Antioxidant Supplementation and Adaptive Response to Training: A Systematic Review

Abstract

Background: Antioxidant supplementation has become a common practice among athletes to theoretically achieve a reduction in oxidative stress, promote recovery and improve performance. Objective: To assess the effect of antioxidant supplements on exercise. Methods: A systematic literature search was performed up to January 2019 in MEDLINE via EBSCO and Pubmed, and in Web of Sciences based on the following terms: “antioxidants” [Major] AND “exercise” AND “adaptation”; “antioxidant supplement” AND “(exercise or physical activity)” AND “(adaptation or adjustment)” [MesH]. Thirty-six articles were finally included. Results: Exhaustive exercise induces an antioxidant response in neutrophils through an increase in antioxidant enzymes, and antioxidant low-level supplementation does not block this adaptive cellular response. Supplementation with antioxidants appears to decrease oxidative damage blocking cell-signaling pathways associated with muscle hypertrophy. However, upregulation of endogenous antioxidant enzymes after resistance training is blocked by exogenous antioxidant supplementation. Supplementation with antioxidants does not affect the performance improvement induced by resistance exercise. The effects of antioxidant supplementation on physical performance and redox status may vary depending on baseline levels. Conclusion: The antioxidant response to exercise has two components: At the time of stress and adaptation through genetic modulation processes in front of persistent pro-oxidant situation. Acute administration of antioxidants immediately before or during an exercise session can have beneficial effects, such as a delay in the onset of fatigue and a reduction in the recovery period. Chronic administration of antioxidant supplements may impair exercise adaptations, and is only beneficial in subjects with low basal levels of antioxidants.