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

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 D3 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 D3 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.