Conclusion Despite the limitations of the current evidence , the prevalence of vitamin D inadequacy in athletes is prominent .
The risk significantly increases in higher latitudes , in winter and early spring seasons , and for indoor sport activities .
The prevalence of injuries in athletes is notable but its association with  vitamin D status is unclear .
Background Vitamin D is essential for maintaining optimal bone health .
The prevalence of vitamin D inadequacy in athletes is currently unclear .
Objective The objective of this study is to determine the prevalence of vitamin D inadequacy in athletes .
Serum 25(OH)D is measured to clinical ly determine vitamin D status .
Association between serum 25(OH)D concentrations and bone stress fractures in Finnish young men.
UNLABELLED Low vitamin D level may predict rickets , osteomalacia , or osteoporosis . We examined serum 25(OH)D concentration as a predisposing factor for bone stress fracture in 756 military recruits . The average serum 25(OH)D concentration was significantly lower in the group with fracture , suggesting a relationship between vitamin D and fatigue bone stress fracture . INTRODUCTION Low vitamin D level may predict rickets , osteomalacia , or osteoporosis . Fatigue bone stress fracture is one of the most frequently seen types of overuse injuries in athletes and military recruits . An association was recently shown between vitamin D and BMC . A correlation has also been found between low femoral BMD and stress fractures . We measured serum 25(OH)D concentration in a population sample of military recruits to determine if vitamin D is a predisposing factor for fatigue bone stress fracture . MATERIAL S AND METHODS We prospect ively followed 800 r and omly selected , healthy Finnish military recruits with a mean age of 19 years for developing stress fractures in homogenous circumstances . Blood for serum 25(OH)D concentration was drawn at entry into military service , and the weight , height , body mass index ( BMI ) , muscle strength , and 12-minute running were measured for all subjects . Serum 25(OH)D concentrations were measured with enzyme immunoassay . At end of the 90-day follow-up , 756 subjects completed the study . Subjects without fracture constituted controls . RESULTS Twenty-two recruits with stress fracture were identified ( 2.9 % ) , the incidence being 11.6 ( 95 % CI : 6.8 - 16.5 ) per 100 person-years . In the final multivariate analysis , the significant risk factor for stress fracture in conscripts was a below median serum 25(OH)D level ( 75.8 nM ) , OR being 3.6 ( 95 % CI : 1.2 - 11.1 ) . No significant associations between BMI ( p = 0.255 ) , age ( p = 0.216 ) , or smoking ( p = 0.851 ) and bone stress fracture were found in this study population . CONCLUSIONS A lower level of serum 25(OH)D concentration may be a generally predisposing element for bone stress fractures . Considering the obvious need of additional vitamin D in prevention of stress fractures , the effects of vitamin D fortification of foods and supplementation will be subjects of interest for future research
Conclusion Despite the limitations of the current evidence , the prevalence of vitamin D inadequacy in athletes is prominent .
The risk significantly increases in higher latitudes , in winter and early spring seasons , and for indoor sport activities .
The prevalence of injuries in athletes is notable but its association with  vitamin D status is unclear .
Background Vitamin D is essential for maintaining optimal bone health .
The prevalence of vitamin D inadequacy in athletes is currently unclear .
Objective The objective of this study is to determine the prevalence of vitamin D inadequacy in athletes .
Serum 25(OH)D is measured to clinical ly determine vitamin D status .