Higher Isoflavone Intake Linked to Better Symptoms and Health Status in Former Smokers With COPD: Study
USA: Researchers have discovered in a new study that among former smokers with chronic obstructive pulmonary disease (COPD), higher consumption of isoflavones—compounds commonly found in soy products and legumes—was associated with improved overall health status and fewer cough symptoms. Increasing total isoflavone intake was also linked to a significant reduction in a biomarker of platelet activation, suggesting potential anti-inflammatory or vascular benefits.
The findings, published in Chronic Obstructive Pulmonary Diseases: Journal of the COPD Foundation, come from a study led by Daniel C. Belz of the Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, and colleagues. The researchers noted that although isoflavones have been associated with reduced risks of several chronic diseases, including coronary heart disease, their potential role in COPD has received limited attention.
The researchers conducted a prospective cohort study involving 99 former smokers with COPD, assessing respiratory health at baseline, three months, and six months using validated symptom and quality-of-life questionnaires. Lung function, platelet activation, inflammation, oxidative stress, and dietary intake were also evaluated.
Participants had a mean age of 66.4 years, and more than half were women. The average predicted FEV₁ was 49.8%, indicating moderate to severe airflow limitation. Total isoflavone intake was estimated from a validated food frequency questionnaire based on five major dietary isoflavones.
Key findings include:
- Higher total isoflavone intake was associated with better overall COPD health status, reflected by lower COPD Assessment Test (CAT) scores.
- Increased isoflavone consumption was also linked to improved Clinical COPD Questionnaire (CCQ) scores.
- Participants with higher isoflavone intake reported significantly fewer cough and sputum clearance symptoms, as measured by ECSC scores.
- Each standard deviation increase in isoflavone intake was associated with a 7.4% reduction in urinary 11-dehydro-thromboxane B2, a marker of platelet activation.
- A trend toward improved St George's Respiratory Questionnaire (SGRQ) scores was observed, although it did not reach statistical significance.
- Isoflavone intake was not significantly associated with breathlessness measured by the mMRC scale or with COPD exacerbation frequency.
The authors noted several limitations. Higher isoflavone intake may reflect an overall healthier diet and lifestyle rather than a direct effect of isoflavones. Dietary intake was self-reported, the sample size was relatively small, limiting biomarker analyses and some clinical comparisons, and no adjustment was made for multiple statistical testing.
Overall, the findings suggest that higher isoflavone intake is associated with improved respiratory health and lower platelet activation in former smokers with COPD. The researchers conclude that isoflavone-rich diets may offer a potential nutritional strategy to reduce COPD morbidity, although larger studies are needed to confirm these findings and better understand the underlying mechanisms.
Reference:
Belz DC, Quiroz E, Woo H, et al. Isoflavone intake is associated with decreased chronic obstructive pulmonary disease morbidity. Chronic Obstr Pulm Dis. 2026; 13(2): 125-135. doi: http://doi.org/10.15326/jcopdf.2025.0695
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