Comparative cholesterol lowering properties of vegetable oils: beyond fatty acids.
OBJECTIVE
Our laboratory has previously reported that the hypolipidemic effect of rice bran oil (RBO) is not entirely explained by its fatty acid composition. Although RBO has up to three times more serum cholesterol-raising saturated fatty acids (SATS) than some unsaturated vegetable oils, we hypothesized that its greater content of the unsaponifiables would compensate for its high SATS and yield comparable cholesterol-lowering properties to other vegetable oils with less SATS.


METHODS
To study the comparative effects of different unsaturated vegetable oils on serum lipoprotein levels, nine cynomologus monkeys (Macaca fascicularis) were fed diets, for four weeks, in a Latin square design, containing rice bran, canola or corn oils (as 20% of energy) in a basal mixture of other fats to yield a final dietary fat concentration of 30% of energy. All animals were fed a baseline diet containing 36% of energy as fat with 15% SATS, 15% monounsaturated fatty acids (MONOS) and 6% polyunsaturated fatty acids (POLYS).


RESULTS
Despite the lower SATS and higher MONOS content of canola oil and the higher POLYS content of corn oil, RBO produced similar reductions in serum total cholesterol (TC) (-25%) and low density lipoprotein cholesterol (LDL-C) (-30%). In addition, as compared to the baseline diet, the reduction in serum TC and LDL-C cholesterol with RBO was not accompanied by reductions in high density lipoprotein cholesterol (HDL-C) which occurred with the other two dietary oils. Using predictive equations developed from data gathered from several studies with non-human primates, we noted that the observed serum TC and LDL-C lowering capabilities of the RBO diet were in excess of those predicted based on the fatty acid composition of RBO.


CONCLUSIONS
These studies suggest that non-fatty acid components (unsaponifiables) of RBO can contribute significantly to its cholesterol-lowering capability.
Wilson
T A
TA
Department of Health and Clinical Science, Center for Chronic Disease Control and Prevention, University of Massachusetts, Lowell 01854-5125, USA.
Ausman
L M
LM
Lawton
C W
CW
Hegsted
D M
DM
Nicolosi
R J
RJ
D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D002784:Cholesterol / Q000097:blood*; D008078:Cholesterol, LDL / Q000097:blood; D004041:Dietary Fats / Q000097:blood*; D005227:Fatty Acids / Q000008:administration & dosage; D008252:Macaca fascicularis; D008297:Male; D010938:Plant Oils / Q000008:administration & dosage / Q000737:chemistry* / Q000494:pharmacology; D000073879:Rice Bran Oil
D000924:Anticholesteremic Agents; D008078:Cholesterol, LDL; D004041:Dietary Fats; D005227:Fatty Acids; D010938:Plant Oils; D002784:Cholesterol; D000073879:Rice Bran Oil