27 May 2015 --- Although some data have suggested that supplementation with soy isoflavone may be an effective treatment for patients with poor asthma control, a randomized trial that included nearly 400 children and adults found that use of the supplement did not result in improved lung function or clinical outcomes, including asthma symptoms and episodes of poor asthma control, according to a study in the May 26 issue of JAMA. Soy isoflavones are plant (soybean) derived chemicals that have anti-oxidant effects.