Cereal Dietary Fibre Research Articles

Liberated bioactive bound phenolics during in vitro gastrointestinal digestion and colonic fermentation boost the prebiotic effects of triticale insoluble dietary fiber

Phenolics in bound form extensively exist in cereal dietary fiber, especially insoluble fiber, while their release profile in gastrointestinal tract and contribution to the potential positive effects of dietary fiber in modulating gut microbiota still needs to be disclosed. In this work, the composition of bound phenolics (BPs) in triticale insoluble dietary fiber (TIDF) was studied, and in vitro gastrointestinal digestion as well as colonic fermentation were performed to investigate BPs liberation and their role in regulating intestinal flora of TIDF. It turned out that most BPs were unaccessible in digestion but partly released continuously during fermentation. 16 s rRNA sequencing demonstrated that TIDF possessed prebiotic effects by promoting anti-inflammatory while inhibiting proinflammatory bacteria alongside boosting SCFAs production and antioxidative BPs contributed a lot to these effects. Results indicated that TIDF held capabilities to regulate intestinal flora and BPs were important functional components to the health benefits of cereal dietary fiber.

NSPASES: CAN THOSE EXOGENOUS ENZYMES REALLY CONSTITUTE NATURAL GROWTH COFACTORS IN BROILER CHICKENS?

In the quest to improve public and animal health, white meat is considered to be one of the major causes of antibioresistance identified in medicine, through uncontrolled use of antibiotics in poultry farming as growth promoters (GPA). Thus, this use needs to be reconsidered at large scale. This reconsideration involves the substitution of GPAs by natural alternatives, particularly enzymes degrading non-starch polysaccharides (NSPases) which will allow:1) modulation of the intestinal microbiota, to attenuate the anti-nutritional effects of insoluble NSPs, 2)reduction of the non-digested portion of the substrate and 3) improvement of the zootechnical performance of the chicken. Non-starch polysaccharides contain two main families, namely: water-insoluble NSPs including cellulose and partially water-soluble NSPs. However, despite the fact that these components constitute the major part of cereal dietary fiber, they have an anti-nutritional effect associated with the viscous nature of these polysaccharides and their interaction with the intestinal microflora due to the fact that poultry does not produce enough endogenous enzymes to hydrolyze NSPs. The use of NSPases produced mainly by fungi and bacteria allows counterbalancing the anti-nutritional properties of dietary fibers by increasing the digestibility of starch and improving the zootechnical performance of broilers, particularly the conversion index.Thus, this literature review aims to shed light on the effects of NSPases on the zootechnical parameters of chickens, the intestinal microflora as well as on nutritional digestibility in order to use them as alternatives to GPAs and limit the aggravation of the phenomenon of antibioresistance. This approach is therefore, part of the world famous concept of one world one health and which applies to the design and implementation of programs, policies, legislations and research for which several sectors communicate and collaborate to improve public health outcomes.

Process-Induced Changes in the Quantity and Characteristics of Grain Dietary Fiber

Daily use of wholegrain foods is generally recommended due to strong epidemiological evidence of reduced risk of chronic diseases. Cereal grains, especially the bran part, have a high content of dietary fiber (DF). Cereal DF is an umbrella concept of heterogeneous polysaccharides of variable chemical composition and molecular weight, which are combined in a complex network in cereal cell walls. Cereal DF and its distinct components influence food digestion throughout the gastrointestinal tract and influence nutrient absorption and other physiological reactions. After repeated consumption of especially whole grain cereal foods, these effects manifest in well-demonstrated health benefits. As cereal DF is always consumed in the form of processed cereal food, it is important to know the effects of processing on DF to understand, safeguard and maximize these health effects. Endogenous and microbial enzymes, heat and mechanical energy during germination, fermentation, baking and extrusion destructurize the food and DF matrix and affect the quantity and properties of grain DF components: arabinoxylans (AX), beta-glucans, fructans and resistant starch (RS). Depolymerization is the most common change, leading to solubilization and loss of viscosity of DF polymers, which influences postprandial responses to food. Extensive hydrolysis may also remove oligosaccharides and change the colonic fermentability of DF. On the other hand, aggregation may also occur, leading to an increased amount of insoluble DF and the formation of RS. To understand the structure–function relationship of DF and to develop foods with targeted physiological benefits, it is important to invest in thorough characterization of DF present in processed cereal foods. Such understanding also demands collaborative work between food and nutritional sciences.

Prebiotic Potential of Cereal Components.

One type of functional food that has been receiving much attention is food rich in prebiotics. The old but still valid definition of prebiotics defines them as non-digestible food components that selectively stimulate the growth and/or activity of the beneficial bacteria in the colon and, as a result, improve the host health. Cereals, as one of the main components in the human diet, contain substantial levels of dietary fiber with probable prebiotic potential. In addition, dietary fiber, particularly soluble dietary fiber, has recently emerged as a promising natural highly functional food ingredient in food production. This review focuses on the prebiotic potential of cereal dietary fiber types and covers the achievements and developments regarding its isolation. First, the probiotic and prebiotic concepts will be discussed. Next, different components of dietary fiber and their effect on the host bacteria through in vitro and/or in vivo studies will be reviewed. In a last part, this paper also discusses means of boosting the prebiotic properties of cereal components and innovative strategies for the extraction of cereal dietary fiber. The review focuses on wheat as a leading cereal crop that is widely and intensely used throughout the world in food production.

Effects of cereal fibers on short-chain fatty acids in healthy subjects and patients: a meta-analysis of randomized clinical trials.

Short-chain fatty acids (SCFAs) are involved in the regulation of a wide array of diseases. However, the effect of cereal dietary fibers on SCFA production remains unclear. We reviewed relevant clinical studies between 1950 and 2021 and aimed to evaluate the effect of cereal fiber consumption on SCFA production in healthy subjects and patients. PubMed, Web of Science, and the Cochrane Library databases were used for systematically searching published relevant trials with adults and a minimum intervention duration of 2 weeks. The effect size was estimated using standardized mean difference (SMD) and 95% confidence interval (CI). Of the 555 identified studies, 14 intervention groups involving 205 participants aged between 20 and 69 years are eligible. The results of meta-analysis revealed that cereal fiber supplementation significantly increased acetate [SMD: 0.86, 95% CI (0.46, 1.25), p < 0.0001], propionate [SMD: 0.48, 95% CI: (0.15, 0.81), p = 0.004], butyrate [SMD: 0.61, 95% CI: (0.20, 1.01), p = 0.003], and total SCFA [SMD, 0.96, 95% CI: (0.54, 1.39), p < 0.00001] concentrations. Subgroup analysis suggested that a long intervention duration (>4 weeks) significantly promoted acetate and propionate production, whereas a short intervention duration (≤4 weeks) significantly facilitated butyrate production. Cereal fiber supplementation had a more significant impact on overweight and obese subjects with body mass index (BMI) >29 kg m-2 than on individuals with BMI ≤29 kg m-2. Furthermore, we found that cereal fibers and wheat/rye arabinoxylan oligosaccharides, rather than wheat bran fibers, barley fibers, and barley β-glucan, could significantly elevate the SCFA concentration. Overall, our meta-analysis demonstrated that cereal fiber supplementation is helpful in increasing the SCFA concentration, which provided strong proof for the beneficial role of cereal fibers.

Effect of thermally treated barley dietary fiber against hypercholesterolemia.

Dietary fiber is a nondigestible constituent of vegetal foods, formed by insoluble and soluble dietary fiber. The intake of dietary fiber, especially soluble dietary fiber, is limited and demands researcher's attention. The modification of cereal's dietary fiber, predominantly insoluble fiber, could be one possible solution. The current study evaluated the comparative effects of several thermal treatments on the modification of insoluble dietary fiber in barley and explored their therapeutic potential in vivo against hypercholesterolemia. The two cultivars of barley, Haider‐93 and Jau‐87, were thermally treated using different techniques, and dietary fiber was extracted. Successively, the intake of these dietary fibers was evaluated for its antilipidemic activity in normal and hypercholesterolemic rats. In the first phase, thermal treatments especially cooking without soaking increased the soluble fiber (68.08%). The roasting all increased the soluble fiber contents, however, at relatively lower rate (53.91%). The results of efficacy study revealed that biochemical parameters in control animals were within the normal clinical ranges, thus appraising the safe status of the experimental diets. The thermally treated barley fiber decreased total cholesterol (12.14%–12.63%), low‐density lipoprotein (14.12%–14.85%), and triglycerides (2.25%–4.32%). The study recorded increasing trends for high‐density lipoprotein in both normal and hypercholesterolemic rats. In the nutshell, thermal modification of dietary fiber increased the ratio of soluble to insoluble dietary fiber that improved its hypocholesterolemic potential. The thermally treated barley dietary fiber is effective in reducing the lipid profile in Sprague–dawley rats than untreated dietary fiber and, therefore, can be considered as a functional food and ingredient to cope different lifestyle diseases.

Cereal dietary fibres influence retention time of digesta solid and liquid phases along the gastrointestinal tract

Nutrient digestion kinetics are determined by gastric emptying (GE) in the stomach and apparent mean retention time (aMRT) along the small and large intestine. This study aimed to evaluate the effects of cereal dietary fibres (DF), either as intrinsic components of plant foods or added ingredients, on the retention of solid and liquid phases of digesta along the gastrointestinal (GI) tract. Thirty pigs were fed one of five diets containing whole wheat (WW), wheat starch (WS) or wheat starch partially replaced by wheat arabinoxylan (AX) or oat β-glucan (βG), or in combination (WSAXβG). Indigestible solid and liquid phase markers were added to each diet and fed at i) constant and ii) pulse dose intervals. Constant markers (acid insoluble ash and chromium) provided aMRT along 11 sections of the GI tract, while pulse dose markers (cerium, ytterbium and cobalt), fed 2–6 h before anaesthesia, provided a GE time. aMRT was slowest in the caecum and large intestine (LI, 15.4h), followed by the small intestine (SI, 3.4h) and stomach (2.6h) with liquid phases moving faster compared to solid phases. Between DF, AX but not βG, delayed GE of solid and liquid contents and showed longer retention time in SI and LI. In the absence of isolated soluble fibres, WS and WW diets showed similar flow characteristics of solid and liquid phases. The aMRT was shown to be dependent on the structure and swellability of added DF.

Exploring the Role of Cereal Dietary Fiber in Digestion.

Increasing the dietary fiber of staple foods such as bread is an attractive way to promote healthy eating in a large part of the population, where dietary fiber consumption is reportedly below the recommended values. However, many consumers prefer white breads, which are typically low in dietary fiber. In this work, white bread was made from two wheat cultivars with differing fiber contents. The resulting breads showed similar quality parameters (volume, specific volume, firmness, inner structure characteristics) with any differences maintained below 7%. Bread digestibility was evaluated using a novel dynamic in vitro digestion model. Reduced digestion rates of 30% were estimated for the high-fiber white bread compared to that in the control. Overall, this work demonstrates the potential to produce healthy, high-fiber white breads that are acceptable to consumers, with a reduced rate of starch digestion, by exploiting a genetic variation in the dietary fiber content of wheat cultivars.

Aggregation and microstructure of cereal β-glucan and its association with other biomolecules

A plethora of studies have shown the ability of cereal dietary fiber to improve intestinal health and to protect the colon from diseases. Lowering of blood cholesterol levels and a reduced risk of coronary heart diseases are just examples for beneficial health effects often directly related to β-glucan from cereal grains. β-Glucan is one of the major components of dietary fiber and is found with highest abundance in oat and barley. Yet, although intensively studied, there is no definitive theory on the mechanisms of β-glucan during human digestion established. It was suggested that its solution and aggregation behavior, in addition to its ability to form viscous slurries in the gut, govern the claimed beneficial health effects. Therefore, attempts have been made to investigate extracted β-glucan to improve current knowledge concerning the aggregation and solution behavior of β-glucan found in food products.β-Glucan was found to have high molar masses and large sizes. A combination of several analytical techniques showed the presence of highly aggregated structures in a widely distributed, loose β-glucan network. Barley β-glucan showed, in addition, surprisingly well-defined and dense aggregates. There were no proteins covalently bound to the β-glucan, but a direct relation between proteins and β-glucan was found suggesting electrostatic interactions to play an important role during aggregation. During in vitro gastric and gastrointestinal digestion studies, digestive enzymes were not found to have any impact on β-glucan conformation. Nevertheless, bile acids showed a molecular interaction with β-glucan from oats able to cause a reduction in blood cholesterol.

Carbohydrate quality and quantity and risk of coronary heart disease among US women and men

The carbohydrate-to-fiber ratio is a recommended measure of carbohydrate quality; however, its relation to incident coronary heart disease (CHD) is not currently known. We aimed to assess the relation between various measures of carbohydrate quality and incident CHD. Data on diet and lifestyle behaviors were prospectively collected on 75,020 women and 42,865 men participating in the Nurses' Health Study (NHS) and the Health Professionals Follow-Up Study (HPFS) starting in 1984 and 1986, respectively, and every 2-4 y thereafter until 2012. All participants were free of known diabetes mellitus, cancer, or cardiovascular disease at baseline. Cox proportional hazards regression models were used to assess the relation between dietary measures of carbohydrate quality and incident CHD. After 1,905,047 (NHS) and 921,975 (HPFS) person-years of follow-up, we identified 7,320 cases of incident CHD. In models adjusted for age, lifestyle behaviors, and dietary variables, the highest quintile of carbohydrate intake was not associated with incident CHD (pooled-RR=1.04; 95% CI: 0.96, 1.14; P-trend=0.31). Total fiber intake was not associated with risk of CHD (pooled-RR=0.94; 95% CI: 0.85, 1.03; P-trend=0.72), while cereal fiber was associated with a lower risk for incident CHD (pooled-RR=0.80; 95% CI: 0.74, 0.87; P-trend<0.0001). In fully adjusted models, the carbohydrate-to-total fiber ratio was not associated with incident CHD (pooled-RR=1.04; 95% CI: 0.96, 1.13; P-trend=0.46). However, the carbohydrate-to-cereal fiber ratio and the starch-to-cereal fiber ratio were associated with an increased risk for incident CHD (pooled-RR=1.20; 95% CI: 1.11, 1.29; P-trend<0.0001, and pooled-RR=1.17; 95%CI: 1.09, 1.27; P-trend<0.0001, respectively). Dietary cereal fiber appears to be an important component of carbohydrate quality. The carbohydrate-to-cereal fiber ratio and the starch-to-cereal fiber ratio, but not the carbohydrate-to-fiber ratio, was associated with an increased risk for incident CHD. Future research should focus on how various measures of carbohydrate quality are associated with CHD prevention. This trial was registered at clinicaltrials.gov as NCT03214861.

The effect of extrusion screw-speed on the water extractability and molecular weight distribution of arabinoxylans from defatted rice bran.

Arabinoxylans (AXs) are major dietary fibre in cereals. Recently, AXs have attracted a great deal of attention because of their biological activities. These activities have been suggested to be related to the content of low molecular weight (Mw) AXs, in particular those with Mw below 32kDa. Rice bran is a rich source of AXs. However, water extraction of AXs is difficult and often gives low yield. Extrusion processing has been used to increase the solubility of cereal dietary fibre. The aim of this research was to study the effect of extrusion screw-speeds (80 and 160)rpm on the extraction yield and Mw of water extractable AXs from rice bran. It was found that the extraction of AXs increased significantly with an increase in screw speed and was accompanied by a significant decrease in the Mw of AXs from extruded rice bran. The percentage of very low molecular weight AXs (0.79-1.58kDa) significantly increased with increasing screw speed.

Effects of pectin on fermentation characteristics, carbohydrate utilization, and microbial community composition in the gastrointestinal tract of weaning pigs.

We aimed to investigate the effects of three different soluble pectins on the digestion of other consumed carbohydrates, and the consequent alterations of microbiota composition and SCFA levels in the intestine of pigs. Piglets were fed a low-methyl esterified pectin enriched diet (LMP), a high-methyl esterified pectin enriched diet (HMP), a hydrothermal treated soybean meal enriched diet (aSBM) or a control diet (CONT). LMP significantly decreased the ileal digestibility of starch resulting in more starch fermentation in the proximal colon. In the ileum, low-methyl esterified pectin present was more efficiently fermented by the microbiota than high-methyl esterified pectin present which was mainly fermented by the microbiota in the proximal colon. Treated soybean meal was mainly fermented in the proximal colon and shifted the fermentation of cereal dietary fiber to more distal parts, resulting in high SCFA levels in the mid colon. LMP, HMP, and aSBM decreased the relative abundance of the genus Lactobacillus and increased that of Prevotella in the colon. The LMP, HMP, and aSBM, differently affected the digestion processes compared to the control diet and shaped the colonic microbiota from a Lactobacillus-dominating flora to a Prevotella-dominating community, with potential health-promoting effects.

Lipolysis and thermogenesis in adipose tissues as new potential mechanisms for metabolic benefits of dietary fiber

ObjectiveDietary fiber consumption is associated with reduced risk for the development of noncommunicable diseases. The aim of the present study was to evaluate the effects of cereal dietary fiber on the levels of proteins involved in lipolysis and thermogenesis in white adipose tissue (WAT) and brown adipose tissue (BAT) of C57 BL/6 J mice fed a high-fat diet (HFD). MethodsMale C57BL/6 J mice were fed normal chow diet (Chow), HFD, HFD plus oat fiber (H-oat), or HFD plus wheat bran fiber (H-wheat) for 24 wk. Body weight and food intake were recorded weekly. Serum adiponectin was assayed by an enzyme-linked immunosorbent assay kit. Western blotting was used to assess the protein expressions of adipose triacylglycerol lipase (ATGL), cAMP protein kinase catalytic subunit (cAMP), protein kinase A (PKA), perilipin A, hormone-sensitive lipase (HSL), uncoupling protein 1 (UCP1), fibroblast growth factor 21 (FGF-21), β3-adrenergic receptor (β3AR), and proliferator-activated receptor gamma coactivator-1 α (PGC-1 α) in the WAT and BAT. ResultsAt the end of the feeding period, body and adipose tissues weight in both H-oat and H-wheat groups were lower than in the HFD group. Mice in the H-oat and H-wheat groups showed an increasing trend in serum adiponectin level. Compared with the HFD group, cereal dietary fiber increased protein expressions involved in the lipolysis and browning process. Compared with the H-wheat group, H-oat was more effective in protein expressions of PKA, PGC-1 α, and UCP1 of the WAT samples. Compared with the H-oat group, H-wheat was more effective in protein expressions of PKA, ATGL, UCP1, β3AR, and FGF-21 of the BAT samples. ConclusionsTaken together, our results suggested that cereal dietary fiber enhanced adipocyte lipolysis by the cAMP–PKA–HSL pathway and promoted WAT browning by activation of UCP1, and consequently reduced visceral fat mass in response to HFD feeding.

Abstract MP23: Carbohydrate Quality and Quantity and Risk of Coronary Heart Disease Among US Women

Background: Poor carbohydrate quality has been associated with increased risk of coronary heart disease (CHD), however the association between the novel carbohydrate to fiber ratio and CHD is unknown. Objective: To prospectively examine the relationship between various carbohydrate quality measures, including the carbohydrate to fiber ratios, and incident CHD in US women. Methods: Dietary and lifestyle behavior data were prospectively collected (1984-2012) in 71,639 women of the Nurses’ Health Study at baseline and every 2-4 years. Participants were free of diabetes, cancer or cardiovascular disease at baseline. Cox regression was used to assess the relationship between carbohydrate quality measures and incident CHD. Results: After 24 years (1,905,240 person-years) of follow-up, we identified 3,267 cases of incident CHD. After adjusting for age, BMI, lifestyle and dietary variables, carbohydrate (RR=1.01, 95% CI: 0.89-1.14, P-trend=0.76), starch (RR=1.11, 95% CI: 0.97 - 1.27, P-trend=0.13) and total fiber intake (RR=0.89, 95% CI: 0.77 - 1.01, P-trend=0.23) were not associated with incident CHD, comparing extreme quintiles of intake. Cereal fiber intake was associated with reduced risk of CHD (RR=0.76, 95% CI: 0.67 - 0.85, P-trend &lt; 0.0001), comparing extreme quintiles of intake, but fruit and vegetable fiber were not associated with incident CHD. In fully adjusted models, the carbohydrate to total fiber (RR=1.08, 95%CI: 0.96 - 1.22, P-trend=0.27) and the starch to total fiber ratios (RR=0.95, 95% CI: 0.84 - 1.08, P-trend=0.80) were not associated with incident CHD, but the carbohydrate to cereal fiber and the starch to cereal fiber ratios were associated with increased risk of CHD (RR=1.19, 95% CI: 1.06 -1.33, P-trend=0.002, and RR=1.23, 95% CI: 1.09-1.39, P-trend &lt;0.0001, respectively), comparing extreme quintiles of intake. Conclusion: Dietary cereal fiber appears to be an important component of carbohydrate quality. The carbohydrate to cereal fiber and the starch to cereal fiber ratios, but not the carbohydrate to total fiber ratio, were associated with an increased risk of CHD.

Effects of cereal soluble dietary fibres on hydrolysis of p-nitrophenyl laurate by pancreatin.

The aim of this study was to investigate the effects of cereal soluble dietary fibres (SDFs), β-glucans (BG) from oat and barley as well as arabinoxylans (AX) from wheat and rye, on the lipolysis of p-nitrophenyl laurate (p-NP laurate). p-NP laurate emulsions were prepared in the presence of increasing concentrations of SDFs (0.1%, 1.0% and 1.5% w/v), and lipolysis of emulsions by pancreatic lipase, particle size distribution of the p-NP laurate droplets, and viscosity of emulsions with soluble dietary fibres were measured. It was found that with increasing viscosity of SDFs, the rate of lipolysis decreased while the initial droplet size of the emulsion increased. Rate coefficients were more consistently correlated with average droplet size than with viscosity, suggesting that SDFs inhibited lipolysis primarily by increasing the size of droplets through flocculation, thereby decreasing the available surface area for lipase action.

Quantitative analysis of absorption, metabolism, and excretion of benzoxazinoids in humans after the consumption of high- and low-benzoxazinoid diets with similar contents of cereal dietary fibres: a crossover study.

Benzoxazinoids (BXs) are a group of wholegrain phytochemicals with potential pharmacological properties; however, limited information exists on their absorption, metabolism, and excretion in humans. The aim of this study was to investigate the dose-dependent uptake and excretion of dietary BXs in a healthy population. Blood and urine were collected from 19 healthy participants from a crossover study after a washout, a LOW BX diet or HIGH BX diet, and analysed for 12 BXs and 4 phenoxazinone derivatives. We found that the plasma BX level peaked approximately 3h after food intake, whereas BXs in urine were present even at 36h after consuming a meal. No phenoxazinone derivatives could be detected in either plasma or urine. The dominant BX metabolite in both plasma and urine was 2-β-D-glucopyranosyloxy-1,4-benzoxazin-3-one (HBOA-Glc), even though 2-β-D-glucopyranosyloxy-4-hydroxy-1,4-benzoxazin-3-one (DIBOA-Glc) was the major component in the diet. The dietary BX treatment correlated well with the plasma and urine levels, illustrating strong dose-dependent BX absorption, which also had a rapid washout, especially from the plasma compartment.

Dietary fiber prevents obesity-related liver lipotoxicity by modulating sterol-regulatory element binding protein pathway in C57BL/6J mice fed a high-fat/cholesterol diet.

Adequate intake of dietary fibers has proven metabolic and cardiovascular benefits, molecular mechanisms remain still limited. This study was aimed to investigate the effects of cereal dietary fiber on obesity-related liver lipotoxicity in C57BL/6J mice fed a high-fat/cholesterol (HFC) diet and underlying mechanism. Forty-eight adult male C57BL/6J mice were randomly given a reference chow diet, or a high fat/choleserol (HFC) diet supplemented with or without oat fiber or wheat bran fiber for 24 weeks. Our results showed mice fed oat or wheat bran fiber exhibtied lower weight gain, lipid profiles and insulin resistance, compared with HFC diet. The two cereal dietary fibers potently decreased protein expressions of sterol regulatory element binding protein-1 and key factors involved in lipogenesis, including fatty acid synthase and acetyl-CoA carboxylase in target tissues. At molecular level, the two cereal dietary fibers augmented protein expressions of peroxisome proliferator-activated receptor alpha and gamma, liver X receptor alpha, and ATP-binding cassette transporter A1 in target tissues. Our findings indicated that cereal dietary fiber supplementation abrogated obesity-related liver lipotoxicity and dyslipidemia in C57BL/6J mice fed a HFC diet. In addition, the efficacy of oat fiber is greater than wheat bran fiber in normalizing these metabolic disorders and pathological profiles.

Structural Transformation of 8-5-Coupled Dehydrodiferulates by Human Intestinal Microbiota.

Ingested dehydrodiferulates (DFAs) are partially released from cereal dietary fiber by human colonic microbiota, but little research has explored the further microbial metabolism of 8-5-coupled DFAs. This study investigated the in vitro microbial metabolism and elucidated major metabolites of free 8-5-DFAs (benzofuran and open forms) and an esterified analogue, 8-5-DFA diethyl ester (benzofuran). Synthesized standard compounds were incubated with fresh human fecal suspensions. Metabolites were isolated and structurally elucidated using high-resolution-LC-time-of-flight-(ToF)-MS, GC-MS, and NMR. Nine metabolite structures were unambiguously characterized with NMR, and four additional metabolites were tentatively identified to reveal structural conversion motifs: propenyl side chain hydrogenation (all substrates), O-demethylation and reductive ring-opening (8-5-DFA diethyl ester and free 8-5-DFA [benzofuran]), and de-esterification (8-5-DFA diethyl ester). A pathway of microbial 8-5-DFA metabolism was proposed based on metabolite formation kinetics. Importantly, de-esterification of the 8-5-DFA diethyl ester occurred primarily after and/or concurrently with other metabolism steps. Cleavage to monomers was not observed.

Distinct difference in absorption pattern in pigs of betaine provided as a supplement or present naturally in cereal dietary fiber.

The net absorption of betaine and choline was determined for 4 h after the first meal of the day in three experiments with porto-arterial catheterized pigs in which betaine was added as a supplement to a low-betaine diet (n=4 pigs) and compared to the net absorption of betaine and choline from high-fiber breads differing in amount and source of dietary fiber (two experiments, n=6 pigs each). Plasma betaine peaked after 30 min when betaine was fed as a supplement, whereas it peaked after 120-180 min when high-fiber breads were fed. Plasma betaine showed no diet×time interaction after feeding with high-fiber breads, indicating that the absorption kinetic did not differ between fiber sources. The net absorption of choline was not affected by the experimental diets. In conclusion, betaine in cereal sources has to be liberated from the matrix prior to absorption, causing delayed absorption.

Effects of cereal fiber on bowel function: A systematic review of intervention trials.

To comprehensively review and quantitatively summarize results from intervention studies that examined the effects of intact cereal dietary fiber on parameters of bowel function. A systematic literature search was conducted using PubMed and EMBASE. Supplementary literature searches included screening reference lists from relevant studies and reviews. Eligible outcomes were stool wet and dry weight, percentage water in stools, stool frequency and consistency, and total transit time. Weighted regression analyses generated mean change (± SD) in these measures per g/d of dietary fiber. Sixty-five intervention studies among generally healthy populations were identified. A quantitative examination of the effects of non-wheat sources of intact cereal dietary fibers was not possible due to an insufficient number of studies. Weighted regression analyses demonstrated that each extra g/d of wheat fiber increased total stool weight by 3.7 ± 0.09 g/d (P < 0.0001; 95%CI: 3.50-3.84), dry stool weight by 0.75 ± 0.03 g/d (P < 0.0001; 95%CI: 0.69-0.82), and stool frequency by 0.004 ± 0.002 times/d (P = 0.0346; 95%CI: 0.0003-0.0078). Transit time decreased by 0.78 ± 0.13 h per additional g/d (P < 0.0001; 95%CI: 0.53-1.04) of wheat fiber among those with an initial transit time greater than 48 h. Wheat dietary fiber, and predominately wheat bran dietary fiber, improves measures of bowel function.