Key Point

Vitamin D is associated with better lung function (better FEV1 and FVC). Future research will show if it can benefit patients with pulmonary diseases.

AUCKLAND, NEW ZEALAND—New observational research suggests that high serum levels of vitamin D are associated with higher lung function.¹

Peter Black, MB, and Robert Scragg, MB, PhD, evaluated serum levels of 25-hydroxyvitamin D, lung function, body mass index (BMI), smoking history, and physical activity in 14,091 adult particpants in the Third National Health and Nutrition Examination Survey (NHANES). Dr. Black, Associate Professor of Medicine at the University of Auckland in New Zealand, said, "Our findings are interesting because of the strong association seen between vitamin D levels and lung function compared with other environmental factors. However, it is too early to know if there are any implications for clinical practice."

VITAMIN D AND LUNG FUNCTION

The mean difference in FEV₁ in participants with serum 25-hydroxyvitamin D levels in the highest versus the lowest quintiles was 126 mL, after adjustment for sex, age, ethnicity, BMI, and smoking status. This compared to a mean adjusted difference of 345 mL in FEV₁ between never smokers and people who currently smoked 20 cigarettes a day. The difference in FVC between those in the highest and lowest quintiles of serum vitamin D was 172 mL. Interestingly, the relationship between FEV₁ and vitamin D levels was significant among participants over 60, never smokers, ex-smokers, and current smokers.

The authors also adjusted for levels of physical activity, intake of milk and vitamin D supplements, and levels of antioxidants. The association between high serum levels of vitamin D and lung function was attenuated, but still significant. The adjusted mean difference in FEV₁ in those with serum vitamin D levels in the highest versus lowest quintiles was 106 mL; the adjusted mean difference in FVC was 142 mL. Dr. Black warned that the association between vitamin D levels and lung function appears to be valid, but "no [observational] study such as this can prove beyond all doubt that the association is real."

Drs. Black and Scragg believe that vitamin D may modulate tissue remodeling and repair in the lungs. To establish a causal link, they propose an intervention study among patients with low levels of vitamin D. Alternatively, a large study could establish whether vitamin D reduces the decline in lung function over time.

In an editorial, Rosalind Wright, MD, explains that causation can be proven by studies that demonstrate the following: "biological plausibility, strength of the association, reduced likelihood of an alternative explanation, and consistency across studies in different populations."² She also notes that the importance of future studies cannot be underestimated, because vitamin D supplementation "would be a simple, low-cost intervention that would likely have high compliance to potentially prevent or slow the loss of lung function in susceptible subgroups."

—Tamara Gibb

Reference
1. Black PN, Scragg R. Relationship between serum 25-hydroxyvitamin D and pulmonary function in the Third National Health and Nutrition Examination Survey. Chest. 2005;128:3792-3798.
2. Wright RJ. Make no bones about it: increasing epidemiologic evidence links vitamin D to pulmonary function and COPD. Chest. 2005;128:3781-3783.

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