Journal Articles

Background & aims: Inadequate dietary fibre (DF) intake is associated with suboptimal gut function and increased risk of several human diseases. Bread is commonly consumed and is ideal to incorporate cereal bran to increase DF content. No human studies have investigated the effects of defatted rice bran (DRB) in bread, which has triple the DF of white bread, purported hypo-allergenicity and a unique nutrient profile, as a dietary intervention in healthy adults. This study aims to assess the relative abundances of a composite of key faecal microbial genera and species involved in DF fermentation and metabolism following the habitual intake of DRB-fortified bread and its influence on other biological markers of host and microbial interactions, cardiovascular risk profile, patient-reported outcomes, total DF intake, and gut physiology in healthy adults with low baseline DF intake. Methods: Fifty-six healthy adults with low baseline DF intake (<18 g/day (females), <22 g/day (males)) completed a two-arm, placebo-controlled, double-blind, randomised, crossover study. Participants consumed three (females) or four (males) slices of DRB-fortified bread or control bread daily as part of their usual diet for four weeks, with the intervention periods separated by a two-week washout. Outcomes included faecal microbiota composite (primary outcome); relative abundances (taxa and gene); faecal moisture content and bile acid concentrations; plasma and faecal organic acid concentrations; cardiovascular risk profile; gut comfort, psychological wellbeing parameters; total DF intake; whole gut transit time, and were measured at baseline and following each intervention phase. Additionally, in a sub-study, 15 participants ingested gas-sensing capsules to assess whole and regional gut transit times, and total and regional colonic hydrogen and carbon dioxide concentrations at the same timepoints. Results: DRB-fortified bread consumption significantly increased total DF intake from 20.7 g/day to 43.4 g/day (p < 0.001). No significant differences were observed in the primary outcome, microbial taxa composite within and between groups (False Discovery Rate (FDR) correction, p > 0.10). As compared to control, the DRB group had increased relative abundances of Faecalibacterium prausnitzii (unadjusted p = 0.04), Bifidobacterium longum (unadjusted p = 0.12), and Bacteroides ovatus (unadjusted p = 0.10); lower relative abundances in Coprococcus genus (unadjusted p = 0.09), Roseburia faecis (unadjusted p = 0.02) and Prevotella copri species (unadjusted p = 0.05). However, no significant differences were observed in the relative abundances of these taxa within and between groups (FDR correction p > 0.10) and for most of the other outcomes between groups (p > 0.05). Only mean serum high-density lipoprotein (HDL) concentrations significantly increased (p = 0.006), and mean total cholesterol (TC) to HDL concentration ratio significantly lowered (p = 0.02) in the DRB group compared to the control group. Conclusion: This is the first human study to show that a high-DF DRB-fortified bread improved DF intake, HDL cholesterol profiles, and may affect the gut microbiota composition in healthy adults with low DF intake. These findings support the substitution of white bread with DRB-fortified bread as an effective method to improve DF intake, which may have subsequent benefits on gut physiology and metabolic health.

Quercetin, a polyphenol antioxidant, is widely distributed in food in the form of glycoside rutin, which is not readily absorbed in the gastrointestinal tract. The microbiota of the colon is known to biotransform rutin, generating quercetin aglycones that can be absorbed. We investigated the role of the ileal and colonic microbiota in rutin biotransformation using established in vitro fermentation models. Overall, a higher rate of rutin biotransformation was observed during colonic fermentation compared with ileal fermentation. The colonic microbiome showed higher potential for rutin conversion to quercetin through an increased abundance of α-rhamnosidase- and β-glucosidase-encoding genes compared to the ileal microbiome. Nonetheless, rutin metabolism occurred rapidly during ileal fermentation (∼20% rutin disappearance after 1 h). The appearance of quercetin varied depending on the ileal inoculum and correlated with an increased abundance of Firmicutes, suggesting that quercetin absorption could be improved via modulation of the ileal microbiota.

Journal Articles

Browse

Filters

Settings

Sort By

Results per page

Search Results