Impact of beetroot juice on oxidative stress in untrained individuals: A systematic review and meta-analysis

Antecedents: Oxidative stress arises from an imbalance between reactive oxygen species and antioxidant defenses, contributing to chronic diseases. While extensively studied in athletes, its relevance in untrained individuals and the role of nutritional interventions such as beetroot juice (Beta vulgaris) (BRJ) remain less explored. Objective: To systematically evaluate the effects of BRJ on oxidative stress biomarkers and antioxidant capacity in non-athletic adults. Methods: A systematic review and meta-analysis were conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Cochrane guidelines. Experimental studies comparing BRJ to placebo in untrained adults, assessing redox biomarkers, were included. Risk of bias was assessed using RoB-2, certainty of evidence with GRADE, and pooled effects calculated using a random effects model. Results: Seven studies (n = 360) met inclusion criteria. BRJ significantly reduced oxidative damage biomarkers (SMD = −0.42; 95% CI: −0.75 to −0.09; p = 0.01) with moderate heterogeneity (I² = 55%), particularly improving the GSH/GSSG ratio. It also significantly increased total antioxidant capacity (SMD = 0.82; 95% CI: 0.36 to 1.27; p < 0.001), though with high heterogeneity (I² = 81%). Overall risk of bias was low and certainty of evidence high. Conclusion: BRJ supplementation improves oxidative status in untrained adults. Standardization of dose, duration, and product quality is needed to support clinical and public health recommendations.