title: Effect of a soy isoflavone supplement on lung function and clinical outcomes in patients with poorly controlled asthma: a randomized clinical trial.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  METHODS
  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.
  
  
  METHODS
  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
  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.
  
  
  BACKGROUND
  clinicaltrials.gov Identifier: NCT01052116.
authors.affiliation: Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.
authors.forename: Lewis J
authors.initials: LJ
authors.lastname: Smith
authors.affiliation: Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.
authors.forename: Ravi
authors.initials: R
authors.lastname: Kalhan
authors.affiliation: Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Wise
authors.affiliation: Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Sugar
authors.affiliation: Nemours Children's Clinic, Jacksonville, Florida.
authors.forename: John J
authors.initials: JJ
authors.lastname: Lima
authors.affiliation: Department of Medicine, University of Vermont, Burlington.
authors.forename: Charles G
authors.initials: CG
authors.lastname: Irvin
authors.affiliation: Department of Pediatrics, New York Medical College, Valhalla.
authors.forename: Allen J
authors.initials: AJ
authors.lastname: Dozor
authors.affiliation: Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Janet T
authors.initials: JT
authors.lastname: Holbrook
mesh_terms: D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000188:drug therapy* / Q000503:physiopathology; D002648:Child; D019587:Dietary Supplements / Q000009:adverse effects; D004311:Double-Blind Method; D005260:Female; D005541:Forced Expiratory Volume; D019833:Genistein / Q000097:blood; D006801:Humans; D007529:Isoflavones / Q000009:adverse effects / Q000627:therapeutic use*; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008517:Phytotherapy; D010936:Plant Extracts / Q000009:adverse effects / Q000627:therapeutic use*; D030262:Soybean Proteins / Q000009:adverse effects / Q000627:therapeutic use*; D055815:Young Adult
chemical_list: D007529:Isoflavones; D010936:Plant Extracts; D030262:Soybean Proteins; D019833:Genistein