We tested whether nutrient intakes estimated from 4-d diet records were associated with plasma lipoprotein subclasses in 103 men who were randomly assigned to a low-fat (24% fat) and a high-fat (46% fat) diet for 6 wk each in a crossover design. Postheparin plasma lipoprotein lipase (LPL) and hepatic lipase (HL) activities were also determined in a subset of 43 men. Changes in intake (ie, high fat minus low fat) of total saturated fatty acids, as well as myristic (14:0) and palmitic (16:0) acids, were positively correlated (P < 0.01) with increases in mass of large LDL particles [measured by analytic ultra-centrifugation as mass of lipoproteins of flotation rate (Sf) 7-12] and with LDL peak particle diameter and flotation rate, but not with changes in LDL-cholesterol concentration. Changes in total saturated fatty acids as well as myristic and palmitic acids were also inversely associated with changes in HL activity (P < 0.05). With the high-fat diet only, variation in dietary total saturated fatty acid intake was inversely correlated (P < 0.01) with concentrations of small, dense LDL of Sf 0-5. This correlation was significant specifically for myristic acid (P < 0.001). Stearic acid (18:0), monounsaturates, and polyunsaturates showed no significant associations with lipoprotein concentrations. These data indicate that a high saturated fat intake (especially 14:0 and 16:0) is associated with increased concentrations of larger, cholesterol-enriched LDL and this occurs in association with decreased HL activity.

Background:We found previously that men with a predominance of large LDL particles (phenotype A) consuming highfat diets (40-46% fat) show less lipoprotein benefits of low-fat diets (20-24% fat) than do men with a high-risk lipoprotein profile characterized by a predominance of small LDL (phenotype B). Furthermore, one-third of men with phenotype A consuming a high-fat diet converted to phenotype B with a low-fat diet. Objective: We investigated effects of further reduction in dietary fat in men with persistence of LDL subclass phenotype A during both high-and low-fat diets. Design: Thirty-eight men who had shown phenotype A after 4-6 wk of both high-and low-fat diets consumed for 10 d a 10%-fat diet (2.7% saturates) with replacement of fat with carbohydrate and no change in cholesterol content or ratio of polyunsaturates to saturates. Results: In 26 men, phenotype A persisted (stable A group) whereas 12 converted to phenotype B (change group). LDL cholesterol did not differ from previous values for 20-24%-fat diets in either group, whereas in the change group there were higher concentrations of triacylglycerol and apolipoprotein B; greater mass of HDL, large LDL-I, small LDL-III and LDL-IV, and HDL 3 ; lower concentrations of HDL cholesterol, apolipoprotein A-I; and lower mass of large LDL-I and HDL 2 . Conclusions: There is no apparent lipoprotein benefit of reduction in dietary fat from 20-24% to 10% in men with large LDL particles: LDL-cholesterol concentration was not reduced, and in a subset of subjects there was a shift to small LDL along with increased triacylglycerol and reduced HDL-cholesterol concentrations.Am J Clin Nutr 1999;69:411-8. KEY WORDSLipoproteins, low-fat diet, LDL subclasses, HDL, men, coronary artery disease, LDL phenotype INTRODUCTIONLDLs comprise a spectrum of particles that differ in physical and chemical properties (1-3) and in metabolic characteristics (4). Studies have shown that risk of coronary artery disease is significantly greater in individuals with a predominance of small, dense LDL (LDL subclass phenotype B) than in those with larger LDL particles (phenotype A) (5-8).We previously carried out 2 studies of effects of high-fat (40-46% fat) and low-fat (20-24% fat) diets on plasma lipoproteins in healthy, normolipidemic men (9, 10). In both studies, the reduction in LDL cholesterol with the low-fat diet was significantly less in men with phenotype A during the high-fat diet than in those with phenotype B. Moreover, in men with phenotype A, there was a shift in LDL particle mass from larger, lipid-enriched LDL to smaller, lipid-depleted LDL subfractions, indicative of a change in LDL composition with minimal change in particle number and consistent with the observation of reduced plasma LDL cholesterol without reduced apolipoprotein (apo) B (11). In one-third of the men with phenotype A, this shift resulted in conversion to phenotype B with the low-fat diet (9-11).The present study was designed to investigate effects on concentrations and distributions of LDL particles...

Low-density lipoprotein (LDL) subclass pattern B is a common genetically influenced lipoprotein profile characterized by a predominance of small, dense LDL particles, and associated with increased levels of triglyceride-rich lipoproteins, reductions in high-density lipoprotein cholesterol (HDL-C), and increased risk of coronary artery disease compared to individuals with a predominance of larger LDL (pattern A). We sought to determine whether LDL subclass patterns are associated with response of plasma lipoprotein levels to changes in dietary fat and carbohydrate content. In a randomized cross-over study, 105 men consumed, for six weeks each, high-fat (46%) and low-fat (24%) solid food diets, with replacement of fat by carbohydrate. Diet-induced changes in subjects who exhibited pattern B (n = 18) following the high-fat diet differed significantly from those in subjects with pattern A (n = 87): in pattern B subjects LDL cholesterol (LDL-C) reductions were two-fold greater and plasma apolipoprotein (apo) B levels decreased significantly. These differences remained significant after adjustment for levels of plasma LDL-C, apo B, HDL-C, and body mass index. Thus, LDL subclass pattern is a factor that contributes significantly to interindividual variation of plasma lipoprotein response to a low-fat, high-carbohydrate diet.