Serum 25-Hydroxyvitamin D Concentration and Aerobic Performance in Estonian Female Adolescent Athletes

Vitamin D insufficiency is highly prevalent in athletic populations residing at northern latitudes, particularly among young athletes training predominantly indoors. The impact of vitamin D on musculoskeletal health is well-established, while its influence on physical performance is not entirely clear. The aim of this study was to determine the prevalence of vitamin D insufficiency in Estonian female adolescent athletes and to examine associations of serum 25-hydroxyvitamin D [25(OH)D] with body composition, energy intake, physical performance and ferritin. Seventy-three female athletes aged 14–18 years participated. Body composition was assessed by dual-energy X-ray absorptiometry; physical performance by peak oxygen consumption (VO2peak/kg) and countermovement jumps; dietary intake was estimated using repeated 24 h recalls; and fasting blood samples were analyzed for 25(OH)D and ferritin. The mean serum 25(OH)D concentration was 67.6 ± 21.4 nmol.L−1 and ranged from 27.4 to 118.0 nmol.L−1. Vitamin D insufficiency (25(OH)D < 75 nmol.L−1) was present in 67% of participants, leaving only one-third with sufficient levels. Serum 25(OH)D concentration was positively associated with VO2peak/kg (r = 0.26; p = 0.043) independent of confounding variables. In conclusion, these findings suggest that vitamin D insufficiency is highly prevalent among Estonian female adolescent athletes, and 25(OH)D concentration is associated with aerobic performance.