Vitamin K Intake and Risk of Lung Cancer: The Japan Collaborative Cohort Study

BACKGROUND: Limited reports from prospective human studies investigated the possible role of vitamin K in the development of lung cancer although vitamin K’s anticarcinogenic activities were verified from several in vitro and in vivo studies. We investigated the associations between total vitamin K intake from food and the development of lung cancer based on this large prospective cohort study. METHODS: A validated food frequency questionnaire was used to examine vitamin K intake among 42,166 (16,341 men and 25,825 women) at the Japan Collaborative Cohort Study’s baseline (1988–1990). Hazard ratios (HRs) and 95% confidence intervals (CIs) of incident lung cancer were calculated using the Cox proportional hazard regression method based on vitamin K consumption quartiles. RESULTS: 430 cases (308 males and 122 women) of lung cancer were documented during a total of 564,127 person-years of follow-up (median follow-up, 14.6 years). Vitamin K consumption was shown to be inversely related to lung cancer risk; the multivariable hazard ratio [HR] for the highest versus lowest quartiles was 0.67 (95% confidence interval [CI], 0.46–0.96; P for trend = 0.010). This relationship appears to be stronger in males (HR 0.62; 95% CI, 0.40–0.96; P for trend = 0.016) than in females (HR 0.82; 95% CI, 0.42–1.61; P for trend = 0.39) (P for interaction = 0.012), and in ever smokers (HR 0.57; 95% CI, 0.36–0.91; P for trend = 0.006) than in never smokers (HR 0.79; 95% CI, 0.40–1.55; P for trend = 0.37) (P for interaction = 0.30). The individuals’ age, body mass index, or alcohol consumption status had no effect on the observed connection. CONCLUSION: Vitamin K consumption reduces the risk of lung cancer. More research is needed to clarify the molecular processes behind this connection.