Dietary Supplementation With Soy Isoflavones in Asthma

This is a prospective pilot study to be conducted in 20 subjects with asthma. The participant will undergo the following procedures: 1. Completion of a questionnaire that asks for information about asthma including symptoms, medications, and ability to participate in activities. 2. Measurement of exhaled nitric oxide (NO) in which subjects will breathe slowly into a tube. This test takes about 5 minutes. 3. Collection of the air exhaled from the lungs and condensing it into a liquid form. This is called an exhaled breath condensate. This procedure involves breathing slowing into a tube for a period of 15 minutes. The measurements determined by this method are exclusively for research purposes and not used in routine clinical settings. 4. Measurement of lung function with a spirometer. This involves breathing in and out forcefully through a mouthpiece. 5. Collection of 60 ml (4 tablespoons) of blood to measure genistein (the major component of the soy isoflavone) levels and eosinophil function. These measurements are also for research purposes and not routinely used clinically. Each of the above measurements will be made before and after the 4 week period of dietary supplementation with soy isoflavones.