Vitamin D levels of 12-24-month-old healthy children in Turkey who received vitamin D supplementation until the age of one year

Introduction: The aim of this study was to evaluate vitamin D levels between 12-24 monthold healthy children supplemented with vitamin D (400 IU/day) during the first year. Methods: Descriptive-sectional study conducted between June 2015, and May 2016, in Istanbul (latitude 41 degrees N). Children aged 12-24 months followed up by the well-child clinic who had vitamin D supplementation in the first year were included in the study. The levels of calcium, phosphorus, alkaline phosphatase, parathyroid hormone and 25-hydroxyvitamin D [25(OH)D] were measured. Vitamin D status was defined as >20 ng/mL: sufficiency, 15-20 ng/mL: insufficiency and <15 ng/mL: deficiency. Results: The study was completed with 197 children. 26.9 % of children (n = 53) went on receiving supplementation after one year (mean dose 491 +/- 267 IU/day). The mean 25(OH)D level was 38.0 +/- 13.9 ng/mL. It was found that regular vitamin D intake under one year of age (p = 0.008) and continued support after one year of age (p = 0.042) increased level of 25(OH)D in children aged 12-24 months. Vitamin D deficiency was found in 4.1 % and vitamin D insufficiency in 7.1 %. Mother's education (p = 0.009) and use of formula (p = 0.012) were protective factors in relation to development of vitamin D deficiency or insufficiency. Conclusions: The level of 25(OH)D was sufficient in 88.8 % of children aged 12-24 months receiving 400 IU/day vitamin D supplementation in the first year. Vitamin D supplementation could not be required in healthy children aged 12- 24 months who received properly vitamin D supplementation in the first year.