The demand for products supporting digestive health is on the rise and more consumers today are making the connection between fiber and good health. To meet this growing demand, Cargill, Minneapolis, MN, has developed Soluble Wheat Bran Extract—a food-grade, fiber-rich extract of wheat bran for use in food or beverage products, including dairy and non-dairy beverages, ready-to-eat cereals and cereal bars, cookies and biscuits, bread and pastry.
 
The Science Behind the Fiber
The source material for the Soluble Wheat Bran Extract is wheat bran. The arabinoxylan-oligosaccharide (AXOS) fraction in Soluble Wheat Bran Extract is derived from partial enzymatic hydrolysis of wheat bran arabinoxylans (AX), the main hemicellulose type in the cell walls of cereals.
 
Soluble Wheat Bran Extract is principally (>70%) composed of AXOS, which are a mixture of low molecular weight xylo- and arabinoxylo-oligosaccharides. The AXOS in Soluble Wheat Bran Extract have an average degree of polymerization (avDP) between 3 and 8 and an arabinose to xylose (A/X) ratio, also referred to as the average degree of arabinose substitution (avDS), between 0.18 and 0.30. A further 20% of the Soluble Wheat Bran Extract is composed of other bran-extracted poly- and oligosaccharides contributing to the cereal cell walls.
 
Soluble Wheat Bran Extract comprises between 1 and 3% ferulic acid, virtually all of which is bound to AXOS. Ferulic acid is well known for its antioxidant properties.
 
Providing Soluble Dietary Fiber
The non-digestibility of wheat or wheat bran AX has been previously investigated in human ileostomy patients and studies found nearly complete recovery of wheat bran AX at the end of the small intestine, indicative that wheat bran AX are not digested in the stomach and small intestine (Holloway et al., 1980; Sandberg et al., 1981; Englyst and Cummings, 1985).
 
Digestive Health Benefits
The benefits of Soluble Wheat Bran Extract support digestive health in two key ways. First, it encourages the generation of beneficial Short-Chain Fatty Acids (SCFA) resulting from carbohydrate fermentation, at the expense of protein fermentation in the colon. Protein fermentation is known to create toxic compounds that may have carcinogenic potential. Secondly, Soluble Wheat Bran Extract offers a prebiotic effect.
 
Production of Short-Chain Fatty Acids (SCFA). A randomized controlled trial in healthy adults conducted by François et al. (2012) showed significantly lower fecal pH, increased total levels of fecal SCFA and individual levels of acetic acid, propionic acid and butyric acid relative to placebo intake (P<0.05) at an intake level of 10g/day of the Soluble Wheat Bran Extract. Additionally, at the lower dose of 3g/day of Soluble Wheat Bran Extract a significant increase in fecal propionic acid levels was observed (p<0.05).
 
In vitro studies using the SHIME reactor (Sanchez et al. 2009) simulating the ascendant, transverse and descendant colon showed the mid-colon compartment to be the main site of AXOS fermentation. Lower generation of putrefactive compounds, such as phenol and p-cresol, induced by AXOS fermentation was observed mainly in the transverse and descendant colon vessels. This is an important observation as it is mainly in the distal colon that intestinal-related diseases occur resulting from the presence of toxic metabolites.
 
These finding support observations made by Cloetens et al. (2010) who found significantly decreased levels of p-cresol in urine of human subjects participating in a randomized, placebo-controlled, crossover trial, after 2 weeks of consumption of the Soluble Wheat Bran Extract (10g/day) when compared to placebo (p<0.05). Similar outcomes were found in a study conducted by François et al. (2012) after 2 weeks of administration of Soluble Wheat Bran Extract (10g/day).
 
A recent study conducted in healthy, pre-adolescent children (François et al. 2014) also found a significant decrease in markers of protein fermentation upon intake of Soluble Wheat Bran Extract as indicated by low fecal levels of isobutyric acid and isovaleric acid when compared with placebo (p<0.05).
 
Prebiotic Effect. Four randomized controlled trials, three in healthy adults (Maki et al. 2012; François et al. 2012; Cloetens et al. 2010) and one in children (François et al. 2014) present evidence in relation to fecal bacteria content upon supplementation with Soluble Wheat Bran Extract (doses 6.25-14g/day). All trials compared the AXOS-supplemented groups to either non-supplemented, or maltodextrin control groups. The effect of AXOS supplementation on increasing fecal Bifidobacterium spp. content relative to control groups is consistent among studies. No significant changes in total bacteria or other bacterial groups were found in the respective studies.
 
In the study of Maki et al. (2012) the prebiotic effect of AXOS in ready-to-eat cereal was shown at a dose of 5g/day in a double-blind, randomized, controlled, crossover trial in healthy adults. Three weeks of supplementation resulted in a selective increase in Bifidobacterium spp. when compared to placebo (p<0.05). Interestingly, postprandial levels of ferulic acid in the plasma of volunteers showed a dose-dependent increase in response to consumption of AXOS (2 and 5g/day). Ferulic acid is a phenolic compound that has known antioxidant properties and is present in Soluble Wheat Bran Extract as linked with AXOS. The finding of increasing plasma levels indicates that ferulic acid is readily available for absorption upon AXOS ingestion.
 
The prebiotic effect of Soluble Wheat Bran Extract has recently been repeated in a randomized, double-blind, placebo-controlled, crossover trial in healthy, pre-adolescent children (François et al. 2014) showing a significantly increase in fecal levels of Bifidobacterium spp. (% of total microbiota) after 3 weeks consumption of 5g/d, when compared to placebo (p<0.05). Importantly, Soluble Wheat Bran Extract did not cause a change in gastrointestinal distress for any of the surveyed symptoms (flatulence, abdominal pain/cramps, urge to vomit) in this population group.
 
Gentle on the Stomach
Very recently, a placebo-controlled, crossover, human study (François et al. 2014) was conducted to test the tolerance of Soluble Wheat Bran Extract. Gradually increasing dosages of Soluble Wheat Bran Extract were given in a liquid form to adult volunteers: 15g/day in the first week and 30g/day in the second week (compared to equal levels of oligofructose) versus placebo. At 15g/day of Soluble Wheat Bran Extract, no gastrointestinal symptoms, with the only exception of mild flatulence, were reported. Contrary to oligofructose treatment that increased overall gastrointestinal symptom score by 1.9-fold (vs. placebo), dosages up to 30g/day of Soluble Wheat Bran Extract did not affect overall gastrointestinal symptom score and were reported as well tolerated.
 
Douwina Bosscher holds a PhD in Pharmaceutical Sciences. She is a lecturer of Nutrition and Food Sciences at the University of Antwerp, Belgium (Dept. Pharmaceutical Sciences). Her current position at Cargill is leader nutrition sciences, Global R&D, Food Ingredient Systems and in this role she is member of the Global Food Research Leadership Team.
 
References
Englyst HN, Cummings JH. Digestion of the polysaccharides of some cereal foods in the human small intestine. Am J Clin Nutr 1985;42:778-787.
 
Cloetens L, Broekaert WF, Delaedt Y, Ollevier F, Courtin CM, Delcour JA, Rutgeerts P, Verbeke K. Tolerance of arabinoxylan-oligosaccharides and their prebiotic activity in healthy subjects: a randomised, placebo-controlled cross-over study. Brit J Nutr 2010;103: 703–713.
 
François IEJA, Lescroart O, Veraverbeke WS, Marzorati M, Possemiers S, Hamer H, Windey K, Welling GW, Delcour JA, Courtin CM, Verbeke K, Broekaert WF. Effects of Wheat Bran Extract Containing Arabinoxylan Oligosaccharides on Gastrointestinal Parameters in Healthy Preadolescent Children. JPGN 2014;58: 647–653.
 
François IEJA, Lescroart O, Veraverbeke WA, Marzorati M, Possemiers S, Evenepoel P, Hamer H, Houben E, Windey K, Welling GW, Delcour JA, Courtin CM, Verbeke K, Broekaert WF. Effects of a wheat bran extract containing arabinoxylan oligosaccharides on gastrointestinal health parameters in healthy adult human volunteers: a double-blind, randomised, placebo controlled, cross-over trial. Brit J Nutr 2012;108: 2229–2242.
 
François IEJA, Lescroart O, Veraverbeke WS, Windey K, Verbeke K, Broekaert WF. Tolerance and the effect of high doses of Wheat Bran Extract (WBE), containing arabinoxylan oligosaccharides (AXOS), and Oligofructose on faecal output: a double-blind, randomized, placebo-controlled, crossover trial. Journal of Nutritional Sciences, In press.
 
Holloway WD, Tasman-Jones C, Bell E. The hemicellulose component of dietary fiber. Am J Clin Nutr 1980;33:260-263.
 
Maki KC, Gibson GR, Dickmann RS, Kendall CWC, Chen C-Y O, Costabile A, Comelli EM, McKay DL, Almeida NG, Jenkins D, Zello GA, Blumberg JB. Digestive and physiologic effects of a wheat bran extract, arabino-xylan-oligosaccharide, in breakfast cereal. Nutrition 2012;28:1115-21.
 
Sanchez JI, Marzorati M, Grootaert C, Baran M, Van Craeyveld V, Courtin CM et al. Arabinoxylan-oligosaccharides (AXOS) affects the protein/carbohydrate fermentation balance and microbial population dynamics of the Simulator of Human Intestinal Microbial Ecosystem. Microbiol Biotechnol. 2009;2:101-113.
 
Sandberg AS,  Andersson B, Hallgren B, Hasselblad K, Isakson B. Experimental model for in vivo determination of dietary fibre and its effect on the absorption of nutrients in the small intestine. Brit J Nutr 1981;45:283-294.