title: Randomised, double blind, placebo-controlled trial of selenium supplementation in adult asthma.
abstract: BACKGROUND
  Epidemiological evidence from observational studies has suggested that blood levels and dietary intake of selenium of adults with asthma are lower than those of controls. The only previous trial of selenium supplementation in adults with asthma found no objective evidence of benefit but involved only 24 participants.
  
  
  METHODS
  A randomised, double blind, placebo-controlled trial of selenium supplementation was performed in adults with asthma in London, UK, the majority of whom (75%) reported inhaled steroid use at baseline. 197 participants were randomised to receive either a high-selenium yeast preparation (100 microg daily, n=99) or placebo (yeast only, n=98) for 24 weeks. The primary outcome was asthma-related quality of life (QoL) score. Secondary outcomes included lung function, asthma symptom scores, peak flow and bronchodilator usage. Linear regression was used to analyse the change in outcome between the two treatment arms by "intention to treat".
  
  
  RESULTS
  There was a 48% increase in plasma selenium between baseline and end of trial in the active treatment group but no change in the placebo group. While the QoL score improved more in the active treatment group than in the placebo group, the difference in change in score between the two groups was not significant (-0.05 (95% CI -0.19 to 0.09); p=0.47). Selenium supplementation was not associated with any significant improvement in secondary outcomes compared with placebo.
  
  
  CONCLUSIONS
  Selenium supplementation had no clinical benefit in adults with asthma, the majority of whom were taking inhaled steroids.
authors.affiliation: Respiratory Epidemiology and Public Health Group, NHLI at Imperial College London, Emmanuel Kaye Building, Manresa Road, London SW3 6LR, UK. s.shaheen@imperial.ac.uk
authors.forename: Seif O
authors.initials: SO
authors.lastname: Shaheen
authors.forename: Roger B
authors.initials: RB
authors.lastname: Newson
authors.forename: Margaret P
authors.initials: MP
authors.lastname: Rayman
authors.forename: Angela P-L
authors.initials: AP
authors.lastname: Wong
authors.forename: Michael K
authors.initials: MK
authors.lastname: Tumilty
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Phillips
authors.forename: James F
authors.initials: JF
authors.lastname: Potts
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Kelly
authors.forename: Patrick T
authors.initials: PT
authors.lastname: White
authors.forename: Peter G J
authors.initials: PG
authors.lastname: Burney
mesh_terms: D000293:Adolescent; D000328:Adult; D018927:Anti-Asthmatic Agents / Q000008:administration & dosage*; D000975:Antioxidants / Q000008:administration & dosage*; D001249:Asthma / Q000097:blood / Q000178:diet therapy* / Q000188:drug therapy; D001993:Bronchodilator Agents / Q000627:therapeutic use; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D012129:Respiratory Function Tests; D012643:Selenium / Q000008:administration & dosage* / Q000172:deficiency
chemical_list: D018927:Anti-Asthmatic Agents; D000975:Antioxidants; D001993:Bronchodilator Agents; D012643:Selenium