The Study of Soy Isoflavones in Asthma

Inclusion Criteria

• Age 12 or older
• Physician diagnosed asthma
• FEV1 equal or greater than 50% predicted pre-bronchodilator
• At least 12% increase in FEV1 15-3 minutes after inhaling 2-4 puffs of albuterol or positive methacholine challenge (20% fall in FEV1 at less than 8 mg/mL). Either of these can be available from the previous 2 years
• Currently prescribed daily controller asthma medication
• Poor asthma control (at least one of the following)
• A score of 1.5 or greater on the Juniper Asthma Control Questionnaire
• Use of beta-agonist for asthma symptoms two or more times per week
• Nocturnal awakening with asthma symptoms more than once per week
• Two or more episodes of asthma symptoms in the past 12 months with each requiring at least one of the following: emergency department visit, unscheduled physician visit, prednisone course, hospitalization
• Smoking status
• Non-smoker for 6 months or longer
• Less than 10 pack-years smoking history

Exclusion Criteria

• Pulmonary function
• FEV1 less than 50% predicted pre-bronchodilator
• Other major chronic illnesses
• Conditions which in the judgment of the study physician would interfere with participation in the study, e.g., non-skin cancer, endocrine disease, coronary artery disease, severe hypertension, immunodeficiency states
• History of thyroid disease, breast cancer, ovarian, or endometrial cancer
• History of physician diagnosis of chronic bronchitis, emphysema, or COPD
• Medication use
• Current consumption of soy isoflavone supplements
• Oral corticosteroid use within the past 6 weeks
• Use of tamoxifen
• Use of an investigational treatment in the previous 30 days
• "Drug" allergy
• Known adverse reaction to genistein, other phytoestrogens, or soy products
• Females of childbearing potential
• Pregnant or lactating. Participants must agree to use effective contraception during the trial.
• Non-adherence
• Inability or unwillingness to provide consent or, in the case of children, inability or unwillingness of the child to provide assent
• Inability to swallow study medication
• Inability to perform baseline measurements
• Completion of less than 10 of the last 14 days diary entries during screening period
• Inability to be contacted by telephone
• Intention to move out of the area within 6 months
• Other
• Recent asthma exacerbation (within 6 weeks)
• Recent upper respiratory infection (within 2 weeks)
• Body weight less than 77 pounds (35 kg)
• Intake of soy or soy-enriched foods 1 or more times a week
• Change in diet over the past month or expected change in diet during the study