Perspective: Physiologic Importance of Short-Chain Fatty Acids from Nondigestible Carbohydrate Fermentation.

In recent years, it has become increasingly obvious that dietary fiber or nondigestible carbohydrate (NDC) consumption is critical for maintaining optimal health and managing symptoms of metabolic disease. In accordance with this, the US FDA released its first official definition of dietary fiber in 2016 for regulation of Nutrition and Supplement Facts labels. Included in this definition is the requirement of an isolated or synthetic NDC to produce an accepted physiologic health benefit, such as improved laxation or reduced fasting cholesterol concentrations, upon consumption. Even though NDC fermentation and production of short-chain fatty acids elicit many physiologic effects, including serving as a source of energy for colonocytes, curbing glycemic response and satiety, promoting weight loss, enhancing mineral absorption, reducing systemic inflammation, and improving intestinal health, the process of fermentation is not considered a physiologic endpoint. Instead, expensive and laborious clinical trials must be conducted and an accepted physiologic benefit observed. In this review, we discuss the physiologic importance of NDC fermentation through extensive examination of clinical evidence and propose that the degree of fermentability of an NDC, rather than the endpoints of a clinical trial, may be appropriate for classifying it as a dietary fiber.

Effect of a viscous fiber-containing nutrition bar on satiety of patients with type 2 diabetes.

To assess the satiety-promoting effect of a novel viscous fiber-containing nutrition bar, overweight and obese adult subjects with type 2 diabetes (n=99) were randomized into a double blind, crossover study. They were fed a 300kcal lunch consisting of viscous fiber-containing nutrition bars (VF) or commercial nutrition control bars designed for people with diabetes (CH). VF resulted in a 27.1% increase in fullness (p<0.05), a 15.8% decrease in prospective consumption (p<0.001), and a 14.2% decrease in hunger (p<0.001) in the 120-240min post-lunch areas under the curve (AUC) compared to CH, but no differences were observed for nausea or thirst (p>0.05). Similar results were noted for 0-300min AUC values. VF were associated with greater frequencies and intensities of abdominal distention (p<0.001) and flatulence (p<0.001), and greater frequency of stools (p<0.001) compared to CH, but there were no differences in mean or maximum (loosest) stool consistency (p>0.05). Overall, these results suggest that VF could be a useful tool in weight management of type 2 diabetes.

An oral supplement enriched with fish oil, soluble fiber, and antioxidants for corticosteroid sparing in ulcerative colitis: a randomized, controlled trial.

BACKGROUND & AIMS: N-3 fatty acids from fish oil, antioxidants, and short-chain fatty acids (SCFAs) produced during the fermentation of soluble fiber may attenuate inflammation associated with ulcerative colitis (UC). We assessed the efficacy of a nutritionally balanced oral supplement enriched with fish oil, fructooligosaccharides, gum arabic, vitamin E, vitamin C, and selenium on disease activity and medication use in adults with mild to moderate UC. METHODS: A total of 121 patients with UC and a disease activity index (DAI) from 3-9 on a 12-point scale were block randomized for extent of disease and smoking status. In addition to their usual diet, patients consumed 18 oz of the oral supplement or a carbohydrate-based placebo formula each day for 6 months. Clinical and histologic responses were assessed at 3 and 6 months or at the final visit. A change in average prednisone use between groups was tested by using a linear mixed-effects model. RESULTS: Eighty-six patients completed the study. Baseline characteristics were not different between groups except for a higher total DAI score in the oral supplement group (7.3 +/- 1.3; n = 36) compared with the placebo group (6.2 +/- 2.0; n = 50) ( P < .05). Both groups showed significant and similar degree of improvement at 6 months in DAI (-2.5 for oral supplement and -2.8 for placebo) and histologic index (-1.9 for oral supplement vs. -2.0 for placebo). Both intent-to-treat and completed patients given oral supplement had a significantly greater rate of decrease in the dose of prednisone required to control clinical symptoms over 6 months as compared with the placebo group ( P < .001). CONCLUSIONS: The improvement in clinical response combined with a decreased requirement for corticosteroids suggest that this enriched oral supplement can be a useful adjuvant therapy in patients with UC.

Inclusion of guar gum and alginate into a crispy bar improves postprandial glycemia in humans.

A novel induced viscosity fiber (IVF) crispy bar was formulated with the viscous dietary fibers alginate and guar gum. To evaluate the glycemic response and gastrointestinal tolerance to IVF crispy bars, nondiabetic healthy adult subjects (n = 48) were studied in a randomized, double-masked, crossover design. The control crispy bars and IVF crispy bars were identical except for the 2 dietary fibers contained in the experimental (IVF) bars. After an overnight fast, subjects consumed test bars containing 50 g carbohydrate. Their capillary blood glucose response was determined for 180 min postprandially. When subjects consumed IVF, the incremental blood glucose excursions were reduced (P < 0.05) at 15, 30, 45, and 120 min. At 180 min, the subjects' blood glucose concentration was maintained above the basal blood glucose concentration for both bars. Compared with controls, the incremental peak blood glucose concentration was reduced (P < 0.001) 30% when subjects consumed IVF. When subjects consumed IVF, the positive incremental area under the curve for glucose was reduced (P < 0.01) by 33% compared with controls. In the 24-h postprandial period after each treatment, the frequency and intensity of gastrointestinal tolerance symptoms did not differ. In conclusion, compared with a control crispy bar, the IVF crispy bar attenuated the postprandial glycemic excursion without gastrointestinal intolerance in healthy adult subjects.

Pullulan is a slowly digested carbohydrate in humans.

Pullulan is an extracellular polysaccharide excreted by the fungus Aureobasidium pullulans. To evaluate the glycemic and breath hydrogen responses and gastrointestinal tolerance to pullulan, nondiabetic healthy adult subjects (n = 28) were studied in a randomized, double-masked, crossover design. After an overnight fast, subjects consumed beverages containing 50 g of carbohydrate from either maltodextrin (control) or pullulan. Capillary blood glucose response was determined for 180 min postprandially. Breath hydrogen response was determined for 8 h postprandially. Compared with control, incremental peak blood glucose concentration was reduced (P < 0.01) when subjects consumed pullulan (4.24 +/- 0.35 vs. 1.97 +/- 0.10 mmol/L). In addition, pullulan reduced (P < 0.01) the positive incremental area under the glucose curve by 50%. When subjects consumed pullulan, the incremental blood glucose excursions were reduced (P < 0.01) at 15, 30, 45, 60 and 90 min, but were maintained above basal glucose concentrations at 150 and 180 min. At 180 min, the blood glucose concentration was higher (P < 0.05) when subjects consumed pullulan compared with control, supporting the hypothesis that pullulan is digested slowly. Breath hydrogen concentrations were increased (P < 0.01) at 3, 4, 5, 6, 7 and 8 h postprandially when subjects consumed pullulan. In the first 24-h postprandial period, the frequency and intensity of flatulence was higher (P < 0.05) after subjects consumed pullulan compared with control. In conclusion, pullulan attenuated the postprandial glycemic excursion compared with an equivalent maltodextrin challenge. Pullulan also increased breath hydrogen excretion and the incidence of gastrointestinal intolerance symptoms, indicating that a portion of pullulan was malabsorbed.

Fructooligosaccharides and Lactobacillus acidophilus modify gut microbial populations, total tract nutrient digestibilities and fecal protein catabolite concentrations in healthy adult dogs.

The objective of this research was to determine whether fructooligosaccharides (FOS) and (or) Lactobacillus acidophilus (LAC) affected concentrations of gut microbial populations, fermentative end products and nutrient digestibilities in healthy adult dogs. Two experiments were performed using 40 adult dogs (20 dogs/experiment). Dogs in each experiment were randomly assigned to one of 4 treatments. Twice daily, treatments were given orally via gelatin capsules: 1) 2 g sucrose + 80 mg cellulose; 2) 2 g FOS + 80 mg cellulose; 3) 2 g sucrose + 1 x 10(9) colony forming units (cfu) LAC; or 4) 2 g FOS + 1 x 10(9) cfu LAC. Data were analyzed by the General Linear Models procedure of SAS. In Experiment 1, FOS resulted in lower (P = 0.08) Clostridium perfringens and greater fecal butyrate (P = 0.06) and lactate (P < 0.05) concentrations. In Experiment 2, FOS supplementation increased (P < 0.05) bifidobacteria, increased lactobacilli (P = 0.08), increased fecal lactate (P = 0.06) and butyrate (P < 0.05), and decreased (P < 0.05) fecal ammonia, isobutyrate, isovalerate and total branched-chain fatty acid concentrations. Dogs fed LAC had the highest fecal concentrations of hydrogen sulfide and methanethiol in Experiment 1 and dimethyl sulfide in Experiment 2, whereas dogs fed FOS had the lowest concentrations of these compounds. Overall, FOS appeared to enhance indices of gut health by positively altering gut microbial ecology and fecal protein catabolites, whereas LAC was more effective when fed in combination with FOS rather than fed alone.

Fructooligosaccharides and Lactobacillus acidophilus modify bowel function and protein catabolites excreted by healthy humans.

The objective of this experiment was to determine whether supplementation with fructooligosaccharides (FOS) and (or) Lactobacillus acidophilus (LAC) affected bowel function and fermentative end-product concentrations in feces of healthy humans. Subjects (n = 68) were enrolled in a randomized, double-blind, placebo-controlled, parallel study design. After a 4-wk baseline period, subjects consumed one of the following treatments twice daily for 4 wk: 1) 3 g sucrose + 80 mg cornstarch; 2) 3 g FOS + 80 mg cornstarch; 3) 3 g sucrose + 1 x 10(9) colony-forming units (cfu) LAC; or 4) 3 g FOS + 1 x 10(9) cfu LAC. Subjects completed 7-d bowel function forms and 3-d dietary records before collection of fresh stool samples at wk 4, 6 and 8. Statistical analyses were performed on differences from baseline using the General Linear Models procedure of SAS. Fructooligosaccharides decreased fecal ammonia (P = 0.07) and isovalerate (P = 0.12) concentrations at wk 6. At wk 8, FOS tended (P = 0.11) to increase fecal putrescine concentrations. Lactobacillus decreased fecal organic matter percentage at wk 6 (P < 0.05) and 8 (P = 0.07). At wk 6 and 8, LAC increased (P < 0.05) fecal 2-methylindole, total indole, and total indole and phenol concentrations. At wk 8, LAC decreased fecal agmatine (P = 0.08) and phenylethylamine (P < 0.05) concentrations. In conclusion, FOS and LAC modified several metabolites associated with gut health, with FOS tending to be beneficial (decreased fecal protein catabolites) and LAC being negative (increased fecal protein catabolites).

Glycemic and insulinemic responses of nondiabetic healthy adult subjects to an experimental acid-induced viscosity complex incorporated into a glucose beverage.

OBJECTIVE: An acid-induced-viscosity (I-V) complex containing alginate, citrate, and insoluble calcium was incorporated into a glucose-based beverage. We hypothesized that the acid I-V beverage would become viscous in the stomach (due to the solubilization of calcium and its interaction with alginate and citrate) and would blunt glycemia. METHODS: Thirty subjects were used in a double-masked, placebo-controlled crossover study evaluating the acid I-V complex. The placebo was a glucose-based beverage that had a similar total dietary fiber level and initial viscosity (Control). After a 12-h overnight fast, serum glucose and insulin were monitored over a 3-h postprandial period. RESULTS: The postprandial mean peak incremental change from baseline in serum glucose tended (P < 0.06) to be lower for the acid I-V product. The net incremental area under the curve (AUC) for serum glucose was reduced 75% (P < 0.01) by the acid I-V product, which was due mainly to an increased undershoot. The mean peak incremental change from baseline in serum insulin was higher (P < 0.05) for the acid I-V product. Net incremental AUC for serum insulin did not differ (P > 0.20) between products. CONCLUSIONS: Results of this study suggested that the acid I-V complex may attenuate the postprandial glycemic response to a glucose challenge in healthy subjects.

Supplemental fructose attenuates postprandial glycemia in Zucker fatty fa/fa rats.

Experiments were conducted to evaluate the effects of supplemental fructose on postprandial glycemia. After overnight food deprivation, Zucker fatty fa/fa rats were given a meal glucose tolerance test. Plasma glucose response was determined for 180 min postprandially. At a dose of 0.16 g/kg body, fructose reduced (P < 0.05) the incremental area under the curve (AUC) by 34% when supplemented to a glucose challenge and by 32% when supplemented to a maltodextrin (a rapidly digested starch) challenge. Similarly, sucrose reduced (P = 0.0575) the incremental AUC for plasma glucose when rats were challenged with maltodextrin. Second-meal glycemic response was not affected by fructose supplementation to the first meal, and fructose supplementation to the second meal reduced (P < 0.05) postprandial glycemia when fructose had been supplemented to the first meal. In a dose-response study (0.1, 0.2, and 0.5 g/kg body), supplemental fructose reduced (P < 0.01) the peak rise in plasma glucose (linear and quadratic effects). In the final experiment, a low dose of fructose (0.075 g/kg body) reduced (P < 0.05) the incremental AUC by 18%. These data support the hypothesis that small amounts of oral fructose or sucrose may be useful in lowering the postprandial blood glucose response.