Effects of 8-week chokeberry extract supplementation on nitric oxide metabolites, immune markers, and oxidative stress in elite rowers: a randomized controlled trial

This randomized controlled trial investigated the effects of 8-week chokeberry extract supplementation on nitric oxide (NO) metabolites, oxidative stress markers, inflammatory cytokines, and white blood cell (WBC) profiles in elite male rowers. Fifteen athletes received either chokeberry extract ( n = 7; 3 × 200 mg/day) or placebo ( n = 8). A 2000-m rowing test was performed before and after supplementation, with blood collected pre-exercise, post-exercise, and 24 h post-exercise. After supplementation, the chokeberry group showed higher plasma nitrite concentrations post-exercise ( p = 0.0183, d = 1.95) and during recovery ( p = 0.0034, d = 2.99), higher post-exercise nitrate levels ( p = 0.0242, d = 1.45) as well as a higher total NOx (NO₂⁻ + NO₃⁻) post-exercise ( p = 0.0114, d = 1.57) compared with placebo. Group differences were also observed in WBC subsets during the post-supplementation test, including lower lymphocytes post-exercise ( p = 0.0075, d = 1.19), higher monocytes pre-exercise ( p = 0.0128, d = 1.03) and post-exercise ( p = 0.0086, d = 1.45), and higher granulocytes post-exercise ( p = 0.0077, d = 1.40) in the supplemented group. No between-group effects were detected for TAOC, TBARS, IL-2, IL-10, or TNF-α. Additionally, after supplementation before exercise, IL-6 levels were higher in the supplemented group compared to the placebo group ( p = 0.0407, d = 1.05). These findings indicate that chokeberry extract supplementation modifies NO-related biomarkers and selected immune parameters during exercise and recovery in elite rowers. The results demonstrate that chokeberry extract can influence physiological responses to intensive training in this athletic population. Trial registration : The study was registered on clinicaltrials.gov ID NCT06133751.