Comparison of the effect of the amount and degree of unsaturation of dietary fat on plasma low density lipoproteins in vervet monkeys

The effects of the degree of unsaturation and of the amount of dietary fat on low density lipoprotein (LDL) concentration and composition were determined in vervet monkeys. Diets with fat contents of 41, 31 and 18% energy, each with a low and a high polyunsaturated to saturated fatty acid ratio (P/S; 0.27–0.38 and 1.13–1.47) were fed to six female vervet monkeys for two months. Another six females were given a low fat, high P/S diet for the same period of time, to serve as a reference. The cholesterol contents of the diets were low (21–33 mg per day) and relatively constant. LDL cholesterol concentrations decreased significantly (P≤0.01) when the dietary fat content decreased from 31 to 18% of energy. The dietary P/S ratio only affected LDL cholesterol concentrations during moderate (31% of energy) fat intake, where LDL cholesterol increased (P≤0.01) with a decrease in dietary P/S. Substantial individual variations were observed in LDL cholesterol concentration responses to dietary fat changes. The changes in LDL cholesterol concentrations were the result of changes in the concentration of LDL particles, as the molecular composition did not differ significantly between dietary periods. The high density lipoprotein choelsterol and the plasma triacylglycerol concentrations were not influenced by the dietary fat changes. During the high P/S diets, the percentage of 18∶2 (linoleic acid) increased (P≤0.01) and that of 18∶1 (oleic acid) decreased (P≤0.01) in LDL esterified cholesterol, as compared to the low P/S diets. In adipose tissue triacylglycerol the percentage of 18∶2 was three times higher (P≤0.01) during the high P/S diets than during the low P/S diets. A decrease in the amount of dietary fat (from 31 to 18% of energy) was associated with an increase in the percentage of 18∶1 in LDL esterified cholesterol.