June 26 (HealthDay News) -- Consuming lots of soy foods such as tofu and soy milk may improve lung function and lower the chances of developing chronic obstructive pulmonary disease (COPD), new research suggests.

Researchers asked 300 COPD patients in Japan and 340 age-matched healthy people about their soy intake. The results, published online in the journal Respiratory Research, indicate that consumption of soy products is associated with better lung function and reduced risk of COPD.

Long-term smoking causes 90 percent of cases of COPD, which is characterized by a progressive decline in lung function and includes chronic bronchitis and emphysema, according to background information provided in a news release from the journal's publisher.

Previous research has suggested that soy can reduce cholesterol and ease menopause symptoms. This new study is the first to link soy intake and reduced COPD risk.

"It has been suggested that flavonoids from soy foods act as an anti-inflammatory agent in the lung, and can protect against tobacco carcinogens for smokers. However, further research is needed to understand the underlying biological mechanism," study author Fumi Hirayama said in a news release.

SOURCE: BioMed Central, news release, June 25, 2009