Low vitamin D levels may worsen lung function in smokers: Study

Data from 626 men indicated that vitamin D deficient smokers had a lower lung function than smokers with sufficient levels of the sunshine vitamin, according to findings published in the American Journal of Respiratory and Critical Care Medicine​.

“Our most novel and important finding was the interaction between vitamin D deficiency and smoking in the effect on lung function, both in cross-sectional models examining level of lung function, and longitudinal models examining rates of lung function decline over time,”​ wrote the researchers, led by Nancy Lange, MD, from Brigham and Women’s Hospital.

“These results suggest that vitamin D potentially mitigates the damaging effects of smoking on lung function. In additional exploratory analyses, we noted that we had similar findings of the protective effect of vitamin D sufficiency on FEV1 [forced expiratory volume at one second – a measure of lung function,] decline when subjects with COPD were excluded, implying that smokers who have not yet developed COPD may have the potential for protection based on vitamin D status.”​

Caution​

Commenting independently on the findings, Alexander White MD, chair of the American Thoracic Society’s Tobacco Action Committee, said: “While these results are intriguing, the health hazards associated with smoking far outweigh any protective effect that vitamin D may have on lung function. First and foremost, patients who smoke should be fully informed about the health consequences of smoking and in addition be given all possible assistance to help them quit smoking.”​

The study is observational and only reports an association between low vitamin D levels and impaired lung function. It does not report that increased vitamin D levels would improve lung function in smokers -

“If confirmed, our findings could have immense public health importance in the potential for prevention of COPD and other exposure-related lung diseases,”​ wrote the researchers.

“Additional investigations as to whether vitamin D may protect against lung damage from other sources, such as biomass fuel or air pollution, would also have profound import. Long-term interventional studies of vitamin D supplementation, including several currently ongoing trials in COPD, will be essential to further explore these associations.”​

Study details​

The Boston-based researchers analyzed data from participants of the Normative Aging Study. Vitamin D deficiency was defined as bloods levels of 25(OH)D lower than 20 ng/ml.

While no effects of vitamin D deficiency on lung function were observed for the overall group, analysis of smokers only revealed that vitamin D deficiency in smokers was associated with lower lung function and more rapid rates of decline in FEV1, compared to subjects who were vitamin D sufficient.

“Our results suggest that vitamin D might modify the damaging effects of smoking on lung function,”​ said Dr Lange. “These effects might be due to vitamin D’s anti-inflammatory and anti-oxidant properties.”​

Confirmation required​

“This study presents evidence that vitamin D sufficiency, defined as vitamin D > 20ng/ml, may protect against lower lung function and more rapid lung function decline in smokers,” ​wrote the researchers.

“Further studies and interventional trials are needed to confirm these findings. ​

“Potential implications include the possibility of a simple intervention such as vitamin D supplementation in smokers to prevent rapid lung function decline.”​

Source: American Journal of Respiratory and Critical Care Medicine​
Published online ahead of print, doi:
“Vitamin D deficiency, Smoking, and Lung Function in the Normative Aging Study”​
Authors: N.E. Lange, D. Sparrow, P. Vokonas, A.A. Litonjua