A prospective cohort study found that higher dietary isoflavone intake is associated with reduced respiratory morbidity among patients with COPD, suggesting a potential role for dietary modification in disease management.1
“While the findings do not establish causality… they suggest that dietary modification may be a practical adjunct to routine COPD care,” study coauthor Mariah K. Jackson, PhD, RDN, LMNT, said. “Given the persistent symptom burden and limited therapeutic options available for many patients, nutritional strategies that promote higher isoflavone intake could complement established pharmacologic and nonpharmacologic interventions. Importantly, these approaches may provide patients with an opportunity to actively participate in disease management, potentially enhancing quality of life, symptom control, and self-efficacy.”
The study, published in Chronic Obstructive Pulmonary Diseases: Journal of the COPD Foundation, evaluated 99 patients with moderate to severe COPD and a history of smoking who were enrolled in the urban arm of the Comparing Urban and Rural Effects of Poverty on COPD initiative.1–3 Participants were followed longitudinally for six months, with detailed dietary assessments using a validated food frequency questionnaire and repeated measures of clinical outcomes, including the COPD Assessment Test (CAT), Clinical COPD Questionnaire (CCQ), St. George’s Respiratory questionnaire (SGRQ), and Ease of Cough and Sputum Clearance (ECSC).1
According to the researchers, isoflavones—phytoestrogen compounds primarily found in soy and legumes—have been previously associated with cardiovascular and anti-inflammatory benefits, but their impact on COPD morbidity has not been fully explored.
After adjusting for demographic and clinical covariates, the investigators found that higher isoflavone intake was significantly associated with improved respiratory symptoms. Each standard deviation increase in isoflavone intake was associated with a two-point reduction in CAT scores (P = .011), meeting the minimal clinically important difference threshold. Improvements were also observed in CCQ scores (P = .029) and ECSC scores (P < .001), according to the data. No significant associations were seen with dyspnea or exacerbation rates, suggesting that dietary isoflavones may primarily influence symptom burden rather than acute disease events.1
The researchers also explored biological pathways underlying these associations. Higher isoflavone intake correlated with a 7.4% reduction in urinary 11-dehydro-thromboxane B2 (11dTxB2), a marker of platelet activation (P = .047) that has been increasingly recognized as a contributor to COPD pathophysiology and symptom burden.
Dr. Jackson, who is Assistant Professor in the Medical Nutrition Program in the College of Allied Health Professions at the University of Nebraska Medical Center, said that platelet activation is a biologically plausible mechanism linking isoflavone intake to improved respiratory outcomes.
“Our study cannot definitively establish that platelet activation is the primary pathway driving the observed symptom improvements,” she said. “Platelet activation is known to be increased in COPD and has been associated with greater respiratory morbidity. Experimental studies have shown that the isoflavones genistein and daidzein can inhibit platelet activation by reducing thromboxane A2 synthesis, the precursor of urinary 11dTxB2,” Dr. Jackson said.
The study cohort consisted predominantly of older, lower-income, urban patients, with a mean age of 66.4 years and an average FEV1 of 49.8% predicted. Mean isoflavone intake was relatively low (1.8 mg/day), below national averages, raising the possibility that greater dietary exposure could yield more pronounced effects. The authors noted that isoflavone intake tends to be higher in populations with healthier dietary patterns and higher socioeconomic status.
These findings may also reflect broader behavioral patterns.
“It remains possible that higher intake of isoflavone-rich foods reflects broader health-conscious dietary and lifestyle behaviors that contribute to better respiratory health,” Dr. Jackson said.
Additionally, interaction analyses revealed that the beneficial association between isoflavones and symptom scores was more pronounced in participants with lower omega-3 fatty acid intake, suggesting potential dietary synergy or compensatory effects.
These findings contribute to a growing body of evidence linking dietary patterns to COPD outcomes, according to the authors. They noted that while Mediterranean-style diets and omega-3 fatty acids have previously been associated with improved morbidity, the present study adds isoflavones as a potentially important, modifiable dietary component.
From a practical standpoint, the investigators emphasized food-based approaches over supplementation.
“Foods rich in isoflavones represent a generally safe, well-tolerated, and cost-effective approach that can be incorporated into broader dietary strategies aimed at improving respiratory health,” Dr. Jackson said. “Importantly, it is possible that the benefits of isoflavones are enhanced when consumed as part of a healthy dietary pattern rather than as an isolated nutrient.”
However, because the study was observational, small, and did not show associations with mMRC dyspnea or exacerbations, the findings should be viewed as hypothesis-generating. They support further clinical trials of isoflavone-rich dietary interventions but do not yet justify recommending isoflavone supplementation as a COPD therapy.
References
1. 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:10.15326/jcopdf.2025.0695
2. National Institute of Environmental Health Sciences. Comparing Urban and Rural Effects of Poverty on COPD (CURE COPD).
3. Raju S, Keet CA, Paulin LM, et al. Rural Residence and poverty are independent risk factors for chronic obstructive pulmonary disease in the United States. Am J Respir Crit Care Med. 2019;199(8):961-969. doi:10.1164/rccm.201807-1374OC
