RESUMO
BACKGROUND/OBJECTIVES: Controversies surround the actual requirements of vitamin D in adolescents. We aimed to assess the efficacy and safety of different doses of vitamin D in high schoolchildren of Taleghan (latitude 36.5°N) near Tehran. SUBJECTS/METHODS: In a randomized double-blind, placebo-controlled trial, 210 subjects, aged 14-20 years, 105 boys and 105 girls were assigned to three groups; group A (n=70) received 50 000 U oral cholecalciferol monthly (equal to 1600 U per day), group B (n=70), 50 000 U bimonthly (equal to 800 U/day) and group C (n=70), placebo. The study began in November 2007 and continued until April 2008. Serum 25(OH)D, parathyroid hormone (PTH), calcium (Ca) and bone markers were measured. RESULTS: At baseline, girls had significantly lower concentrations of 25(OH)D than boys (19.25±16 vs 40.5±14 nmol/l). Mean 25(OH)D increased from 32±22 to 60±27.5 and 28.25±14.5 to 45.75±24 in groups A and B, respectively (P<0.001); however, it did not change over time in group C (29±18 vs 29±17.5). Increment of mean 25(OH)D was higher in group A than in group B (P<0.01). In all groups, girls had lower concentrations of 25(OH)D than boys (P<0.001). Serum Ca increased and PTH decreased in groups A and B (P<0.001). In group A, osteocalcin (OC) and bone-specific alkaline phosphatase increased (P<0.001), but in group B only OC increased (P<0.001). Urine C telopeptide and Ca did not change in all three groups; no case of hypercalcemia was observed. CONCLUSIONS: Although monthly administration of 50 000 U vitamin D(3) increased serum 25(OH)D significantly, it was apparently not enough to correct vitamin D deficiency, especially in girls.
