title: Antioxidant micronutrients for lung disease in cystic fibrosis.
abstract: BACKGROUND
  Airway infection leads to progressive damage of the lungs in cystic fibrosis (CF), partly due to oxidative stress. Supplementation of antioxidant micronutrients (vitamin E, vitamin C, ß-carotene and selenium) may help maintain an oxidant-antioxidant balance. Current literature suggests a relationship between oxidative status and lung function.
  
  
  OBJECTIVE
  To synthesize existing knowledge of the effect of vitamin C, vitamin E, ß-carotene and selenium in CF lung disease.
  
  
  METHODS
  The Cochrane CF and Genetic Disorders Group CF Trials Register, PubMed, CINAHL and AMED were searched using detailed search strategies. We contacted authors of included studies and checked reference lists of these studies for additional, potentially relevant studies.Last search of CF Trials Register: 09 September 2010.
  
  
  METHODS
  Randomized controlled trials and quasi-randomized controlled trials of people with CF with explicitly stated diagnostic criteria, comparing vitamin E, vitamin C, ß-carotene and selenium (individually or in combination) to placebo or standard care.
  
  
  METHODS
  Two authors independently selected trials, extracted data and assessed risk of bias. We contacted trialists to obtain missing information. Primary outcomes are lung function and quality of life; secondary outcomes are oxidative stress, inflammation, body mass index, days on antibiotics and adverse events during supplementation. If meta-analysed, studies were subgrouped according to combined or single antioxidant supplementation.
  
  
  RESULTS
  Four randomized controlled trials and one quasi-randomized controlled trial were included; only three trials (87 participants) presented data suitable for analysis. Based on two trials, there was no significant improvement in lung function; one trial indicated significant improvement in quality of life favouring control, mean difference -0.06 points on the quality of well-being scale (95% confidence interval -0.12 to -0.01). Based on two trials, selenium-dependent glutathione peroxidase enzyme significantly improved in favour of combined supplementation, mean difference 1.60 units per gram of haemoglobin (95% CI 0.30 to 2.90) and selenium supplementation, mean difference 10.20 units per gram of haemoglobin (95% CI 2.22 to 18.18). All plasma antioxidant levels, except vitamin C, significantly improved with supplementation.
  
  
  CONCLUSIONS
  There appears to be conflicting evidence regarding the clinical effectiveness of antioxidant supplementation in CF. Based on the evidence, antioxidants appear to decrease quality of life and oxidative stress; however, few trials contributed data towards analysis. Further trials examining clinically important outcomes and elucidation of a clear biological pathway of oxidative stress in CF are necessary before a firm conclusion regarding effects of antioxidants supplementation can be drawn.
authors.affiliation: Ottawa Methods Centre, Clinical Epidemiology Program, Ottawa Hospital Research Institute, 501 Smyth Road, Box 208, Ottawa, Ontario, Canada, K1H 8L6.
authors.forename: Larissa
authors.initials: L
authors.lastname: Shamseer
authors.forename: Denise
authors.initials: D
authors.lastname: Adams
authors.forename: Neil
authors.initials: N
authors.lastname: Brown
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Johnson
authors.forename: Sunita
authors.initials: S
authors.lastname: Vohra
mesh_terms: D000328:Adult; D000975:Antioxidants / Q000627:therapeutic use*; D001205:Ascorbic Acid / Q000627:therapeutic use; D002648:Child; D003550:Cystic Fibrosis / Q000188:drug therapy*; D006801:Humans; D018977:Micronutrients / Q000627:therapeutic use*; D018384:Oxidative Stress; D011788:Quality of Life; D016032:Randomized Controlled Trials as Topic; D012643:Selenium / Q000627:therapeutic use; D014810:Vitamin E / Q000627:therapeutic use; D014815:Vitamins / Q000627:therapeutic use
chemical_list: D000975:Antioxidants; D018977:Micronutrients; D014815:Vitamins; D014810:Vitamin E; D012643:Selenium; D001205:Ascorbic Acid