Table 1

Vitamin D and lung disease

Disease	Epidemiology	In vitro research	Clinical research
Asthma	↓levels associate with severity ↑maternal concentrations associate with childhood atopy	1,25-OHD alters Th1–Th2 balance	Supplementation trial under way
COPD	↓levels associate with ↓FEV₁ ↓levels in half of patients with COPD	1,25-OHD ↑clearance of Pseudomonas and Staphyloccus spp	Supplementation trial under way
TB	↓levels in patients with TB	1,25-OHD ↑clearance of mycobacteria	1 RCT of supplementation: no benefit Further trials under way
Lung cancer	↓levels associate with cancer incidence ↑levels associate with better response to treatment	25-OHD supplements ↓metastasis in murine models	Supplementation trials under way in a range of malignancies

The table summarises some of the existing evidence supporting a role for vitamin D in lung disease. Original references for these studies can be found in recent editorials/reviews,1–3 being omitted here in order to simplify the text in the table.
COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 s; 25-OHD, 25-hydroxyvitamin D; 1,25-OHD, 1,25-dihydroxyvitamin D; RCT, randomised controlled trial; TB, tuberculosis; Th, T helper.