High soy intake linked to reduced risk of lung disorder

MedWire News: Eating a lot of soy-based foods is associated with improved lung health and a reduced risk of chronic obstructive pulmonary disease, study results suggest.

Writing in the journal Respiratory Research, Dr Fumi Hirayama, from Curtin University of Technology in Perth, Western Australia, and team explain: “Chronic obstructive pulmonary disease is a leading cause of morbidity [disability due to illness] and mortality worldwide, with cigarette smoking being established as the principle risk factor.”

They add: “However, while 95% of chronic obstructive pulmonary disease patients are, or have been, cigarette smokers, only 20% of smokers develop chronic obstructive pulmonary disease. Therefore, other factors such as dietary and environmental exposures may protect against, or contribute to, disease development.”

As previous research has indicated that a diet high in tofu, bean sprouts and other soy foods may be associated with a number of health benefits, such as reduced cholesterol levels, the team investigated whether the consumption of soy foods is also associated with lung health.

They studied 278 patients, aged 50–75 years, from six Japanese hospitals who had been diagnosed with chronic obstructive pulmonary disease within the past 4 years and 340 similarly aged members of the general public without the lung condition.

All the participants completed questionnaires on demographics, lifestyle characteristics and habitual food consumption and also underwent lung function tests.

The researchers found that average daily soy intake was significantly lower among the patients with chronic obstructive pulmonary disease, at an average of 28.50 g/day, than in those without the condition, at 50.23 g/day.

Dividing the participants into four groups based on daily soy consumption, the team found that those in the group with the highest daily intake were around 60% less likely to have chronic obstructive pulmonary disease than those in the group with the lowest intake.

The researchers also found that a higher intake of soy foods was associated with improved lung function and a lower risk of respiratory symptoms, such as breathlessness.

The findings remained true after accounting for factors such as smoking, body mass index, alcohol consumption and other variables.

Dr Hirayama concluded: “Soy consumption was found to be positively correlated with lung function and inversely associated with the risk of chronic obstructive pulmonary disease.”

He added: “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."