Keith A. Garleb’s research while affiliated with University of Illinois Urbana-Champaign and other places

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Publications (68)


In vitro fermentation profiles of NDCs obtained with the use of human fecal inoculum 1
Perspective: Physiologic Importance of Short-Chain Fatty Acids from Nondigestible Carbohydrate Fermentation
  • Literature Review
  • Full-text available

April 2019

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700 Reads

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178 Citations

Advances in Nutrition

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Keith A. Garleb

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.

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In vitro fermentation characteristics, in vivo ileal and total tract nutrient digestibilities, and fecal microbiota responses of dogs to α-cyclodextrin

May 2016

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28 Reads

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L.L. Bauer

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K.A. Garleb

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The objectives were to examine in vitro fermentation characteristics, in vivo nutrient digestibility, fecal microbiota, and serum lipid profiles as affected by α-cyclodextrin (ACD) supplementation. Short-chain fatty acid (SCFA) production was measured after in vitro fermentation for 3, 6, 9, and 12 h of ACD, β-cyclodextrin, and γ-cyclodextrin. Five mixed-breed hounds were used in a Latin square design. Each experimental period comprised 14 d, including 10 d for diet adaptation and 4 d for fecal collection. Dogs were fed, twice a day, an extruded diet made with poultry byproduct meal and brewer’s rice as the main ingredients. Dogs were supplemented with 0, 1, 2, 3, or 4 g of ACD diluted in 15 mL of water twice daily for a total of 0, 2, 4, 6, and 8 g ACD/d. Maximal in vitro production of total SCFA was lowest for ACD. However, the greatest maximal production of propionate was noted for ACD treatment. Total tract nutrient digestibility and fecal DM concentration linearly decreased (P < 0.05) for treatment groups receiving ACD; no changes were observed for ileal digestibility. Serum cholesterol and triglyceride concentrations were within normal ranges for dogs and were not different among treatments. Similarly, no changes in fecal microbiota were observed. Overall, ACD supplementation appears to have no effect on nutrient absorption in the small intestine but may alter fermentation in the large bowel, which could lead to a higher proportion of propionate production as observed in the in vitro experiment. © 2016 American Society of Animal Science. All rights reserved.


In vitro fermentation characteristics, in vivo ileal and total tract nutrient digestibilities, and fecal microbiota responses of dogs to α-cyclodextrin

May 2016

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47 Reads

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1 Citation

Journal of Animal Science

The objectives were to examine in vitro fermentation characteristics, in vivo nutrient digestibility, fecal microbiota, and serum lipid profiles as affected by α-cyclodextrin (ACD) supplementation. Short-chain fatty acid (SCFA) production was measured after in vitro fermentation for 3, 6, 9, and 12 h of ACD, β-cyclodextrin, and γ-cyclodextrin. Five mixed-breed hounds were used in a Latin square design. Each experimental period comprised 14 d, including 10 d for diet adaptation and 4 d for fecal collection. Dogs were fed, twice a day, an extruded diet made with poultry byproduct meal and brewer's rice as the main ingredients. Dogs were supplemented with 0, 1, 2, 3, or 4 g of ACD diluted in 15 mL of water twice daily for a total of 0, 2, 4, 6, and 8 g ACD/d. Maximal in vitro production of total SCFA was lowest for ACD. However, the greatest maximal production of propionate was noted for ACD treatment. Total tract nutrient digestibility and fecal DM concentration linearly decreased ( < 0.05) for treatment groups receiving ACD; no changes were observed for ileal digestibility. Serum cholesterol and triglyceride concentrations were within normal ranges for dogs and were not different among treatments. Similarly, no changes in fecal microbiota were observed. Overall, ACD supplementation appears to have no effect on nutrient absorption in the small intestine but may alter fermentation in the large bowel, which could lead to a higher proportion of propionate production as observed in the in vitro experiment.


Serum lipid profiles, total tract nutrient digestibility, and gastrointestinal tolerance by dogs of α-Cyclodextrin

May 2015

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14 Reads

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6 Citations

The objectives were to quantify gastrointestinal tolerance, total tract nutrient digestibility, and serum lipid profiles of dogs as affected by α-cyclodextrin (ACD) supplementation and to validate the accuracy of fat analyses techniques using novel ACD-fat complexes. The ACD was hydrolyzed and free sugars and hydrolyzed monosaccharides were quantified using high performance liquid chromatography. Known amount of fats were complexed with ACD, and fat content of complexes were determined using the ether extraction and acid-hydrolyzed fat methods. Nine mixed-breed hounds were used in a crossover design with 3 periods of 10 d each, including 6 d for diet adaptation and 4 d for fecal collection. Dogs were fed twice daily a diet with poultry byproduct meal and brewer’s rice as the main ingredients, and chromic oxide (0.2%) was included as a digestion marker. Dogs were supplemented with either 0, 3, or 6 g of ACD diluted in 15 mL of water twice per day for a total of 0, 6, and 12 g ACD per day. The ACD had a very low free sugar concentration and, once hydrolyzed, released only glucose, as expected. Average daily food intake, fecal output (DM basis), and fecal scores were not significantly different among treatments. Body weight and condition score and serum triglycerides and cholesterol concentrations remained unaltered throughout the duration of the experiment. Dry matter, OM, and fat digestibility coefficients were lower (P < 0.05) for both treatment groups compared to the control. The acid-hydrolyzed fat method was valid to measure fat that was bound to ACD. Intake of ACD lowered fat digestibility somewhat but not to the extent previously reported, without affecting serum lipid concentrations or outcomes related to tolerance. Therefore, ACD supplementation resulted in a small decrease in fat digestibility, but ACD supplementation might have potential in modifying serum lipid profiles. © 2015 American Society of Animal Science. All rights reserved.


Serum lipid profiles, total tract nutrient digestibility, and gastrointestinal tolerance by dogs of α-cyclodextrin

May 2015

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68 Reads

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6 Citations

Journal of Animal Science

The objectives were to quantify gastrointestinal tolerance, total tract nutrient digestibility, and serum lipid profiles of dogs as affected by α-cyclodextrin (ACD) supplementation and to validate the accuracy of fat analyses techniques using novel ACD-fat complexes. The ACD was hydrolyzed and free sugars and hydrolyzed monosaccharides were quantified using high performance liquid chromatography. Known amount of fats were complexed with ACD, and fat content of complexes were determined using the ether extraction and acid-hydrolyzed fat methods. Nine mixed-breed hounds were used in a crossover design with 3 periods of 10 d each, including 6 d for diet adaptation and 4 d for fecal collection. Dogs were fed twice daily a diet with poultry byproduct meal and brewer's rice as the main ingredients, and chromic oxide (0.2%) was included as a digestion marker. Dogs were supplemented with either 0, 3, or 6 g of ACD diluted in 15 mL of water twice per day for a total of 0, 6, and 12 g ACD per day. The ACD had a very low free sugar concentration and, once hydrolyzed, released only glucose, as expected. Average daily food intake, fecal output (DM basis), and fecal scores were not significantly different among treatments. Body weight and condition score and serum triglycerides and cholesterol concentrations remained unaltered throughout the duration of the experiment. Dry matter, OM, and fat digestibility coefficients were lower ( < 0.05) for both treatment groups compared to the control. The acid-hydrolyzed fat method was valid to measure fat that was bound to ACD. Intake of ACD lowered fat digestibility somewhat but not to the extent previously reported, without affecting serum lipid concentrations or outcomes related to tolerance. Therefore, ACD supplementation resulted in a small decrease in fat digestibility, but ACD supplementation might have potential in modifying serum lipid profiles.


Methods for improving tolerance, digestion, and lipid soluble nutrient absorption in an infant, toddler, or child

June 2014

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16 Reads

Disclosed are nutritional formulations including predigested fats that can be administered to preterm infants, infants, toddlers, and children for improving tolerance, digestion, and absorption of nutrients and for reducing the incidence of necrotizing enterocolitis, colic, and short bowel syndrome. The predigested fats include fatty acid-containing monoglycerides and/or a fatty acid component.


Polymer controlled induced viscosity fiber system and uses thereof

September 2013

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7 Reads

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2 Citations

The present invention relates generally to a method of blunting the postprandial glycemic response in a human by feeding an induced viscosity fiber system. The invention also relates to an induced viscosity fiber system and the liquid products that incorporate the induced viscosity fiber system. Further, the invention relates to a method of incorporating soluble fiber into a liquid product without the typical negative organoleptic or physical stability issues. The invention also relates to a method of inducing the feeling of fullness and satiety by feeding the induced viscosity fiber system.


Dietary Fructo-oligosaccharide Modulates Large Intestinal Inflammatory Responses to Clostridium difficile in Antibiotic-compromised Mice

July 2009

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65 Reads

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30 Citations

Microbial Ecology in Health and Disease

Intestinal inflammatory parameters and microbiological changes were examined in antibiotic-compromised mice in response to Clostridium difficile, a causative agent of pseudomembranous colitis. C57BL/6NHsd mice were treated orally with a broad- spectrum antibiotic and then fed a low-residue diet (Ensure®) with or without the fermentable substrate fructo-oligosaccharide (FOS). Animals were infected with C. difficile 6 d after antibiotic treatment. Three days after antibiotic challenge, total anaerobes were lower for antibiotic-treated mice than for controls (no antibiotic) in the Ensure-fed group. However, when the diet was supplemented with FOS, total anaerobe concentrations were higher for antibiotic-treated mice than for controls. Levels of C. difficile were higher for antibiotic-treated animals on day 12 in the FOS-supplemented group and in both diet groups 4 d post-infection. Toxin A litres were significantly elevated 1 d and 4 d post C. difficile challenge only in the antibiotic treated mice not receiving FOS. Antibiotic effects on intestinal immune cell populations were also dependent on diet. Dendritic and γδ T-cell numbers in the caecum were increased by antibiotic treatment in mice fed Ensure only, while tissue concentrations of the bioactive lipid prostaglandin E2 were decreased. Alternatively, antibiotic treatment increased macrophage numbers in the caecum of FOS-supplemented mice without affecting dendritic and γδ T-cell numbers or prostaglandin E2 concentrations. Notably, alterations in immune parameters in response to antibiotic were observed predominantly in the caecum, where bacterial density is highest and where C. difficile-induced lesions are localised in the mouse.


Safety and Tolerance of Lactobacillus reuteri in Healthy Adult Male Subjects

July 2009

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264 Reads

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75 Citations

Microbial Ecology in Health and Disease

Thirty healthy, male subjects (age 18 to 75 yrs) were used in a two-group, double-blinded, parallel design to evaluate the safety and tolerance of a potential probiotic organism, Lactobacillus reuteri. Subjects (15/treatment) consumed two gelatin capsules daily for 21 d that contained either a freeze dried L. reuteri preparation in a cryoprotectant, or a placebo (cryoprotectant). The concentration of L. reuteri was such that subjects consumed 1 × 1011 CFU per day. The study was 28 d in length with daily documentation of the presence of gastrointestinal symptoms (nausea, diarrhoea, cramping, distention, flatulence, vomiting, constipation, burping and reflux). In addition, serum chemistries, haematology, urinalysis, urinary indican excretion, and faecal microbiota (L. reuteri and total Lactobacillus spp. enumeration) were measured weekly (day 0, 7, 14, 21 and 28). A physical exam was given on day 0, 21, and 28. An additional faecal sample was obtained on day 77 for microbial enumeration. Subjects could consume their regular diets; however, alcohol was not allowed. Physical exam and urinalysis parameters were not clinically different between treatments. Supplemental L. reuteri reduced (P < 0.05) urinary indican excretion at day 7, but had no effect (P > 0.05) on subsequent urine collections. Although significant differences were observed for a few of the serum chemistry and haematology variables, all of the values remained within the expected normal range for healthy adult males. Subjects consuming supplemental L. reuteri had increased (P < 0.01) levels of L. reuteri in their faeces on day 7, 14, 21, and 28. However, colonisation was lost within 2 mths of termination of L. reuteri consumption (day 77). Levels of total Lactobacillus spp. never differed (P > 0.05) between treatments; however, the ratio of L. reuteri: total Lactobacillus spp. increased (P < 0.05) for subjects consuming supplemental L. reuteri. Incidence of subjective tolerance factors was infrequent and similar for both treatments. In conclusion, supplemental L. reuteri may be fed at 1 × 1011 CFU/day without any clinically significant safety or tolerance problems. Intake of L. reuteri (1 × 1011 CFU/day) results in colonisation (as measured by faecal level) within 7 d of consumption and is maintained for at least 7 d post consumption; however, colonisation is lost within 2 mths of washout.


Effect of Fructooligosaccharide Containing Enteral Formulas on Subjective Tolerance Factors, Serum Chemistry Profiles, and Faecal Bifidobacteria in Healthy Adult Male Subjects

July 2009

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156 Reads

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27 Citations

Microbial Ecology in Health and Disease

Fructooligosaccharides (FOS) are an ingredient which may be incorporated into enteral products. However, prior to the addition of FOS to such products, studies related to the identification of any negative side effects associated with their consumption must be conducted. This double-blind study was conducted to assess the effect of FOS-containing enteral formulas on subjective tolerance factors, serum chemistry profiles and faecal bifidobacteria in healthy male college students. Three dietary formulas were investigated including a low residue polymeric formula (A), A+5 g FOS/L (B), and A+10 g FOS/L (C). Twenty-seven students (nine subjects/treatment) were randomly assigned to one of the dietary treatments. Subjects consumed the specified formula as their sole source of nutrition for 14 d. The amount of formula consumed by each subject was recorded daily and caloric intakes were adjusted to maintain the subjects' initial body weight. Faecal and blood samples were collected at baseline (day 0) and day 14. Using a daily questionnaire, subjects were asked to report the frequency of the following gastrointestinal symptoms: nausea, cramping, diarrhoea, distention, flatus, vomiting and regurgitation. Daily consumptions of FOS (g ± SEM) were 0 ± 0, 15 ± 1·0, and 31 ± 2·6 for dietary treatments A, B, and C, respectively. Tolerance to all dietary treatments was good. Few complaints of nausea, cramping, diarrhoea, marked distention, vomiting or regurgitation were reported regardless of treatment. More complaints of flatus and slight distention were reported with the FOS-containing diets, particularly diet C, compared with A. These symptoms were mild and subsided as the study progressed. No clinically significant differences in serum chemistries were detected as a function of formula intake. Faecal microbiota changes, as a function of diet, were detected. Specifically, the ingestion of diets B and C resulted in greater (P<0·001) bifidobacteria levels in faeces compared with A on day 14. Results indicate that fructooligosaccharides do not compromise serum chemistries, are well tolerated particularly at an intake of 15 g/d, and are a bifidogenic factor in low residue polymeric formulas.


Citations (60)


... 21 FOS exert both proliferative and anti-apoptotic effects on intestinal epithelial cells (IEC) in neonatal pigs. 22,23 FOS intake was also reported to promote epigenetic changes and increase intestinal Ca 2þ absorption in rats. 24,25 In Caco-2 cells, FOS suppress NF-kB activity and downstream signaling, and enhance barrier function. ...

Reference:

Inhibitory effect of fructo‐oligosaccharides on inflammation‐associated apoptosis in GLP‐1 secreting L cells via inhibition of iNOS and cleaved caspase‐3 expression
Effects of Dietary Supplementation with Fructooligosaccharides on Colonic Microbiota Populations and Epithelial Cell Proliferation in Neonatal Pigs
  • Citing Article
  • October 1995

Journal of Pediatric Gastroenterology and Nutrition

... For example, in batch cultures of pig intestinal digesta, while β-glucan-grown cultures yielded the highest level of lactate, flaxseed or fenugreek gum-containing cultures generated a significant amount of acetate, propionate, and butyrate (Lin et al., 2011). In another study, 20 soluble fibers (alginate, apple pectin, arabinogalactan, carrageenan, carboxymethylcellulose, citrus pectin, gellan gum, guar gum, gum arabic, gum ghatti, gum karaya, hydrolyzed guar gum, konjac flour, locust bean gum, methylcellulose, oat β-glucan, psyllium, tomato pectin, tragacanth gum, and xanthan gum) were tested in vitro for their fermentation profile using three human fecal inocula (Hussein et al.,2008). Although all are soluble, and therefore supposed to be quite highly fermentable, significant differences were observed after 24 hours for dry matter disappearance (between 20% and more than 91%) and gas production, with some fiber having no gas produced. ...

In Vitro Fermentation Characteristics of Native Soluble Fiber Sources by Human Colonic Bacteria
  • Citing Article
  • March 2008

The FASEB Journal

... The HP and LP diets naturally differed in protein sources, and hence the contribution of a difference in protein ''quality'' as well as protein intake to protein fermentation cannot be discounted. Regardless, increased fermentation of protein and subsequent absorption of ammonia will increase PUN levels because NH 3 is converted to urea in the liver for excretion through urine (Younes et al. 1998). Another source of circulating PUN is unbalanced or excess dietary proteins that are not used for body protein synthesis, and are catabolised through several metabolic pathways such as gluconeogenesis. ...

Dietary fiber stimulates the extra-renal route of nitrogen excretion in partially nephrectomized rats
  • Citing Article
  • January 1998

... SCFAs are saturated, 1 to 6 carbon-containing compounds, namely formate (1C), acetate (2C), propionate (3C), butyrate (4C), valerate (5C), and caproate (6C). These are the body's energy source and could provide 10% of the daily required calories (Alexander et al., 2019). Formate, often called formic acid, is produced as a byproduct during methanol metabolism, and sometimes it causes metabolic acidosis. ...

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

Advances in Nutrition

... To date research has shown most about the role of probiotics in promoting healthy GI tract functioning (Guandalini et al., 2000;Mach, 2006;Ouwehand, 2002;Saavedra et al., 1994;Shornikova, 1997;Yan and Polk, 2006). Lactobacillus reuteri has been tested for host tolerance in healthy adults (Wolf et al., 1995), the young (Ruiz-Palaccious et al., 1992) and those who are immunosuppressed (Wolf et al., 1998), with no undesirable medical side effects observed on giving the highest prescription of 10 10 CFUs per day and no significant differences in blood count, urinalysis, metabolism and liver function tests between participants taking Lactobacillus reuteri or a placebo. What is clear is that there is a lack of research focus and minimal evidence-base from which to advise childbearing women in relation to probiotic consumption. ...

Safety and Tolerance of Lactobacillus reuteri in Healthy Adult Male Subjects
  • Citing Article
  • March 1994

Microbial Ecology in Health and Disease

... The fiber supplementation also improved the disrupted cell morphology, which developed due to the diseased state of the colon. Hemicellulose-derived XOS not only reduced the inflammation, but also helped to maintain the colon crypt cell integrity in attenuated chronic colitis in rats (73). These oligomers are fermented with varied efficiency depending upon the gut microbiota diversity. ...

Sulfasalazine or Enteral Diets Containing Fish Oil or Oligosaccharides Attenuate Chronic Colitis in Rats
  • Citing Article
  • November 1997

Inflammatory Bowel Diseases

... Based on availability to impart viscosity, almost any gum could act as a potential satiety-enhancing agent. From a compositional point of view there are basically two types of gums, with some variation within each type: neutral hydrocolloids, including guar, locust bean gum and konjac, which simply hydrate to a fully extended form, creating viscosity through polymer entanglement, and charged hydrocolloids such as alginate, pectin, carrageenan and gellan gum, which also develop maximum viscosity with full hydration in water but may also develop additional viscosity through association with mono-and divalent ions and, in some cases, hydrogen ions (Aimutis et al., 2007; Boers, Strom, & Wiseman, 2008; Wolf, Blidner, Garleb, Laie, & Schenz, 2007). If these hydrocolloids are dispersed in a milk beverage, some calcium ions released from the milk micelles can help them to form gels during acidification in the stomach. ...

Polymer controlled induced viscosity fiber system and uses thereof
  • Citing Patent
  • September 2013

... In the study conducted by Guevara et al. [60], α-cyclodextrin supplementation in dogs was investigated for its effects on in vitro fermentation characteristics, nutrient digestibility, fecal microbiota, and serum lipid profiles. Dogs were fed diets with varying amounts of α-cyclodextrin. ...

In vitro fermentation characteristics, in vivo ileal and total tract nutrient digestibilities, and fecal microbiota responses of dogs to α-cyclodextrin
  • Citing Article
  • May 2016

Journal of Animal Science

... In the GIT, the inflammatory capacity of commensal bacteria varies because some bacteria are proinflammatory, whereas others attenuate inflammatory responses. Wolf et al. (2005) provide an overview of the medical uses of FOS at levels found in enteral products. The use of these products to provide total nutrition will deliver efficacious amounts of prebiotic fiber to hospitalized patients, generally in the range of 10À15 g/day. ...

Medical Foods and Fructooligosaccharides
  • Citing Chapter
  • November 2004