Effects of Quercetin and Citrulline on Nitric Oxide Metabolites and Antioxidant Biomarkers in Trained Cyclists
Abstract
BACKGROUND: Quercetin (QCT) and citrulline (CIT) have been independently associated with improved antioxidant capacity and nitric oxide (NO) production, potentially enhancing cardiovascular function and exercise performance. This study aimed to evaluate the combined and independent effects of QCT and CIT supplementation on NO metabolites and antioxidant biomarkers in 50 trained cyclists undergoing a 20 km cycling time trial (TT).
METHODS: In a randomized, double-blind, placebo-controlled design, forty-two male and eight female trained cyclists were assigned to QCT + CIT, QCT, CIT, or placebo (PL) groups. Supplements were consumed twice daily for 28 days. Biochemical assessments included NO metabolites (nitrate/nitrite), ferric reducing antioxidant power (FRAP), superoxide dismutase (SOD) activity, and antioxidant capacity, measured pre- and post-TT.
RESULTS: NO metabolites were significantly elevated post-supplementation (p = 0.03); however, no significant interaction effects were observed for NO metabolites, FRAP, SOD, or antioxidant capacity across the groups (p > 0.05). Post-hoc analyses revealed that QCT significantly reduced FRAP concentrations compared to PL (p = 0.01), while no significant changes in SOD or antioxidant capacity were found across any groups.
CONCLUSIONS: These findings suggest that combined and independent QCT and CIT supplementation did not significantly improve these biomarkers, suggesting that baseline training adaptations, supplementation timing,…
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design.
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