Effects of walnut consumption on biomarkers of oxidative stress: A systematic review and meta-analysis of randomized controlled trials

Oxidative stress is caused by an imbalance between accumulation and production of oxygen reactive species (ROS) in tissues and cells and play a key role in many diseases. This systematic review and meta-analysis of randomized controlled trials (RCTs) was performed to analyze the effects of walnut consumption on biomarkers of oxidative stress. Databases including PubMed, Scopus, Embase and Web of science were searched until November 30th, 2024. Data were subjected to meta-analysis using a random effects model to examine the effect sizes of the pooled results. Four studies were identified eligible to be included in current meta-analysis. Walnut consumption resulted in a significant increase in catalase activity (CAT) (WMD: 42.20; 95 % CI: 34.28, 50.11). Walnut consumption did not affect other biomarkers of oxidative stress such as lipid peroxidation (LPO), reduced glutathione (GSH), oxidized glutathione (GSSG) and oxygen radical absorbance capacity (ORAC). Overall, this meta-analysis demonstrated walnut consumption increase CAT, but did not affect other biomarkers of oxidative stress. This suggests that walnut may have played an indirect and mild role in health. However, due to the limited number of studies, further investigations is suggested in this regard.