Influence of Vitamin D Supplementation on Growth, Body Composition, and Pubertal Development Among School-aged Children in an Area With a High Prevalence of Vitamin D Deficiency

Abstract

ImportanceVitamin D deficiency (defined as 25-hydroxyvitamin D [25(OH)D] <20 ng/mL) is prevalent among children living in temperate climates and has been reported to associate independently with stunting, obesity, and early activation of the hypothalamic-pituitary-gonadal axis. Phase 3 randomized clinical trials to investigate the influence of long-term vitamin D replacement on growth, body composition, and pubertal development of school-aged children with vitamin D deficiency are lacking.ObjectiveTo determine whether weekly oral vitamin D supplementation influences linear growth, body composition, or pubertal development in school-aged children living in a setting where vitamin D deficiency is highly prevalent.Design, Setting, and ParticipantsThis secondary analysis of a double-blind, placebo-controlled randomized clinical trial was conducted from June 2016 to June 2019 at 18 grade schools in Ulaanbaatar, Mongolia. School-aged children (6 to 13 years at baseline) attending participating schools were included. Exclusion criteria included a positive QuantiFERON-TB Gold in-tube assay result, conditions or medications associated with altered vitamin D metabolism, use of vitamin D supplements, signs of rickets, or intention to move from Ulaanbaatar within 4 years. Of 11 475 children invited to participate in the study, 9814 underwent QFT testing, and 8851 with negative results were included in the study. All but 1 participant in the placebo group completed follow-up and were included in the present analysis. Data were analyzed from November 2021 to February 2022.InterventionsWeekly oral doses of vitamin D3, 14 000 IU, (n = 4418), or placebo (n = 4433) for 3 years.Main Outcomes and MeasuresMean z scores for height for age, body mass index for age, and waist-to-height ratio; mean percentage body fat, fat mass, and fat-free mass; and mean Tanner scores for pubertal development.ResultsOf 8851 participants, 4366 (49.3%) were female, and 8165 (92.2%) were of Khalkh ethnicity; the mean (SD) age was 9.4 (1.6) years. A total of 8453 participants (95.5%) were vitamin D deficient at baseline, and mean end-of-study 25(OH)D concentrations among participants randomized to vitamin D vs placebo were 31.0 vs 10.7 ng/mL (mean difference, 20.3; 95% CI; 19.9-20.6). However, vitamin D supplementation did not influence mean height for age, body mass index for age, waist-to-height ratio, percentage body fat, fat mass, fat-free mass, or Tanner scores, either overall or within subgroups defined by baseline 25(OH)D concentration less than 10 ng/mL vs 10 ng/mL or greater, estimated calcium intake less than 500 mg/d vs 500 mg/d or greater, or male vs female sex.Conclusions and RelevanceIn school-aged children in this study with low baseline vitamin D status, oral vitamin D3 supplementation at a dose of 14 000 IU per week for 3 years was effective in elevating 25(OH)D concentrations but did not influence growth, body composition, or pubertal development.Trial RegistrationClinicalTrials.gov Identifier: NCT02276755

Influence of vitamin D supplementation on muscle strength and exercise capacity in South African schoolchildren: a randomised controlled trial (ViDiKids)

“…Our null findings for grip strength and VO 2peak are in keeping with those from a similarly designed Phase 3 RCT conducted in Mongolia, where effects of a 3-year course of 14,000 IU vitamin D/week were investigated. [32][33][34][35] Our finding of a small borderline-significant positive effect of vitamin D supplementation on long jump distance supports the concept that vitamin D has a physiological role in supporting muscle strength. 5 However, the fact that this was not associated with an effect on grip strength, plus the observation that no such effect was seen in Mongolian children (who had a significantly higher baseline prevalence of vitamin D deficiency than participants in the current study) 10 11 suggests that this result may have arisen as a result of type 1 error arising as a result of investigating multiple secondary outcomes.…”

Micronutrient deficiency and supplements in schoolchildren and teenagers

“…A secondary analysis of a RCT conducted in Mongolia in 8851 school-aged children (mean age 9.4 years) living in a setting where vitamin D deficiency is highly prevalent, testing weekly oral doses of 14 000 IU vitamin D3 for 3 years, showed that 95.5% were deficient at baseline. The intervention was effective in elevating 25(OH)D blood concentrations but did not influence growth, nor self-assessed pubertal development [37 ▪ ].…”

Influence of vitamin D supplementation on muscle strength and exercise capacity in Mongolian schoolchildren: a randomised controlled trial

“…An opportunity to address this gap in the literature arose during conduct of a phase 3 randomised controlled trial of vitamin D supplementation in 8,851 school children aged 6 -13 years living in Mongolia who were given weekly oral vitamin D supplementation over 3 years. [23][24][25] The primary aim of the trial was to test whether this intervention reduced risk of incident tuberculosis infection; null results for this outcome have been reported elsewhere. 23 This paper reports findings for secondary outcomes including grip strength and standing long jump distance, measured at annual intervals in all participants; peak oxygen uptake (VO 2peak ), estimated using 20 metre shuttle run tests performed at annual intervals in a subset of 632 participants; and spirometric outcomes, measured at 3-year follow-up in a subset of 1,343 participants.…”