Effects of Walnut Consumption on Blood Lipid Profile and Apolipoproteins in Adults: A <scp>GRADE</scp> ‐Assessed Systematic Review and Dose–Response Meta‐Analysis of 49 Randomized Controlled Trials

Walnuts (<i>Juglans regia</i> L.) are rich in polyunsaturated fatty acids (PUFAs), fiber, and bioactive compounds that may positively affect lipid metabolism. Although several clinical trials have examined their impact on the lipid profile, results have been inconsistent, and evidence regarding their effects on apolipoproteins is limited. This meta-analysis aims to systematically assess the impact of walnut consumption on blood lipid profile and apolipoproteins in adults. A comprehensive search of major databases was conducted up to August 2025 to find relevant randomized controlled trials (RCTs) evaluating the effects of walnut intake on triglycerides (TG), total cholesterol (TC), low- and high-density lipoprotein cholesterol (LDL-C and HDL-C), apolipoproteins A1 and B (Apo-A1 and Apo-B). Pooled effect sizes were estimated using a random-effects model. The pooled analysis of 49 RCTs (57 effect sizes; 4611 participants) showed that Walnut consumption significantly reduced and TG (WMD: -6.24 mg/dL, 95% CI: [-9.49, -2.99], <i>p</i> < 0.001), TC (WMD: -6.39 mg/dL, 95% CI: [-8.54, -4.23], <i>p</i> < 0.001), and LDL-C (WMD: -5.68 mg/dL; 95% CI: [-7,89, -3.47], <i>p</i> < 0.001), while no significant effect was observed on HDL-C (WMD: 0.71 mg/dL, 95% CI: [-0.24, 1.68], <i>p</i> = 0.145), Apo-A1 (WMD: 0.0, 95% CI: [-0.01, 0.00], <i>p</i> = 0.573), or Apo-B (WMD: 0.1, 95% CI: [-0.02, 0.05], <i>p</i> = 0.462). However, subgroup analyses indicated significant reductions in Apo-B at higher walnut doses (> 50 g/day) and increases in HDL-C in the low-dose intervention (< 50 g/day). In conclusion, walnut supplementation improves the lipid profile by significantly lowering TC, LDL-C, and TG levels. However, effects on HDL-C and apolipoproteins remain inconclusive. These findings support the incorporation of walnuts as part of a heart-healthy dietary pattern.