Factors Influencing Serum Vitamin D Concentration in Turkish Children Residing in Izmir: A Single-Center Experience

Objective: The aim of this study was to examine the vitamin D status of children and to determine the factors influencing serum 25-hydroxyvitamin D [25(OH)D] concentration in Turkish infants living in Izmir. Methods: In this study, we examined the serum 25(OH)D levels of 100 infants aged 1 to 24 months and of 22 mothers from Izmir, Turkey. The study also included a questionnaire given to the mothers to acquire data on the demographic characteristics of the infants and their mothers as well as information on vitamin D supplementation, clothing habits, and sunlight exposure. Results: Vitamin D deficiency was present in 31% of infants and 81.8% of mothers. Twenty-four male (42.9%) and 7 female (15.9%) infants were found to be vitamin D deficient (<20 mg/dL); 9 male (16.1%) and 17 female (38.6%) infants to be vitamin D insufficient (20-30 mg/dL); and 23 male (41.1%) and 20 female (45.5%) infants were vitamin D sufficient (>30 mg/dL). Only 63% of the infants were receiving vitamin D supplementation and 52% were said to be having regular exposure to sunlight. Mean serum vitamin D levels were lower in infants whose mothers were dressed according to the culture of traditional covered clothing (44%) compared to those infants whose mothers' dressing style provided more exposure to sunlight. Conclusion: We conclude that low exposure to sunlight, inadequate use of vitamin D supplementation, and large family size are factors influencing the vitamin D status of Turkish children living in the inner city of Izmir.