Effect of oral nut supplementation on endothelium-dependent vasodilation - a meta-analysis

Background. An inverse association was found between nut supplementation and the risk of cardiovascular disease. Identifying the direct effect of nut supplementation on endothelium-dependent vasodilation may partly explain that association. Methods: Human intervention studies were identified by systematic electronic search of the databases EMBASE, MEDLINE, Pubmed and Web of Science through January 2017 and by manually searching related articles. Subgroup analyses were performed to identify the source of heterogeneity among studies. Results: In total, 11 eligible articles involving 468 participants were included in the meta-analysis. Overall, the results of the 13 trials showed that nut supplementation significantly increased flow-mediated dilation [weighted mean differences (WMD): 1.03%, 95% Cl 0.26-1.79%, P = 0.008], There was significant heterogeneity among studies (P = 0.006) that might partly be explained by the different types of nuts. No significant association between nut supplementation and endothelium-independent vasodilatation was observed in a fixed effect model (WMD: 1.10% 95% Cl: -0.19-2.38%, P = 0.09). Conclusions: Supplementation of nuts significantly improves the vascular endothelial function without affecting endothelium-independent vasodilatation.