Vitamin D and Glucocorticoid Sensitivity in Obesity-Associated Asthma: A Narrative Review

Vitamin D restores glucocorticoid sensitivity in vitro, but this effect has not been demonstrated clinically in obese patients with asthma. This narrative review analyses experimental and clinical data from 2006–2026 on the links between obesity, vitamin D deficiency and corticosteroid insensitivity. Obese asthma patients show reduced corticosteroid efficacy and lower vitamin D levels. In vitro, vitamin D restored dexamethasone-induced IL-10 secretion and MKP-1 expression; observationally, higher vitamin D levels were associated with better lung function and steroid response. However, high-dose vitamin D3 did not reduce treatment failure in the VIDA trial. An individual participant data meta-analysis showed fewer exacerbations requiring systemic corticosteroids, particularly with severe deficiency, whereas a 2023 Cochrane update did not confirm an overall benefit. A blunted response to supplementation in obesity may partly explain these discrepancies. Trials in obese asthma with weight-adjusted dosing, monitoring of serum levels and corticosteroid response as the primary outcome are needed.