Practical Nutritional Strategies to Attenuate Physiological Stress in Adolescent Soccer Players: A Comparative Trial of CoQ10 and Taurine.

Background/Objectives: Intensified training in adolescent soccer players increases oxidative stress, muscle damage, inflammation, and immune suppression, but direct comparisons of nutritional countermeasures are lacking. This randomised, double-blind, placebo-controlled trial compared the effects of 14-day coenzyme Q10 (CoQ10) versus taurine supplementation on haematological, oxidative, muscle damage, inflammatory, hormonal, and immune biomarkers in under-19 soccer players undergoing three repeated 90 min Soccer Match Simulation (SMS) sessions. Methods: Twenty-four male players (age 17.9 ± 0.7 years) received placebo (n = 8), CoQ10 (300 mg/day, n = 8), or taurine (4 g/day plus 4 g pre-session, n = 8). Blood was collected at baseline (T0), post-first session (T1), post-third session (T2), and 24 h post-third session (T3). Biomarkers included creatine kinase (CK), lactate dehydrogenase (LDH), malondialdehyde (MDA), total antioxidant capacity (TAC), interleukins (IL-6, IL-10, TNF-α), cortisol, testosterone, CD4/CD8 ratio, immunoglobulins (IgA, IgG), and plasma volume (Dill-Costill). Data were analysed by two-way repeated-measures ANOVA. Results: CoQ10 was superior in reducing MDA (T2: 0.83 ± 0.02 vs. 1.24 ± 0.03 μmol/L, p < 0.001), LDH (434 ± 9 vs. 684 ± 12 U/L, p < 0.001), and cortisol (20.2 ± 0.6 vs. 30.4 ± 0.8 μg/dL, p < 0.001), and preserved the testosterone:cortisol ratio (24.5 ± 1.1 vs. 13.6 ± 1.0 × 10-3, p < 0.001). CoQ10 was more effective than taurine in lowering IL-6 at T2 (3.5 ± 0.2 vs. 3.9 ± 0.2 pg/mL, p = 0.03), whereas taurine was more effective in increasing IL-10 (7.5 ± 0.2 vs. 5.7 ± 0.2 pg/mL, p = 0.005). Both supplements preserved CD4 counts (CoQ10: 790 ± 13, taurine: 795 ± 14 vs. placebo: 680 ± 15 cells/μL, p < 0.01) and the CD4/CD8 ratio, as well as IgA and IgG levels, with no between-supplement differences for immune outcomes (p > 0.05). No adverse events occurred. Conclusions: For adolescent soccer players undergoing intensified training, CoQ10 may be preferred when the goal is reducing oxidative stress, muscle damage, and catabolic load; taurine may be preferred for targeted anti-inflammatory support (IL-10 elevation). Either supplement effectively attenuated changes in circulating immune biomarkers. These preliminary findings provide evidence-based guidance for targeted sports nutrition, pending confirmation in larger trials.