Healthy diet is associated with better lung function, especially in individuals with COPD: findings from the...

To investigate whether the association between diet and lung function (LF) differs according to asthma or COPD status in the Lifelines cohort study.

We included adults from Lifelines with valid dietary and spirometry data. Dietary quality was calculated at baseline using the Lifelines diet score (LLDS) (range 0-48, where higher scores indicate a healthier diet). LF was assessed via pre-bronchodilator spirometry (forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC) and FEV₁/FVC) at baseline and two follow-ups (∼10 years). Cross-sectional associations between diet and LF were examined using linear regression and longitudinal associations with linear mixed-effects models. Interactions between diet and asthma or COPD were included.

Higher LLDS was associated with higher LF and slower decline. In cross-sectional analyses (n=83 460, 59% female, mean age 44±13 years), higher LLDS was associated with higher FEV₁ and FEV₁/FVC levels in participants with asthma (FEV₁ β_interaction (β_int)=2.48 mL, 95% CI 0.68-4.27; FEV₁/FVC β_int=0.027%, 0.003-0.052) and COPD (FEV₁ β_int=8.31 mL, 6.93-9.69; FEV₁/FVC β_int= 0.094%, 0.079-0.109) compared with those without asthma or COPD. In longitudinal analyses (n=37 752, 59% female, age 46±11 years) in COPD-patients higher LLDS was associated with slower FEV₁ decline (β_int=0.18 mL·yr^-1, 0.04-0.33), FVC (β_int=0.23 mL·yr^-1, 0.04-0.41) and FEV₁/FVC (β_int=0.002%·yr^-1, 0.000-0.005) compared with those without COPD.

Higher diet quality was associated with better LF, particularly in those with asthma or COPD, and with slower decline in participants with COPD. These findings suggest that diet may be a modifiable factor in respiratory health.