The optimal dose of vitamin D in growing girls during academic years: a randomized trial

Aim: Prevalence of vitamin D deficiency is remarkable during childhood and adolescence throughout the world. Sufficient intake of vitamin D contributes to a number of health outcomes. The aim of this study was to specify the optimal dose of vitamin D in growing girls in a Muslim country during an academic year. Materials and methods: This randomized clinical trial study was carried out in Yazd in the center of Iran in 2007;120 junior high school girls (aged 12-15 years) were randomly divided into 4 groups. Sixty students in groups I and II were treated for vitamin D deficiency with 300,000 IU vitamin D3 and then randomly received 50,000 U/monthly or 100,000IU/3 months vitamin D3; 60 other students in groups III and IV received 50,000 IU/3 months and 100,000/3 months from the beginning of the academic year. Medication continued for the entire academic year; 1 month after the last dose, serum 25(OH)D levels were measured. Results: The mean level of 25 (OH) D was 29.7 +/- 4.60 ng/mL in group land 30 +/- 5.61 ng/mL in group II. Mean serum levels of 25 (OH) D were 15.2 +/- 6 ng/mL and 23 +/- 6.8 ng/mL for groups III and IV, respectively. Conclusion: Neither doses of about 800 IU/day nor 1000 IU/day are sufficient to maintain 25(OH)D in optimal level (>20 ng/mL) for all, but after the treatment of deficiency, intakes of about 1000 IU/day or 2000 IU/day of vitamin D maintained optimal level in all of the students.