Background: Epidemiological evidence from observational studies has suggested that the selenium status of asthmatic adults is lower than that 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: We carried out a randomised, double- blind, placebo-controlled trial of selenium supplementation 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 (SelenoPreciseTM 100 μg 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. Whilst 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: There was no clinical benefit of selenium supplementation in adults with asthma, the majority of whom were taking inhaled steroids.
- adult asthma
- randomised controlled trial
- selenium supplementation