[The full text of this article is available free at http://jcem.endojournals.org/cgi/rapidpdf/jc.2007-2530v1
Background: Hypovitaminosis D [insufficient vitamin D] is prevalent in youth worldwide, but the safety of vitamin D at doses exceeding 200 IU/day is unknown in this age group.
We assessed the safety of high doses of vitamin D3 administered to apparently healthy school children.
Short term safety: 25 subjects randomly received placebo or vitamin D3 at doses of 14,000 IU/wk for 8 weeks.
Long term safety: 340 subjects randomly received placebo, vitamin D3 as 1400 IU or 14,000 IU/week for one year. [Note: 1,400 IU/wk is the current recommendation for this age group; 14,000 IU/wk is half the dose considered safe for adults]
Biochemical variables were monitored at 0, 2, 4, 6, 8 weeks, and 8 weeks off therapy in the short term study and at 0, 6 and 12 months in the long term study.
In both the short term and long term studies, mean serum calcium and 1,25-OHD levels did not change in any group.
In the short term study, mean 25-OHD concentrations increased from 44 (+/- 11) ng/ml to 54 (+/- 19) ng/ml in the treated groups (P=0.033).
In the long term study, mean 25-OHD levels increased from 15+/-8 to 19+/-7 ng/ml (p<0.0001) in subjects receiving 1400 IU/wk; and from 15+/-7 to 36+/-22ng/ml in the group receiving 14,000 IU/wk (p<0.0001).
No subject developed vitamin D intoxication.
Conclusion: Vitamin D3 at doses equivalent to 2,000 IU/day for one year is safe in adolescents and results in desirable vitamin D levels.
Source: The Journal of Clinical Endocrinology & Metabolism, April 29, 2008. [Epub ahead of print] PMID: 18445674, by Maalouf J, Nabulsi M, Vieth R, Kimball S, El-Rassi R, Mahfoud Z, El-Hajj Fuleihan G. Schools of Medicine and Health Sciences, American University of Beirut, Lebanon; Department of Nutritional Sciences, University of Toronto, Canada. [E-mail: Ghada E-Hajj Fuleihan, MD, MPH