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

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

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Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States of America.
Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, United States of America.
Health Sciences University of Mongolia, Ulaanbaatar, Mongolia.
Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, United States of America.
Connors Center for Women's Health and Gender Biology, Brigham and Women's Hospital, Boston, MA, United States of America.
Population Medicine, Harvard Pilgrim Health Care Institute and Harvard Medical School, Boston, MA, United States of America.
Endocrine, Diabetes and Nutrition Section, Department of Medicine, Boston University Medical Center, Boston, MA, United States of America.
Department of Pediatric Oncology, Dana Farber Cancer Institute, Boston, MA, United States of America.



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.


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.


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.


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.


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.

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