Oat beta-glucan increases bile acid excretion and a fiber-rich barley fraction increases cholesterol excretion in ileostomy subjects.

The purpose of this study was to investigate whether oat beta-glucan is responsible for the increased bile acid excretion previously observed with oat-fiber diets. The excretion patterns in ileostomy subjects given diets containing oat-bran bread with and without added beta-glucanase, a beta-glucan-degrading enzyme, were compared. The effect of a beta-glucan-rich barley fraction on sterol excretion was also investigated. Nine ileostomy subjects were served four diets in random order, each diet for 2 consecutive days. Four different kinds of bread, mainly made from oat bran (OB diet, 12.5 g beta-glucan/d), oat bran with beta-glucanase (OBE diet, 3.8 g beta-glucan/d), barley (B diet, 13.0 g beta-glucan/d), or wheat flour (W diet, 1.2 g beta-glucan/d) were added to a basal diet. The 24-h excretion of bile acids was 53% higher in the OB diet period than in the OBE diet period (P < 0.05) and also was significantly higher than in the B and W diet periods (P < 0.05). Median (range) bile acid excretion was 851 (232-1550), 463 (123-1414), 755 (133-1187), and 606 (101-980) mg/d in the OB, OBE, B, and W diet periods, respectively. The excretion of cholesterol was significantly higher in the B diet period than in the OBE and W diet periods (P < 0.05), but the mechanism behind this effect of barley fiber is unknown. In oat bran, however, beta-glucan mediates an increase in bile acid excretion, which most probably explains the effect of oat fiber in lowering serum lipids.