Vitamin D Supplementation Alters Plasma Copper/Zinc Ratio Differently in Athletes and Non-Athletes: A Prospective Cohort Study

Vitamin D supplementation is widely recognized for its benefits beyond bone health, but its effects on trace element balance, particularly the copper/zinc (Cu/Zn) ratio, remain underexplored. This prospective cohort study investigated the impact of a 30-day, 1000-IU daily vitamin D supplementation on plasma Cu/Zn ratios in young male athletes (n=30) and non-athletes (n=30). Participants were matched for age and dietary intake, with athletes engaged in intensive training (≥3 sessions/week) and non-athletes seden-tary. Fasting blood samples were collected pre- and post-intervention, and serum Cu/Zn levels were ana-lyzed via colorimetric assays (Hitachi 717 auto-analyzer). Statistical analyses included Pearson’s correla-tions, independent and paired t-tests, and ANCOVA. Results revealed that vitamin D supplementation sig-nificantly increased serum copper concentrations in non-athletes (p=0.01) but not athletes, leading to an elevated Cu/Zn ratio in the non-athlete group (p<0.001). In contrast, athletes maintained stable Cu/Zn ra-tios, suggesting exercise may mitigate vitamin D-induced copper accumulation. A negative correlation between Cu levels and BMI was observed post-intervention (r=−0.508, p<0.001). These findings highlight divergent metabolic responses to vitamin D based on physical activity status, implying that exercise pro-tects against trace element imbalance during supplementation. The study underscores the need for per-sonalized nutritional strategies, particularly for sedentary individuals who may benefit from zinc co-supplementation to counter vitamin D-driven copper elevation. Limitations include a small sample size and short intervention period, warranting further research.