Findings on the effect of walnut consumption on endothelial function are conflicting. Therefore, the present systematic review and meta-analysis summarized available trials in this regard. A systematic search was performed in online databases including PubMed-Medline, Scopus, and ISI Web of Science up to October 2023. Articles that reported the effect of walnut intake on flow-mediated dilation (FMD), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and stimulus-adjusted response measure (SARM) were included. Random effects models for a weighted mean difference (WMD) or standardized mean difference (SMD) were used to test for the overall effect. Six eligible trials were analyzed (250 participants). Walnut intake significantly increased FMD (WMD: 0.94%, 95% CI: 0.12 to 1.75; p = 0.02). However, meta-analysis could not show any beneficial effect of walnut intake on ICAM-1 (SMD: -0.23, 95% CI: -0.68 to 0.22; p = 0.31), VCAM-1 (SMD: -0.02, 95% CI: -1.38 to 1.34; p = 0.97), and SARM (WMD: 0.01%, 95% CI: -0.01 to 0.04; p = 0.28). In conclusion, the present meta-analysis suggests that walnuts may reduce cardiovascular disease risk by improving FMD. However, further studies should be performed on adults to determine the effect of walnut intake on endothelial function.
Keywords: endothelial function; flow-mediated dilation; meta-analysis; walnut.
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