Substituting walnuts for monounsaturated fat improves the serum lipid profile of hypercholesterolemic men and women - A randomized crossover trial

Background: It has been reported that walnuts reduce serum cholesterol leve ls in normal young men. Objective: To assess the acceptability of walnuts and their effects on seru m lipid levels and low-density lipoprotein (LDL) oxidizability in free-livi ng hypercholesterolemic persons. Design: Randomized, crossover feeding trial. Setting: Lipid clinic at a university hospital. Patients: 55 men and women (mean age, 56 years) with polygenic hypercholest erolemia. Intervention: A cholesterol-lowering Mediterranean diet and a diet of simil ar energy and fat content in which walnuts replaced approximately 35% of th e energy obtained from monounsaturated fat. Patients followed each diet for 6 weeks. Measurements: Low-density lipoprotein fatty acids (to assess compliance), s erum lipid levels, lipoprotein(a) levels, and LDL resistance to in vitro ox idative stress. Results: 49 persons completed the trial. The walnut diet was well tolerated . Planned and observed diets were closely matched. Compared with the Medite rranean diet, the walnut diet produced mean changes of -4.1% in total chole sterol level, -5.9% in LDL cholesterol level, and -6.2% in lipoprotein(a) l evel. The mean differences in the changes in serum lipid levels were -0.28 mmol/L (95% CI, -0.43 to -0.12 mmol/L) (-10.8 mg/dL [-16.8 to -4.8 mg/dL]) (P < 0.001) for total cholesterol level, -0.29 mmol/L (CI, -0.41 to -0.15 m mol/L) (-11.2 mg/dL [-16.3 to -6.1 mg/dL]) (P < 0.001) for LDL cholesterol level, and -0.021 g/L (CI, -0.042 to -0.001 g/L) (P = 0.042) for lipoprotei n(a) level. Lipid changes were similar in men and women except for lipoprot ein(a) levels, which decreased only in men. Low-density lipoprotein particl es were enriched with polyunsaturated fatty acids from walnuts, but their r esistance to oxidation was preserved. Conclusion: Substituting walnuts for part of the monounsaturated fat in a c holesterol-lowering Mediterranean diet further reduced total and LDL choles terol levels in men and women with hypercholesterolemia.