Today’s consumers are more attentive to their diet and its impact on their overall health and well-being.
The role of fiber in maintaining a healthy body and mind is becoming better understood by the scientific community and more widely recognized and accepted by consumers.
In fact, the global dietary fiber market is projected to grow at a CAGR of 13.23% between 2021 and 2026, with Europe leading the way. A growing awareness of the role of the gut in overall health and well-being is helping to fuel the rise of fiber.
This growing consumer awareness is also validated by Puratos’s proprietary Taste Tomorrow research, which recently found that 83% of Europeans believe that fiber has a positive impact on digestion. This research also confirmed that two-thirds (61%) of Taste Tomorrow respondents are interested in foods that improve gut health or digestion.
Nutritional and Health Benefits of a Fiber-Rich Diet
The World Health Organization (WHO) states that dietary fiber intake should be 25-30g/day for a healthy lifestyle1. According to consumer research, the public is aware of the benefits of fiber and most people believe they are getting enough fiber. However, national food consumption surveys indicate that up to 95% of American adults and children do not consume the recommended levels of fiber, as dietary fiber intake is just 16.2g1.
Current recommendations for adult dietary fiber intake in most European countries, including the UK, are between 30–35 g per day for men and between 25–32g per day for women. According to research carried out by the European Commission, actual dietary fiber intake in most European countries is significantly lower than this level, at almost half the recommended amount2.
The benefits of a high fiber diet relate to the digestive process and a healthier intestinal tract. Fiber is crucial to the digestive process, as it reduces the time it takes for food to pass through the intestinal tract, while increasing bulk and stool production, and thereby preventing constipation. It also increases the feeling of satiety, resulting in reduced calorie intake, which can help with weight management. In addition, dietary fiber is associated with benefits beyond digestive health, such as reduced risk of heart disease, stroke, hypertension, certain gastrointestinal disorders, obesity, type 2 diabetes, and certain cancers1.
Furthermore, high intake of mixed dietary fiber intake may up-regulate both colonic fermentation and the relative abundance of colonic bacteria within the human colonic microbiota. However, not all fibers perform the same regarding colonic fermentation capability.
Dietary fiber is not just a collection of indigestible plant materials that pass through the human GI tract. Depending on their physicochemical characteristics, certain dietary fibers are fermentable by the GI tract microbiota. These fermentation products of fiber, known as prebiotics, have been shown to benefit various aspects of human health.
Prebiotics are frequently equated with dietary fibers, but only a subset of dietary fibers qualify as prebiotics. According to the scientific consensus definition of International Scientific Association for Probiotics and Prebiotics (ISAPP), a prebiotic compound must have a beneficial physiological effect on the host. This effect should result from the utilization of the compound by resident microbes.
Wheat bran fiber
Wheat bran is an important by-product of grain cereals, and is produced in large quantities throughout the world. It is a complex substrate composed of abundant nutrients and bioactive components, mainly dietary fiber (36–52 wt%), proteins (15–22 wt%), starch (10–20 wt%), and lignin (4–8 wt%)5.
The rich bioactive components in wheat bran make it a potential candidate for value-added uses, indeed it is already used in many products such as whole grain baking or in foods offering extra dietary fiber. It has been confirmed that a sufficient intake of dietary fiber from wheat bran with appropriate physiological functions is beneficial for human health4. However, the incorporation of the wheat bran into food products such as baked goods, results in undesirable taste and texture5.
Fermentation can improve the nutritional, functional, and sensory properties of wheat bran. Bio-processing causes hydrolysis and solubilization of proteins and fibers allowing the delivery of bioactive and potentially protective compounds when consumed.
Arabinoxylan (AX) is the main hemicellulose component in wheat bran accounting for ∼26 wt% in dry weight5. AX are pentosan non-starch polysaccharides and major constituents of cereal grains and therefore flours (e.g., in wheat flour).
In cereal grains, AX are localized in the cell walls of the endosperm and the aleurone layer, in the bran tissues and in the husk of some cereals. AX from cereals consist of a backbone of beta-(1-4)-linked D-xylose residues, which are substituted at the C(O)-3 and/or C(O)-2 position(s) with mainly monomeric-alpha-L-arabinose side chains (arabinose)6.
AX can be divided into either water-extractable AX (WE-AX) or water-unextractable AX (WU-AX), both of which have a similar structure but differ in the level of cross-linking with other natural polymers. The unique physiochemical properties of AX largely affect bread characteristics7.
Special endoxylanases enzymes can hydrolyze internal linkages in the AX chain, thereby affecting the structure and physicochemical properties of AX. This hydrolysis leads to the formation of arabinoxylan oligosaccharides (AXOS). This hydrolysis increases the levels of WE-AX with beneficial effects on microbiome modulation. AXOS was shown to have a prebiotic potential in preclinical and human clinical studies and in vitro human colon simulator models.
Prebiotic potential of wheat fiber components – AXOS
In the last decade, natural prebiotics, mainly dietary fibers, have gained considerable importance in consumers diet given the number of studies that link them with a wide range of beneficial effects that lead to significant health improvements. One such prebiotic fibers are Arabinoxylan oligosaccharides (AXOS) deriving from arabinoxylans. The prebiotic properties and health effects (e.g., digestive health, lowering cholesterol and reduction in the plasma ceramide levels) of AXOS have been widely described. The production of short-chain fatty acids (SCFAs) in the colon due to AXOS fermentation is another well know effect that can be linked to an improvement in metabolic health.
The prebiotic potential of AXOS, has been shown in several in vitro intestinal models, animal studies and human studies8-15. An array of clinical studies gave supporting evidence that AXOS has a selective bifidogenic effect. AXOS has a selective bifidogenic effect which can be linked to the average degree of polymerization (avDP). AXOS with a lower (5-20 avDP) results in high levels of Bifidobacteria.
Clinical studies ran by Puratos and collaborators have shown that a consumption of breads with in situ produced AXOS (containing 2.2 of AXOS with a avDP between 5 and 25) by healthy volunteers promotes bifidobacterial growth in the colon 16,17. Faecal levels of Bifidobacteria increased compared with control breads and remained elevated throughout the study. Production of SCFA were also shown to be elevated with consume of AXOS wheat breads16,17.
In the bakery sector, endoxylanase enzyme has been extensively used to improve dough consistency, bread volume and crumb structure all while solubilizing arabinoxylans. At Puratos, through a proprietary technology, we in situ generate in bread, AXOs from the hydrolysis of arabinoxylan with a combination of lactic acid bacteria fermentation and enzymatic hydrolysis16,17.
In our recent collaboration with Prof. Marco Gobbetti and Andrea Polo from Bolzano, we have explored the effect of AXOS derived from different cereal bran flours (wheat, oat and rye) on the gut microbiome (composition and metabolite production) by studying the middle-term dynamics of the bacterial populations with the SHIME human gut in vitro model18.
The analysis of the microbial population shows a clear effect linked to the addition of fermented and hydrolyzed brans when compared to non-fermented non-hydrolyzed wheat bran. SHIME systems fed with the fermented hydrolyzed brans show a shift in the relative abundance of specific bacterial groups that can be linked to potential health benefits. For example we observed (Fig. 1) an enhanced relative abundance in Bifidobacterium and genera belonging to lactic acid bacteria (Lactiplantibacillus, Lentilactobacillus and Levilactobacillus) after feeding the SHIME reactors with the fermented hydrolyzed brans which can be considered as a beneficial effect due to the ability of members of these groups to prevent the growth of pathogenic bacteria through niche or nutrient competition as well as their ability to produce antimicrobial compounds.
Figure 1. Relative abundance at genus level of the bacterial microbiota, before (T0), during one and two weeks (T1 and T2, respectively) of feeding with hydrolyzed and fermented oat bran (MOB), rye bran (MRB) and wheat bran (MWB), and wheat bran (WB), and after two weeks of wash out period (T3), in the proximal and distal colon tracts (PC and DC).
In addition to changes in the microbial composition, feeding the SHIME reactors with the different fermented hydrolyzed brans also had an impact on the concentrations of SCFA (Fig. 2). For example, a significant increase was seen just after one week of feeding the fermented hydrolyzed brans when compared to the control non-fermented non-hydrolyzed wheat bran.
Overall, our latest study shows that fermented hydrolyzed bran cereals containing AXOS significantly increase the synthesis of short-chain fatty acids by colonic bacteria and promote changes in the microbial composition favoring the increase in the relative abundance of those bacterial groups linked to potential health benefits.
These results suggest that hydrolyzed AXOS obtained through fermentation by lactic acid bacteria such as Lactiplantibacillus plantarum could have a more powerful prebiotic effect when compared to non-hydrolyzed and non-fermented wheat bran, shaping the colon microbiome and its metabolic answer.
Sources
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18 Polo A., Albiac M.A., Da Ros A., Nolla Ardèvol V., Verte F., Di Cagno R., Gobebetti M. The Effect of Hydrolyzed and Fermented Arabinoxylan-OligoSaccharides (AXOS) Intake on the Middle-Term Gut Microbiome Modulation and Its Metabolic Answer. Nutrients 2023, 15(3), 590;
Probiota 2023
At Puratos we constantly strive to grow our positive impact by creating innovative food solutions that promote health & well-being and steadily move businesses, customers, people and the planet forward. We continiously invest in research and consumer understanding to develop the most irresistible products with gut health benefits.
Delivering postbiotics through baked applications
We are embarked on a mission to transform bread, a global staple food product, into a vehicle to deliver postbiotic compounds to help consumers maintain a healthy and stable gut microbiome.
Producing probiotics for fermented food solutions & nutraceuticals
THT aims to demonstrate the health benefits of lactic acid bacteria present in sourdough. In addition, THT provides consumers with valuable lactic acid bacteria strains for nutraceutical applications.
