CHOLESTEROL-LOWERING BY RICE BRAN AND RICE BRAN OIL UNSAPONIFIABLE MATTER IN HAMSTERS

Unsaponfiable matter (U) was prepared from both raw and extrusion stab ilized (130 degrees C) rice bran and tested for cholesterol-lowering a ctivity in hamsters by addition to diets containing cellulose, raw ric e bran, or stabilized rice bran at either the level found in the rice bran diet (0.4%, 1X) or twice that level (2X). All diets contained 0.3 % cholesterol, 10% total dietary fiber, 10.1% fat, and 3% N (same plan t-to-animal N ratio). After 21 days, plasma cholesterol was significan tly reduced by rice bran diets containing added U compared to the cell ulose control diet, while the high density lipoprotein cholesterol-to- low density lipoprotein cholesterol ratio remained unchanged in all tr eatment groups. Liver cholesterol was significantly reduced by all ric e bran-containing diets and with cellulose diets containing 2X added U when compared to the control diet. Rice bran diets plus added U resul ted in cholesterol values lower than cellulose diets containing the sa me level of U. Stabilization of rice bran did not appear to affect the plasma and liver cholesterol responses to the unsaponifiable matter p repared from the extracted oil. There appears to be a dose response to rice bran unsaponifiable matter in plasma and liver cholesterol reduc tions. After 2 weeks, fecal fat and neutral sterol excretion were sign ificantly greater with all treatment diets compared to the control die t. Fecal fat was negatively correlated with liver as well as plasma ch olesterol (r = -0.97, P less than or equal to 0.0001 and -0.91, P less than or equal to 0.0006, respectively). Under the conditions of this study, cholesterol-lowering activity of rice bran is present in its un saponifiable matter in addition to other components. Increased fecal e xcretion of fat and neutral sterols appears to be a possible mechanism for cholesterol-lowering by rice bran.