Supplementary Material for: Seasonal differences of 25-hydroxyvitamin D concentrations in children and adolescents from Mexico City and Metropolitan Area

Introduction: Vitamin D deficiency is associated with bone metabolism and immune disorders. Radiation's seasonal variation affects vitamin D status more at the poles. In Mexico, near the equator, there have been reports of 10-20% vitamin D deficiency in children. There is no consensus on the definition of vitamin D deficiency, different organizations consider that a vitamin D level should be above 20 to 30 ng/ml. This study aimed to analyze vitamin D serum concentrations in children and adolescents from Mexico City and the Metropolitan Area (MA) during different seasons. Methods: Cross-sectional study in children and adolescents aged 5-20 years from Mexico City and Metropolitan Area, from autumn 2016 to winter 2017. Variables of interest such as anthropometric measurements, food consumption, and physical activity were analyzed. Results: A total of 816 children and adolescents were included. A high frequency of vitamin D deficiency was detected in 40.7% of the sample. The lowest vitamin D status occurred in winter 2016 and winter 2017. Conclusion: We found a higher frequency of vitamin D deficiency during winter in children and adolescents in Mexico City and MA. This risk persisted after adjusting for age, sex, BMI Z-score, milk consumption, physical activity, and screen time.