June 3, 2015
Soy Isoflavone Supplements No Help in Asthma Control

Chicago—Despite hopes that soy isoflavone supplements could help patients with poor asthma control, a randomized trial found no improved lung function with the treatment.

Results of the trial, which included nearly 400 children and adults, were reported recently in the Journal of the American Medical Association (JAMA).

Soy isoflavones, plant derived chemicals that have antioxidant effects, did not reduce asthma symptoms or episodes of poor asthma control, according to the study led by Northwestern University researchers.

According to background information in the article, soy isoflavone supplements are used to treat several chronic diseases, although the data supporting their use are limited. Some data have suggested that supplementation with soy isoflavone may be an effective treatment for patients with poorly controlled asthma because the phytoestrogen genistein inhibits a key pathway that may contribute to asthma severity.

The study, conducted from May 2010 to August 2012, involved 386 adults and children age 12 years or older with symptomatic asthma while taking a “controller” medicine—either inhaled corticosteroids and/or a leukotriene modifier—and low dietary soy intake at 19 pulmonary allergy centers in the American Lung Association’s Asthma Clinical Research Centers network.

Half of the participants were assigned to receive soy isoflavone supplements containing 100 mg of total isoflavones in two divided doses administered daily for 24 weeks. The other half received a matching placebo on the same dosage schedule. Most, 89%, completed spirometry at week 24.

Results indicate that average changes in prebronchodilator forced expiratory volume in the first second (FEV1) over 24 weeks were not significantly different between the soy isoflavone group and the placebo group. No improvement was detected in other aspects of asthma control, including additional measures of lung function, symptoms, quality of life, and airway and systemic inflammation.

“These findings suggest that this supplement should not be used for patients with poorly controlled asthma,” the authors conclude.

U.S. Pharmacist Social Connect