Vitamin D3 Dose Requirement to Raise 25‐Hydroxyvitamin D to Desirable Levels in Adolescents: Results from a Randomized Controlled Trial

Several organizations issued recommendations on desirable serum 25‐hydroxy vitamin D [25(OH)D] levels and doses of vitamin D needed to achieve them. Trials allowing the formulation of evidence‐based recommendations in adolescents are scarce. We investigated the ability of two doses of vitamin D3 in achieving recommended vitamin D levels in this age group. Post hoc analyses on data from a 1‐year double‐blind trial that randomized 336 Lebanese adolescents, aged 13 ± 2 years, to placebo, vitamin D3 at 200 IU/day (low dose), or 2000 IU/day (high dose). Serum 25(OH)D level and proportions of children achieving levels ≥20 ng/mL and 30 ng/mL were determined. At baseline, mean 25(OH)D was 15 ± 7 ng/mL, 16.4 ± 7 ng/mL in boys, and 14 ± 8 ng/mL in girls, p = 0.003, with a level ≥20 ng/mL in 18% and ≥30 ng/mL in 5% of subjects. At 1 year, mean levels were 18.6 ± 6.6 ng/mL in the low‐dose group, 17.1 ± 6 ng/mL in girls, and 20.2 ± 7 ng/mL in boys, p = 0.01, and 36.3 ± 22.3 ng/mL in the high‐dose group, with no sex differences. 25(OH)D increased to ≥20 ng/mL in 34% of children in the low‐dose and 96% in the high‐dose group, being higher in boys in the low‐dose arm only; it remained ≥30 ng/mL in 4% of children in the low‐dose arm but increased to 64% in the high‐dose arm. Baseline 25(OH)D level, body mass index (BMI), and vitamin D dose assigned were the most significant predictors for reaching a 25(OH)D level ≥20 ng/mL and 30 ng/mL. A daily dose of 2000 IU raised 25(OH)D level ≥20 ng/mL in 96% of adolescents (98% boys versus 93% girls). Dose‐response studies are needed to determine in a definitive manner the daily allowance of vitamin D for Middle Eastern adolescents with a similar profile. © 2014 American Society for Bone and Mineral Research.