title: Short- and long-term safety of weekly high-dose vitamin D3 supplementation in school children.
abstract: BACKGROUND
  Hypovitaminosis D is prevalent in youth worldwide, but the safety of vitamin D at doses exceeding 200 IU/d is unknown in this age group. We assessed the safety of high doses of vitamin D(3) administered to apparently healthy schoolchildren.
  
  
  METHODS
  To assess short-term safety, 25 subjects randomly received placebo or vitamin D(3) at doses of 14,000 IU/wk for 8 wk. To assess long-term safety, 340 subjects randomly received placebo, vitamin D(3) as 1,400 IU/wk or 14,000 IU/wk for 1 yr. Biochemical variables were monitored at 0, 2, 4, 6, and 8 wk and 8 wk off therapy in the short-term study and at 0, 6, and 12 months in the long-term study.
  
  
  RESULTS
  In both the short- and long-term studies, mean serum calcium and 1,25-hydroxyvitamin levels did not change in any group. In the short-term study, mean 25-hydroxyvitamin concentrations increased from 44 (+/- 11) to 54 (+/- 19) ng/ml in the treated groups (P = 0.033). In the long-term study, mean 25-hydroxyvitamin D levels increased from 15 +/- 8 to 19 +/- 7 ng/ml (P < 0.0001) in subjects receiving 1,400 IU/wk and from 15 +/- 7 to 36 +/- 22 ng/ml (P < 0.0001) in the group receiving 14,000 IU/wk. No subject developed vitamin D intoxication.
  
  
  CONCLUSIONS
  Vitamin D(3) at doses equivalent to 2000 IU/d for 1 yr is safe in adolescents and results in desirable vitamin D levels.
authors.affiliation: Calcium Metabolism and Osteoporosis Program, American University of Beirut-Medical Center, Bliss Street, Beirut, Lebanon.
authors.forename: Joyce
authors.initials: J
authors.lastname: Maalouf
authors.forename: Mona
authors.initials: M
authors.lastname: Nabulsi
authors.forename: Reinhold
authors.initials: R
authors.lastname: Vieth
authors.forename: Samantha
authors.initials: S
authors.lastname: Kimball
authors.forename: Rola
authors.initials: R
authors.lastname: El-Rassi
authors.forename: Ziyad
authors.initials: Z
authors.lastname: Mahfoud
authors.forename: Ghada
authors.initials: G
authors.lastname: El-Hajj Fuleihan
mesh_terms: D000293:Adolescent; D002118:Calcium / Q000097:blood; D002648:Child; D002762:Cholecalciferol / Q000008:administration & dosage* / Q000009:adverse effects; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D014807:Vitamin D; D002762:Cholecalciferol; C104450:25-hydroxyvitamin D; D002118:Calcium