Effects of dietary fat restriction on particle size of plasma lipoproteins in postmenopausal women

Hypertriglyceridemia is an independent risk factor for coronary artery disease (CAD) and is also commonly associated with other coronary risk factors, ie, small, dense low-density lipoprotein (LDL) particles and low plasma levels of high-density lipoprotein cholesterol (HDL-C). Dietary fat restriction is recommended for the prevention of nutrition-related cancers. Low-fat, high-carbohydrate intake can increase plasma triglyceride (TG) and decrease HDL-C. In general, plasma TG levels are inversely related to the particle size of LDL. We investigated the effects of dietary fat restriction on the concentration and particle size of plasma lipoproteins in 14 healthy postmenopausal women (aged 61 ± 11 years). During a 4-month period of eucaloric controlled feeding, dietary fat was reduced stepwise from a habitual intake of 33% ± 3% to 23% and then to 14% of daily energy. Changes in the plasma lipid level and particle size of very-low-density lipoprotein (VLDL), LDL, and HDL were determined at the end of each dietary phase. Increasing carbohydrate intake without weight loss was associated with an increase in plasma TG (1.86 ± 0.30 v 2.47 ± 0.37 mmol/L) and decreases in total cholesterol (5.82 ± 0.25 v 5.40 ± 0.21 mmol/L), LDL-C (3.07 ± 0.18 v 2.61 ± 0.21 mmol/L), HDL-C (1.42 ± 0.1 v 1.24 ± 0.1 mmol/L), and apolipoprotein (apo) A1 (5.14 ± 0.25 v 4.61 ± 0.36 mmol/L), whereas plasma apo B did not change. The particle size of VLDL increased (42.7 ± 1.4 v 47.0 ± 0.9 nm). However, there was no change in either LDL (25.1 ± 0.2 v 25.3 ± 0.2 nm) or HDL particle size. Although at each level of dietary fat intake LDL particle size correlated inversely with plasma TG and ape B, there was no relationship between the increase in plasma TG and LDL particle size. These results show that hypertriglyceridemia caused by a eucaloric high- carbohydrate intake is not associated with a decrease in LDL particle size. Therefore, carbohydrate-induced hypertriglyceridemia may not have the same atherogenic potential as genetic hypertriglyceridemias.