Dr. Fumi Hirayama and Andy Lee from Curtin University of Technology in Australia worked with a team of respiratory physicians to poll 300 patients with COPD from six Japanese hospitals and 340 age-matched control subjects from the same areas as the patients about their soy intake.
"Soy consumption was found to be positively correlated with lung function and inversely associated with the risk of COPD," Hirayama said in a statement. "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."
Soy is a constituent of many Japanese foods, including tofu, or soybean curd; natto, or fermented soybeans; miso soup, or fermented soybean paste; bean sprouts and soy milk.
COPD is characterized by progressive decline in lung function and encompasses chronic bronchitis and emphysema. Long-term cigarette smoking causes almost 90 percent of COPD.