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 < 200 mg/d (Step 2 diet). There is debate as to whether the remaining fat in the diet should be relatively high in monounsaturated or polyunsaturated fatty acids. We examined this issue by testing the effects of diets meeting the aforementioned guidelines that were enriched in three different vegetable oils on plasma lipids in the fasting and postprandial states in a clinically relevant population. Female and male subjects (n = 15, mean age, 61 years) with low-density lipoprotein cholesterol (LDL-C) concentrations > 130 mg/dL were studied under strictly controlled conditions. Subjects were first placed on a diet similar to that currently consumed in the United States to stabilize plasma lipids with respect to identical fat and cholesterol intakes. The subjects then 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 cholesterol concentrations declined after consumption of diets enriched in all the 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, and olive oil, respectively), and the magnitude of the declines was statistically indistinguishable among the test oils. Mean plasma high-density lipoprotein cholesterol (HDL-C) concentrations declined after consumption of the baseline diet, and these declines were significant for the canola (7%) and corn (9%) oil-enriched diets. Changes in LDL apolipoprotein (apo)B concentrations paralleled those of LDL-C. Switching from the baseline to the vegetable oil--enriched diets had no significant effect on plasma triglyceride, apoA-I, and lipoprotein(a) concentrations or the total cholesterol to HDL-C ratio. LDL apoB to apoA-I ratios were significantly reduced when the subjects consumed the vegetable oil--enriched diets. Differences similar to those observed in the fasting state were observed in the postprandial state.(ABSTRACT TRUNCATED AT 400 WORDS)