MECHANISM OF SERUM-CHOLESTEROL REDUCTION BY OAT BRAN

Nine normolipidemic young men consumed a constant diet for 2 mo into w hich oat bran was incorporated during the second month so that we migh t test the hypotheses that oats lower serum cholesterol concentrations by decreasing bile acid and fat absorption and increasing bile acid s ynthesis. Bile acid kinetics were determined by measuring the C-13 enr ichment of serum cholic and chenodeoxycholic acids. Oat bran consumpti on decreased serum cholesterol levels (p < 0.01) and cholic acid pool size (p < 0.05). Deoxycholic acid pool size (p < 0.01) and the synthes is and fractional turnover rates of both primary bile acids (p < 0.05) increased. Total bile acid pool size did not change. Fecal excretion of total bile acids, the two secondary bile acids and fat increased si gnificantly. The results demonstrate that oat bran lowers serum choles terol levels in part by altering bile acid metabolism. in addition, th e substantial increase in the proportion of the total bile acid pool t hat was deoxycholic acid is consistent with the hypothesis that oat br an also decreases cholesterol synthesis.