Although previous studies have linked soy intake with decreased asthma severity, new research suggests otherwise, Philly.com reported.

Researchers Northwestern Medicine and the American Lung Association Asthma Clinical Research Network found that soy supplements do not improve lung function for patients with asthma.

"You are what you eat, but that's a whole constellation of foods, not just a single food or a single component of a food," Dr. Lewis Smith, first author of the study, said in a statement. "Instead of focusing on supplements, we should be taking a more holistic approach."

For the study, researchers examined the effects of soy in 386 adults and children aged 12 or older with poorly controlled asthma. All were taking medicine to treat their asthma -- either corticosteroids or leukotriene modifiers -- but none were consuming soy. In the randomized, double-blind study, half of the participants took a soy isoflavone supplement twice daily for six months, and the other half took a placebo.

They found that the supplement, did not improve lung function, symptoms or measures of inflammation in these individuals, Science 2.0 reported.

While analyzing the results of a study on diet and asthma, Smith and colleagues previously noticed that asthmatics taking soy isoflavone had better lung functioning than their counterparts. The soy supplement was able to increase blood levels of the key soy isoflavone genistein.

The findings are detailed in the Journal of the American Medical Association.