Zambón, D., J. Sabate´, S. Muñoz, B. Campero, E. Casals, M. Merlos, J.C. Laguna, E. Ros, MD, 2000. Substituting walnuts for monounsaturated fat improves the serum lipid profile of hypercholesterolemic men and women a randomized crossover trial. Ann Intern Med. 132:538-546.
Background: It has been reported that walnuts reduce serum cholesterol levels in normal young men. Objective: To assess the acceptability of walnuts and their effects on serum lipid levels and low-density lipoprotein (LDL) oxidizability in free-living 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 hypercholesterolemia. Intervention: A cholesterol-lowering Mediterranean diet and a diet of similar energy and fat content in which walnuts replaced approximately 35% of the energy obtained from monounsaturated fat. Patients followed each diet for 6 weeks. Measurements: Low-density lipoprotein fatty acids (to assess compliance), serum lipid levels, lipoprotein (a) levels, and LDL resistance to in vitro oxidative stress. Results: 49 persons completed the trial. The walnut diet was well tolerated. Planned and observed diets were closely matched. Compared with the Mediterranean diet, the walnut diet produced mean changes of -4.1% in total cholesterol level, -5.9% in LDL cholesterol level, and -6.2% in lipoprotein(a) level. The mean differences in the changes in serum lipid levels were 20.28 mmol/L (95% CI, 20.43 to 20.12 mmol/L) (-10.8 mg/dL [0-16.8 to -4.8 mg/dL]) (P< 0.001) for total cholesterol level, -0.29 mmol/L (CI, -0.41 to -0.15 mmol/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 lipoprotein ( a) level. Lipid changes were similar in men and women except for lipoprotein (a) levels, which decreased only in men. Low-density lipoprotein particles were enriched with polyunsaturated fatty acids from walnuts, but their resistance to oxidation was preserved. Conclusion: Substituting walnuts for part of the monounsaturated fat in a cholesterol-lowering Mediterranean diet further reduced total and LDL cholesterol levels in men and women with hypercholesterolemia.
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