Exploring factors associated with vitamin D nutritional status in Japanese baseball players.

Background: Vitamin D is a nutrient necessary for conditioning athletes. This cross-sectional study aimed to determine the nutritional status of vitamin D in farm-league professional baseball players to examine vitamin D requirements.

Methods: This study included 35 players enrolled in farm team A of the Nippon Professional Baseball Organization in the spring of 2022. The survey items included anthropometric measurements, serum 25-hydroxyvitamin D [25(OH)D] levels as an indicator of vitamin D nutritional status, a simple questionnaire for predicting vitamin D deficiency in Japanese adults, mean daily sun exposure duration, and body surface area (BSA).

Results: The serum 25(OH)D level was 29.8±1.8 ng/mL, and 17 (49%) participants were vitamin D deficient (<30 ng/mL). The serum 25(OH)D levels showed positive correlations with body height (r=0.459, P<0.01), fat-free mass (r=0.347, P<0.05), muscle mass (r=0.341, P<0.05), and BSA (r=0.434, P<0.01). Furthermore, the consumption frequency of fish with high vitamin D levels in regular diets, BSA, and body fat mass were identified as predictors of the serum nutritional status of vitamin D.

Conclusions: Athletes engaged in outdoor sports, such as the study participants, had inadequate vitamin D levels. In addition, the frequency of consumption of fish with high vitamin D levels in regular diets, BSA, and body fat mass were identified as predictors of the serum nutritional status of vitamin D. Further studies of the relationship between vitamin D supplementation and performance are needed.