Wholegrain foods made from a novel high-amylose barley variety (Himalaya 292) improve indices of bowel health in human subjects. Br J Nutr. 2008;99:1032-1040. [PMID: 17919346 DOI: 10.1017/s000711450783902x]

Prevotella enterotype associates with diets supporting acidic faecal pH and production of propionic acid by microbiota

Metabolism of dietary fibres by colon microbiota plays an important role for human health. Personal data from a nutrition study (57 subjects) were analysed to elucidate quantitative associations between the diet, faecal microbiome, organic acid concentrations and pH. Ratios of the predominant acids acetate, butyrate and propionate ranged from 1:0.67:0.27 to 1:0.17:0.36. Pectin-rich diets resulted in higher faecal acetate concentrations. Negative correlation between faecal pH and BSS was observed. Higher faecal pH and lower acid concentrations were related to the higher abundance of amino acid degrading Clostridium, Odoribacter and Eubacterium coprostanoligenes, which are weak carbohydrate fermenting taxa. Propionic acid correlated especially to high abundance of Prevotella and low abundance of proteobacteria. The acetate to propionate ratio of the Prevotella enterotype was about half of that of the Bacteroides enterotype. Based on the results we suggest the measurement of faecal pH and organic acid composition for research and diagnostic purposes.

The Development and Evaluation of a Literature-Based Dietary Index for Gut Microbiota

The aim of the study was to develop and evaluate a novel dietary index for gut microbiota (DI-GM) that captures dietary composition related to gut microbiota profiles. We conducted a literature review of longitudinal studies on the association of diet with gut microbiota in adult populations and extracted those dietary components with evidence of beneficial or unfavorable effects. Dietary recall data from the National Health and Nutrition Examination Survey (NHANES, 2005-2010, n = 3812) were used to compute the DI-GM, and associations with biomarkers of gut microbiota diversity (urinary enterodiol and enterolactone) were examined using linear regression. From a review of 106 articles, 14 foods or nutrients were identified as components of the DI-GM, including fermented dairy, chickpeas, soybean, whole grains, fiber, cranberries, avocados, broccoli, coffee, and green tea as beneficial components, and red meat, processed meat, refined grains, and high-fat diet (≥40% of energy from fat) as unfavorable components. Each component was scored 0 or 1 based on sex-specific median intakes, and scores were summed to develop the overall DI-GM score. In the NHANES, DI-GM scores ranged from 0-13 with a mean of 4.8 (SE = 0.04). Positive associations between DI-GM and urinary enterodiol and enterolactone were observed. The association of the novel DI-GM with markers of gut microbiota diversity demonstrates the potential utility of this index for gut health-related studies.

Swapping White for High-Fibre Bread Increases Faecal Abundance of Short-Chain Fatty Acid-Producing Bacteria and Microbiome Diversity: A Randomized, Controlled, Decentralized Trial

A low-fibre diet leads to gut microbiota imbalance, characterized by low diversity and reduced ability to produce beneficial metabolites, such as short-chain fatty acids (SCFAs). This imbalance is associated with poor gastrointestinal and metabolic health. We aimed to determine whether one dietary change, substitution of white bread with high-fibre bread, improves gut microbiota diversity and SCFA-producing capability. Twenty-two healthy adults completed a two-phase randomized, cross-over trial. The participants consumed three slices of a high-fibre bread (Prebiotic Cape Seed Loaf with BARLEYmax®) or control white bread as part of their usual diet for 2 weeks, with the treatment periods separated by a 4-week washout. High-fibre bread consumption increased total dietary fibre intake to 40 g/d, which was double the amount of fibre consumed at baseline or during the white bread intervention. Compared to white bread, the high-fibre bread intervention resulted in higher faecal alpha diversity (Shannon, p = 0.014) and relative abundance of the Lachnospiracae ND3007 group (p < 0.001, FDR = 0.019) and tended to increase the butyrate-producing capability (p = 0.062). In conclusion, substituting white bread with a high-fibre bread improved the diversity of gut microbiota and specific microbes involved in SCFA production and may enhance the butyrate-producing capability of gut microbiota in healthy adults. These findings suggest that a single dietary change involving high-fibre bread provides a practical way for adults to exceed recommended dietary fibre intake levels that improve gut microbiota composition and support gastrointestinal and metabolic health.

Effects of a wholegrain-rich diet on markers of colonic fermentation and bowel function and their associations with the gut microbiome: a randomised controlled cross-over trial

Background

Diets rich in whole grains are associated with health benefits. Yet, it remains unclear whether the benefits are mediated by changes in gut function and fermentation.

Objective

We explored the effects of whole-grain vs. refined-grain diets on markers of colonic fermentation and bowel function, as well as their associations with the gut microbiome.

Methods

Fifty overweight individuals with increased metabolic risk and a high habitual intake of whole grains (~69 g/day) completed a randomised cross-over trial with two 8-week dietary intervention periods comprising a whole-grain diet (≥75 g/day) and a refined-grain diet (<10 g/day), separated by a washout period of ≥6  weeks. A range of markers of colonic fermentation and bowel function were assessed before and after each intervention.

Results

The whole-grain diet increased the levels of faecal butyrate (p = 0.015) and caproate (p = 0.013) compared to the refined-grain diet. No changes in other faecal SCFA, BCFA or urinary levels of microbial-derived proteolytic markers between the two interventions were observed. Similarly, faecal pH remained unchanged. Faecal pH did however increase (p = 0.030) after the refined-grain diet compared to the baseline. Stool frequency was lower at the end of the refined-grain period compared to the end of the whole-grain diet (p = 0.001). No difference in faecal water content was observed between the intervention periods, however, faecal water content increased following the whole-grain period compared to the baseline (p = 0.007). Dry stool energy density was unaffected by the dietary interventions. Nevertheless, it explained 4.7% of the gut microbiome variation at the end of the refined-grain diet, while faecal pH and colonic transit time explained 4.3 and 5%, respectively. Several butyrate-producers (e.g., Faecalibacterium, Roseburia, Butyriciococcus) were inversely associated with colonic transit time and/or faecal pH, while the mucin-degraders Akkermansia and Ruminococcaceae showed the opposite association.

Conclusion

Compared with the refined-grain diet, the whole-grain diet increased faecal butyrate and caproate concentrations as well as stool frequency, emphasising that differences between whole and refined grains affect both colonic fermentation and bowel habits.

A Randomized Dietary Intervention to Increase Colonic and Peripheral Blood Short-Chain Fatty Acids Modulates the Blood B- and T-cell Compartments in Healthy Humans

BACKGROUND

Short-chain fatty acids (SCFA) have immune-modulating effects in animal models of disease. However, there is limited evidence that this may occur in humans.

OBJECTIVES

This study aimed to determine the effects of increased exposure to SCFA via dietary manipulation on colonic fermentation and adaptive immune cells.

METHODS

Twenty healthy, young adults (18-45 years of age) underwent a blinded, randomized, cross-over dietary intervention, consuming a high-SCFA producing diet and matched low-SCFA diet for 21 days with 21-day wash-out in between. SCFA were provided through resistant starch, inulin and apple cider vinegar. Blood and 3-day total fecal output were collected at baseline and at the end of each diet. Gas chromatography was used to measure fecal and plasma SCFA. Flow cytometry was used for peripheral blood immuno-phenotyping.

RESULTS

High-SCFA diet was associated with significantly (paired samples Wilcoxon test) higher median [IQR] fecal SCFA concentrations (86.6 [59.0] vs 75.4 [56.2] µmol/g, P = 0.02) and significantly lower median fecal ammonia concentrations (26.2 [14.7] vs 33.4 [18.5] µmol/g, P = 0.04) than the low-SCFA diet. Plasma propionate (9.87 [12.3] vs 4.72 [7.6] µmol/L, P = 0.049) and butyrate (2.85 [1.35] vs 2.02 [1.29] µmol/L, P = 0.03) were significantly higher after high-SCFA diet than after low-SCFA diet. Blood total B cells (184 [112] vs 199 [143] cells/µL, P = 0.04), naive B cells (83 [66] vs 95 [89] cells/µL, P = 0.02), Th1 cells (22 [19] vs 29 [16] cells/µL, P = 0.03) and mucosal-associated invariant T (MAIT) cells (62 [83] vs 69 [114] cells/µL, P = 0.02) were significantly lower after high-SCFA diet than low-SCFA diet.

CONCLUSION

Increasing colonic and peripheral blood SCFA has discrete effects on circulating immune cells in healthy humans following 3-week intervention. Further studies, e.g., in patients with inflammatory disease, are necessary to determine if these changes have immunomodulatory effects, whether these are therapeutically beneficial, and whether prolonged intake might be required. Clinical trial registry: Australian New Zealand Clinical trials registry: ACTRN12618001054202. <https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=375342&isReview=true>.

Substitution of Refined Conventional Wheat Flour with Wheat High in Resistant Starch Modulates the Intestinal Microbiota and Fecal Metabolites in Healthy Adults: A Randomized, Controlled Trial

BACKGROUND

Resistant starch (RS) confers many health benefits, mostly through the microbial production of SCFAs, but foods containing appreciable RS are limited. High-amylose wheat (HAW) is high in RS and lowers the glycemic response of foods, but whether it can improve gastrointestinal health measures is unknown.

OBJECTIVES

The objective of this study was to determine whether daily consumption of HAW food products improved markers of gastrointestinal health in healthy men and women compared with similar foods made from conventional wheat.

METHODS

Eighty healthy adults (47 women and 33 men) were enrolled in a 4-arm parallel, randomized-controlled, double-blind trial. After a 2-wk low-dietary fiber run-in period, they were randomly allocated to 1 of 4 treatment groups: low-amylose wheat (LAW)-refined (LAW-R), LAW-wholemeal (LAW-W), HAW-refined (HAW-R), and HAW-wholemeal (HAW-W) and consumed the assigned test bread (160 g/d) and biscuits (75 g/d) for 4 wk. Fecal biochemical markers were measured at baseline and 4 wk. Microbial abundance and diversity were quantified using 16S ribosomal RNA sequencing and perceived gut comfort by a semiquantitative questionnaire completed at baseline, 2 wk, and 4 wk.

RESULTS

HAW showed similar effects on fecal output and excretion of total SCFA compared with LAW, but changes were observed in secondary measures for the refined treatment groups. At 4 wk, the HAW-R group had 38% higher fecal butyrate excretion than the LAW-R group (P < 0.05), and higher fecal SCFA-producing bacteria, Roseburia inulinivorans (P < 0.001), than at baseline. In comparison with baseline, LAW-R increased fecal p-cresol concentration, and fecal abundance of a p-cresol-producing bacterium, Clostridium from the Peptostreptococcaceae family, but both were reduced by HAW-R. Amylose level did not affect measures of fecal consistency or adversely affecting digestive comfort.

CONCLUSIONS

Increasing RS intake of healthy adults by substituting refined conventional wheat with refined HAW modulates fecal metabolites and microbes associated with gastrointestinal health.This trial was registered at anzctr.org.au as ACTRN12618001060235.

Tolerability and SCFA production after resistant starch supplementation in humans: a systematic review of randomized controlled studies

BACKGROUND

Resistant starches (RSs) have been advocated as a dietary supplement to address microbiota dysbiosis. They are postulated to act through the production of SCFAs. Their clinical tolerability and effect on SCFA production has not been systematically evaluated.

OBJECTIVES

We conducted a systematic review of RS supplementation as an intervention in adults (healthy individuals and persons with medical conditions) participating in randomized controlled trials. The primary outcome was tolerability of RS supplementation, the secondary outcome was SCFA production.

METHODS

MEDLINE, Embase, and the Cochrane Central Register were searched. Articles were screened, and data extracted, independently and in duplicate.

RESULTS

A total of 39 trials met eligibility criteria, including a total of 2263 patients. Twenty-seven (69%) studies evaluated the impact of RS supplementation in healthy subjects whereas 12 (31%) studies included individuals with an underlying medical condition (e.g., obesity, prediabetes). Type 2 RS was most frequently investigated (29 studies). Of 12 studies performed in subjects with health conditions, 11 reported on tolerability. All studies showed that RS supplementation was tolerated; 9 of these studies used type 2 RS with doses of 20-40 g/d for >4 wk. Of 27 studies performed in healthy subjects, 20 reported on tolerability. In 14 studies, RS supplementation was tolerated, and the majority used type 2 RS with a dose between 20 and 40 g/d. Twenty-one (78%) studies reporting SCFAs used type 2 RS with a dose of 20-40 g/d for 1-4 wk. In 16 of 23 studies (70%), SCFA production was increased, in 7 studies there was no change in SCFA concentration before and after RS supplementation, and in 1 study SCFA concentration decreased.

CONCLUSIONS

Available evidence suggests that RS supplementation is tolerated in both healthy subjects and in those with an underlying medical condition. In addition, SCFA production was increased in most of the studies.

Chemical Characterization and In Vitro Anti-Cancer Activities of a Hot Water Soluble Polysaccharide from Hulless Barley Grass

Hulless barley grass may confer many health benefits attributed to its bioactive functional components, such as polysaccharides. Here, a hot water soluble polysaccharide was extracted from hulless barley grass, and its chemical characterization and in vitro anti-cancer activities were investigated. The yield of hulless barley grass polysaccharide (HBGP) was 2.3%, and the purity reached 99.1% with a polydispersity index (PDI) of 1.11 after purification by a diethylaminoethyl cellulose (DE-32) column and an S-400 high resolution (HR) column. The molecular weight and number-average molecular weight of HBGP were 3.3 × 104 and 2.9 × 104 Da, respectively. The monosaccharide composition of HBGP included 35.1% galactose, 25.6% arabinose, 5.5% glucose, and 5.3% xylose. Based on infrared spectrum analysis, HBGP possessed pyranose and galactose residues. In addition, this water-soluble polysaccharide showed significant cell proliferation inhibitory effects against cancer cell lines HT29, Caco-2, 4T1, and CT26.WT in a dose-dependent manner, especially for HT29 (the half-inhibitory concentration IC50 value = 2.72 mg/mL). The results provide a basis for the development and utilization of hulless barley grass in functional foods to aid in preventing cancer.

Barley: a potential cereal for producing healthy and functional foods

Barley is the fourth largest cereal crop in the world. It is mainly used for feeding, beer production and food. Barley is receiving more attention from both agricultural and food scientists because of its special chemical composition and health benefits. In comparison with other cereal crops, including wheat, rice and maize, barley grains are rich in dietary fiber (such as β-glucan) and tocols, which are beneficial to human health. It is well proved that diets rich in those chemicals can provide protection against hypertension, cardiovascular disease, and diabetes. Barley has been widely recognized to be great potential as a healthy or functional food. In this review, we present the information about the studies on physical structure of barley grain and the distribution of main chemical components, nutrient and functional composition of barley grain and their health benefits, and the approaches of improving and utilizing the nutrient and functional chemicals in barley grain. With the development of processing technologies, functional components in barley grains, especially β-glucan, can be efficiently extracted and concentrated. Moreover, nutrient and functional components in barley grains can be efficiently improved by precise breeding and agronomic approaches. The review highlights the great potential of barley used as healthy and functional foods, and may be instructive for better utilization of barley in food processing.

An extensive review: How starch and gluten impact dough machinability and resultant bread qualities

Wheat flour can form dough with a three-dimensional viscoelastic structure that is responsible for gas holding during fermentation and oven-rise, creating a typical fixed, open-cell foam structure of bread after baking. As the major components of dough, the continuous reticular skeleton formed by gluten proteins and the concentrated starch granules entrapped in gluten matrix predominantly determine dough rheological behaviors and bread qualities. This review surveys the latest literatures and draws out a conclusion from a plethora of information related to the filling effects of starch granules on gluten matrix and the cross-linking mechanisms between gluten proteins and starch granules, which is of great significance to provide sufficient scientific knowledge for development of bread with satisfactory attributes and quality control of end products.

Fiber-Rich Barley Increases Butyric Acid-Producing Bacteria in the Human Gut Microbiota

Butyric acid produced in the intestine by butyric acid-producing bacteria (BAPB) is known to suppress excessive inflammatory response and may prevent chronic disease development. We evaluated whether fiber-rich barley intake increases BAPB in the gut and concomitantly butyric acid in feces. Eighteen healthy adults received granola containing functional barley (BARLEYmax^®) once daily for four weeks. Fecal DNA before intake, after intake, and one month after intake was analyzed using 16S rRNA gene sequencing to assess microbial diversity, microbial composition at the order level, and the proportion of BAPB. Fecal butyric acid concentration was also measured. There were no significant differences in diversities and microbial composition between samples. The proportion of BAPB increased significantly after the intake (from 5.9% to 8.2%). However, one month after stopping the intake, the proportion of BAPB returned to the original value (5.4%). Fecal butyric acid concentration increased significantly from 0.99 mg/g feces before intake to 1.43 mg/g after intake (p = 0.028), which decreased significantly to 0.87 mg/g after stopping intake (p = 0.008). As BAPB produce butyric acid by degrading dietary fiber, functional barley may act as a prebiotic, increasing BAPB and consequently butyric acid in the intestine.

Superior haplotypes towards development of low glycemic index rice with preferred grain and cooking quality

Increasing trends in the occurrence of diabetes underline the need to develop low glycemic index (GI) rice with preferred grain quality. In the current study, a diverse set of 3 K sub-panel of rice consisting of 150 accessions was evaluated for resistant starch and predicted glycemic index, including nine other quality traits under transplanted situation. Significant variations were noticed among the accessions for the traits evaluated. Trait associations had shown that amylose content possess significant positive and negative association with resistant starch and predicted glycemic index. Genome-wide association studies with 500 K SNPs based on MLM model resulted in a total of 41 marker-trait associations (MTAs), which were further confirmed and validated with mrMLM multi-locus model. We have also determined the allelic effect of identified MTAs for 11 targeted traits and found favorable SNPs for 8 traits. A total of 11 genes were selected for haplo-pheno analysis to identify the superior haplotypes for the target traits where haplotypes ranges from 2 (Os10g0469000-GC) to 15 (Os06g18720-AC). Superior haplotypes for RS and PGI, the candidate gene Os06g11100 (H4-3.28% for high RS) and Os08g12590 (H13-62.52 as intermediate PGI). The identified superior donors possessing superior haplotype combinations may be utilized in Haplotype-based breeding to developing next-generation tailor-made high quality healthier rice varieties suiting consumer preference and market demand.

Understanding the regulatory relationship of abscisic acid and bZIP transcription factors towards amylose biosynthesis in wheat

Starch is biosynthesized during seed development and this process is regulated by many bZIP proteins in bread wheat. Abscisic acid (ABA), an important phyto-hormone involved in various physiological processes mediated by bZIPs in plants including seed development. The 'Group A' TabZIP transcription factors play important roles in the ABA signaling pathway in Arabidopsis, rice and other cereal crops but their role in regulation of amylose biosynthesis in wheat is limited. In this study 83 'Group A' TabZIPs were characterized by gene expression analysis in wheat amylose mutants. A set of 17 TabZIPs was selected on the basis of differential expression (> 2 fold) in low and high amylose mutants from RNA-seq data and validated by qRT PCR. Based on qRT PCR and correlation analysis out of the 17 TabZIPs six differentially expressed candidate TabZIPs were identified, involving in high amylose biosynthesis. The TabZIP175.2, identified as upregulated in all high amylose lines and TabZIP90.2, TabZIP129.1, TabZIP132.2, TabZIP143 and TabZIP159.2 were found downregulated in all low amylose lines, after exogenous supply of ABA. Proximal promoter analysis of starch pathway genes revealed the presence of ABA-responsive elements (ABREs) that are putative binding sites for bZIPs. Collectively, these findings indicated the involvement of putative six candidate TabZIPs as transcriptional regulators of amylose related genes via an ABA-dependent pathway in wheat. This study could help the investigators to make an informed decision to edit wheat genome for high/low amylose content using gene-editing technologies.

Minor Changes in the Composition and Function of the Gut Microbiota During a 12-Week Whole Grain Wheat or Refined Wheat Intervention Correlate with Liver Fat in Overweight and Obese Adults

BACKGROUND

Whole grain wheat (WGW) products are advocated as a healthy choice when compared with refined wheat (RW). One proposed mechanism for these health benefits is via the microbiota, because WGW contains multiple fibers. WGW consumption has been proposed to ameliorate nonalcoholic fatty liver disease, in which microbiota might play a role.

OBJECTIVES

We investigated the effect of WGW compared with RW intervention on the fecal microbiota composition and functionality, and correlated intervention-induced changes in bacteria with changes in liver health parameters in adults with overweight or obesity.

METHODS

We used data of a 12-wk double-blind, randomized, controlled, parallel trial to examine the effects of a WGW (98 g/d) or RW (98 g/d) intervention on the secondary outcomes fecal microbiota composition, predicted microbiota functionality, and stool consistency in 37 women and men (aged 45-70 y, BMI 25-35 kg/m2). The changes in microbiota composition, measured using 16S ribosomal RNA gene sequencing, after a 12-wk intervention were analyzed with nonparametric tests, and correlated with changes in liver fat and circulating concentrations of liver enzymes including alanine transaminase, aspartate transaminase, γ-glutamyltransferase, and serum amyloid A.

RESULTS

The WGW intervention increased the mean (± SD) relative abundances of Ruminococcaceae_UCG-014 (baseline: 2.2 ± 4.6%, differential change over time (Δ) 0.51 ± 4.2%), Ruminiclostridium_9 (baseline: 0.065 ± 0.11%, Δ 0.054 ± 0.14%), and Ruminococcaceae_NK4A214_group (baseline: 0.37 ± 0.56%, Δ 0.17 ± 0.83%), and also the predicted pathway acetyl-CoA fermentation to butyrate II (baseline: 0.23 ± 0.062%, Δ 0.035 ± 0.059%), compared with the RW intervention (P values <0.05). A change in Ruminococcaceae_NK4A214_group was positively correlated with the change in liver fat, in both the WGW (ρ = 0.54; P = 0.026) and RW (ρ = 0.67; P = 0.024) groups.

CONCLUSIONS

In middle-aged overweight and obese adults, a 12-wk WGW intervention increased the relative abundance of a number of bacterial taxa from the family Ruminococcaceae and increased predicted fermentation pathways when compared with an RW intervention. Potential protective health effects of replacement of RW by WGW on metabolic organs, such as the liver, via modulation of the microbiota, deserve further investigation.This trial was registered at clinicaltrials.gov as NCT02385149.

Health benefits of whole grain: effects on dietary carbohydrate quality, the gut microbiome, and consequences of processing

Grains are important sources of carbohydrates in global dietary patterns. The majority of these carbohydrates, especially in refined-grain products, are digestible. Most carbohydrate digestion takes place in the small intestine where monosaccharides (predominantly glucose) are absorbed, delivering energy to the body. However, a considerable part of the carbohydrates, especially in whole grains, is indigestible dietary fibers. These impact gut motility and transit and are useful substrates for the gut microbiota affecting its composition and quality. For the most part, the profile of digestible and indigestible carbohydrates and their complexity determine the nutritional quality of carbohydrates. Whole grains are more complex than refined grains and are promoted as part of a healthy and sustainable diet mainly because the contribution of indigestible carbohydrates, and their co-passenger nutrients, is significantly higher. Higher consumption of whole grain is recommended because it is associated with lower incidence of, and mortality from, CVD, type 2 diabetes, and some cancers. This may be due in part to effects on the gut microbiota. Although processing of cereals during milling and food manufacturing is necessary to make them edible, it also offers the opportunity to still further improve the nutritional quality of whole-grain flours and foods made from them. Changing the composition and availability of grain carbohydrates and phytochemicals during processing may positively affect the gut microbiota and improve health.

Characterisation of Cellulose Synthase Like F6 (CslF6) Mutants Shows Altered Carbon Metabolism in β-D-(1,3;1,4)-Glucan Deficient Grain in Brachypodium distachyon

Brachypodium distachyon is a small, fast growing grass species in the Pooideae subfamily that has become established as a model for other temperate cereals of agricultural significance, such as barley (Hordeum vulgare) and wheat (Triticum aestivum). The unusually high content in whole grains of β-D-(1,3;1,4)-glucan or mixed linkage glucan (MLG), considered a valuable dietary fibre due to its increased solubility in water compared with cellulose, makes B. distachyon an attractive model for these polysaccharides. The carbohydrate composition of grain in B. distachyon is interesting not only in understanding the synthesis of MLG, but more broadly in the mechanism(s) of carbon partitioning in cereal grains. Several mutants in the major MLG synthase, cellulose synthase like (CSL) F6, were identified in a screen of a TILLING population that show a loss of function in vitro. Surprisingly, loss of cslf6 synthase capacity appears to have a severe impact on survival, growth, and development in B. distachyon in contrast to equivalent mutants in barley and rice. One mutant, A656T, which showed milder growth impacts in heterozygotes shows a 21% (w/w) reduction in average grain MLG and more than doubling of starch compared with wildtype. The endosperm architecture of grains with the A656T mutation is altered, with a reduction in wall thickness and increased deposition of starch in larger granules than typical of wildtype B. distachyon. Together these changes demonstrate an alteration in the carbon storage of cslf6 mutant grains in response to reduced MLG synthase capacity and a possible cross-regulation with starch synthesis which should be a focus in future work in composition of these grains. The consequences of these findings for the use of B. distachyon as a model species for understanding MLG synthesis, and more broadly the implications for improving the nutritional value of cereal grains through alteration of soluble dietary fibre content are discussed.

Gut microbiome responses to dietary intake of grain-based fibers with the potential to modulate markers of metabolic disease: a systematic literature review

CONTEXT

Cereal fiber modulates the gut microbiome and benefits metabolic health. The potential link between these effects is of interest.0.

OBJECTIVE

The aim for this systematic review was to assess evidence surrounding the influence of cereal fiber intake on microbiome composition, microbiome diversity, short-chain fatty acid production, and risk factors for metabolic syndrome.

DATA SOURCES AND EXTRACTION

The MEDLINE, PubMed, CINAHL, and Cochrane Library databases were searched systematically, and quality of studies was assessed using the Cochrane Risk of Bias 2.0 tool. Evidence relating to study design, dietary data collection, and outcomes was qualitatively synthesized on the basis of fiber type.

DATA ANALYSIS

Forty-six primary publications and 2 secondary analyses were included. Cereal fiber modulated the microbiome in most studies; however, taxonomic changes indicated high heterogeneity. Short-chain fatty acid production, microbiome diversity, and metabolic-related outcomes varied and did not always occur in parallel with microbiome changes. Poor dietary data were a further limitation.

CONCLUSIONS

Cereal fiber may modulate the gut microbiome; however, evidence of the link between this and metabolic outcomes is limited. Additional research is required with a focus on robust and consistent methodology.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42018107117.

Molecular Mechanism of Functional Ingredients in Barley to Combat Human Chronic Diseases

Barley plays an important role in health and civilization of human migration from Africa to Asia, later to Eurasia. We demonstrated the systematic mechanism of functional ingredients in barley to combat chronic diseases, based on PubMed, CNKI, and ISI Web of Science databases from 2004 to 2020. Barley and its extracts are rich in 30 ingredients to combat more than 20 chronic diseases, which include the 14 similar and 9 different chronic diseases between grains and grass, due to the major molecular mechanism of six functional ingredients of barley grass (GABA, flavonoids, SOD, K-Ca, vitamins, and tryptophan) and grains (β-glucans, polyphenols, arabinoxylan, phytosterols, tocols, and resistant starch). The antioxidant activity of barley grass and grain has the same and different functional components. These results support findings that barley grain and its grass are the best functional food, promoting ancient Babylonian and Egyptian civilizations, and further show the depending functional ingredients for diet from Pliocene hominids in Africa and Neanderthals in Europe to modern humans in the world. This review paper not only reveals the formation and action mechanism of barley diet overcoming human chronic diseases, but also provides scientific basis for the development of health products and drugs for the prevention and treatment of human chronic diseases.

Effect of whole-grain consumption on changes in fecal microbiota: a review of human intervention trials

Whole-grain (WG) consumption is known to have beneficial effects on human health. However, the influence of WGs on the microbiota is not well understood. To evaluate how WG intake modulates the gut microbiota composition, a literature review of human intervention studies was conducted. Whole grain, whether a mixed WG food or diet (n = 5) or specific WG intervention (WG wheat [n = 5], barley [n = 2], rye [n = 2] or rice, corn, or oats [n = 1 for each]), generally modified microbiota composition but did so inconsistently across measurements of microbial diversity and taxa. Interventions used both parallel and crossover designs and varied from single product substitutions to fully controlled diets with WG exposures of 3-12 weeks. The effect of amount of WG was difficult to capture due to variable reporting of WG. Methods used to measure microbiota varied in ability to resolve changes at different taxonomic levels, and comparisons of interventions using similar methods was lacking. Because many dietary components besides WGs alter gut microbiota, further research is needed, particularly in linking microbiota changes to health outcomes, and study design recommendations for future research on WGs and microbiota are warranted.

Effects of BARLEYmax and high-β-glucan barley line on short-chain fatty acids production and microbiota from the cecum to the distal colon in rats

We investigated whether supplementation with the barley line BARLEYmax (Tantangara; BM), which contains three fermentable fibers (fructan, β-glucan, and resistant starch), modifies the microbiota in cecal and distal colonic digesta in addition to short-chain fatty acids (SCFAs) production more favorably than supplementation with a high-β-glucan barley line (BG012; BG). Male Sprague-Dawley rats were randomly divided into 3 groups that were fed an AIN-93G-based diet that contained 5% fiber provided by cellulose (control), BM or BG. Four weeks after starting the respective diets, the animals were sacrificed and digesta from the cecum, proximal colon and distal colon were collected and the SCFA concentrations were quantified. Microbiota in the cecal and distal colonic digesta were analyzed by 16S rRNA sequencing. The concentrations of acetate and n-butyrate in cecal digesta were significantly higher in the BM and BG groups than in the control group, whereas the concentration of total SCFAs in cecal digesta was significantly higher only in the BM group than in the control group. The concentrations of acetate and total SCFAs in the distal colonic digesta were significantly higher only in the BM group than in the control group. The abundance of Bacteroidetes in cecal digesta was significantly higher in the BM group than in the control group. In contrast, the abundance of Firmicutes in cecal digesta was significantly lower in the BM and BG groups than in the control group. These results indicated that BM increased the concentration of total SCFAs in the distal colonic digesta. These changes might have been caused by fructan and resistant starch in addition to β-glucan. In conclusion, fermentable fibers in BM reached the distal colon and modified the microbiota, leading to an increase in the concentration of total SCFAs in the distal colonic digesta, more effectively compared with the high-β-glucan barley line (BG).

Analysis of short-chain fatty acids in human feces: A scoping review

Short-chain fatty acids (SCFAs) play a crucial role in maintaining homeostasis in humans, therefore the importance of a good and reliable SCFAs analytical detection has raised a lot in the past few years. The aim of this scoping review is to show the trends in the development of different methods of SCFAs analysis in feces, based on the literature published in the last eleven years in all major indexing databases. The search criteria included analytical quantification techniques of SCFAs in different human clinical and in vivo studies. SCFAs analysis is still predominantly performed using gas chromatography (GC), followed by high performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR) and capillary electrophoresis (CE). Performances, drawbacks and advantages of these methods are discussed, especially in the light of choosing a proper pretreatment, as feces is a complex biological material. Further optimization to develop a simple, cost effective and robust method for routine use is needed.

Optimization of additive content and their combination to improve the quality of pure barley bread

The objective of this study was to model the influence of pregelatinized OSA starch (OSA), wheat gluten (Gl) and xylanase (Xyl) on breadmaking potential of barley flour by using response surface methodology. Addition of these ingredients had significant effect on specific bread volume, crust and crumb lightness, crumb texture, average cell size and crumb density. OSA showed the most pronounced effect on specific bread volume, average cell size, crumb density and hardness. Interaction between OSA and Gl, as well as Gl and Xyl, respectively, increased and decreased the specific bread volume and crumb chewiness, while the interaction between OSA and Xyl decreased the specific volume decrease and increased crumb chewiness. An optimal barley bread formulation appeared to be the one containing 9.68% OSA, 2.0% Gl and 4.51 g/100 kg Xyl. This optimal barley bread formulation predicted an increment of 14-28% in volume and a decrease of 105-217% in crumb chewiness in comparison to formulations containing medium amounts of improvers (1% Gl, 5% OSA, 2.5 g/100 kg Xyl).

The Effects of Moderate Whole Grain Consumption on Fasting Glucose and Lipids, Gastrointestinal Symptoms, and Microbiota

This study was designed to determine if providing wheat, corn, and rice as whole (WG) or refined grains (RG) under free-living conditions will change parameters of health over a six-week intervention in healthy, habitual non-WG consumers. Measurements of body composition, fecal microbiota, fasting blood glucose, total cholesterol, high density lipoprotein (HDL), low density lipoprotein (LDL), and triglycerides were made at baseline and post intervention. Subjects were given adequate servings of either WG or RG products based on their caloric need and asked to keep records of grain consumption, bowel movements, and GI symptoms weekly. After six weeks, subjects repeated baseline testing. Significant decreases in total, LDL, and non-HDL cholesterol were seen after the WG treatments but were not observed in the RG treatment. During Week 6, bowel movement frequency increased with increased WG consumption. No significant differences in microbiota were seen between baseline and post intervention, although, abundance of order Erysipelotrichales increased in RG subjects who ate more than 50% of the RG market basket products. Increasing consumption of WGs can alter parameters of health, but more research is needed to better elucidate the relationship between the amount consumed and the health-related outcome.

Nutrient Intake Is Associated with Longevity Characterization by Metabolites and Element Profiles of Healthy Centenarians

The relationships between diet and metabolites as well as element profiles in healthy centenarians are important but remain inconclusive. Therefore, to test the interesting hypothesis that there would be distinctive features of metabolites and element profiles in healthy centenarians, and that these would be associated with nutrient intake; the short chain fatty acids (SCFAs), total bile acids and ammonia in feces, phenol, p-cresol, uric acid, urea, creatinine and ammonia in urine, and element profiles in fingernails were determined in 90 healthy elderly people, including centenarians from Bama county (China)—a famous longevous region—and elderly people aged 80–99 from the longevous region and a non-longevous region. The partial least squares-discriminant analysis was used for pattern recognition. As a result, the centenarians showed a distinct metabolic pattern. Seven characteristic components closely related to the centenarians were identified, including acetic acid, total SCFA, Mn, Co, propionic acid, butyric acid and valeric acid. Their concentrations were significantly higher in the centenarians group (p < 0.05). Additionally, the dietary fiber intake was positively associated with butyric acid contents in feces (r = 0.896, p < 0.01), and negatively associated with phenol in urine (r = −0.326, p < 0.01). The results suggest that the specific metabolic pattern of centenarians may have an important and positive influence on the formation of the longevity phenomenon. Elevated dietary fiber intake should be a path toward health and longevity.

Positive effects of resistant starch supplementation on bowel function in healthy adults: a systematic review and meta-analysis of randomized controlled trials

Animal experimental studies have found that resistant starch can significantly improve bowel function, but the outcomes are mixed while conducting human studies. Thus, we conducted a systematic review and meta-analysis of randomized controlled trials to evaluate the relationship between resistant starch supplementation and large intestinal function. Three electronic databases (PubMed, Embase, Scopus) were searched to identify eligible studies. The standardized mean difference (SMD) or weighted mean difference (WMD) was calculated using a fixed-effects model or a random-effects model. The pooled findings revealed that resistant starch significantly increased fecal wet weight (WMD 35.51 g/d, 95% CI 1.21, 69.82) and butyrate concentration (SMD 0.61, 95% CI 0.32, 0.89). Also, it significantly reduced fecal PH (WMD -0.19, 95% CI -0.35, -0.03), but the increment of defecation frequency were not statistically significant (WMD 0.04stools/g, 95% CI -0.08, 0.16). To conclude, our study found that resistant starch elicited a beneficial effect on the function of large bowel in healthy adults.[Formula: see text].

A single amino acid mutation of OsSBEIIb contributes to resistant starch accumulation in rice

Foods rich in resistant starch can help prevent various diseases, including diabetes, colon cancers, diarrhea, and chronic renal and hepatic diseases. Variations in starch biosynthesis enzymes could contribute to the high content of resistant starch in some cultivars of rice (Oryza sativa L.). Our previously published work indicated that the sbe3-rs gene in the rice mutant line, 'Jiangtangdao1' was a putative allele of the rice starch branching enzyme gene SBEIIb (previously known as SBE3); sbe3-rs might control the biosynthesis of the high resistant starch content in the rice line. Biomolecular analysis showed that the activity of SBEs was significantly lower in soluble extracts of immature seeds harvested from 'Jiangtangdao1' 15 days after flowering than in the extracts of the wild-type rice line 'Huaqingdao'. We performed gene complementation assays by introducing the wild-type OsSBEIIb into the sbe3-rs mutant 'Jiangtangdao1'. The genetically complemented lines demonstrated restored seed-related traits. The structures of endosperm amylopectin and the morphological and physicochemical properties of the starch granules in the transformants recovered to wild-type levels. This study provides evidence that sbe3-rs is a novel allele of OsSBEIIb, responsible for biosynthesis of high resistant starch in 'Jiangtangdao1'.

Extruded whole grain diets based on brown, soaked and germinated rice. Effects on cecum health, calcium absorption and bone parameters of growing Wistar rats. Part I

The influence of diets with whole rice processed ingredients on cecum health, calcium absorption and bone parameters was studied using an animal model.

Soluble arabinoxylan enhances large intestinal microbial health biomarkers in pigs fed a red meat-containing diet

OBJECTIVES

The aim of this study was to investigate how moderately increased dietary red meat combined with a soluble fiber (wheat arabinoxylan [AX]) alters the large intestinal microbiota in terms of fermentative end products and microbial community profiles in pigs.

METHODS

Four groups of 10 pigs were fed Western-type diets containing two amounts of red meat, with or without a solubilized wheat AX-rich fraction for 4 wk. After euthanasia, fermentative end products (short-chain fatty acids, ammonia) of digesta from four sections of large intestine were measured. Di-amino-pimelic acid was a measure of total microbial biomass, and bacterial profiles were determined using a phylogenetic microarray. A factorial model determined effects of AX and meat content.

RESULTS

Arabinoxylan was highly fermentable in the cecum, as indicated by increased concentrations of short-chain fatty acids (particularly propionate). Protein fermentation end products were decreased, as indicated by the reduced ammonia and branched-chain ratio although this effect was less prominent distally. Microbial profiles in the distal large intestine differed in the presence of AX (including promotion of Faecalibacterium prausnitzii), consistent with an increase in carbohydrate versus protein fermentation. Increased di-amino-pimelic acid (P < 0.0001) suggested increased microbial biomass for animals fed AX.

CONCLUSIONS

Solubilized wheat AX has the potential to counteract the effects of dietary red meat by reducing protein fermentation and its resultant toxic end products such as ammonia, as well as leading to a positive shift in fermentation end products and microbial profiles in the large intestine.

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

AIM

To comprehensively review and quantitatively summarize results from intervention studies that examined the effects of intact cereal dietary fiber on parameters of bowel function.

METHODS

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.

RESULTS

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.

CONCLUSION

Wheat dietary fiber, and predominately wheat bran dietary fiber, improves measures of bowel function.

Effect of Stay-Green Wheat, a Novel Variety of Wheat in China, on Glucose and Lipid Metabolism in High-Fat Diet Induced Type 2 Diabetic Rats

The use of natural hypoglycemic compounds is important in preventing and managing Type 2 diabetes mellitus (T2DM). Forty male Sprague-Dawley rats weighing 150–180 g were divided into four groups to investigate the effects of the compounds in stay-green wheat (SGW), a novel variety of wheat in China, on T2DM rats. The control group (NDC) was fed with a standard diet, while T2DM was induced in the rats belonging to the other three groups by a high-fat diet followed by a streptozotocin (STZ) injection. The T2DM rats were further divided into a T2DM control group (DC), which was fed with the normal diet containing 50% common wheat flour, a high dose SGW group (HGW) fed with a diet containing 50% SGW flour, and a low dose SGW group (LGW) fed with a diet containing 25% SGW flour and 25% common wheat flour. Our results showed that SGW contained cereal antioxidants, particularly high in flavonoids and anthocyanins (46.14 ± 1.80 mg GAE/100 g DW and 1.73 ± 0.14 mg CGE/100 g DW, respectively). Furthermore, SGW exhibited a strong antioxidant activity in vitro (30.33 ± 2.66 μg TE/g DW, p < 0.01). Administration of the SGW at a high and low dose showed significant down-regulatory effects on fasting blood glucose (decreasing by 11.3% and 7.0%, respectively), insulin levels (decreasing by 12.3% and 9.7%, respectively), and lipid status (decreasing by 9.1% and 7.5%, respectively) in T2DM rats (p < 0.01). In addition, the T2DM groups treated with SGW at a high and low dose showed a significant increase in the blood superoxide dismutase (1.17 fold and 1.15 fold, respectively) and glutathione peroxidase activities (1.37 fold and 1.30 fold, respectively) compared with the DC group (p < 0.01). The normalized impaired antioxidant status of the pancreatic islet and of the liver compared with the DC group was also significantly increased. Our results indicated that SGW components exerting a glycemic control and a serum lipid regulation effect may be due to their free radical scavenging capacities to reduce the risk of T2DM in experimental diabetic rats.

Dietary manipulation of oncogenic microRNA expression in human rectal mucosa: a randomized trial

High red meat (HRM) intake is associated with increased colorectal cancer risk, while resistant starch is probably protective. Resistant starch fermentation produces butyrate, which can alter microRNA (miRNA) levels in colorectal cancer cells in vitro; effects of red meat and resistant starch on miRNA expression in vivo were unknown. This study examined whether a HRM diet altered miRNA expression in rectal mucosa tissue of healthy volunteers, and if supplementation with butyrylated resistant starch (HRM+HAMSB) modified this response. In a randomized cross-over design, 23 volunteers undertook four 4-week dietary interventions; an HRM diet (300 g/day lean red meat) and an HRM+HAMSB diet (HRM with 40 g/day butyrylated high amylose maize starch), preceded by an entry diet and separated by a washout. Fecal butyrate increased with the HRM+HAMSB diet. Levels of oncogenic mature miRNAs, including miR17-92 cluster miRNAs and miR21, increased in the rectal mucosa with the HRM diet, whereas the HRM+HAMSB diet restored miR17-92 miRNAs, but not miR21, to baseline levels. Elevated miR17-92 and miR21 in the HRM diet corresponded with increased cell proliferation, and a decrease in miR17-92 target gene transcript levels, including CDKN1A. The oncogenic miR17-92 cluster is differentially regulated by dietary factors that increase or decrease risk for colorectal cancer, and this may explain, at least in part, the respective risk profiles of HRM and resistant starch. These findings support increased resistant starch consumption as a means of reducing risk associated with an HRM diet.

New starch phenotypes produced by TILLING in barley

Barley grain starch is formed by amylose and amylopectin in a 1∶3 ratio, and is packed into granules of different dimensions. The distribution of granule dimension is bimodal, with a majority of small spherical B-granules and a smaller amount of large discoidal A-granules containing the majority of the starch. Starch granules are semi-crystalline structures with characteristic X-ray diffraction patterns. Distinct features of starch granules are controlled by different enzymes and are relevant for nutritional value or industrial applications. Here, the Targeting-Induced Local Lesions IN Genomes (TILLING) approach was applied on the barley TILLMore TILLING population to identify 29 new alleles in five genes related to starch metabolism known to be expressed in the endosperm during grain filling: BMY1 (Beta-amylase 1), GBSSI (Granule Bound Starch Synthase I), LDA1 (Limit Dextrinase 1), SSI (Starch Synthase I), SSIIa (Starch Synthase IIa). Reserve starch of nine M3 mutant lines carrying missense or nonsense mutations was analysed for granule size, crystallinity and amylose/amylopectin content. Seven mutant lines presented starches with different features in respect to the wild-type: (i) a mutant line with a missense mutation in GBSSI showed a 4-fold reduced amylose/amylopectin ratio; (ii) a missense mutations in SSI resulted in 2-fold increase in A:B granule ratio; (iii) a nonsense mutation in SSIIa was associated with shrunken seeds with a 2-fold increased amylose/amylopectin ratio and different type of crystal packing in the granule; (iv) the remaining four missense mutations suggested a role of LDA1 in granule initiation, and of SSIIa in determining the size of A-granules. We demonstrate the feasibility of the TILLING approach to identify new alleles in genes related to starch metabolism in barley. Based on their novel physicochemical properties, some of the identified new mutations may have nutritional and/or industrial applications.

Resistant starch: promise for improving human health

Ongoing research to develop digestion-resistant starch for human health promotion integrates the disciplines of starch chemistry, agronomy, analytical chemistry, food science, nutrition, pathology, and microbiology. The objectives of this research include identifying components of starch structure that confer digestion resistance, developing novel plants and starches, and modifying foods to incorporate these starches. Furthermore, recent and ongoing studies address the impact of digestion-resistant starches on the prevention and control of chronic human diseases, including diabetes, colon cancer, and obesity. This review provides a transdisciplinary overview of this field, including a description of types of resistant starches; factors in plants that affect digestion resistance; methods for starch analysis; challenges in developing food products with resistant starches; mammalian intestinal and gut bacterial metabolism; potential effects on gut microbiota; and impacts and mechanisms for the prevention and control of colon cancer, diabetes, and obesity. Although this has been an active area of research and considerable progress has been made, many questions regarding how to best use digestion-resistant starches in human diets for disease prevention must be answered before the full potential of resistant starches can be realized.

Whole grain and body weight changes in apparently healthy adults: a systematic review and meta-analysis of randomized controlled studies

BACKGROUND

Whole grains have received increased attention for their potential role in weight regulation. A high intake has been associated with smaller weight gain in prospective cohort studies, whereas the evidence from randomized controlled studies has been less consistent.

OBJECTIVE

We assessed the effects of whole-grain compared with non-whole-grain foods on changes in body weight, percentage of body fat, and waist circumference by using a meta-analytic approach.

DESIGN

We conducted a systematic literature search in selected databases. Studies were included in the review if they were randomized controlled studies of whole-grain compared with a non-whole-grain control in adults. A total of 2516 articles were screened for eligibility, and relevant data were extracted from 26 studies. Weighted mean differences were calculated, and a metaregression analysis was performed by using the whole-grain dose (g/d).

RESULTS

Data from 2060 participants were included. Whole-grain intake did not show any effect on body weight (weighted difference: 0.06 kg; 95% CI: -0.09, 0.20 kg; P = 0.45), but a small effect on the percentage of body fat was seen (weighted difference: -0.48%; 95% CI: -0.95%, -0.01%; P = 0.04) compared with that for a control. An examination of the impact of daily whole-grain intake could predict differences between groups, but there was no significant association (β = -0.0013 kg × g/d; 95% CI: -0.011, 0.009 kg × g/d).

CONCLUSIONS

Whole-grain consumption does not decrease body weight compared with control consumption, but a small beneficial effect on body fat may be present. The relatively short duration of intervention studies (≤16 wk) may explain the lack of difference in body weight and fat. Discrepancies between studies may be caused by differences in study design.

The potential role of phytochemicals in wholegrain cereals for the prevention of type-2 diabetes

Diets high in wholegrains are associated with a 20-30% reduction in risk of developing type-2 diabetes (T2D), which is attributed to a variety of wholegrain components, notably dietary fibre, vitamins, minerals and phytochemicals. Most phytochemicals function as antioxidants in vitro and have the potential to mitigate oxidative stress and inflammation which are implicated in the pathogenesis of T2D. In this review we compare the content and bioavailability of phytochemicals in wheat, barley, rice, rye and oat varieties and critically evaluate the evidence for wholegrain cereals and cereal fractions increasing plasma phytochemical concentrations and reducing oxidative stress and inflammation in humans. Phytochemical content varies considerably within and among the major cereal varieties. Differences in genetics and agro-climatic conditions explain much of the variation. For a number of the major phytochemicals, such as phenolics and flavanoids, their content in grains may be high but because these compounds are tightly bound to the cell wall matrix, their bioavailability is often limited. Clinical trials show that postprandial plasma phenolic concentrations are increased after consumption of wholegrain wheat or wheat bran however the magnitude of the response is usually modest and transient. Whether this is sufficient to bolster antioxidant defences and translates into improved health outcomes is still uncertain. Increased phytochemical bioavailability may be achieved through bio-processing of grains but the improvements so far are small and have not yet led to changes in clinical or physiological markers associated with reduced risk of T2D. Furthermore, the effect of wholegrain cereals and cereal fractions on biomarkers of oxidative stress or strengthening antioxidant defence in healthy individuals is generally small or nonexistent, whereas biomarkers of systemic inflammation tend to be reduced in people consuming high intakes of wholegrains. Future dietary intervention studies seeking to establish a direct role of phytochemicals in mediating the metabolic health benefits of wholegrains, and their potential for mitigating disease progression, should consider using varieties that deliver the highest possible levels of bioavailable phytochemicals in the context of whole foods and diets. Both postprandial and prolonged responses in systemic phytochemical concentrations and markers of inflammation and oxidative stress should be assessed along with changes related to health outcomes in healthy individuals as well as those with metabolic disease.

Fructan extracts from wheat stem and barley grain stimulate large bowel fermentation in rats

The benefits of inulin-type fructans for bowel health are well established, but less so for other fructan sources. In vitro data suggest that fructans extracted from cereals are readily fermented and produce favorable short-chain fatty acid profiles; however, whether this occurs in vivo is unknown. We hypothesized that in rats, fructans extracted from wheat stem and barley grain would have similar effects on fermentation as oligofructose (OF). Fifty-six male Sprague-Dawley rats were randomly assigned to 1 of 7 dietary treatments that contained either 2% or 5% fructan, provided by a barley grain fructan extract (BGFE), a wheat stem fructan extract, or OF or no added fructan (control). The duration of the feeding study was 14 days. Rats fed diets containing 5% fructan had higher cecal digesta weights; larger acetate, propionate, and total short-chain fatty acid pools; and lower pHs in comparison with the control group. In addition, only the 5% OF and 5% BGFE groups increased cecal butyrate pools, and 5% BGFE was the only group in which colonic digesta pH was lower than that of the control. Diets containing 2% fructan did not affect any of these fermentation end points. Whereas bifidobacteria numbers in cecal digesta of 2% and 5% OF were higher than that in the control group, they were not different from those in rats fed diets containing BGFE and wheat stem fructan extract. Barley grain and wheat stem fructans produced similar large bowel fermentation patterns to OF when fed to rats at 5% of the diet.