Inhibition of low density lipoprotein synthesis by dietary omega-3 fatty acids in humans.

Diets rich in omega-3 fatty acids derived from fish oils lower the plasma concentra- tions of low density lipoproteins (LDL) and very low density lipoproteins in humans. The present study was designed to examine the mechanism(s) by which diets en- riched in omega-3 fatty acids reduce plasma LDL cholesterol levels in normal sub- jects. Seven healthy volunteers with normal plasma lipid levels consumed two meta- bolically controlled diets for a period of 4 weeks each. The control diet contained predominantly saturated and monounsaturated fatty acids, whereas the fish-oil diet contained 24 gm of omega-3 fatty acids per day. The total fat and cholesterol content of the two diets were similar for each subject. Total and LDL cholesterol levels de- creased from 162 ± 26 mg/dl and 103 ± 27 mg/dl on the control diet to 124 ± 26 mg/dl and 82 ± 27 mg/dl on the omega-3-rich diet. Triglyceride levels fell from 91 ± 34 mg/dl to 52 ± 19 mg/dl. Kinetic studies of 125 I-LDL metabolism disclosed a significantly lower rate of synthesis of LDL apoprotein B on the omega-3-rich diet (9.5 ± 1.3 mg/kg/ day) as compared to the control diet (13.6 ± 3.7 mg/kg/day; p < 0.05). In contrast, the fractional catabolic rate was similar on both diets. We conclude that dietary omega-3 fatty acids lower plasma LDL levels in normal human subjects by reducing the rate of synthesis of apoprotein B. (Arteriosclerosis 4:270-275, May/June 1984)