Wheat bran with reduced particle size increases serum SCFAs in obese subjects without improving health parameters compared with a maltodextrin placebo

Abstract

Wheat bran (WB) has been associated with improved gastrointestinal health and a reduced risk of metabolic disorders. Reducing the particle size of WB might increase its fermentability and facilitate cross-feeding between the gut bacteria and in this way produce health effects. We investigated the impact of WB with reduced particle size (WB RPS) on colonic fermentation and host health in normal-weight (NW) and obese (OB) participants compared with placebo (PL). During 1 mo, 36 NW and 14 OB participants daily consumed 20 g WB RPS or PL (maltodextrin). Before and after the intervention, fasting serum and fecal SCFAs, fecal metabolite profiles, and microbiota composition were measured as fermentation parameters. Fecal output, fecal dry weight (%), fat excretion, transit, stool consistency, intestinal permeability, and serum total cholesterol, triglyceride, and C-reactive protein concentrations were measured as health parameters. The impact of WB RPS on the fermentation of other carbohydrates was assessed by quantifying postprandial cumulative serum 13C-SCFA after a challenge with 13C-inulin. WB RPS increased fasting serum acetate (P<0.05) and total SCFA (P<0.05) concentrations in OB participants. Fasting serum propionate concentrations were lower in OB than in NW participants at baseline (NW: 1.57±0.75 µmol/L; OB: 0.89±0.52 µmol/L; P<0.01), but not after WB RPS (NW: 1.75±0.77 µmol/L; OB: 1.35±0.63 µmol/L; P=not significant). WB RPS did not enhance colonic fermentation of 13C-inulin and did not affect microbiota composition. Health parameters were not affected by the WB RPS intervention, either in NW or in OB participants. WB RPS increased fasting serum SCFA concentrations in OB participants. These changes were not associated with beneficial effects on host health.