Soy supplements seem to do little to improve asthma control

THE QUESTION People with asthma sometimes consider herbal remedies, including soy supplements, as an alternative or complementary treatment. Should soy be one to try?

THIS STUDY involved 386 adults and teenagers who had asthma that was not well controlled. All participants used an inhaler, mostly one that combined a corticosteroid and a long-acting beta-agonist. None of the participants were smokers, and they all consumed little soy in their diets. They were randomly assigned to take a soy supplement (49 milligrams, with genistein, daidzein and glycitein the main active ingredients) or a placebo twice a day for about six months. During that time, periodic tests and assessments found virtually no difference in various measures of lung function or in symptoms, flare-ups, airway inflammation or quality of life.

WHO MAY BE AFFECTED? People with poorly controlled asthma. About 25 million people in the United States have asthma, a number that health officials say is increasing. With asthma, the lungs are overly sensitive to allergens and irritants in the air, causing the airways to become swollen, narrow and mucus-filled, resulting in labored breathing or wheezing, chest tightness and coughing. While there is no cure for asthma, the goal of treatment is to keep symptoms under control and prevent attacks.

CAVEATS Some data came from records of symptoms kept by the participants and from their responses on questionnaires. The researchers noted that a higher soy dosage or a longer treatment period might have produced a more positive effect. The content of dietary supplements can vary from one maker or batch to another because supplements do not have to adhere to the same strict regulatory standards that drugs do; thus, different soy supplements might yield different results

FIND THIS STUDY May 26 issue of JAMA, Journal of the American Medical Association (


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The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.