The Association between Vitamin D Status and Muscle Strength Among Adolescents

BACKGROUND: Although previous studies have described a positive correlation between physical activity and 25-hydroxyvitamin D levels (25(OH)D), the relationship between participation in school sports and 25(OH)D levels among children has not been well characterized. METHODS: The present study analyzed data from participants aged 5 to 15 years in the National Health and Nutrition Examination Survey cycle 2013-2014. General linear models adjusted for potential confounders were assembled to examine 25(OH)D levels according to participation in school sports. RESULTS: Of 1,670 children in the study sample, 17.9% were defined as having 25(OH)D inadequacy (< 50 nmol/L). Overall, 38% of children reported participation in school sports. In general, 25(OH)D levels were increased among children examined between May 1(st) and Oct 31(st) non-Hispanic whites, normal weight, higher income, and daily vitamin D intake ≥ 400 IU/d. After adjusting for potential confounders, 25(OH)D levels were 3.7 nmol/L higher among children who played in any school sports than those who did not. In general, higher 25(OH)D levels were seen among children examined during summer and fall seasons than those during winter and spring seasons, regardless the type of sport activities. Moreover, children who played mixed sports during summer and fall seasons had significantly higher 25(OH)D levels than their physically inactive counterparts. CONCLUSIONS: 25(OH)D concentrations were significantly higher in children playing school sports than those who did not. Thus, children's participation in school sports, particularly during summer and fall seasons should be considered as an effective public health intervention to reach optimal 25(OH)D levels.