Walnut-enriched diet reduces fasting non-HDL-cholesterol and apolipoprotein B in healthy Caucasian subjects: A randomized controlled cross-over clinical trial

Abstract Background Walnut consumption is associated with reduced risk of coronary heart disease (CHD). Objective We assessed the effect of walnuts on lipid and glucose metabolism, adipokines, inflammation and endothelial function in healthy Caucasian men and postmenopausal women ≥ 50 years old. Design Forty subjects (mean ± SEM: age 60 ± 1 years, BMI 24.9 ± 0.6 kg/m2 ; 30 females) were included in a controlled, cross-over study and randomized to receive first a walnut-enriched (43 g/d) and then a Western-type (control) diet or vice-versa, with each lasting 8 weeks and separated by a 2-week wash-out. At the beginning and end of each diet phase, measurements of fasting values, a mixed meal test and an assessment of postprandial endothelial function (determination of microcirculation by peripheral artery tonometry) were conducted. Area under the curve (AUC), incremental AUC (iAUC) and treatment × time interaction (shape of the curve) were evaluated for postprandial triglycerides, VLDL-triglycerides, chylomicron-triglycerides, glucose and insulin. Results Compared with the control diet, the walnut diet significantly reduced non-HDL-cholesterol (walnut vs. control: − 10 ± 3 vs. − 3 ± 2 mg/dL; p = 0.025) and apolipoprotein-B (− 5.0 ± 1.3 vs. − 0.2 ± 1.1 mg/dL; p = 0.009) after adjusting for age, gender, BMI and diet sequence. Total cholesterol showed a trend toward reduction (p = 0.073). Fasting VLDL-cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides and glucose, insulin, HOMA-IR, and HbA1c did not change significantly. Similarly, fasting adipokines, C-reactive protein, biomarkers of endothelial dysfunction, postprandial lipid and glucose metabolism and endothelial function were unaffected. Conclusion Daily consumption of 43 g of walnuts for 8 weeks significantly reduced non-HDL-cholesterol and apolipoprotein-B, which may explain in part the epidemiological observation that regular walnut consumption decreases CHD risk.