4 Clinical evidence base suggesting the improvement in health outcomes with vitamin D3 supplementation in people aged ≥ 50 years in Ireland and the UK

BackgroundVitamin D deficiency, defined as a circulating 25-hydroxyvitamin D [25(OH)D] concentration <25nmol/L, is a global health issue associated with fractures, all-cause mortality and cancer mortality. Optimizing vitamin D status through supplementation, therefore may improve health-related quality of life, whilst simultaneously reducing healthcare costs associated with these conditions.ObjectivesThis clinical review investigates the effects of vitamin D3 supplementation on these outcomes in adults.MethodsLiterature review was undertaken between 1st February – 31stMarch, 2021. Search terms included ‘vitamin D supplementation’, ‘vitamin D status’ and ‘risk of fracture’, ‘cancer mortality’ and ‘all-cause mortality’.ResultsA total of 11 systematic reviews and meta-analyses in populations aged ≥50 years of age were reviewed. Six reviews demonstrated a significant reduction in the risk of fracture, cancer mortality, and all-cause mortality following vitamin D supplementation (table 1). Of the five reviews showing no effect of supplementation, all were conducted in fracture risk populations. Three meta-analyses included studies with participants with an inadequate baseline vitamin D status [25(OH)D < 50nmol/L]; of these, one review, which investigated fracture risk, showed no benefit of supplementation. Potential beneficial effects of supplementation may have been masked in some studies through the inclusion of vitamin D replete populations.ConclusionWhile there is some evidence of a beneficial effect of vitamin D supplementation in reducing fracture risk, all-cause mortality and cancer morality, further research is required. Conflicting findings are likely due to the heterogeneity in study design with the inclusion of young populations, short follow-up times, and vitamin D replete participants at baseline potentially concealing the beneficial effects of supplementation. Further clinical research in vitamin D insufficient/deficient populations ≥50 years of age within the UK and Ireland is warranted, with the results informing the clinical effectiveness and cost-effectiveness of vitamin D3 supplementation at the population level.