The Effect of Vitamin D3 Supplementation on Vitamin D Status and Associated Health Outcomes in Children: A Randomized Controlled Trial

Emily Royle; Dominique U Glatt; Emeir M McSorley; L Kirsty Pourshahidi; David J Armstrong; Laura Grimley; Mary M Slevin; Cealan O Henry; James E McMullan; R Revuelta Iniesta; Jane T McCluskey; Nigel Gleeson; Pamela J Magee

doi:10.1016/j.tjnut.2026.101493

The Effect of Vitamin D3 Supplementation on Vitamin D Status and Associated Health Outcomes in Children: A Randomized Controlled Trial

Emily Royle
, Dominique U Glatt
, Emeir M McSorley
, L Kirsty Pourshahidi
, David J Armstrong
, Laura Grimley
, Mary M Slevin
, Cealan O Henry
, James E McMullan
, R Revuelta Iniesta
, Jane T McCluskey
, Nigel Gleeson
, Pamela J Magee

Research output: Contribution to journal › Article › peer-review

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Abstract

Background: Vitamin D is a key regulator of musculoskeletal growth, immune regulation, and cognitive function in children. As children in the United Kingdom (UK) and Ireland are at risk of vitamin D deficiency due to the northern latitude, supplementation is recommended. To our knowledge, the effect of supplementation on status and related health outcomes has not been investigated in children residing in the UK/Ireland. Objectives: To examine the effect of vitamin D ₃ supplementation on vitamin D status and related health outcomes in children. Methods: The D vitamin in children study was a double-blind, randomized, placebo-controlled trial, conducted among healthy children (aged 4–11 y). Children received 12 wk of either 10 μg/d vitamin D ₃ or a placebo devoid of vitamin D (control) in the form of an oral spray. The primary outcome, plasma 25-hydroxyvitamin D, and secondary outcomes, including grip strength, balance, cognitive function, winter status, immune markers, and bone turnover markers, were assessed pre- and postintervention. Results: One hundred eighteen participants completed the study (mean age 8.1 ± 1.8 y; 51% girls). Supplementation significantly increased 25-hydroxyvitamin D concentration (from 66.31 ± 17.26 nmol/L to 69.04 ± 16.93 nmol/L) compared to a decline in the placebo group (63.67 ± 19.48 nmol/L to 56.29 ± 18.58 nmol/L; P < 0.001) and prevented deficiency during the extended winter months. No effects were observed on muscle function, cognitive function, immune function, or bone turnover markers. Conclusions: Vitamin D insufficiency is prevalent in UK/Irish children, and supplementation in the form of an oral spray is effective in achieving/maintaining an adequate status in most children. Further research is warranted to elucidate mechanisms underpinning nonresponse to supplementation and to further investigate the potential beneficial effects of supplementation on cognitive function.This trial was registered at clinicaltrials.gov as NCT05018988.

Original language	English
Article number	101493
Pages (from-to)	1-10
Number of pages	10
Journal	The Journal of nutrition
Early online date	24 Mar 2026
DOIs	https://doi.org/10.1016/j.tjnut.2026.101493
Publication status	Published online - 24 Mar 2026

Bibliographical note

Data Availability Statement

Data described in the manuscript, code book, and analytic
code will be made available from the corresponding author upon
request, pending application and approval

Funding

This study was supported by grants from the Department for the Economy (DfE), a Queen Margaret University PhD student ship, and BetterYou Ltd to support the analysis of immune and bone turnover markers. Additionally, BetterYou Ltd provided the supplement and placebo control sprays for the study. This project was completed in collaboration with Queen Margaret University. Neither DfE nor BetterYou Ltd had any involvement in the study design, data collection, analysis, or interpretation.

Keywords

Cognitive Function
Muscle strength
Balance
Immune Function
25(OH)D status
Vitamin D Supplementation
Bone turnover markers
Children
cognitive function
muscle strength
balance
children
immune function
bone turnover markers
vitamin D supplementation

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Royle, E., Glatt, D. U., McSorley, E. M., Pourshahidi, L. K., Armstrong, D. J., Grimley, L., Slevin, M. M., Henry, C. O., McMullan, J. E., Revuelta Iniesta, R., McCluskey, J. T., Gleeson, N., & Magee, P. J. (2026). The Effect of Vitamin D3 Supplementation on Vitamin D Status and Associated Health Outcomes in Children: A Randomized Controlled Trial. The Journal of nutrition, 1-10. Article 101493. Advance online publication. https://doi.org/10.1016/j.tjnut.2026.101493

@article{5e584d826ede4548935eca5aea94b71d,

title = "The Effect of Vitamin D3 Supplementation on Vitamin D Status and Associated Health Outcomes in Children: A Randomized Controlled Trial",

abstract = "Background: Vitamin D is a key regulator of musculoskeletal growth, immune regulation, and cognitive function in children. As children in the United Kingdom (UK) and Ireland are at risk of vitamin D deficiency due to the northern latitude, supplementation is recommended. To our knowledge, the effect of supplementation on status and related health outcomes has not been investigated in children residing in the UK/Ireland. Objectives: To examine the effect of vitamin D 3 supplementation on vitamin D status and related health outcomes in children. Methods: The D vitamin in children study was a double-blind, randomized, placebo-controlled trial, conducted among healthy children (aged 4–11 y). Children received 12 wk of either 10 μg/d vitamin D 3 or a placebo devoid of vitamin D (control) in the form of an oral spray. The primary outcome, plasma 25-hydroxyvitamin D, and secondary outcomes, including grip strength, balance, cognitive function, winter status, immune markers, and bone turnover markers, were assessed pre- and postintervention. Results: One hundred eighteen participants completed the study (mean age 8.1 ± 1.8 y; 51\% girls). Supplementation significantly increased 25-hydroxyvitamin D concentration (from 66.31 ± 17.26 nmol/L to 69.04 ± 16.93 nmol/L) compared to a decline in the placebo group (63.67 ± 19.48 nmol/L to 56.29 ± 18.58 nmol/L; P < 0.001) and prevented deficiency during the extended winter months. No effects were observed on muscle function, cognitive function, immune function, or bone turnover markers. Conclusions: Vitamin D insufficiency is prevalent in UK/Irish children, and supplementation in the form of an oral spray is effective in achieving/maintaining an adequate status in most children. Further research is warranted to elucidate mechanisms underpinning nonresponse to supplementation and to further investigate the potential beneficial effects of supplementation on cognitive function.This trial was registered at clinicaltrials.gov as NCT05018988.",

keywords = "Cognitive Function, Muscle strength, Balance, Immune Function, 25(OH)D status, Vitamin D Supplementation, Bone turnover markers, Children, cognitive function, muscle strength, balance, children, immune function, bone turnover markers, vitamin D supplementation",

author = "Emily Royle and Glatt, \{Dominique U\} and McSorley, \{Emeir M\} and Pourshahidi, \{L Kirsty\} and Armstrong, \{David J\} and Laura Grimley and Slevin, \{Mary M\} and Henry, \{Cealan O\} and McMullan, \{James E\} and \{Revuelta Iniesta\}, R and McCluskey, \{Jane T\} and Nigel Gleeson and Magee, \{Pamela J\}",

note = "{\textcopyright} 2026 The Authors. Published by Elsevier Inc. on behalf of American Society for Nutrition. ",

year = "2026",

month = mar,

day = "24",

doi = "10.1016/j.tjnut.2026.101493",

language = "English",

pages = "1--10",

journal = "The Journal of nutrition",

issn = "0022-3166",

publisher = "Elsevier BV",

}

Royle, E, Glatt, DU, McSorley, EM , Pourshahidi, LK, Armstrong, DJ, Grimley, L, Slevin, MM, Henry, CO, McMullan, JE, Revuelta Iniesta, R, McCluskey, JT, Gleeson, N & Magee, PJ 2026, 'The Effect of Vitamin D3 Supplementation on Vitamin D Status and Associated Health Outcomes in Children: A Randomized Controlled Trial', The Journal of nutrition, pp. 1-10. https://doi.org/10.1016/j.tjnut.2026.101493

TY - JOUR

T1 - The Effect of Vitamin D3 Supplementation on Vitamin D Status and Associated Health Outcomes in Children: A Randomized Controlled Trial

AU - Royle, Emily

AU - Glatt, Dominique U

AU - McSorley, Emeir M

AU - Pourshahidi, L Kirsty

AU - Armstrong, David J

AU - Grimley, Laura

AU - Slevin, Mary M

AU - Henry, Cealan O

AU - McMullan, James E

AU - Revuelta Iniesta, R

AU - McCluskey, Jane T

AU - Gleeson, Nigel

AU - Magee, Pamela J

PY - 2026/3/24

Y1 - 2026/3/24

N2 - Background: Vitamin D is a key regulator of musculoskeletal growth, immune regulation, and cognitive function in children. As children in the United Kingdom (UK) and Ireland are at risk of vitamin D deficiency due to the northern latitude, supplementation is recommended. To our knowledge, the effect of supplementation on status and related health outcomes has not been investigated in children residing in the UK/Ireland. Objectives: To examine the effect of vitamin D 3 supplementation on vitamin D status and related health outcomes in children. Methods: The D vitamin in children study was a double-blind, randomized, placebo-controlled trial, conducted among healthy children (aged 4–11 y). Children received 12 wk of either 10 μg/d vitamin D 3 or a placebo devoid of vitamin D (control) in the form of an oral spray. The primary outcome, plasma 25-hydroxyvitamin D, and secondary outcomes, including grip strength, balance, cognitive function, winter status, immune markers, and bone turnover markers, were assessed pre- and postintervention. Results: One hundred eighteen participants completed the study (mean age 8.1 ± 1.8 y; 51% girls). Supplementation significantly increased 25-hydroxyvitamin D concentration (from 66.31 ± 17.26 nmol/L to 69.04 ± 16.93 nmol/L) compared to a decline in the placebo group (63.67 ± 19.48 nmol/L to 56.29 ± 18.58 nmol/L; P < 0.001) and prevented deficiency during the extended winter months. No effects were observed on muscle function, cognitive function, immune function, or bone turnover markers. Conclusions: Vitamin D insufficiency is prevalent in UK/Irish children, and supplementation in the form of an oral spray is effective in achieving/maintaining an adequate status in most children. Further research is warranted to elucidate mechanisms underpinning nonresponse to supplementation and to further investigate the potential beneficial effects of supplementation on cognitive function.This trial was registered at clinicaltrials.gov as NCT05018988.

AB - Background: Vitamin D is a key regulator of musculoskeletal growth, immune regulation, and cognitive function in children. As children in the United Kingdom (UK) and Ireland are at risk of vitamin D deficiency due to the northern latitude, supplementation is recommended. To our knowledge, the effect of supplementation on status and related health outcomes has not been investigated in children residing in the UK/Ireland. Objectives: To examine the effect of vitamin D 3 supplementation on vitamin D status and related health outcomes in children. Methods: The D vitamin in children study was a double-blind, randomized, placebo-controlled trial, conducted among healthy children (aged 4–11 y). Children received 12 wk of either 10 μg/d vitamin D 3 or a placebo devoid of vitamin D (control) in the form of an oral spray. The primary outcome, plasma 25-hydroxyvitamin D, and secondary outcomes, including grip strength, balance, cognitive function, winter status, immune markers, and bone turnover markers, were assessed pre- and postintervention. Results: One hundred eighteen participants completed the study (mean age 8.1 ± 1.8 y; 51% girls). Supplementation significantly increased 25-hydroxyvitamin D concentration (from 66.31 ± 17.26 nmol/L to 69.04 ± 16.93 nmol/L) compared to a decline in the placebo group (63.67 ± 19.48 nmol/L to 56.29 ± 18.58 nmol/L; P < 0.001) and prevented deficiency during the extended winter months. No effects were observed on muscle function, cognitive function, immune function, or bone turnover markers. Conclusions: Vitamin D insufficiency is prevalent in UK/Irish children, and supplementation in the form of an oral spray is effective in achieving/maintaining an adequate status in most children. Further research is warranted to elucidate mechanisms underpinning nonresponse to supplementation and to further investigate the potential beneficial effects of supplementation on cognitive function.This trial was registered at clinicaltrials.gov as NCT05018988.

KW - Cognitive Function

KW - Muscle strength

KW - Balance

KW - Immune Function

KW - 25(OH)D status

KW - Vitamin D Supplementation

KW - Bone turnover markers

KW - Children

KW - cognitive function

KW - muscle strength

KW - balance

KW - children

KW - immune function

KW - bone turnover markers

KW - vitamin D supplementation

UR - https://pure.ulster.ac.uk/en/publications/5e584d82-6ede-4548-935e-ca5aea94b71d

UR - https://www.scopus.com/pages/publications/105036241604

U2 - 10.1016/j.tjnut.2026.101493

DO - 10.1016/j.tjnut.2026.101493

M3 - Article

C2 - 41887286

SN - 0022-3166

SP - 1

EP - 10

JO - The Journal of nutrition

JF - The Journal of nutrition

M1 - 101493

ER -

The Effect of Vitamin D3 Supplementation on Vitamin D Status and Associated Health Outcomes in Children: A Randomized Controlled Trial

Abstract

Bibliographical note

Data Availability Statement

Funding

Keywords

Access to Document

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