PURE healthy diet score associated with lower asthma odds: a case–control study

Abstract Asthma is a chronic inflammatory airway disease. Diet may influence asthma through oxidative stress, inflammation, and gut–lung axis interactions. Evidence on the PURE Healthy Diet Score (PHDS) remains scarce. This study investigated PHDS adherence in relation to asthma odds, pulmonary function, asthma control, biomarkers, and quality of life in adults. This age‑matched case–control study included 200 adults with physician‑diagnosed asthma and 200 healthy controls. Dietary intake was assessed using a validated food frequency questionnaire, and PHDS (0–24) was calculated from fruits, vegetables, legumes, nuts, fish, and dairy. Spirometry, Asthma Control Test (ACT), Asthma Quality of Life Questionnaire (AQLQ), and biomarkers of inflammation, oxidative stress, and gut–lung axis were measured. Logistic regression and mediation analyses were performed. Healthy controls had a significantly higher PHDS than asthma cases (14.4 ± 2.7 vs. 10.4 ± 2.7, P < 0.001). Higher PHDS was associated with significantly lower odds of asthma (per 1‑point increase: OR = 0.89; 95% CI 0.83–0.96; P < 0.001), with a significant inverse quartile-based pattern across PHDS quartiles (fully adjusted model, Q4 vs. Q1: OR = 0.28; 95% CI 0.12–0.57; P-trend < 0.001). Higher PHDS also correlated with better lung function (FEV₁, FVC, PEF), higher ACT and AQLQ scores (all P‑trend < 0.05), and lower FeNO. Gut–lung axis biomarkers (zonulin, LPS, and TMAO) were significantly lower across higher PHDS quartiles, indicating an inverse association with circulating zonulin, LPS, and TMAO concentrations (all P-trend < 0.05). Exploratory mediation analyses identified statistical associations of systemic inflammatory and gut–lung axis-related biomarkers with the PHDS–asthma association; these model-based findings are exploratory and do not establish causal mediation or biological mechanisms. Higher adherence to the PURE Healthy Diet Score was associated with lower asthma odds, better respiratory health, and improved asthma control, together with a more favorable inflammatory and gut–lung axis-related biomarker profile; these observational associations do not establish causal pathways.