Abstract/Summary

Background Dietary components which impact the gut microbiota may beneficially affect cardiometabolic health, possibly by altered bile acid metabolism. However, impacts of these foods on postprandial bile acids, gut microbiota and cardiometabolic risk markers are unclear. Objective To determine chronic effects of probiotics, oats and apples on postprandial bile acids, gut microbiota and cardiometabolic health biomarkers. Design Using an acute within chronic parallel design, 61 volunteers (mean±SD, age 52±12 y and BMI 24.8±3.4 kg/m2) were randomized to consume 40g cornflakes (control), 40g oats or 2 Renetta Canada apples each with 2 placebo capsules/day or 40g cornflakes with 2 Lactobacillus reuteri capsules (>5×109 CFU)/day, for 8 weeks. Fasting and postprandial serum/plasma bile acids and cardiometabolic health markers, fecal bile acids and gut microbiota composition were determined. Results At week 0, oats and apples significantly decreased postprandial serum insulin [area under the curve (AUC): 25.6 (17.4,33.8) and 23.4 (15.4,31.4) vs 42.0 (33.7,50.2) pmol/L*min and incremental AUC (iAUC): 17.8 (11.6,24.0) and 13.7 (7.7,19.8) vs 29.6 (23.3,35.8) pmol/L x min] and C-peptide responses [AUC: 599 (514,684) and 550 (467,632) vs 750 (665,835) ng/ml* min], while non-esterified fatty acids were increased [AUC 135 (117,153) vs 86.3 (67.9,105) and iAUC 96.2 (78.8,114) vs 60 (42.1,77.9) mmol/L*min] after the apples vs control (p≤0.05). Postprandial unconjugated [AUC: predicted means (95%CI) 1469 (1101,1837) vs 363 (-28,754) µmol/l*min and iAUC: 923 (682,1165) vs 22.0 (-235,279) µmol/l*min)] and hydrophobic [iAUC: 1210 (911,1510) vs 487 (168,806) µmol/l*min] bile acid responses were increased after 8 weeks probiotic intervention vs control (p≤0.049). None of the interventions modulated the gut microbiota. Conclusions These results support beneficial effects of apples and oats on postprandial glycemia and the ability of the probiotic Lactobacillus reuteri to modulate postprandial plasma bile acid profiles compared to control (cornflakes), with no relationship evident between circulating bile acids and cardiometabolic health biomarkers