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

Abstract

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 I and 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. IntroductionVitamin D is an essential hormone for growth and development of bones in children and strong skeletal structure in adults (1). In vitamin D deficiency, only 10%-15% of calcium of normal diet is absorbed. This amount increases to 40% in the presence of adequate vitamin D (2,3). Moreover, epidemiologic studies show vitamin D deficiency increases the risk of important diseases like malignancy, cardiovascular disease, hypertension, stroke, diabetes, multiple sclerosis, rheumatoid arthritis, and inflammatory bowel disease (4). Many studies in recent years have demonstrated that vitamin D deficiency could exist in children and young adults without any obvious sign or symptoms (5-12). Girls particularly are more prone to vitamin D deficiency because of their less exposure to the sun and also their limited outdoor activities (5). Since about 35% of bone mass is acquired during 4 years around puberty (13) it seems rational to pay special attention to this age group. Diagnosis, treatment, and prevention of vitamin D deficiency in adolescents could, therefore, be very important for their future health (14). In Iran, primary evaluation demonstrated a high percentage of vitamin D deficiency in different age groups and in various locations especially in winter (15-19).There are different ways to receive sufficient vitamin D: either enough exposure to sunshine or consumption of supplements separately or in combination with fortified foods. Considering the importance of puberty, in some countries (e.g. France and Argentina) in which foods are not fortified, vitamin D supplements are offered to the girls in bolus doses ev...