Effects of Walnut (Juglans regia L.) on Blood Pressure and Endothelial Function in Adults: A Systematic Review and Dose-Response Meta-Analysis.

BACKGROUND: Walnuts (Juglans regia L.) are rich in bioactive compounds with anti-inflammatory and antioxidant properties, which may benefit cardiovascular health. However, the evidence regarding their effects on blood pressure (BP) and endothelial function remains inconclusive. OBJECTIVE: This systematic review and meta-analysis aimed to evaluate the effects of walnut consumption on systolic and diastolic BP (SBP and DBP), and endothelial function markers, including flow-mediated dilation (FMD), intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in adults. METHODS: A systematic search of PubMed, Web of Science and Scopus was conducted through February 2026 to identify relevant randomized controlled trials (RCTs). Weighted mean differences (WMDs) with corresponding 95% confidence intervals (CIs) were estimated using a random-effects model. Subgroup analyses were conducted based on intervention duration and walnut dosage. Dose-response associations were further examined using both linear and nonlinear modelling approaches. RESULTS: Pooled analysis data from 36 RCTs showed no significant overall effect of walnut consumption on SBP (WMD: -0.65 mmHg; 95% CI: -1.61 to 0.30, p = 0.183) or DBP (WMD: -0.68 mmHg; 95% CI: -1.56 to 0.19, p = 0.125). However, significant reductions in DBP were observed in studies lasting ≥ 12 weeks. Walnut intake significantly increased FMD (WMD: 0.93%; 95% CI: 0.27 to 1.59, p = 0.006), but had no overall significant effect on ICAM-1 (WMD = -0.56 ng/mL; 95% CI: -2.50 to 1.38; p = 0.571) and VCAM-1 (WMD: -8.68 ng/mL, p = 0.663). Subgroup analysis indicated a reduction in ICAM-1 in participants at high cardiovascular risk. The dose-response analysis supported a greater effect on ICAM-1 at higher walnut intakes. CONCLUSION: Walnut supplementation may improve vascular health by reducing endothelial dysfunction and promoting a dose-dependent reduction in endothelial inflammation. TRIAL REGISTRATION: International Prospective Register of Systematic Reviews (PROSPERO): CRD420261461684.