Effect of a soy isoflavone supplement on lung function and clinical outcomes in patients with poorly controlled asthma: a randomized clinical trial.

JAMA

May 2015

DOI: 10.1001/jama.2015.5024

Citations:50

Influential Citations:1

Interventional (Human) Studies

Enhanced Details

Methods

Multisite randomized, double-blind, placebo-controlled, parallel-group clinical trial. Participants: 386 individuals aged 12 years or older with symptomatic, poorly controlled asthma on at least one controller medication; majority female; 59% from minority groups; baseline FEV1 ~82% predicted; median age 36; 345 completed.

Intervention

Two tablets daily (twice daily) for 6 months; each tablet contains 49 mg of soy isoflavones (genistein, daidzein, glycitein).

Results

No improvement in lung function or clinical outcomes with soy isoflavone supplementation versus placebo over 6 months. Primary outcome (change in prebronchodilator FEV1 at 24 weeks): +0.03 L in placebo vs −0.001 L with soy (not significant). Secondary outcomes (ACT score, quality of life, episodes of poor asthma control) showed no meaningful differences. Exhaled nitric oxide declined slightly with placebo but not with soy; plasma genistein increased with treatment but did not correlate with FEV1 changes. Adverse events were similar between groups. Conclusion: soy isoflavone supplementation should not be used for poorly controlled asthma in patients aged 12+ on controller medications.

Limitations

Baseline inflammation was low, potentially limiting detectable benefit; 6-month duration may be insufficient for secondary outcomes; possible dietary changes during the trial; asthma is heterogeneous, possibly benefiting only subgroups; wide inter-individual variability in genistein absorption.

Abstract

IMPORTANCE Soy isoflavone supplements are used to treat several chronic diseases, although the data supporting their use are limited. Some data suggest that supplementation with soy isoflavone may be an effective treatment for patients with poor asthma control. OBJECTIVE To determine whether a soy isoflavone supplement improves asthma control in adolescent and adult patients with poorly controlled disease. DESIGN, SETTING, AND PARTICIPANTS Multicenter, randomized, double-blind, placebo-controlled trial conducted between May 2010 and August 2012 at 19 adult and pediatric pulmonary and allergy centers in the American Lung Association Asthma Clinical Research Centers network. Three hundred eighty-six adults and children aged 12 years or older with symptomatic asthma while taking a controller medicine and low dietary soy intake were randomized, and 345 (89%) completed spirometry at week 24. INTERVENTIONS Participants were randomly assigned to receive soy isoflavone supplement containing 100 mg of total isoflavones (n=193) or matching placebo (n=193) in 2 divided doses administered daily for 24 weeks. MAIN OUTCOMES AND MEASURES The primary outcome measure was change in forced expiratory volume in the first second (FEV1) at 24 weeks. Secondary outcome measures were symptoms, episodes of poor asthma control, Asthma Control Test score (range, 5-25; higher scores indicate better control), and systemic and airway biomarkers of inflammation. RESULTS Mean changes in prebronchodilator FEV1 over 24 weeks were 0.03 L (95% CI, -0.01 to 0.08 L) in the placebo group and 0.01 L (95% CI, -0.07 to 0.07 L) in the soy isoflavone group, which were not significantly different (P = .36). 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. Mean plasma genistein level increased from 4.87 ng/mL to 37.67 ng/mL (P < .001) in participants receiving the supplement. CONCLUSIONS AND RELEVANCE Among adults and children aged 12 years or older with poorly controlled asthma while taking a controller medication, use of a soy isoflavone supplement, compared with placebo, did not result in improved lung function or clinical outcomes. These findings suggest that this supplement should not be used for patients with poorly controlled asthma. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01052116. show less