Inhaled Vitamin D should help COPD - May 2026
Reconsidering Vitamin D Supplementation in Pulmonary Disease: The Case for Targeted Respiratory Delivery
Chronic Obstr Pulm Dis. 2026; 13(3): 249-254. http://doi.org/10.15326/jcopdf.2025.0713
Kevin D. Schichlein, PhD1 Ilona Jaspers, PhD2 M. Bradley Drummond, MD, MHS3
Summary by Claude AI June 2026
This is a Perspective piece (not original research) from the Journal of the COPD Foundation, published March 2026 by Schichlein, Jaspers, and Drummond at UNC Chapel Hill.
The core argument:
There's a well-documented "vitamin D paradox" in pulmonary medicine: observational studies repeatedly link low vitamin D to worse outcomes (more exacerbations, lower lung function, more hospitalizations) in COPD, asthma, and cystic fibrosis — yet RCTs of oral supplementation have consistently failed to show clinically meaningful benefit. They cite the 2024 Cochrane COPD review (no change in exacerbations, lung capacity, or QoL) and the 2023 Cochrane asthma review, which actually reversed its earlier 2016 positive conclusion. Even cystic fibrosis, where ~90% of patients are deficient from malabsorption, shows no benefit from correcting blood levels.
Their proposed explanation — it's the delivery route, not the molecule:
Oral vitamin D undergoes hepatic metabolism and systemic dilution before reaching the lung. Critically, they point to a 2020 finding that CYP24A1 (the vitamin D–inactivating enzyme) is highly expressed in pulmonary vascular endothelium — so circulating vitamin D may be degraded before it ever reaches the airway lumen. Meanwhile, the respiratory epithelium has the full activation machinery (CYP27B1, VDR) to use vitamin D locally for antimicrobial peptides (cathelicidin, β-defensins), barrier function, anti-inflammatory and antioxidant effects.
Their proposal: treat vitamin D as a local respiratory therapeutic delivered by inhalation/nebulization rather than a systemic supplement.
Have they actually tried it?
Not in humans — and not by these authors as a trial. This is explicitly a hypothesis/call-to-action paper. The authors state plainly that, to their knowledge, no clinical trials have investigated pulmonary vitamin D delivery in people with chronic lung disease.
What has been done is entirely preclinical — animal and in vitro:
- Nebulized calcitriol reduced inflammation and protected barrier function in LPS-exposed mice without changing systemic levels (Serré 2022)
- Inhaled vitamin D improved hypersensitivity pneumonitis / fibrosis endpoints in mice (Lemieszek/Chojnacki, 2023–2025)
- Pulmonary vitamin D induced alveolar regeneration in mouse COPD models (Horiguchi 2016; Akita 2020)
- Dry-powder calcitriol as TB adjunct in mice (Reddy 2022, 2024)
- Intranasal vitamin D in rhinitis/sinonasal/infection mouse models
- Air-liquid interface human airway cell studies showing apical vitamin D boosts antimicrobial peptides and protects against pollutant oxidative stress — one of these (Schichlein 2025, ozone) is the lead author's own work
So: promising mechanistic and animal signals, no hypercalcemia seen, but the honest bottom line is that the authors flag the key limitation themselves — mostly short-exposure ex vivo and animal studies, zero human data. The paper is a pitch for someone to run the first human safety/PK/dosing trials.
Related in Vitamin D Life
- Inhaled vitamin D helps lungs - many studies
- Inhaled vitamin D helped lungs of new-born (rats)
- Childhood pneumonia not treated by 100,000 IU of vitamin D – Cochrane (need more, inhaled)
- Nanoemulsion Vitamin D is faster and better - many studies
- A Call for the use of Vitamin D with COPD
- COPD treated by Vitamin D – meta-analysis