Scholten, S. D., Madsen, B. J., Overweg, T. A., & Sergeev, I. N. (2012). Effects of Quercetin supplementation on performance and oxidative stress measures in endurance runners. Presentation 1026 at the 59th Annual Meeting of the American College of Sports Medicine, San Francisco, California; May 29-June 2, 2012.

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"Quercetin, a polyphenolic flavonoid with high antioxidant activity, is used for improving endurance in athletes however, mechanisms of this effect have not been investigated using a chronic training period."

This study investigated the effects of dietary Quercetin supplementation on oxidative stress, antioxidant activity, and performance measures in trained endurance runners (N = 8). It was hypothesized that Quercetin would improve antioxidant status and, thus, increase exercise performance in endurance athletes. For six weeks after a two-week washout period, received Quercetin (1000 mg/d) or placebo while maintaining current training schedules. Blood samples were collected at baseline, post-VO2peak test, and post-10K time-trial. Commercially available kits (Cell BioLabs) were used to measure total antioxidant capacity, superoxide dismutase activity, protein oxidation (protein carbonyl), and lipid peroxidation (malondialdehyde (MDA) in serum). Peak oxygen uptake (VO2peak) and steady state oxygen consumption during a self-selected-speed 10K time-trial (at 3K, 6K, 9K) were evaluated before and after supplementation.

Following six weeks of supplementation, there was a significant interaction between treatment and time with the lipid peroxidation variable. There were no significant pre-treatment to post-treatment changes in total antioxidant capacity, superoxide dismutase activity, or protein oxidation. There were no significant pre-treatment to post-treatment differences in VO2peak or running economy during the 10K time-trial.

Implication. While Quercetin supplementation may be related to lipid peroxidation, it is not related to performance as measured by VO2peak and running economy. This is another study where a physiological change and/or relationship is shown but does not translate into performance improvements.

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