Does Walnut Supplementation Have Favourable Effect Apolipoprotein A, B and Blood Pressure? A Systematic Review, Meta‐Analysis and Meta‐Evidence of Randomised Clinical Trials

BACKGROUNDS: Many randomised controlled trials (RCTs) have revealed the benefits of walnut on apolipoproteins and blood pressure, but the results are inconclusive. This meta-analysis of RCTs aimed to assess the effects of walnut on Apolipoprotein B (ApoB), apolipoprotein A1 (ApoA1) and blood pressure. METHODS: A systematic review of PubMed, Scopus, Web of Science, Cochrane and Embase databases was conducted, and the search time frame was from the establishment of the database up to January of 2025. A random effects model was applied to estimate weighted mean differences (WMDs) and 95% confidence intervals (CIs). RESULTS: Twenty-five RCTs comprising 26 intervention arms with 2155 patients were included. Walnut significantly decreased ApoB (WMD = -0.06; 95% CI: -0.10, -0.01, p = 0.002), but did not affect ApoA1 (WMD = -0.50; 95% CI: -1.34, 0.33, p = 0.249), systolic blood pressure (SBP) (WMD = -1.20; 95% CI: -4.02, 1.61, p = 0.401) and diastolic blood pressure (DBP) (WMD = -0.44; 95% CI: -2.55, 1.67, p = 0.682). CONCLUSION: Walnut intake was associated with reduced ApoB levels, with no significant effects observed on ApoA1, SBP, or DBP. Future research involving large-scale, international RCTs is essential to validate its therapeutic potential further.