Impact of a vitamin D supplementation initiative in an NHS prison health care service during the COVID-19 pandemic

Int J Prison Health (2024). 2026 Jan 19:1-10. doi: 10.1108/IJOPH-06-2025-0045. Online ahead of print.

ABSTRACT

PURPOSE: Vitamin D deficiency is a global concern, disproportionately affecting vulnerable populations, including prisoners. Vitamin D was found to be protective against Covid-19 during the pandemic. As a response, Nottinghamshire Healthcare NHS Foundation Trust implemented a vitamin D supplementation policy across three prison health-care settings in the UK. The purpose of this study was to assess the overall impact of this policy on supplementation rates and Vitamin D deficiency.

DESIGN/METHODOLOGY/APPROACH: This pragmatic cross-sectional study retrospectively evaluated the impact of the vitamin D supplementation policy on supplementation uptake and deficiency rates. Vitamin D deficiency was defined as less than 50 nmol/L. Cross-sectional data were collected from 768 prisoners for periods of two years before and two years after introduction of the policy.

FINDINGS: Overall supplementation rates were lower after the policy introduction (43%, n = 330 versus 35%, n = 270; McNemar’s χ2, p = 0.004). However, there was increased uptake among previously untreated individuals – 40% (n = 175) of those previously untreated (n = 438) received supplementation after policy implementation. There was an overall reduction in vitamin D deficiency from 71% to 55% after policy introduction (χ2 = 12.3, Cramer’s V = 0.13, p < 0.001). Mean vitamin D levels increased from 41.3 nmol/L to 50.3 nmol/L. In a small subsample (n = 23) in whom vitamin D levels were available before and after the policy, paired sample analysis showed significant mean vitamin D level increase (p < 0.001). An exploratory analysis using binary logistic regression suggested the specific prison location and pre-existing vitamin D deficiency as significant predictors of deficiency post-policy.

ORIGINALITY/VALUE: The findings highlight the potential effectiveness of a simple, population-wide supplementation strategy in reducing vitamin D deficiency within prisons. Future research should use prospective designs and explore factors influencing supplementation adherence and long-term health outcomes, toward developing the most effective strategies.

PMID:41549738 | DOI:10.1108/IJOPH-06-2025-0045