Olive oil instead of butter increases net cholesterol excretion from the small bowel

Butter was replaced by olive oil in a controlled 100 g fat diet in order to study the effect of saturated fats (SAFA) versus monounsaturated fats (MUFA) on small-bowel sterol excretion in eleven healthy ileostomates. Bile acids and neutral sterols were measured by gas-liquid chromatography. Net cholesterol excretion (excretion minus intake) was 84 +/- 25 mg/24 h (mean +/- SE) on the SAFA diet and increased to 218 +/- 32 mg/24 h on the MUFA diet (P less than 0.01). The bile acid excretion tended to be somewhat lower on the MUFA diet, but this was significant only for chenodeoxycholic acid. Net sterol excretion (the sum of excretion of net cholesterol and bile acids) was significantly lower on the SAFA diet than on the MUFA diet (443 +/- 60 and 529 +/- 58 mg/24 h, respectively). The immediately increased excretion of cholesterol from the small bowel could thus explain the serum cholesterol-lowering effect of a change from a SAFA-rich to a MUFA-rich diet, though the mechanism for this change is still unclear.