Vitamin D and lung cancer risk: a comprehensive review and meta-analysis.

BACKGROUND/AIM Vitamin D has been suggested to have important roles against cancer development. There were several published studies on the association between vitamin D and lung cancer risk, but not conclusive results were available. METHODS To clarify the role of vitamin D in lung carcinogenesis, we performed a comprehensive review of the literature and a meta-analysis to evaluate the association of serum vitamin D levels and dietary vitamin D intake with lung cancer risk. Twelve studies (9 prospective cohort and 3 nested case-control studies) with a total of 288,778 individuals were included. The summary relative risk (RR) with 95% confidence interval (CI) was used to assess lung cancer risk. RESULTS Meta-analysis of total 12 studies showed that RR for the association of high vitamin D status with lung cancer was 0.84 (95%CI 0.78-0.90, P < 0.001). The RR of lung cancer for the highest versus lowest quintile of serum vitamin D levels was 0.83 (95%CI 0.77-0.90, P < 0.001). The RR of lung cancer for the highest versus lowest quintile of vitamin D intake was 0.89 (95%CI 0.74-1.06, P = 0.184). CONCLUSION Current data suggest an inverse association between serum vitamin D and lung cancer risk. Further studies are needed to investigate the effect of vitamin D intake on lung cancer risk and to evaluate whether vitamin D supplementation can prevent lung cancer.