Dietary omega-3 fatty acids prevent carbohydrate-induced hypertriglyceridemia

Dietary fish oils rich in omega-3 fatty acids are remarkably hypotriglyceridemic in both normal and hypertriglyceridemic subjects. This present study was designed to examine the hypothesis that dietary fish oils could prevent the usual sharp increase in plasma triglyceride and very low-density lipoprotein (VLDL) levels that occur physiologically after the induction by a high-carbohydrate diet. Seven healthy volunteers consumed three experimental liquid formula diets: the baseline diet (45% fat, 10% protein, 45% carbohydrate) and two high-carbohydrate diets (15% fat, 10% protein, 75% carbohydrate), one as a control diet and the other containing fish oil. The baseline and control dietary fats were a mixture of peanut oil and cocoa butter, whereas the fish oil diet contained high levels of omega-3 fatty acids. The plasma triglyceride levels rose from 105 mg/dL during baseline diet to 194 mg/dL during the high-CHO control diet (P < 0.005). VLDL triglyceride levels increased from 69 to 156 mg/dL (P < 0.005) and VLDL cholesterol from 18 to 34 mg/dL (P < 0.005). When fish oil was substituted for the control fats, plasma triglyceride levels fell from 194 to 75 mg/dL (P < 0.005), VLDL triglyceride and cholesterol levels were reduced from 156 to 34 mg/dL (P < 0.005) and from 34 to 12 mg/dL (P < 0.005), respectively. These effects were noted by two to three days after beginning the fish oil diet. Thus, dietary omega-3 fatty acids from fish oil rapidly and markedly reduced VLDL triglyceride levels even in the face of a high-carbohydrate diet. We hypothesize that fish oil lowered plasma triglyceride levels by inhibiting the synthesis of VLDL triglyceride or by enhancing its clearance in the periphery.