Vitamin D supplementation in intensive care: real benefit or statistical illusion?

Vitamin D deficiency is extremely common in intensive care, and it is associated with poor prognosis. Beyond its classical role in calcium homeostasis, vitamin D influences the immune response, endothelial function and muscle integrity. Observational studies have shown consistent correlations between vitamin D deficiency and increased mortality, sepsis or prolonged duration of mechanical ventilation. However, randomized clinical trials (VITdAL-ICU, VIOLET) have not confirmed robust benefits on mortality, but only possible favorable effects in subgroups with severe deficiency. Recent meta-analyses remain heterogeneous, with evidence of low certainty and statistical fragility. In critical conditions, hepatic and renal dysfunction, systemic inflammation and hypoalbuminemia affect the conversion and transport of vitamin D, suggesting the limits of supplementation with classical vitamin D alone (D₂/‌D₃), without the use of active metabolites. Correction of vitamin D deficiency remains warranted as part of general care in the ICU, but supplementation cannot yet be recommended as standard therapy to reduce mortality. Future research needs to clarify the dose, the optimal form (cholecalciferol, calcifediol, or calcitriol), route of administration, and timing of administration.