female (n = 7) subjects at risk for type 2 DM. All subjects consumed bread containing 12 g of added RS or control bread (no added RS) for 6 weeks, separated by a 2-week washout period. There were no significant differences in the subjects' fasting plasma glucose levels due to the consumption of the RS bread versus the control bread. Fructosamine levels were significantly lower after consumption of both RS and control bread than at baseline. However, we found no significant difference in fructosamine levels due to treatment effects, i.e., RS bread intake versus the control bread. There were no significant differences in insulin or C-reactive protein levels due to treatment, gender, or sequence effects. Mean homeostasis model assessment of insulin resistance decreased to normal values (>2.5) at the end of the 14-week study, although there were no significant treatment effects. The results of this study suggest that African Americans may need to consume more than 12 g/day of RS to lower their risk for type 2 DM.

Failure of d-psicose absorbed in the small intestine to metabolize into energy and its low large intestinal fermentability in humans

Experiments with rats have produced data on the metabolism and energy value of d-psicose; however, no such data have been obtained in humans. The authors assessed the availability of d-psicose absorbed in the small intestine by measuring carbohydrate energy expenditure (CEE) by indirect calorimetry. They measured the urinary excretion rate by quantifying d-psicose in urine for 48 hours. To examine d-psicose fermentation in the large intestine, the authors measured breath hydrogen gas and fermentability using 35 strains of intestinal bacteria. Six healthy subjects participated in the CEE test, and 14 participated in breath hydrogen gas and urine tests. d-Psicose fermentation subsequent to an 8-week adaptation period was also assessed by measuring hydrogen gas in 8 subjects. d-Psicose absorbed in the small intestine was not metabolized into energy, unlike glucose, because CEE did not increase within 3 hours of d-psicose ingestion (0.35 g/kg body weight [BW]). The accumulated d-psicose urinary excretion rates were around 70% for 0.34, 0.17, and 0.08 g/kg BW of ingested d-psicose. Low d-psicose fermentability was observed in intestinal bacteria and breath hydrogen gas tests, in which fructooligosaccharide (0.34, 0.17, and 0.08 g/kg BW) was used as a positive control because its available energy is known to be 8.4 kJ/g. Based on the results of the plot of breath hydrogen concentration vs calories ingested, the energy value of d-psicose was expected to be less than 1.6 kJ/g. Incremental d-psicose fermentability subsequent to an adaptation period was not observed.

Evaluation of the effect of four fibers on laxation, gastrointestinal tolerance and serum markers in healthy humans

BACKGROUND

Average dietary fiber intake in the United States is roughly half of the recommended amount. As new dietary fiber products are introduced to increase fiber intake, it is critical to evaluate the physiological effects of such fibers.

AIMS

This study examined the effect of 4 fibers derived from maize or tapioca on fecal chemistry, gastrointestinal (GI) symptoms and serum markers of chronic disease.

METHODS

Twenty healthy subjects completed the single-blind crossover study in which 12 g/day of fiber (pullulan, Promitor Resistant Starch, soluble fiber dextrin or Promitor Soluble Corn Fiber) or placebo (maltodextrin) were consumed for 14 days followed by a 21-day washout. GI symptom surveys were completed (days 3 and 14), stools were collected (days 11-14), diet was recorded (days 12-14) and fasting blood samples were obtained (day 15).

RESULTS

The 4 test fibers were well tolerated, with mild to moderate GI symptoms. Total short-chain fatty acid (SCFA) concentrations did not differ among the treatments. Fecal pH and individual SCFAs were affected by some treatments. Stool weight and serum markers of chronic disease did not change with these treatments.

CONCLUSION

Increasing fiber intake by 12 g/day was well tolerated and may have a positive impact on colon health due to fermentation.

Acute effects of intravenous and rectal acetate on glucagon-like peptide-1, peptide YY, ghrelin, adiponectin and tumour necrosis factor-alpha

In animals, colonic infusion of SCFA does not affect glucagon-like peptide-1 (GLP-1) release whereas intravenous infusion does and SCFA may directly stimulate peptide YY (PYY) release. It is unknown whether SCFA and their route of administration affect human blood concentrations of GLP-1 and PYY. Our aim was to conduct a pilot study to determine the effects of intravenous and rectal acetate on blood concentrations of GLP-1, PYY, ghrelin, adiponectin and TNF-alpha in hyperinsulinaemic human subjects. Six hyperinsulinaemic female subjects were given 20 mmol sodium acetate intravenously, 60 mmol acetate rectally, or normal saline rectally or intravenously on four separate occasions in randomised order, with blood samples collected at 0, 10, 15, 30, 45 and 60 min. Change in plasma PYY was significantly higher after acetate and rectal infusions (9.69 and 13.78 pg/ml) compared with saline and intravenous (0.60 and - 3.1 pg/ml; P < 0.01), respectively. Change in plasma GLP-1 was increased by rectal and acetate infusions (0.25 and 0.23 mmol/l) v. intravenous and saline ( - 0.26 and - 0.19 mmol/l; P < 0.01). Acetate decreased TNF-alpha v. saline ( - 0.8 and 0.15 pg/ml; P < 0.05). Rectal infusions increased TNF-alpha and ghrelin (0.2 and 98.27 pg/ml) v. intravenous ( - 0.9 and - 40 pg/ml; P < 0.01). There was no effect of treatment on plasma adiponectin. These preliminary results suggest that acetate raises plasma PYY and GLP-1, and suppresses TNF-alpha. Also, distending the rectum increases PYY, GLP-1, TNF-alpha and ghrelin in hyperinsulinaemic females. Increasing colonic fermentation products, particularly acetate, could yield a new mechanism for modifying weight gain.

Gastrointestinal effects of low-digestible carbohydrates

Low-digestible carbohydrates (LDCs) are carbohydrates that are incompletely or not absorbed in the small intestine but are at least partly fermented by bacteria in the large intestine. Fiber, resistant starch, and sugar alcohols are types of LDCs. Given potential health benefits (including a reduced caloric content, reduced or no effect on blood glucose levels, non-cariogenic effect) the prevalence of LDCs in processed foods is increasing. Many of the benefits of LDCs are related to the inability of human digestive enzymes to break down completely the carbohydrates into absorbable saccharides and the subsequent fermentation of unabsorbed carbohydrates in the colon. As a result, LDCs may affect laxation and cause gastrointestinal effects, including abdominal discomfort, flatus, and diarrhea, especially at higher or excessive intakes. Such responses, though transient, affect the perception of the well-being of consumers and their acceptance of food products containing LDCs. Current recommendations for fiber intake do not consider total LDC consumption nor recommend an upper limit for LDC intake based on potential gastrointestinal effects. Therefore, a review of published studies reporting gastrointestinal effects of LDCs was conducted. We included only studies published in refereed journals in English. Additionally, we excluded studies of subjects with incomplete or abnormal functioning gastrointestinal tracts or where antibiotics, stimulant laxatives, or other drugs affecting motility were included. Only in studies with a control period, either placebo treatment or no LDC treatment, were included. Studies must have included an acceptable measure of gastrointestinal effect. Sixty-eight studies and six review articles were evaluated. This review describes definitions, classifications, and mechanisms of LDCs, evaluates published human feeding studies of fifteen LDCs for associations between gastrointestinal effects and levels of LDC intake, and presents recommendations for LDC consumption and further research.

Influence of dietary fiber on inflammatory bowel disease and colon cancer: importance of fermentation pattern

The benefits of dietary fiber on inflammatory bowel disease may be related to the fermentative production of butyrate in the colon, which appears to decrease the inflammatory response. The benefits of dietary fiber against colon cancer may be related to both fermentative and non-fermentative processes, although poorly fermentable fibers appear more influential. Dietary fiber fermentation profiles are important in determining optimal fibers for colonic health, and may be a function of structure, processing conditions, and other food components. A greater understanding of the relationships between fermentation rate and dietary fiber structure would allow for development of dietary fibers for optimum colonic health.

Effects of GI and content of indigestible carbohydrates of cereal-based evening meals on glucose tolerance at a subsequent standardised breakfast

OBJECTIVE

To evaluate the impact of four low-glycaemic index (GI) and one high-GI cereal-based evening meals on glucose tolerance at a subsequent standardised breakfast.

DESIGN

Wheat kernels, barley kernels, spaghetti, spaghetti with added wheat bran and white wheat bread (WWB) were consumed in the evening in a random order at five different occasions. At the subsequent breakfast, blood glucose, serum insulin, plasma short chain fatty acid, plasma free fatty acid (FFA) and breath hydrogen were measured.

SETTING

The study was performed at Applied Nutrition and Food Chemistry, Lund University, Sweden.

SUBJECTS

Fifteen healthy volunteers were recruited. One subject was later excluded owing to abnormal blood glucose values.

RESULTS

The blood glucose response (0-120 min) to the standardised breakfast was significantly lower after consuming barley kernels in the evening compared with evening meals with WWB (P=0.019) or spaghetti+wheat bran (P=0.046). There were no significant differences in insulin concentrations at breakfast. Breath hydrogen excretion at breakfast was significantly higher after an evening meal with barley kernels compared with WWB, wheat kernels or spaghetti (P=0.026, 0.026 and 0.015, respectively), and the concentration of plasma propionate at breakfast was significantly higher following an evening meal with barley kernels compared with an evening meal with WWB (P=0.041). In parallel, FFA concentrations were significantly lower after barley kernels compared with WWB (P=0.042) or spaghetti evening meals (P=0.019).

CONCLUSIONS

The improved glucose tolerance at breakfast, following an evening meal with barley kernels appeared to emanate from suppression of FFA levels, mediated by colonic fermentation of the specific indigestible carbohydrates present in this product, or, to the combination of the low-GI features and colonic fermentation.

Bioavailability of cellobiose by tolerance test and breath hydrogen excretion in humans

OBJECTIVE

Prebiotic substances have the property of intestinal fermentation. Cellobiose has a beta-1,4 linkage, so it is resistant to hydrolysis by human small intestinal disaccharidase and, hence, reaches the colon undigested. Until this study, it was unclear whether cellobiose has fermentability or bioavailability. The objectives of this study were to clarify whether cellobiose is fermented in the large intestine and to estimate the available energy from cellobiose intake by using tolerance tests and breath hydrogen tests in healthy female subjects.

METHODS

Ten healthy young women (20.5 +/- 2.1 y) who did not develop diarrhea after ingesting 30 g of cellobiose in a previous experiment were recruited. Tolerance tests and breath hydrogen tests for 25 g of cellobiose or glucose were carried out at least 2 wk apart. Blood samples were collected before and at 30-min intervals up to 3 h after ingestion. Breath gas samples were collected simultaneously before and at 30-min intervals up to 6 h after ingestion of cellobiose or glucose. Blood glucose and insulin levels and the concentration of breath hydrogen were analyzed.

RESULTS

When 25 g of cellobiose was ingested, there was no increase in blood glucose or insulin secretion, but these markers increased remarkably with glucose ingestion. The excretion of breath hydrogen gas after cellobiose ingestion was significantly greater than that after glucose ingestion.

CONCLUSIONS

Orally ingested cellobiose was well fermented in human large intestine, and its available energy was estimated to be about 2 kcal/g.

The fermentation of different dietary fibers is associated with fecal clostridia levels in men

Only a few reports have compared the fermentation of pectin and cellulose using the hydrogen-breath test, and no studies have examined the relation between the hydrogen breathing pattern and colonic microflora. Using breath-hydrogen measurements, we investigated whether different dietary fibers (DFs) were fermented differently and whether there were individual differences after ingestion of the same DF; we also examined the relation between individual fecal microflora and the fermentation of DF. Results of hydrogen tests in 14 men were compared after they had ingested 20 g of pectin, 20 g of cellulose, or 6 g of lactulose (a DF-like substance). We examined the relation between the breath hydrogen results and the subjects' fecal microflora. We defined significant fermentation (i.e., positive cases) as a continuous rise in hydrogen in the expiratory air of >19 ppm. The subjects were divided into 3 groups according to their hydrogen breath test pattern, i.e., positive for lactulose and pectin (Group LP, n = 4); positive for lactulose alone (Group L, n = 7); and negative for pectin, cellulose, and lactulose (Group N, n = 3). Individual differences were noted in subjects from Group LP and Group L. The detection frequency of lecithinase-negative clostridia was higher in Group LP than in the other groups (P < 0.05), and the detection frequency and the number of lecithinase-positive clostridia were higher in Groups LP and L than in Group N (P < 0.05). These findings suggest that the Clostridium species are associated with hydrogen production. The hydrogen breath test results of DFs depend on both the type of DF and the individual colonic microflora. The amount and constitution of colonic microflora might be predicted by the hydrogen-breath test using different DFs.