Effects of Walnut Intervention on Endothelial Function among People with Type 2 Diabetes: A Randomized Trial

Background Limited data are available on the effects of an intervention with small amount of walnuts on endothelial function in subjects with type 2 diabetes (DM). Objective To test the hypothesis that a 12‐week intervention with one ounce (28 g) of walnuts per day improves endothelial function in people with prevalent DM when compared to usual diet. Methods: A randomized controlled trial of 26 subjects aged 30+ years with prevalent DM. Participants in the walnut group were provided with a 12‐week supply of small walnut bags, and instructed to consume one bag per day as a snack or with a meal. Participants in the control group were instructed to maintain their regular diet. Endothelial function was measured non‐invasively at baseline and after 12 weeks using endoPAT2000. We used ANOVA for repeated measures to examine the effects of the intervention on reactive hyperemia index (RHI), a measure of endothelial function. Results: The mean age at baseline was 64.8 ± 11.6 years, and 61.5% of participants were female. All participants had DM and 15.4% of them also had coronary disease. At baseline, mean ± SE of log‐transformed RHI were 0.64 ± 0.13 in the intervention group and 0.44 ± 0.13 in the control group. At 12 weeks, corresponding values were 0.73 ± 0.07 and 0.63 ± 0.07 suggesting no difference in slope (p =0.12) nor in time‐by‐visit (p=0.58)Conclusions Our results do not support an improvement of endothelial function with daily intake of one ounce of walnuts during 12 weeks among subjects with DM.