Effects of different doses of oral cholecalciferol on serum 25(OH)D, PTH, calcium and bone markers during fall and winter in schoolchildren.

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.