Study Objective: To determine the effects of fish oil supplements low in saturated fat and cholesterol on plasma lipid and lipoprotein levels in hypertriglyceridemic patients.
Design: Single-blind, placebo-controlled (safflower oil), crossover trial with 6-week treatment periods.
Setting: Outpatient lipid clinic in a university medical center.
Patients: Eleven adult patients had isolated hypertriglyceridemia (type IV) and seven had concomitant hypercholesterolemia (Type IIb).
Intervention: Twelve 1-g capsules of either fish oil or placebo (safflower oil) were taken daily during each treatment period.
Measurements and Main Results: Blood was drawn at the fifth and sixth week of each period and analyzed for total lipids; cholesterol in very low, low (LDL), and high density (HDL) lipoproteins (mmol/L); and apoprotein B (mg/ dL). Compared with the placebo, fish oil lowered plasma triglyceride levels (4.0 ± 1.8 to 2.5 ± 1.0), and raised LDL cholesterol levels (3.7 ± 1.75 to 4.25 ± 0.85), apolipoprotein B levels ( 122 ± 29 to 140 ± 34), and the ratio of LDL cholesterol to HDL cholesterol (4.0 ± 0.9 to 4.7 ± 1.4) (P < 0.05; mean ± SD). No significant changes were seen in levels of HDL or HDL cholesterol subfractions. Similar responses were seen in patients with both type IIb and IV lipoprotein phenotypes.
Conclusions: Because the fish oil supplement contributed negligible amounts of cholesterol and saturated fat to the diet, the n-3 fatty acids most likely caused the observed effects. These findings indicate that relatively small amounts of fish oil can have beneficial effects on plasma triglyceride levels in hypertriglyceridemic patients, but the increase in LDL cholesterol and apoprotein B levels, and in the LDL cholesterol to HDL cholesterol ratio suggests the need for careful monitoring of plasma lipoprotein changes during fish oil supplementation, and for a careful evaluation of their long-term benefits.