Independent effects of dietary saturated fat and cholesterol on plasma lipids, lipoproteins, and apolipoprotein E.

Nine normolipidemic males (18-37 years) were fed formula diets containing (as % of calories) egg white protein (15%), glucose polymer:sucrose, 3:1 (54%), and fats (31%) as one of the following: corn oil (corn), corn oil plus 1 gram/day cholesterol (corn+), coconut oil (coco), coconut oil plus 1 gram/day cholesterol (coco+). Two dietary periods of 18 days each were separated by 1 month during which plasma lipid levels returned to prestudy values. A given dietary period consisted of 9 days of either corn or coco feeding allowed by 9 days of corn+ or coco+, respectively. Fasting plasma samples were taken the last 3 days of each 9-day interval. Lipids were determined by standard procedures and the apoE levels in lipoprotein fractions isolated by discontinuous density gradient ultracentrifugation were determined by radioimmunoassay. The biochemical variables measured were: total plasma, VLDL, IDL + LDL, and HDL, cholesterol, triglyceride, and apoE levels, as well as the apoE of plasma d greater than 1.17 g/ml. The effects of apoE phenotype, the type of dietary oil (corn versus coco), the presence or absence of dietary cholesterol, and the day of sampling within triplicates on the above variables were assessed statistically. The type of oil had the only significant effect on any variable. At P less than 0.01, the coconut oil diets were associated with significant elevations (as compared to corn oil) of the following nine variables: total, VLDL, IDL + LDL, and HDL cholesterol; total, VLDL, and IDL + LDL apoE; total and VLDL triglycerides.