Schoolchildren and their state of health, in particular, deficiencies, deserve no less attention than children of early age, while the recognition of the existence of inadequate vitamin D sufficiency in children of all age groups has not yet led to the introduction of mass prophylaxis for hypovitaminosis D. There are a number of factors determining the concentration of 25(OH)D-calcidiol in the blood. However, it is obvious that among many factors one should focus on several most significant and develop a scheme for correcting deficiency in each region.Purpose: to assess vitamin D sufficiency in adolescents living in Moscow, to correct calcidiol status in adolescents on the basis of baseline concentration of the metabolite transported in the blood. Material and methods: 769 adolescents aged 11-18 years for whom 25(OH)D concentration in the blood was evaluated, then 218 patients were randomized into 2 groups: the study group received tableted dietary supplement Minisun® vitamin D3, the controlgroup received placebo. The dosage of cholecalciferol was defined based on the initial level of calcidiol in patients. The study continued for 6 months, then blood was re-sampled to determine the level of calcidiol.Results: the study found low sufficiency with calcidiol among the schoolchildren: 25(OH)D median was 16.3 [11.4-20.8] ng/ml, only 5.2% of patients had normal concentration of calcidiol in the blood. At the second examination, positively significant differences in the status of vitamin D were observed in the study compared to the control group, while patients in the study group,against a background of cholecalciferol donation, demonstrated 25(OH)D median increase from 16.2 [12.25-19.3] ng/ml to 24.2 [21.05-26.4] ng/ml (p <0.001) .Conclusions: a large proportion of the child population (70.6%) have a concentration of 25(OH)D <20 ng/ml. The doses of cholecalciferol used in the study make it possible to eliminate the deficiency of calcidiol and to overcome the threshold of 20 ng/ml, but in order to normalize vitamin D status in the blood of adolescents living in Moscow, it is necessary to use higher dosages that need to be confirmed by further research.

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