Mean changes in symptom scores on the Asthma Control Test ( placebo , 1.98 [ 95 % CI , 1.42-2 .54 ] vs soy isoflavones , 2.20 [ 95 % CI , 1.53-2 .87 ] ; positive values indicate a reduction in symptoms ) , number of episodes of poor asthma control ( placebo , 3.3 [ 95 % CI , 2.7-4 .1 ] vs soy isoflavones , 3.0 [ 95 % CI , 2.4-3 .7 ] ) , and changes in exhaled nitric oxide ( placebo , -3.48 ppb [ 95 % CI , -5.99 to -0.97 ppb ] vs soy isoflavones , 1.39 ppb [ 95 % CI , -1.73 to 4.51 ppb ] ) did not significantly improve more with the soy isoflavone supplement than with placebo .