Walnuts and fatty fish influence different serum lipid fractions in normal to mildly hyperlipidemic individuals: a randomized controlled study

Background: Increased consumption of n-3 (omega-3) fatty acids decreases the incidence of coronary heart disease (CHD). Objective: The objective was to determine whether walnuts (plant n-3 fatty acid) and fatty fish (marine n-3 fatty acid) have similar effects on serum lipid markers at intakes recommended for primary prevention of CHD. Design: In a randomized crossover feeding trial, 25 normal to mildly hyperlipidemic adults consumed 3 isoenergetic diets (approximate to 30% total fat and <10% saturated fat) for 4 wk each: a control diet (no nuts or fish), a walnut diet (42.5 g walnuts/10.1 mJ), or a fish diet (113 g salmon, twice/wk). Fasting blood was drawn at baseline and at the end of each diet period and analyzed for serum lipids. Results: Serum total cholesterol and LDL cholesterol concentrations in adults who followed the walnut diet (4.87 +/- 0.18 and 2.77 +/- 0.15 mmol/L, respectively) were lower than in those who followed the control diet (5.14 +/- 0.18 and 3.06 +/- 0.15 mmol/L, respectively) and those who followed the fish diet (5.33 +/- 0.18 and 3.2 +/- 0.15 mmol/L, respectively; P < 0.0001). The fish diet resulted in decreased serum triglyceride and increased HDL-cholesterol concentrations (1.0 +/- 0.11 and 1.23 +/- 0.05 mmol/L, respectively) compared with the control diet (1.12 +/- 0.11 and 1.19 +/- 0.05 mmol/L, respectively) and the walnut diet (1.11 +/- 0.11 mmol/L, P < 0.05, and 1.18 +/- 0.05 mmol/L, P < 0.001, respectively). The ratios of total cholesterol: HDL cholesterol, LDL cholesterol: HDL cholesterol, and apolipoprotein B: apolipoprotein A-I were lower (P < 0.05) in those who followed the walnut diet compared with those who followed the control and fish diets. Conclusion: Including walnuts and fatty fish in a healthy diet lowered serum cholesterol and triglyceride concentrations, respectively, which affects CHD risk favorably. Am J Clin Nutr 2009; 89(suppl): 1657S-63S.