Isoflavone Intake is Associated With Decreased Chronic Obstructive Pulmonary Disease Morbidity

Isoflavones, phenolic compounds in legumes and soy products, are linked to reduced risk of chronic diseases such as coronary heart disease. However, effects on respiratory diseases like chronic obstructive pulmonary disease (COPD) are understudied.

Former smokers with COPD were enrolled in a prospective cohort study. Morbidity was assessed at baseline, 3, and 6 months using the COPD Assessment Test (CAT), Clinical COPD Questionnaire (CCQ), modified Medical Research Council (mMRC), St George’s Respiratory Questionnaire (SGRQ), Ease of Cough and Sputum Clearance (ECSC), and exacerbation history. Spirometry and biomarkers of platelet activation, inflammation, and oxidative stress were obtained. Dietary intake was assessed via a food frequency questionnaire, with total isoflavone intake calculated as the sum of genistein, daidzein, glycitein, formononetin, and biochanin A. Associations were analyzed with generalized estimating equation regression analysis and adjusted for baseline covariates.

A total of 99 participants (mean age 66.4, 55% female, 41% White, and a baseline forced expiratory volume in 1 second percentage predicted of 49.8%) had a mean isoflavone intake of 1.8mg (standard deviation [SD]=3.1). One SD increase in total isoflavone intake was associated with lower CAT (β=–2.0, p=0.011), CCQ (β=–0.2, p=0.029), and ECSC (β=–0.70, p <0.001) scores, and 7.4% lower urinary 11-dehydro-thromboxane B2 (p=0.047). A trend toward better SGRQ scores was observed but was not significant. Isoflavones were not associated with mMRC or exacerbations.

Increased isoflavone intake was associated with improved respiratory morbidity and reduced platelet activation, suggesting a potential dietary pathway influencing COPD morbidity.