NEW YORK (Reuters Health) – Soy consumption may lower the risk of chronic obstructive pulmonary disease (COPD) and respiratory symptoms, according to a report published online June 26th in Respiratory Research.

“Besides smoking abstinence, habitual soy consumption may offer additional protection against COPD and the breathlessness symptom,” Dr. Andy H. Lee from Curtin University of Technology, Perth, Western Australia, told Reuters Health.

Dr. Lee and his colleagues conducted a case-control study in central Japan to investigate the relationship between soy consumption and the risk of COPD and respiratory symptoms.

Both mean daily intake of soy and frequency of soy consumption were significantly lower among COPD patients than among controls, the authors report.

Decreases in COPD risk were associated with increased intakes of tofu and bean sprouts, and to a lesser extent, natto (fermented soybeans), but the effect of soy milk did not reach statistical significance because of the small number of soy milk drinkers.

All measures of lung function (forced vital capacity; forced expiratory volume in one second; forced vital capacity/forced expiratory volume in one second; and forced expiratory volume in one second % predicted) were positively correlated with total soy consumption, the researchers note.

Similarly, there was an inverse relationship between soy consumption and the presence of such respiratory symptoms as dyspnea and breathlessness.

“More research and/or replications are required to ascertain whether the observed findings can be generalized to other populations, before incorporating these foods into dietary guidelines so as to encourage consumption,” the investigators conclude.

“We plan to investigate whether isoflavones and some polyunsaturated fatty acids (main nutrients of soy foods) are beneficial to lung health and COPD prevention,” Dr. Lee said.

Respir Res 2009;10:56.