RELATIVE EFFECTS OF HIGH SATURATED FATTY-ACID LEVELS IN MEAT, DAIRY-PRODUCTS, AND TROPICAL OILS ON SERUM-LIPOPROTEINS AND LOW-DENSITY-LIPOPROTEIN DEGRADATION BY MONONUCLEAR-CELLS IN HEALTHY-MALES

To determine the effects of three saturated fatty acid combinations on lipoprotein metabolism, we fed 18 21- to 32-year-old men three diets in a crossover design for 28-day periods separated by washout periods of 4 to 6 weeks. The men self-selected a prescribed diet at home empha sizing saturated fat as the visible fat for 1 week. Then, they ate exp erimental diets providing 40%, 15%, 17%, and 7% of food energy, respec tively, as total, saturated, monounsaturated, and polyunsaturated fatt y acids, levels representing amounts available in the US diet. Differe nt test fatty acid combinations, given at 4 to 6 energy% (en%) each, w ere incorporated into food products: 12:0 + 14:0, 14:0 + 16:0, and 16: 0 + 18:0. Test fatty acids were equalized by giving free myristic acid (14:0) with palm kernel oil or butter and sheanut butter (high in 18: 0) with lard. The diet highest in 12:0 + 14:0 also provided 4.2 en% 16 :0, the most common saturated fatty acid in the US diet. Mean apparent absorption of all fatty acids was at least 90%. The three diets produ ced similar concentrations of serum total and low-density lipoprotein (LDL) cholesterol and apolipoprotein (apo) B-100 regardless of the apo E phenotype of the subjects. Compared with baseline, the experimental diets affected serum high-density lipoprotein (HDL) concentrations (P < .06), with the highest values occurring on diet 12:0 + 14:0. When t he change from baseline in receptor-mediated degradation of I-125-LDL in freshly isolated mononuclear cells (MNC) was stratified by apo 6 ph enotype, diet 16:0 + 18:0 produced a 30% increase, compared with a 9% decrease on diet 12:0 + 14:0 and a 6% increase on diet 14:0 + 16:0 in subjects with the apo E3/3 phenotype, These results suggested that dif ferent saturated fatty acid combinations, consumed at levels typical o f availability in the United States and with diets providing ample uns aturated fat, had similar cholesterolemic properties in healthy males despite some subtly different effects on lipoprotein metabolism. (C) 1 996 by W.B. Saunders Company.