title: Vitamin B6, B12, and folic acid supplementation and cognitive function: a systematic review of randomized trials.
abstract: BACKGROUND
  Despite their important role in cognitive function, the value of B vitamin supplementation is unknown. A systematic review of the effect of pyridoxine hydrochloride (hereinafter "vitamin B(6)"), cyanocobalamin or hydroxycobalamin (hereinafter "vitamin B(12)"), and folic acid supplementation on cognitive function was performed.
  
  
  METHODS
  Literature search conducted in MEDLINE with supplemental articles from reviews and domain experts. We included English language randomized controlled trials of vitamins B(6) and/or B(12) and/or folic acid supplementation with cognitive function outcomes.
  
  
  RESULTS
  Fourteen trials met our criteria; most were of low quality and limited applicability. Approximately 50 different cognitive function tests were assessed. Three trials of vitamin B(6) and 6 of vitamin B(12) found no effect overall in a variety of doses, routes of administration, and populations. One of 3 trials of folic acid found a benefit in cognitive function in people with cognitive impairment and low baseline serum folate levels. Six trials of combinations of the B vitamins all concluded that the interventions had no effect on cognitive function. Among 3 trials, those in the placebo arm had greater improvements in a small number of cognitive tests than participants receiving either folic acid or combination B-vitamin supplements. The evidence was limited by a sparsity of studies, small sample size, heterogeneity in outcomes, and a lack of studies that evaluated symptoms or clinical outcomes.
  
  
  CONCLUSIONS
  The evidence does not yet provide adequate evidence of an effect of vitamin B(6) or B(12) or folic acid supplementation, alone or in combination, on cognitive function testing in people with either normal or impaired cognitive function.
authors.affiliation: Tufts-New England Medical Center Evidence-based Practice Center, Institute for Clinical Research and Health Policy Studies, Boston, MA 02111, USA. ebalk@tufts-nemc.org
authors.forename: Ethan M
authors.initials: EM
authors.lastname: Balk
authors.forename: Gowri
authors.initials: G
authors.lastname: Raman
authors.forename: Athina
authors.initials: A
authors.lastname: Tatsioni
authors.forename: Mei
authors.initials: M
authors.lastname: Chung
authors.forename: Joseph
authors.initials: J
authors.lastname: Lau
authors.forename: Irwin H
authors.initials: IH
authors.lastname: Rosenberg
mesh_terms: D003071:Cognition / Q000187:drug effects / Q000502:physiology*; D003072:Cognition Disorders / Q000188:drug therapy / Q000523:psychology; D019587:Dietary Supplements; D005492:Folic Acid / Q000008:administration & dosage*; D006801:Humans; D016032:Randomized Controlled Trials as Topic; D016896:Treatment Outcome; D014805:Vitamin B 12 / Q000008:administration & dosage*; D025101:Vitamin B 6 / Q000008:administration & dosage*; D014803:Vitamin B Complex / Q000008:administration & dosage
chemical_list: D014803:Vitamin B Complex; D025101:Vitamin B 6; D005492:Folic Acid; D014805:Vitamin B 12