title: Effects of daily iron supplementation in 2- to 5-year-old children: systematic review and meta-analysis.
abstract: OBJECTIVE
  Iron deficiency (ID) is the most common cause of anemia worldwide. The prevalence is highest among preschool-aged children. Iron is widely administered to children with or at risk for ID, but evidence of benefit among 2- to 5-year-old children has not been evaluated by systematic review. We summarize the evidence for the benefit and safety of daily iron supplementation with regard to hematologic, growth, and cognitive parameters in 2 to 5 year olds.
  
  
  METHODS
  Electronic databases, regional databases, thesis repositories, gray literature, and references of studies and previous reviews were searched. We included randomized controlled trials that compared daily oral iron supplementation with control in 2 to 5 year olds. A random-effects meta-analysis was used to synthesize predefined outcomes reported by at least 2 studies.
  
  
  RESULTS
  Of 9169 references, 15 studies met the inclusion criteria, none of which were at low risk of bias. Children receiving iron supplementation had a mean end point hemoglobin of 6.97 g/L (P < .00001; I(2) = 82%) greater than controls, whereas mean end point ferritin was 11.64 µg/L (P < .0001; I(2) = 48%) greater. No trials reported the effects of iron supplementation on ID or iron deficiency anemia, and only one reported on anemia. Limited evidence suggested that iron supplementation produced a small improvement in cognitive development but had no effect on physical growth.
  
  
  CONCLUSIONS
  In 2 to 5 year olds, daily iron supplementation increases hemoglobin and ferritin. There is a concerning lack of data on the effect of iron supplementation on clinically important outcomes including anemia, ID anemia, ID, and cognitive development. Additional interventional studies in this age group are needed.
authors.affiliation: School of Medicine, Faculty of Health Sciences, University of Adelaide, South Australia, Australia.
authors.forename: Jane
authors.initials: J
authors.lastname: Thompson
authors.forename: Beverley-Ann
authors.initials: BA
authors.lastname: Biggs
authors.forename: Sant-Rayn
authors.initials: SR
authors.lastname: Pasricha
mesh_terms: D018798:Anemia, Iron-Deficiency / Q000517:prevention & control*; D015415:Biomarkers / Q000097:blood; D002657:Child Development / Q000187:drug effects; D002675:Child, Preschool; D003071:Cognition / Q000187:drug effects; D019587:Dietary Supplements; D004334:Drug Administration Schedule; D005293:Ferritins / Q000097:blood; D006128:Growth / Q000187:drug effects; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007501:Iron / Q000494:pharmacology / Q000627:therapeutic use*; D015233:Models, Statistical; D014131:Trace Elements / Q000494:pharmacology / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; D006454:Hemoglobins; D014131:Trace Elements; D005293:Ferritins; D007501:Iron