Effects of Walnut Consumption on Endothelial Function in People with Type 2 Diabetes: a Randomized Pilot Trial

The aim of this study was to obtain preliminary data to test the hypothesis that (1) a 12-week intervention with 28 g/day of walnuts improves endothelial function in people with type 2 diabetes mellitus (DM) and (2) intake of walnuts improves plasma adipokines after 12 weeks of intervention. In this pilot randomized, single-blinded, controlled trial of 26 adult subjects with prevalent DM, each subject was randomized to a usual diet with 28 g of walnuts per day or usual diet without walnuts (control group). Reactive hyperemia index (RHI), a measure of endothelial function, was measured non-invasively at baseline and after 12 weeks using Endo-PAT2000. We used linear regression to examine the effects of the intervention on RHI. The mean age at baseline was 64.8 ± 11.6 years; 61.5 % of participants were female, and 15.4 % had coronary artery disease. The standard error of RHI was 0.19. The difference in change in RHI during the intervention between the two groups was −0.029 (95 % confidence interval (CI) −0.52, 0.46, p = 0.23). Walnut intervention led to a suggestive increase in adiponectin, albeit non-statistically significant (difference 0.50 μg/ml (95 % CI −0.10, 1.09), p = 0.65). We demonstrated the feasibility of the proposed randomized trial and obtained needed standard deviations to calculate the required sample size to test proposed hypotheses in an efficacy trial.