Dietary vitamin K intakes, chronic obstructive pulmonary disease, adult asthma, and lung function: a prospective cohort study in the UK Biobank

Background: Vitamin K–dependent proteins are important for maintaining lung structure and function, yet few studies have examined dietary vitamin K intake in relation to chronic respiratory disease. Objectives: This study aimed to investigate the associations between dietary intakes of vitamin K₁ and vitamin K₂ and the incidence of chronic obstructive pulmonary disease (COPD), asthma, and lung function. Methods: We analyzed data from 179,062 UK Biobank participants without COPD or asthma. Associations between dietary vitamin K₁ and K₂ intakes, estimated using the Oxford WebQ 24-h recall, and incident COPD and asthma, identified through hospital, death, and primary care records, were examined using Cox proportional hazards models. In cross-sectional analyses, associations of vitamin K intake with forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC), and the FEV₁/FVC ratio were assessed using splines within multiple regression. Stratified analyses were performed by sex, smoking status, and occupation. Results: Over 10.5-y follow-up, higher vitamin K₁ intakes were associated with lower COPD rates, with inverse associations reaching a plateau above ∼250 μg/d [HR_{quintile (Q)5 compared with Q1}: 0.84; 95% confidence interval (CI): 0.75, 0.94], whereas no association was observed for vitamin K₂. No associations were observed between vitamin K₁ or vitamin K₂ intakes and asthma. Higher vitamin K₁ intakes (Q5 compared with Q1) were associated with better lung function (FVC: 44 mL; 95% CI: 35, 53 mL and FEV₁: 32 mL; 95% CI: 25, 40 mL), whereas vitamin K₂ showed weaker and nonlinear associations. Stronger associations between vitamin K₁ and lung function were evident in smokers and participants with high-risk occupations. Conclusions: Higher dietary vitamin K₁ intake was associated with better lung function and a lower rate of COPD. As vitamin K₁ is abundant in green leafy vegetables (e.g., ∼1 serving of kale, ∼1½–2 cups), higher consumption of these foods within a healthy diet may be associated with favorable respiratory health.