These everyday foods are quietly changing what former smokers feel in their lungs

Consuming legumes and soy-based foods may help improve symptoms of chronic obstructive pulmonary disease (COPD) by reducing inflammation and irritation, according to a new study published in the March 2026 issue of Chronic Obstructive Pulmonary Diseases: Journal of the COPD Foundation.

COPD, which includes emphysema and chronic bronchitis, is a progressive, inflammatory lung disease that affects more than 30 million Americans and is the fourth leading cause of death worldwide. Previous research has identified diet and nutrition as modifiable risk factors for chronic lung disease, including COPD.

How the study was conducted

This new study examined how increased isoflavone consumption impacted participants' breathing symptoms, cough, and overall lung health. Isoflavones are a natural substance commonly found in legumes and soy-based foods.

Participants were all former smokers and completed questionnaires regarding diet and symptoms, in addition to lung function tests and clinical assessments, at baseline, three months, and six months. Isoflavone consumption was reported as the average intake at each of the three visits or at all visits that consumption data were available.

What the researchers discovered

Study results showed people with higher isoflavone consumption experienced fewer breathing-related symptoms, including reduced coughing and less difficulty clearing mucus, and improved lung health.

"Research has proven diet and nutrition can impact lung health. We need to further understand which specific nutritional components are responsible for reducing the symptoms of inflammatory conditions like COPD," said Daniel C. Belz, M.D., MPH, of the Division of Pulmonary and Critical Care Medicine and Johns Hopkins University in Baltimore and lead author of the study. "Additionally, larger studies are necessary to explore how increasing isoflavone consumption helps improve COPD symptoms and overall lung health."