CATEGORY: DISEASE PREVENTION
People with the highest intake of vitamin K1 — the form of the vitamin found mainly in leafy green vegetables such as spinach, kale, and broccoli — had about a 16% lower rate of chronic obstructive pulmonary disease (COPD) than those with the lowest intake, according to a large UK study.1 COPD is an umbrella term for progressive lung conditions, including emphysema and chronic bronchitis, that make breathing steadily harder over time.
How the study worked
Researchers at Edith Cowan University drew on data from more than 179,000 participants in the UK Biobank, a long-running health study. They estimated each person’s usual intake of the two main dietary forms of vitamin K: K1, concentrated in leafy greens, and K2, found in foods such as meat, eggs, and dairy. Participants were then followed for an average of about 10.5 years, during which 3,135 developed COPD and 4,269 developed asthma. Lung function was also measured using spirometry, a standard breathing test of how much air a person can forcibly exhale and how quickly.1
What the researchers found
Those with the highest vitamin K1 intake had roughly a 16% lower rate of COPD than those with the lowest, along with better lung function on spirometry. The link was clearest for K1; vitamin K2 did not show the same consistent pattern, and neither form was clearly tied to lower asthma risk. The association also appeared stronger among groups whose lungs face greater strain, such as smokers and people working around dust or fumes.1
A plausible biological explanation
Vitamin K is best known for its role in blood clotting, but it also helps activate proteins that maintain healthy tissue. One of these, matrix Gla protein, is present in the lungs and helps protect elastin — the springy fibers that let the lungs expand and recoil with each breath. When elastin breaks down, as it does in COPD, breathing becomes harder. Still, the researchers caution that vitamin K1-rich foods travel with fiber, antioxidants, and other beneficial compounds, so the greens may be acting as part of a broader healthy eating pattern rather than alone.1
What to keep in mind
This was an observational study, so it can show an association but cannot prove that leafy greens directly protect the lungs; people who eat more vegetables often differ in other ways. The amount of vitamin K1 tied to better outcomes was modest and achievable through ordinary eating — on the order of an extra serving of leafy greens a day. The researchers are emphatic that greens are not a treatment for COPD and do not offset the harms of smoking, which remains the dominant risk factor.1
Key Takeaways
- Higher intake of vitamin K1 from leafy greens was associated with a lower rate of COPD and better lung function in a large UK study.
- The effect was observational and likely reflects an overall healthy diet; leafy greens are not a treatment for lung disease and do not cancel out smoking.
- If you have concerns about your lung health or are thinking about changing your diet, discuss it with your healthcare provider — especially before making changes if you take medications or have a chronic condition.
References
- Li C, Pokharel P, Sim M, et al. Dietary vitamin K intakes, chronic obstructive pulmonary disease, adult asthma, and lung function: a prospective cohort study in the UK Biobank. The American Journal of Clinical Nutrition. 2026;123(6):101324. link.