Scientific Study

OBJECTIVE: To determine the effects of daily walnut consumption on endothelial function; cardiovascular biomarkers; and anthropometric measures in type 2 diabetic individuals. RESEARCH DESIGN AND METHODS: This study was a randomized; controlled; single-blind; crossover trial. Twenty-four participants with type 2 diabetes (mean age 58 years; 14 women and 10 men) were randomly assigned to one of the two possible sequence permutations to receive an ad libitum diet enriched with 56 g (366 kcal) walnuts/day and an ad libitum diet without walnuts for 8 weeks. Subjects underwent endothelial function testing (measured as flow-mediated dilatation [FMD]) and assessment of cardiovascular biomarkers before and after each 8-week treatment phase. The primary outcome measure was the change in FMD after 8 weeks. Secondary outcome measures included changes in plasma lipids; A1C; fasting glucose; insulin sensitivity; and anthropometric measures. RESULTS: Endothelial function significantly improved after consumption of a walnut-enriched ad libitum diet compared with that after consumption of an ad libitum diet without walnuts (2.2 +/- 1.7 vs. 1.2 +/- 1.6%; P = 0.04). The walnut-enriched diet increased fasting serum glucose and lowered serum total cholesterol and LDL cholesterol from baseline (10.0 +/- 20.5 mg/dl; P = 0.04; -9.7 +/- 14.5 mg/dl; P < 0.01; and -7.7 +/- 10 mg/dl; P < 0.01; respectively); although these changes were not significant compared with those for an ad libitum diet without walnuts. There were no significant changes in anthropometric measures; plasma A1C; and insulin sensitivity. CONCLUSIONS: A walnut-enriched ad libitum diet improves endothelium-dependent vasodilatation in type 2 diabetic individuals; suggesting a potential reduction in overall cardiac risk.