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The Lancet


Vitamin D supplements for fracture prevention in schoolchildren in Mongolia: analysis of secondary outcomes from a multicentre, double-blind, randomised, placebo-controlled trial.

Last Revised:
PMID: 38048799
PII: S2213-8587(23)00317-0
PII: S2213-8587(23)00317-0


The study examined the impact of vitamin D supplementation on fracture risk in schoolchildren residing in Mongolia, a population with a high prevalence of vitamin D deficiency. Despite a 3-year regimen of 14,000 IU/week vitamin D supplements, no significant difference in fracture risk was observed between the treatment and placebo groups. The supplementation, however, was found to be safe with no noticeable increase in adverse events.

Key Takeaways

  • Vitamin D supplementation at a dosage of 14,000 IU/week for 3 years was found to be safe for schoolchildren in Mongolia.
  • There was no significant reduction in fracture risk associated with the vitamin D supplementation.
  • The incidence of adverse events did not differ between the vitamin D and placebo groups.

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Davaasambuu Ganmaa, Polyna Khudyakov, Uyanga Buyanjargal, Enkhtsetseg Tserenkhuu, Sumiya Erdenenbaatar, Chuluun-Erdene Achtai, Narankhuu Yansanjav, Baigal Delgererekh, Munkhzaya Ankhbat, Enkhjargal Tsendjav, Batbayar Ochirbat, Badamtsetseg Jargalsaikhan, Davaasambuu Enkhmaa, Adrian R Martineau

Full Abstract

  • BACKGROUND: for 3 years affected fracture risk.
  • METHODS: , once per week) or placebo for 3 years using permuted block randomisation stratified by school of attendance. Participants, care providers, and all trial staff were masked to group assignment during the intervention. Prespecified secondary outcomes were incidence of fractures and adverse events, ascertained using questionnaires. The fracture and safety analyses included participants who completed at least one follow-up fracture questionnaire. We estimated adjusted risk ratios (RRs) and 95% CIs using generalised linear models with binomial distribution and a log link function with adjustment for school of attendance. The trial is registered with, NCT02276755, and the intervention ended in May, 2019.
  • FINDINGS: Between Sept 2, 2015, and March 20, 2017, 11 475 children were invited to participate in the study and 8851 were recruited and randomly assigned to receive either vitamin D (n=4418) or placebo (n=4433). 8348 participants were included in the fracture and safety analyses (4176 [94·5%] in the vitamin D group and 4172 [94·1%] in the placebo group). Of these, 4125 (49·4%) were female, 4223 (50·6%) were male, and 7701 (92·2%) were of Khalkh ancestry. Median age was 9·2 years (IQR 8·0-10·7) and 7975 (95·5%) participants had baseline serum 25-hydroxyvitamin D concentrations less than 50 nmol/L. During a median follow-up of 3·0 years (IQR 2·9-3·1), 268 (6·4%) participants in the vitamin D group and 253 (6·1%) in the placebo group reported one or more fractures (adjusted RR 1·10, 95% CI 0·93-1·29; p=0·27). Incidence of adverse events did not differ between study groups.
  • INTERPRETATION: Oral vitamin D supplementation at a dose of 14 000 IU/week for 3 years was safe, but did not influence fracture risk in schoolchildren living in Mongolia who had a high baseline prevalence of vitamin D deficiency.
  • FUNDING: US National Institutes of Health.


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