Oat bran rapidly increases bile acid excretion and bile acid synthesis:: an ileostomy study

Objective: To study whether oat bran with native b-glucans increases bile acid excretion and bile acid synthesis as measured by serum concentrations of 7 alpha-hydroxy-4-cholesten-3-one (7 alpha-HC). Design: Short-term interventional crossover study evaluating cholesterol absorption, ileal excretion of cholesterol and bile acids, and serum levels of cholesterol and bile acid metabolites. Differences between diets evaluated with Wilcoxon's signed rank-sum test. Setting: Outpatients at a metabolic-ward kitchen. Subjects: Nine volunteers with conventional ileostomies. Methods: Two 3-day-diet periods, with controlled, blinded basal diet including 75 g extruded oat bran breakfast cereal daily, with either 11.6 g native or hydrolysed b-glucans. Results: Native oat bran increased median excretion of bile acids by 144% (P = 0.008). Cholesterol excretion remained unchanged, cholesterol absorption decreased by 19% (P = 0.013), whereas the sum of bile acid and cholesterol excretion increased by 40% (P = 0.008) compared with hydrolysed oat bran. 7 alpha- HC reflecting bile acid synthesis increased by 57% (P = 0.008) within 24 h of consumption, whereas serum lathosterol concentration reflecting cholesterol synthesis increased by 12% (P = 0.015). Conclusions: Oat bran with native b-glucans increases bile acid excretion within 24 h of consumption and this increase can also be detected by rising serum concentrations of 7 alpha- HC. Thus, 7 alpha-HC could be used for rapid detection of dietary effects on bile acid metabolism. These effects could possibly be explained by entrapment of whole micelles in the gut owing to higher viscosity.