Vitamin D and health in school children aged 4-11 years in Northern Ireland

Abstract

Vitamin D plays a critical role in bone health, particularly during childhood, with deficiency associated with rickets and impaired bone development. Although vitamin D has been implicated in other physiological processes, the exact role of the vitamin in non-skeletal health outcomes in children remains uncertain. This thesis aimed to investigate childhood vitamin D status and the effect of vitamin D supplementation on vitamin D status and muscle, cognitive, and immune function.

A systematic review provided insight into the associations between vitamin D status and musculoskeletal health and immune function. Epidemiological studies reported conflicting results, and interpretation of the intervention studies was limited due to vitamin D replete populations. The observational study investigated vitamin D status in n=192 children (4-11 years). An intervention study was conducted to determine the effect of supplementation on a range of health outcomes. Nearly two-thirds of children were vitamin D sufficient (25-hydroxyvitamin D (25(OH)D) ≥50nmol/L); however, almost half were insufficient during winter. Dietary vitamin D intake, assessed by a food frequency questionnaire, ranged from 0.9 – 10.6µg/day. Supplementation with 10µg/day of vitamin D3 for 12-weeks maintained 25(OH)D ≥50nmol/L and enhanced cognitive function through improved child attention. Optimal vitamin D status proved beneficial for muscle function; however, supplementation did not lead to improvements. Following vitamin D3 supplementation, IL-4 and TNF-α increased in children with baseline vitamin D sufficiency compared to those with baseline insufficiency. Overall, this thesis highlights that vitamin D status is sub-optimal in primary school children residing in the north of Ireland, especially in winter. Furthermore, achieving and maintaining a sufficient vitamin D status is possible with a 10µg/day oral spray supplement. Additional benefits to cognitive function, subsidiary to musculoskeletal health, strengthen the need for optimising children's vitamin D status especially during winter months and where there is low dietary intake of vitamin D.

Thesis is embargoed until 30 June 2026

Date of Award	Jun 2024
Original language	English
Sponsors	BetterYou Ltd.
Supervisor	Emeir McSorley (Supervisor), Pamela Magee (Supervisor) & Kirsty Pourshahidi (Supervisor)