Regular, but not acute, green tea supplementation increases total antioxidant status and reduces exercise-induced oxidative stress: a systematic review.

This systematic review aims to investigate the effects of green tea supplementation on exercise-induced oxidative stress. Four electronic databases were searched from inception to December 2020: SPORTDiscuss, PubMed, Scopus, and Web of Science. The search strategy was established in the following manner: (green tea) (Title/Abstract) AND (exercise OR training) (Title/Abstract) AND (oxidative stress OR antioxidant OR oxidation) (Title). After the application of inclusion and exclusion criteria 11, randomized or non-randomized control trials were included, 6 with a parallel design and 5 with a crossover design. Study methodological quality was assessed with the PEDro scale, and all studies were considered of moderate quality. Overall, acute green tea ingestion does not appear to influence antioxidant status or reduce exercise-induced oxidative stress. In contrast, green tea supplementation before exercise, for periods of more than 1 week, in a dose range of 400 to 800 mg of catechins per day, appears to be efficacious to increase total antioxidant status and protect cells against exercise-induced oxidative stress. Future investigations should focus on beginning green tea supplementation more than 7 days before exercise and completing it 2 or 3 days after while monitoring the change of markers of oxidative stress up to 48-72 h after exercise.