The effects of indoor and outdoor sports participation and seasonal changes on vitamin D levels in athletes

OBJECTIVE: Nowadays, people tend to spend more time in the closed areas and benefit less from sunlight. In this study, we examined the results of vitamin D measurements of athletes from different disciplines in different months and aimed to determine if the synthesis of vitamin D decreases or not according to exercise environment and month. METHODS: The study was conducted in participants aged 5–52 years. A total of 555 elite-level sportsmen who were admitted to our Sports Medicine Clinic in the study participated in this study. Indoor and outdoor environmental and seasonal effects on the measurements in different months were statistically evaluated. Independent-samples test and definitive statistics were used for statistical analyses and a p-value less than 0.05 has been considered significant. RESULTS: The study group consisted of 229 male and 326 female athletes. The serum 25-hydroxyvitamin D concentration was observed; 120 (21.6%) athletes have severe serum vitamin D deficiency (<11–20 ng/mL). Vitamin D levels were not significantly different from outdoor athletes (393; 70.8%). Winter measurements of vitamin D levels were significantly lower than those measured in autumn (p = 0.000). CONCLUSION: Increasing vitamin D levels are very important especially in participating athletes and additional supplements are recommended whenever necessary. Gender and indoor/outdoor sports participation showed no statistically significant outcomes on vitamin D levels. However, winter season had a negative effect on vitamin D levels. Therefore, adequate precautions should be taken to increase vitamin D, especially during winter, to maintain the best performance of the athletes.