Abstract P348: The Effects of High Saturated Fat Intake on LDL and HDL Subclasses in Individuals with Atherogenic Dyslipidemia

Previous observations in normolipidemic individuals have indicated that the increase in LDL cholesterol (C) resulting from substitution of dietary saturated fat for carbohydrate or unsaturated fat is primarily due to higher plasma levels of large cholesterol-enriched LDL particles, with minimal effects on smaller LDL, as well as apolipoprotein (apo) B and total-C/HDL-C ratio. In the present study, we tested whether similar effects of saturated fat are observed in individuals with atherogenic dyslipidemia characterized by a preponderance of small LDL particles (LDL phenotype B). Fifty-three phenotype B participants consumed a baseline diet (55% carbohydrate, 15% protein, 30% fat, 8% saturated fat) for 3 weeks, after which they were randomized to either a moderate carbohydrate, high saturated fat diet (HSF; 39% carbohydrate, 25% protein, 36% fat, 18% saturated fat) or a moderate carbohydrate, low saturated fat diet (LSF; 37% carbohydrate, 25% protein, 37% fat, 9% saturated fat) for 3 weeks. The difference in saturated fat was derived primarily from dairy sources. Plasma lipids and lipoproteins were measured after the baseline and randomized diets. Compared to the LSF diet, participants who consumed the HSF diet had a greater percent increase in total-C (p<0.0001), LDL-C (p=0.0002), total-C/HDL-C ratio (p=0.0004) and apoB (p<0.0001) from the baseline diet, with no significant differences in HDL-C or apoAI. The HSF group had a greater percent increase in medium (p=0.05) and small (p=0.02) LDL particle concentrations from baseline compared to the LSF group, with no differences in large and very small LDL. There were also no significant differences in large and small HDL subclasses. The activities of both hepatic lipase (p=0.05) and cholesteryl ester transfer protein (p=0.04) were increased in the HSF group compared to the LSF group. Because medium and small LDL particles have been found to be more highly associated with CVD risk than larger LDL particles, the present results, in conjunction with our previous findings, suggest that adverse effects of very high saturated fat intake on CVD risk may be greater in phenotype B individuals than in those with normal lipoprotein profiles.