The impact of vitamin D deficiency on COVID-19 severity in the UK: a systematic literature review

Vitamin D deficiency, prevalent in up to 40% of the UK population, particularly among ethnic minorities and older adults, may impact COVID-19 outcomes. This systematic review aimed to evaluate the association between vitamin D deficiency and COVID-19 severity and the potential role of supplementation. Following PRISMA 2020 guidelines, 13 UK-based studies were analysed. Some observational studies reported increased odds of severe disease in vitamin D-deficient individuals (OR: 1.43–2.60). However, larger cohort studies, including UK Biobank analyses, found no significant association after adjusting for confounders. Mortality rates in intensive care settings also showed no significant differences. The evidence remains inconsistent, with potential confounding factors such as comorbidities and socioeconomic status. While vitamin D sufficiency is important for general health, current data do not support its use as a targeted intervention against COVID-19 in the UK. Further high-quality, prospective studies are needed.