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Short- and Long-Term Safety of Weekly High-Dose Vitamin D₃ Supplementation in School Children

Calcium Metabolism and Osteoporosis Program (J.M., R.E.-R., G.E.-H.F.), Department of Internal Medicine and Department of Pediatrics (M.N.), School of Medicine, and Department of Epidemiology and Population Health (Z.M.), School of Health Sciences, American University of Beirut, Beirut, Lebanon 113-6044; and Departments of Nutritional Sciences (R.V., S.K.) and Laboratory Medicine (R.V.), University of Toronto, Toronto, Canada M5S 3E2

Address all correspondence and requests for reprints to: Ghada El-Hajj Fuleihan, M.D., M.P.H., Calcium Metabolism and Osteoporosis Program, American University of Beirut-Medical Center, Bliss Street, Beirut, Lebanon 113-6044. E-mail: gf01{at}aub.edu.lb.

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 D₃ administered to apparently healthy schoolchildren.

Methods: To assess short-term safety, 25 subjects randomly received placebo or vitamin D₃ at doses of 14,000 IU/wk for 8 wk. To assess long-term safety, 340 subjects randomly received placebo, vitamin D₃ 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.

Conclusion: Vitamin D₃ at doses equivalent to 2000 IU/d for 1 yr is safe in adolescents and results in desirable vitamin D levels.

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