Fecal Short-chain Fatty Acid Concentrations Research Articles

Daily Intake of High Dietary Fiber Slows Accelerated Colonic Transit Induced by Restrain Stress in Rats

Stress and central corticotropin releasing factor (CRF) are contributing factors to the pathogenesis of irritable bowel syndrome (IBS). It has been shown that restraint stress and central CRF stimulate colonic motility in rats. Short-chain fatty acids (SCFAs) are produced by bacterial fermentation from dietary fibers. It is controversial whether daily intake of dietary fiber is beneficial for patients with diarrhea-predominant IBS. We studied whether dietary fiber intake affects colonic transit and motility stimulated by restraint stress and central CRF in rats. Corn starch is digested almost completely in the small intestine, while potato starch shows substantial resistance to alpha-amylase and its consumption leads to stimulation of large-bowel fermentation. Four weeks after a corn starch, potato starch, or usual diet (rat chow), colonic transit and motility stimulated by restraint stress and intracisternal (ic) injection of CRF were studied. Fecal concentration of SCFAs in the cecum was measured by high-performance liquid chromatography (HPLC). Four-week treatment with potato starch diet significantly increased cecal concentrations of SCFAs, compared to treatment with corn starch diet. Accelerated colonic transit induced by stress and ic injection of CRF (1 microg) were significantly attenuated in rats receiving potato starch diet compared to rats receiving corn starch diet. The incidence of unformed stool (diarrhea) induced by stress and CRF was also reduced in rats receiving potato starch diet compared to rats receiving corn starch diet and usual diet. It is suggested that daily intake of a high-fiber diet may prevent stress- and CRF-induced acceleration of colonic transit and diarrhea. This study may contribute to treatment for the patients of diarrhea-predominant IBS.

Method of extraction influences the detected short chain fatty acid (SCFA) concentration in human fecal samples

Short chain fatty acids including acetate, propionate, and butyrate are produced by colonic bacteria during fermentation of dietary fiber. Fecal SCFA concentrations estimate total SCFA production, although 95% of SCFA are absorbed from the lumen. No “gold standard” for SCFA extraction from fecal samples has been established. This study compared two published SCFA extraction methods (aqueous‐AQ and diethyl ether‐DE) and (1) determined the reproducibility of each method by analyzing 10 samples from 1 common fecal specimen and (2) compared the two methods by extracting SCFA with each method from 10 individual fecal specimens. SCFAs were detected via GC‐FID. Data was compared by ANOVA and Wilcoxon rank‐sum test (SAS 9.1). AQ and DE extraction resulted in significantly different (P = .0001) mean SCFA concentrations when measuring 10 samples from the same fecal specimen. The distribution and means were significantly different for each SCFA when comparing the AQ and DE methods. AQ had higher mean acetate (P = 0.0015) concentrations, while the DE had higher mean propionate (P = 0.0147) and butyrate (P = 0.0002) concentrations. Formic acid, added in the AQ method, may be eluting with acetate causing increased acetate concentration. We conclude that SCFA extraction method significantly affects detected SCFA concentrations. Further research should be conducted to identify the optimal extraction method.

Evaluation of fermentable oligosaccharides in diets fed to dogs in comparison to fiber standards

Blends of fermentable oligosaccharides in combination with nonfermentable fiber, cellulose, were evaluated for their ability to serve as dietary fibers in dog foods. Using a 6 x 6 Latin square design, 6 diets were evaluated that contained either no supplemental fiber, beet pulp, cellulose, or blends of cellulose, fructooligosaccharides, and yeast cell wall added at 2.5% of the diet. Six ileal-cannulated dogs were fed 175 g of their assigned diet twice daily. Chromic oxide served as a digestibility marker. Nutrient digestibility, fecal microbial populations, fermentative end products, and immunological indices were measured. Total tract DM and OM digestibilities were lowest (P < 0.05) for the cellulose treatment. Crude protein digestibility was lower (P < 0.05) for the treatments containing carbohydrate blends. The cellulose treatment had the lowest (P < 0.05) concentration of bacteria, and all diets containing fermentable fiber had greater (P < 0.05) fecal bifidobacteria concentrations compared with the diets without supplemental fermentable fiber. Lactobacilli concentrations tended to be greater (P < 0.08) in treatments containing fermentable fiber compared with the cellulose treatment. Bifidobacteria and lactobacilli concentrations were similar for the beet pulp treatment compared with the fermentable oligosaccharide blends. Total fecal short-chain fatty acid concentration was greater for the beet pulp treatment (P < 0.05) compared with the control and cellulose treatments. The treatments containing fermentable fiber had greater (P < 0.05) fecal butyrate concentrations compared with cellulose and control treatments. Immune indices were not affected by treatment. Our results suggest that dog foods containing blends of fermentable and nonfermentable carbohydrates produce similar physiological results as dog food containing beet pulp as a fiber source. Therefore, blends of these carbohydrates could be useful substitutes for beet pulp in dog foods.

Soyoligosaccharide Increases Fecal Bifidobacteria Counts, Short-Chain Fatty Acids, and Fecal Lipid Concentrations in Young Korean Women

The effects of soyoligosaccharide intake on human fecal characteristics were investigated by measuring the fecal water content, bifidobacteria counts, pH, and concentrations of short-chain fatty acids (SCFAs) and lipids. Sixteen young women were randomly assigned to one of two groups: (1) 1.5 g/day soyoligosaccharide intake group [low soyoligosaccharide (LSO)] or (2) 3 g/day soyoligosaccharide intake group [high soyoligosaccharide (HSO)]. The experimental period was 30 days, and fecal samples were collected every 7 days. The number of bifidobacteria in feces was increased significantly in the HSO group. Of the fecal SCFAs, propionate and butyrate concentrations were significantly increased in the HSO group. The excretions of total lipids in feces were significantly increased in both the LSO and HSO groups. These results demonstrate that a soyoligosaccharide intake of 3 g/day increases fecal bifidobacteria counts, SCFA concentrations, and fecal lipid output in Korean young women.

Konjac acts as a natural laxative by increasing stool bulk and improving colonic ecology in healthy adults

Objective Konjac glucomannan (KGM) has been shown to relieve constipation, which could be associated with increased stool bulk and improved colonic ecology. Methods This placebo-controlled study consisted of a 21-d placebo period, a 7-d adaptation period when volunteers consumed KGM progressively, and a 21-d KGM-supplemented period (1.5 g/meal, 4.5 g/d). Eight healthy adults consumed 7-d cycle menus of typical low-fiber Chinese food throughout the study. The gastrointestinal response was monitored daily. Stools were fully collected on days 15 to 21 of placebo and KGM periods to determine the fecal mass, components, microflora, and short-chain fatty acid contents. Results The KGM supplement significantly increased the mean defecation frequency (number/day), wet stool weight, and dry stool weight (g/d) by ∼27.0% ( P < 0.05), 30.2% ( P < 0.05), and 21.7% ( P < 0.05), respectively. The dry fecal mass increased mainly in the plant and soluble material, whereas bacterial mass tended to increase from 12.9 ± 1.6 to 13.6 ± 2.7 g/d ( P > 0.05). However, KGM significantly promoted the fecal concentrations (log counts/g wet feces) of lactobacilli ( P < 0.05) and total bacteria ( P < 0.05), and promoted the daily output (log counts per day) of bifidobacteria ( P < 0.05), lactobacilli ( P < 0.05), and total bacteria ( P < 0.05) as evaluated by the fluorescence in situ hybridization method. KGM supplement also promoted colonic fermentation as shown in the decreased fecal pH ( P < 0.05) and increased fecal short-chain fatty acid concentrations ( P < 0.05). Conclusion Supplementation of KGM into a low-fiber diet promoted the defecation frequency in healthy adults, possibly by increasing the stool bulk, thus promoting the growth of lactic acid bacteria and colonic fermentation.

Chitosan Shifts the Fermentation Site Toward the Distal Colon and Increases the Fecal Short-Chain Fatty Acids Concentrations in Rats

Chitosan has been shown to have lipid-lowering effects, but little is known about the effect of chitosan on colonic pH value and short-chain fatty acid (SFCA) concentration. This study was designed to investigate the effect of chitosan on colonic bacterial fermentation and fecal bacterial enzyme activity in rats fed a diet enriched in cholesterol. Male Sprague-Dawley rats were fed a diet containing 5% cellulose (CE) or 5% chitosan (CS) for 15 days. Significantly increased fecal cholesterol and triacylglycerols contents were observed in rats fed the chitosan diet. In addition, lower cecal acetate and butyrate concentrations and higher fecal acetate, propionate, and butyrate concentrations were observed in rats fed the CS diet when compared to those fed the CE diet. Although rats fed with the CS diet exhibited an elevated cecal (cecum with contents) weight and higher pH value, no significant difference in fecal pH value was observed between the CE group and the CS group. Chitosan significantly decreased fecal mucinase and beta-glucuronidase activities. Results from this study show that chitosan may alter fecal bacterial enzyme activities and SCFA concentrations and the beneficial effects of chitosan on the colonic environment may occur in the distal colon in rats.

Long-Term Administration of 4G-.BETA.-D-Galactosylsucrose (Lactosucrose) Enhances Intestinal Calcium Absorption in Young Women: A Randomized, Placebo-Controlled 96-wk Study

This study determined the effect of long-term administration of 4(G)-beta-D-galactosylsucrose (lactosucrose; LS) on intestinal calcium absorption. In a randomized, single-blind, parallel-group study, LS (n=9, 6.0 g twice daily) or a placebo (maltose; n=8, 6.0 g twice daily) was administered to healthy young women for 92 wk: the study also included a 4-wk post-administration period. All participants completed the study. Dietary nutrient intake; fecal weight, pH, and moisture content; fecal concentrations of short-chain fatty acids (SCFA), putrefactive products, ammonia, and minerals (calcium, magnesium, phosphorus, and iron); and serum calcium and osteocalcin concentrations were measured every 24 wk. Urinary pyridinoline (PYR) and deoxypyridinoline (DPD), and urinary calcium excretion were measured every 12 wk. Significant effects of oligosaccharide treatment, time, and the interaction between oligosaccharide treatment and time were observed for fecal pH, SCFA, ammonia, and putrefactive product values (p<0.05). Fecal pH, ammonia, and putrefactive product values decreased in the LS group, and the fecal SCFA concentration significantly increased during the administration period; these changes were not observed 4 wk post-administration. To examine the mineral balance of calcium, magnesium, and phosphorus in detail, all the participants completed a 6-d mineral balance study, sometime between week 56 and 60 of the longer study. During the mineral balance study, the daily calcium intake was set at 400 mg; all feces and urine were collected each day for 6 d after an 8-d acclimation period. In the balance study, fecal calcium excretion was significantly lower in the LS group than in the placebo group (p<0.05), and apparent calcium absorption and retention, apparent magnesium and phosphorus absorption, and magnesium retention were significantly higher in the LS group than in the placebo group (p<0.05). Our results suggest that the administration of LS produces a long-term enhancement of intestinal calcium absorption in healthy young women with lower than recommended calcium intakes.

Effects of total enteral nutrition supplemented with a multi-fibre mix on faecal short-chain fatty acids and microbiota

Impaired bowel function is frequent in tube-fed patients, and diarrhoea is associated with decreased faecal short-chain fatty acids (SCFAs) concentrations. The aim of this study was to compare the effects of a multi-fibre-enriched formula (15 g/l) and a fibre-free isoenergetic and isonitrogenous formula on faecal SCFAs and microbiota in long-term enteral nutrition (EN) patients. Fifteen patients [11M/4F, aged 53 (40-73)] on total EN for 43 (1-310) months for dysphagia received a fibre-free formula for 7 days, followed in a random order by either the multi-fibre-enriched formula for 14 days and then the fibre-free formula for 14 days or vice versa. Stool samples were taken at the end of each period for measurement of SCFAs levels and different groups of bacteria. Results were compared with non-parametric tests. After the multi fibre EN, there was a significant median increase in total faecal SCFAs (+84%), butyrate (+20%) and acetate (+147%) compared with baseline. A significant increase in the total number of bacteria as determined with the molecular method was found after the multi-fibre EN period compared with the fibre-free EN period. There were no concomitant changes in the dominant groups of intestinal bacteria. In long-term EN patients, a polymeric enteral formula supplemented with a mixture of six fibres increases faecal SCFAs and total number of bacteria, which may contribute to an improved bowel function.

Fructooligosaccharides and Fiber Partially Prevent the Alterations in Fecal Microbiota and Short-Chain Fatty Acid Concentrations Caused by Standard Enteral Formula in Healthy Humans

The intestinal microbiota are important during enteral tube feeding because they exert colonization resistance and produce SCFAs. However, the effect of the enteral formula composition on major bacterial groups of the microbiota has not been clearly defined. The aim of this study was to investigate the effect of enteral formulas with and without prebiotic fructooligosaccharides (FOS) and fiber on the fecal microbiota and SCFAs. Healthy subjects (n = 10; 4 men, 6 women) consumed both a standard enteral formula and one containing FOS (5.1 g/L) and fiber (8.9 g/L) as a sole source of nutrition for 14 d in a randomized, double-blind, crossover trial with a 6-wk washout phase. Fecal samples were collected at the start and end of each formula phase, and were analyzed for major bacterial groups and SCFA concentrations using fluorescent in situ hybridization and GLC, respectively. Although there were reductions in total fecal bacteria due to both formula treatments, concentrations were higher after the FOS/fiber formula period compared with the standard formula period (11.2 +/- 0.2 vs. 11.0 +/- 0.2 log(10) cells/g, P = 0.005). The FOS/fiber formula increased bifidobacteria (P = 0.004) and reduced clostridia (P = 0.006). Compared with the standard formula, the FOS/fiber formula resulted in higher concentrations of total SCFA (332.4 +/- 133.8 vs. 220.1 +/- 124.5 micromol/g, P = 0.022), acetate (219.6 +/- 96.3 vs. 136.8 +/- 74.5 micromol/g, P = 0.034) and propionate (58.4 +/- 37.4 vs. 35.6 +/- 25.5 micromol/g, P = 0.02). This study demonstrates that standard enteral formula leads to adverse alterations to the fecal microbiota and SCFA concentrations in healthy subjects, and these alterations are partially prevented by fortification of the formula with FOS and fiber.

Effects ofSaccharomyces boulardiion fecal short-chain fatty acids and microflora in patients on long-term total enteral nutrition

Diarrhea is a significant problem in patients on total enteral nutrition (TEN) and may involve changes in intestinal short chain fatty acids or microflora. Recent studies suggest that the probiotic yeast Saccharomyces boulardii (Sb) may decrease its incidence. The aim of this study was to assess the effects of Sb on fecal flora and short-chain fatty acids (SCFA) in patients on long-term TEN. Ten patients (3 females, 7 males, 59+/-5.5 years), on TEN for a median of 13 mo (1-125), and 15 healthy volunteers (4 females, 11 males, 32+/-2.0 years) received Sb (0.5 g bid PO) for 6 d. Two stool samples were taken before, on the last 2 d and 9-10 d after treatment, for SCFA measurement and for culture and bacterial identification. Values (mean+/-SE) were compared using sign tests and ANOVA. Fecal butyrate levels were lower in patients (10.1+/-2.9 mmol/kg) than in controls (19.2+/-3.9, P = 0.02). Treatment with Sb increased total fecal SCFA levels in patients (150.2+/-27.2 vs 107.5+/-18.2 mmol/kg, P = 0.02) but not in controls (129.0+/-28.6 vs 113.0+/-15.2 mmol/kg, NS). At the end of treatment with Sb, patients had higher fecal butyrate (16.0+/-4.4 vs 10.1 [2.9] mmol/kg, P = 0.004). Total SCFAs remained high 9 d after treatment was discontinued. Before the treatment, the anaerobe to aerobe ratio was lower in patients compared to controls (2.4+/-2.3 vs 69.8+/-1.8, P = 0.003). There were no significant changes in the fecal flora of TEN patients. Sb-induced increase of fecal SCFA concentrations (especially butyrate) may explain the preventive effects of this yeast on TEN-induced diarrhea.

Effects of metronidazole and oligofructose on faecal concentrations of sulphate-reducing bacteria and their activity in human volunteers

Objective. Sulphate-reducing bacteria (SRB) have been implicated in the aetiology of ulcerative colitis. Sulphide produced from reduction of sulphate by SRB is highly toxic to colonocytes and can impair their metabolic function. The aim of this study was to investigate the modulation of the colonic bacterial flora using metronidazole and the prebiotic oligofructose on the concentration and activity of SRB. Material and methods. Healthy volunteers were randomly allocated to take metronidazole (5 days), oligofructose (12 days) or both metronidazole (5 days) and oligofructose (12 days). At days 0, 5, 12 and 19, stool samples were cultured, and their pH measured; concentrations of sulphate, hydrogen sulphide, short-chain fatty acids (SCFAs) were measured and the sulphate reduction rates (SRRs) determined. Results. In SRB-positive volunteers (n=16) faecal SRB concentrations fell with metronidazole (95% CI, 2.19, 3.36 p<0.0001) even when combined with oligofructose (95% CI 2.32, 4.01 p<0.0001). Faecal anaerobe concentrations fell with metronidazole and bifidobacterial concentrations rose with oligofructose irrespective of SRB status. Faecal SRRs fell with metronidazole irrespective of the presence of faecal SRB (95% CI 29.0, 56.1 p<0.0001). No changes in faecal sulphate concentrations were seen. Faecal hydrogen sulphide concentrations fell with oligofructose in SRB-positive volunteers (95% CI 0.14, 0.53 p=0.002). Faecal SCFA concentrations fell with metronidazole (−103.7, −19.6, p=0.007) and rose with oligofructose (9.9, 83.1 p=0.016). Conclusions. The study shows that metronidazole, but not oligofructose, reduced the concentration and activity of faecal SRB. This reduction had no impact on faecal concentrations of sulphate and hydrogen sulphide, suggesting that other methods of hydrogen sulphide production are more important. Oligofructose causes a reduction in faecal hydrogen sulphide, and an increase in SCFA concentrations may thus have a therapeutic role in patients with ulcerative colitis.

Randomized placebo‐controlled trial assessing the effect of bifidobacteria‐fermented milk on active ulcerative colitis

Probiotics are efficacious for treating and maintaining remission of ulcerative colitis. To conduct a randomized placebo-controlled trial of bifidobacteria-fermented milk supplementation as a dietary adjunct in treating active ulcerative colitis. Twenty patients with mild to moderate, active, ulcerative colitis randomly received 100 mL/day of bifidobacteria-fermented milk or placebo for 12 weeks with conventional treatment. Clinical and endoscopic activity indices and histological scores were similar in the two groups before treatment. Although improvements were significant in both groups, the clinical activity index was significantly lower in the bifidobacteria-fermented milk than in the placebo group after treatment. The post-treatment endoscopic activity index and histological score were significantly reduced in the bifidobacteria-fermented milk, but not the placebo group. Increases in faecal butyrate, propionate and short-chain fatty acid concentrations were significant in the bifidobacteria-fermented milk, but not the placebo group. No adverse effects were observed in either group. Supplementation with this bifidobacteria-fermented milk product is safe and more effective than conventional treatment alone, suggesting possible beneficial effects in managing active ulcerative colitis. This is a pilot study and further larger studies are required to confirm the result these preliminary results.

Effect of type and level of dietary fibre and starch on ileal and faecal microbial activity and short-chain fatty acid concentrations in growing pigs

AbstractA repeated 4 ✕ 4 Latin square design was conducted with eight ileal cannulated castrated pigs to investigate the effect of source of dietary fibre and starch on ileal and faecal microflora and short-chain fatty acid concentrations. Four experimental diets based on cooked rice were supplied with one of two fibre-rich sources (sugar-beet pulp, S; wheat bran, W) and another two diets were prepared with (P) or without (C) potato starch. The experimental periods were 14 days, consisting of 7 days of adaptation to each diet, followed by 4 days of collection of ileal digesta and 3 days of collection of faeces. Ileal digesta were collected daily in a randomized order 0 (just before feeding the morning meal), 2, 4, 6 and 8 h after feeding the morning meal. Fresh faecal samples were also collected. Ileal pH was lower in pigs given diet P, 2 and 4 h after feeding, respectively. For all four diets ileal pH reached a minimum 4 h after feeding. Faecal pH was higher for diets P and W compared with diets C and S. The highest density of ileal coliform bacteria was found 4 h after feeding for all diets. Compared with other diets, the inclusion of potato starch resulted in an increased density of ileal enterococci at 0 h and an increased density of ileal lactic acid bacteria and lactobacilli, 2 and 6 h after feeding, respectively. The density of ileal enterococci reached a maximum 4 h after feeding for all diets. With the exception of 8 h after feeding, when a higher density of total anaerobes was observed for diet P, no significant differences were seen in the populations of yeasts and total anaerobes between the experimental diets. The concentration of formate in the ileum was high, while low concentrations of acetate, propionate and butyrate were observed for all diets. A lowered level of acetate was found for diet S on all sampling occasions. On a dry-matter basis, the counts of various faecal bacteria were increased by the inclusion of the fibre sources, and a higher level of faecal butyrate was found with the inclusion of potato starch or the fibre sources as compared with diet C, whereas no significant effects on the counts of various bacteria were observed with potato starch supplementation. Overall, the present results indicate that the addition of dietary fibre to pig diets resulted in an enhanced microbial fermentation.

A dose-response experiment evaluating the effects of oligofructose and inulin on nutrient digestibility, stool quality, and fecal protein catabolites in healthy adult dogs.

In this experiment, three concentrations (0.3, 0.6, and 0.9% of diet, as-fed basis) of two fructans, oligofructose (OF) and inulin, were tested against a 0% supplemental fructan control. Seven ileal-cannulated adult female dogs were fed a meat-based, kibbled diet and assigned to treatments in a 7 x 7 Latin square design. Dietary supplementation of fructans had no effect on nutrient intakes or ileal digestibilities. Total-tract digestibilities of DM, OM, and CP decreased (P < 0.05) as a result of dietary OF and inulin supplementation. Dogs fed the control diet had a DM total-tract digestibility of 83.0%. The percentages of fecal DM for dogs fed the control and 0.3, 0.6, and 0.9% OF were 36.6, 33.3, 32.8, and 31.7%, respectively. When compared with the control, OF (P < 0.01) and inulin (P < 0.01) supplementation increased fecal ammonia concentrations. Higher fecal short-chain fatty acid (SCFA; P < 0.10) and isovalerate concentrations (P < 0.01) were noted for dogs fed both fructans. Total fecal SCFA for dogs fed the control diet and 0.3, 0.6, and 0.9% OF were 406.4, 529.9, 538.3, and 568.8 micromol/g of feces (DM basis), respectively. Dogs fed 0.3, 0.6, and 0.9% inulin had total fecal SCFA of 472.2, 468.8, and 471.5 micromol/g of feces (DM basis), respectively. Linear increases were observed in putrescine (P < 0.11), cadaverine (P < 0.07), spermidine (P < 0.12), and total amines (P < 0.05) in feces of dogs fed OF. Lower fecal phenol (P < 0.08) and total phenol (P < 0.04) concentrations occurred in dogs fed inulin, along with a linear decrease (P < 0.08) in total phenols with OF supplementation. Total fecal phenols for dogs fed the control, 0.3, 0.6, and 0.9% inulin were 3.03, 1.86, 1.97, and 2.23 micromol/g of feces (DM basis), respectively. Low-level dietary inclusion of inulin and OF positively affected indices known to be associated with gut health of the dog without seriously compromising nutrient digestibility or stool quality. Overall, the 0.9% OF treatment resulted in the best responses, including no adverse effect on nutrient intakes, ileal digestibilities, or stool quality, as well as increased fecal SCFA and decreased fecal phenols. The biological responses due to inulin were more variable.

Nutrient digestibilities, microbial populations, and protein catabolites as affected by fructan supplementation of dog diets.

Fructans are fermentable carbohydrates and include short-chain fructooligosaccharides (scFOS), inulin, and hydrolyzed inulin (oligofructose, OF). Two studies with dogs were designed to examine the effects of low concentrations of fructans on nutrient digestibilities, fecal microbial populations, and endproducts of protein fermentation, and fecal characteristics. In Exp. 1, 11 adult male beagles were fed corn-based, kibbled diets supplemented with or without OF to provide 1.9 +/- 0.6 g/d. Dietary inclusion of OF decreased (P < 0.05) nutrient digestibilities, but did not affect fecal characteristics. Increasing OF concentration tended (P < 0.06) to linearly decrease fecal ammonia concentrations, but not those of branched-chain fatty acids (BCFA), amines, indole, or phenols. Fecal concentrations of total short-chain fatty acids (SCFA) and butyrate tended to be higher in OF-supplemented dogs (P < 0.10), as was the ratio of bifidobacteria to total anaerobes (P = 0.15). In Exp. 2, ileally cannulated adult female hounds were fed a meat-based kibbled diet and were assigned to four scFOS treatments (0, 1, 2, or 3 g/d) in a 4 x 4 Latin square design. Ileal nutrient digestibilities tended to increase (P < 0.15) with increasing concentrations of scFOS. On a DMI basis, fecal output tended to decrease linearly (P < 0.10) in response to increasing scFOS supplementation, whereas fecal score tended to exhibit a quadratic response (P = 0.12). In general, fecal concentrations of SCFA, BCFA, ammonia, phenols, and indoles were not altered by supplemental scFOS. Supplementation of scFOS increased fecal concentrations of total aerobes (P < 0.05) and decreased concentrations of Clostridium perfringens (P < 0.05). From these data, it seems that low levels of supplemental fructans have divergent effects on nutrient digestibility and fermentative endproducts, but do not adversely affect nutrient digestibility or fecal characteristics and may improve colonic microbial ecology in dogs.

Fermentation and bulking capacity of indigestible carbohydrates: the case of inulin and oligofructose.

The bulking index (i.e. the increase in faecal fresh weight in gram per gram indigestible carbohydrate ingested) with oligofructose and inulin is similar to that produced with other easily fermented fibres such as pectins and gums. Most studies in man have been performed at a level of 15 g/d and more investigations on lower intakes are needed to appoint the least intake for an effect. Concerning short-chain fatty acids (SCFA) most studies have been using oligofructose and points at an increased butyric acid formation in the caecum of rats. In one study on rats with inulin high caecal proportions of propionic acid were obtained. As inulin has a higher molecular weight than oligofructose it might be speculated if this could be a reason to the different SCFA-profile formed. No effects on faecal concentrations of SCFA in humans have been revealed with inulin and oligofructose, which neither is expected as most of the SCFA formed during the fermentation already has been absorbed or utilized by the colonic mucosa.

Fermentation and bulking capacity of indigestible carbohydrates: the case of inulin and oligofructose

The bulking index (i.e. the increase in faecal fresh weight in gram per gram indigestible carbohydrate ingested) with oligofructose and inulin is similar to that produced with other easily fermented fibres such as pectins and gums. Most studies in man have been performed at a level of 15 g/d and more investigations on lower intakes are needed to appoint the least intake for an effect. Concerning short-chain fatty acids (SCFA) most studies have been using oligofructose and points at an increased butyric acid formation in the caecum of rats. In one study on rats with inulin high caecal proportions of propionic acid were obtained. As inulin has a higher molecular weight than oligofructose it might be speculated if this could be a reason to the different SCFA-profile formed. No effects on faecal concentrations of SCFA in humans have been revealed with inulin and oligofructose, which neither is expected as most of the SCFA formed during the fermentation already has been absorbed or utilized by the colonic mucosa.

Diet, length of gestation, and fecal short chain fatty acids in healthy premature neonates.

Excretion of fecal short-chain fatty acids (SCFAs) may indicate changes in colonic or colonocyte metabolism. The aim of this study was to detect the influence of gestational age and feeding practices on SCFA concentrations and profiles in healthy preterm infants. A total of 198 fecal samples (28 infants) were collected from 8 to 21 days of age from 3 groups of preterm infants born at 33 to 37 weeks of gestation and fed either breast milk (group I) or Nutramigen, a lactose-free formula (group II), and extremely preterm infants born before 33 weeks of gestation and fed breast milk (group III). Total SCFA concentrations and SCFA profiles were analyzed using a gas chromographic (GC) procedure. Total fecal SCFA excretion did not differ significantly between group I (mean, 24.0 micromol/g; range, 1.3 to 118.8 micromol/g) and group II (mean, 23.0 micromol/g; range, 3.0 to 73.3 micromol/g). Conversely, differences occurred between SCFA profiles and became significant after day 17. The main differences were a significant increase in the butyric acid concentration (12% versus 30%) with group II. Compared with group I, fecal SCFA concentrations were 3.2-fold lower (7.4 micromol/g; range, 0.3 to 37.4 micromol/g) in group III with no significant changes in the profiles. Fecal SCFA excretion may vary in absence of any digestive disease. During this study, in terms of gestational age, total SCFA concentrations were significantly lower in extremely premature infants compared with infants born less premature, despite their known higher deficiency in intestinal lactase activity. In terms of diet, the absence of lactose did not lead to a decrease in colonic fermentation and induced changes in SCFA patterns. These new baseline data may offer clues to further development of milk formulas.

Effects of fructooligosaccharide on bowel function and indicators of nutritional status in constipated elderly men

Five subjects completed the study consisting of a 30-d low fiber control period and another 30-d experimental period in which 10 g of FO was supplemented to a 3-d cycle menus. Status of large bowel function was monitored daily. Feces were completely collected on last 5 d of each period to determine the fecal characteristics and fecal short-chain fatty acid (SCFA) contents. Nutrient intake, body weight, arm anthropometric parameters, serum albumin, total protein, triglyceride, cholesterol, and electrolytes were measured as indices of nutritional status. Incorporation of FO significantly increased the defecation frequency, daily stool weight, weight per stool and decreased the use of enema. Concentrations of fecal acetate, propionate, i-butyrate, n-butyrate, i-valerate and n-valerate increased by 3–18 fold in the experimental period. Nutrient intake and anthropometric indices remained constant throughout the study. Serum concentrations of Na and K were decreased and concentrations of Ca and P were increased in the experimental period. Other blood biochemical parameters were not affected by the treatment. Therefore, we conclude that supplementation of FO was able to alleviate constipation, increase stool weight and fecal SCFA concentrations without affecting plasma lipid concentrations in the normolipidemic, constipated elderly men.

Rye Bread Improves Bowel Function and Decreases the Concentrations of Some Compounds That Are Putative Colon Cancer Risk Markers in Middle-Aged Women and Men

Cereal fiber may reduce the risk of colorectal cancer by diluting colonic contents due to increased fecal output, by accelerating intestinal transit, by increasing fecal frequency and by altering bacterial metabolism. The effects of whole-meal rye bread on some putative colon cancer risk markers were investigated in 17 healthy Finnish subjects using a randomized crossover trial with two 4-wk bread consumption periods and a 4-wk washout period between the bread periods. White wheat bread was used as a control. Test breads covered a minimum of 20% of the daily energy intake (range, 4330-14, 033 kJ/d). Intestinal transit time, stool weight, fecal bacterial enzyme activities and short-chain fatty acid, ammonia, diacylglycerol (DAG) and bile acid concentrations in feces (expressed per gram wet feces) were measured. Whole-meal rye bread significantly increased fecal output and fecal frequency and shortened mean intestinal transit time compared with wheat bread in both women and men. Activities of beta-glucuronidase and beta-glucosidase (expressed per gram wet feces) were significantly lower in men and urease activity significantly higher in women during the rye bread period (RBP). Fecal butyrate concentration was higher during the RBP in men. Fecal ammonia and DAG concentrations did not differ between bread periods. Fecal total and secondary bile acid concentrations were significantly lower during RBP in both women and men. This study shows that whole-meal rye bread significantly improves bowel function in healthy adults and may decrease the concentration of some compounds that are putative colon cancer risk markers.