EFFECTS OF CANOLA, CORN, AND OLIVE OILS ON FASTING AND POSTPRANDIAL PLASMA-LIPOPROTEINS IN HUMANS AS PART OF A NATIONAL CHOLESTEROL EDUCATION-PROGRAM STEP 2 DIET

The most stringent dietary recommendations of the National Cholesterol Education Program (NCEP) are to limit fat intake to <30% of calories, saturated fat intake to <7% of calories, and cholesterol intake to <2 00 mg/d (Step 2 diet). There is debate as to whether the remaining fat in the diet should be relatively high in monounsaturated or polyunsat urated fatty acids. We examined this issue by testing the effects of d iets meeting the aforementioned guidelines that were enriched in three different vegetable oils on plasma lipids in the fasting and postpran dial states in a clinically relevant population. Female and male subje cts (n = 15, mean age, 61 years) with low-density lipoprotein choleste rol (LDL-C) concentrations > 130 mg/dL were studied under strictly con trolled conditions. Subjects were first placed on a diet similar to th at currently consumed in the United States to stabilize plasma lipids with respect to identical fat and cholesterol intakes. The subjects th en received diets meeting NCEP Step 2 criteria in which two thirds of the fat calories were given either as canola, corn, or olive oil in a randomized, double-blinded fashion for 32 days each. Plasma cholestero l concentrations declined after consumption of diets enriched in all t he test oils; however, the declines were significantly greater for the canola (12%) and corn (13%) than for the olive (7%) oil-enriched diet . Mean plasma LDL-C concentrations declined after consumption of diets enriched in all the test oils (16%, 17%, and 13% for canola, corn, an d olive oil, respectively), and the magnitude of the declines was stat istically indistinguishable among the test oils. Mean plasma high-dens ity lipoprotein cholesterol (HDL-C) concentrations declined after cons umption of the baseline diet, and these declines were significant for the canola (7%) and corn (9%) oil-enriched diets. Changes in LDL apoli poprotein (apo)B concentrations paralleled those of LDL-C. Switching f rom the baseline to the vegetable oil-enriched diets had no significan t effect on plasma triglyceride, apoA-I, and lipoprotein(a) concentrat ions or the total cholesterol to HDL-C ratio. LDL apoB to apoA-I ratio s were significantly reduced when the subjects consumed the vegetable oil-enriched diets. Differences similar to those observed in the fasti ng state were observed in the postprandial state. The major finding of this study is that significant reductions in LDL-C and apoB levels ca n be achieved in middle-aged and elderly women and men with initial LD L-C levels > 130 mg/dL by reducing dietary saturated fat and cholester ol intake and by incorporating vegetable oils rich in either monounsat urated fatty acids (canola and olive oil) or polyunsaturated fatty aci ds (corn oil) as part of an NCEP Step 2 diet. Although differential ef fects were seen after the consumption of the three different oil-enric hed diets in some plasma lipid measures, none of these oils had a sign ificant advantage in terms of altering the overall lipoprotein profile .