Effects of dietary saturated fat on LDL subclasses and apolipoprotein CIII in men

BACKGROUND/OBJECTIVES: Small dense low-density lipoprotein (LDL) particles and apolipoprotein (apo) CIII are risk factors for cardiovascular disease (CVD) that can be modulated by diet, but there is little information regarding the effects of dietary saturated fat on their plasma levels. We tested the effects of high vs low saturated fat intake in the context of a high beef protein diet on levels and composition of LDL subclasses and on apoCIII levels in plasma and LDL. SUBJECTS/METHODS: Following consumption of a baseline diet (50% carbohydrate (CHO), 13% protein, 38% total fat, 15% saturated fat) for 3 weeks, 14 healthy men were randomly assigned to two reduced CHO high beef protein diets (31% CHO, 31% protein, 38% fat) that differed in saturated fat content (15% vs 8%) for 3 weeks each in a crossover design. RESULTS: The high saturated fat (HSF) diet resulted in higher mass concentrations of buoyant LDL I, medium density LDL II and dense LDL III, but not the very dense LDL IV; and significant increases in plasma and LDL apoCIII concentration of 9.4% and 33.5%, respectively. The saturated fat-induced changes in LDL apoCIII were specifically correlated with changes in apoCIII content of LDL IV. CONCLUSIONS: Taken together with previous observations, these findings suggest that, at least in the context of a lower CHO high beef protein diet, HSF intake may increase CVD risk by metabolic processes that involve apoCIII.