Vitamin D supplementation and growth in urban Mongol school children: Results from two randomized clinical trials

PLoS One. 2017 May 8;12(5):e0175237. doi: 10.1371/journal.pone.0175237. eCollection 2017.


Background: Symptomatic vitamin D deficiency is associated with slowed growth in children. It is unknown whether vitamin D repletion in children with asymptomatic serum vitamin D deficiency can restore normal growth.

Objective: We tested the impact of vitamin D-supplementation on serum concentrations of 25-hydroxyvitamin D [25(OH)D] and short-term growth in Mongol children, with very low serum vitamin D levels in winter.

Design: We conducted two randomized, double-blind, placebo-controlled trials in urban school age children without clinical signs of rickets. The Supplementation Study was a 6-month intervention with an 800 IU vitamin D3 supplement daily, compared with placebo, in 113 children aged 12-15 years. A second study, the Fortification Study, was a 7-week intervention with 710 ml of whole milk fortified with 300 IU vitamin D3 daily, compared with unfortified milk, in 235 children aged 9-11 years.

Results: At winter baseline, children had low vitamin D levels, with a mean (±SD) serum 25-hydroxyvitamin D [25(OH)D] concentration of 7.3 (±3.9) ng/ml in the Supplementation Study and 7.5 (±3.8) ng/ml in the Fortification Study. The serum levels increased in both vitamin D groups-by 19.8 (±5.1) ng/ml in the Supplementation Study, and 19.7 (±6.1) ng/ml in the Fortification Study. Multivariable analysis showed a 0.9 (±0.3 SE) cm greater increase in height in the vitamin-D treated children, compared to placebo treated children, in the 6-month Supplementation Study (p = 0.003). Although the children in the 7-week Fortification Study intervention arm grew 0.2 (±0.1) cm more, on average, than placebo children this difference was not statistically significant (p = 0.2). There were no significant effects of vitamin D supplements on differences in changes in weight or body mass index in either trial. For the Fortification Study, girls gained more weight than boys while taking vitamin D 3 (p-value for interaction = 0.03), but sex was not an effect modifier of the relationship between vitamin D3 and change in either height or BMI in either trial.

Conclusions: Correcting vitamin D deficiency in children with very low serum vitamin D levels using 800 IU of vitamin D3 daily for six months increased growth, at least in the short-term, whereas, in a shorter trial of 300 IU of D fortified milk daily for 7 weeks did not.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adolescent
  • Child
  • Double-Blind Method
  • Female
  • Growth*
  • Humans
  • Male
  • Mongolia
  • Placebos
  • Urban Population*
  • Vitamin D / administration & dosage*
  • Vitamin D / blood


  • Placebos
  • Vitamin D

Grant support

This study was funded in part by National Heart, Lung, and Blood Institute (1K99HL089710-01A1) and by an anonymous funder. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.