Role of vitamin D in pre-school children’s health

Vitamin D has pleiotropic effects, including maintaining calcium and phosphate homeostasis, and affecting the immune and endocrine systems. The article summarizes data on the expected biological effects of vitamin D on children’s health. The results of randomized clinical trials evaluating the effect of vitamin D supplementation on the incidence of acute respiratory tract infections are reviewed in detail. It has been shown that daily intake of vitamin D at a dose of 10 to 25 mcg/day (400–1000 IU/day) compared with placebo leads to a significant decrease in the proportion of children and adolescents who have had at least one episode of acute respiratory infection. The criteria for the provision of calciferol and the gradation of the status of vitamin D deficiency and deficiency in different countries are discussed. It has been shown that in the interpretation of the 25 (OH) D results there is a consensus on two points: calcidiol levels below 12 ng/ml (30 nmol/L) are considered clearly insufficient, and levels above 30 ng/ml (75 nmol/L) are considered sufficient in all regions. The incidence of hypovitaminosis D has been reported in children aged 3 to 7 years, where the overall combined assessment, regardless of age group, ethnic composition and breadth of the studied populations, showed that 13% of European children had a serum calcidiol concentration of less than 12 ng/ml (<30 nmol/L), and about 40% had a level of less than 30 ng/ml (<75 nmol/L). The data on the physiological need and the recommended daily dose of vitamin D for preschool children have been analyzed. In each country, the recommended intake of vitamin D is set (from 400 to 4000 IU), depending on the target concentration of serum calcidiol, the level of insolation, and nutritional characteristics. The necessity of conducting clinical studies in the age group from 3 to 7 years to determine an adequate, effective and safe preventive dose of vitamin D for preschool children in the Russian Federation is emphasized