title: What is the optimal level of vitamin D? - separating the evidence from the rhetoric.
abstract: BACKGROUND
  Vitamin D deficiency is thought to be common in Australia. It is unclear when vitamin D supplementation should be prescribed.
  
  
  OBJECTIVE
  We assess the evidence that guides clinical decision-making on supplementation with vitamin D following a vitamin D test result.
  
  
  CONCLUSIONS
  Vitamin D assays are inconsistent and inaccurate and there is weak evidence around the level of 25-hydroxyvitamin D (25(OH)D) that is optimal. Evidence of links between vitamin D deficiency and disease come from observational studies and there is little support from randomised controlled trials of vitamin D supplementation. Where there is evidence of a link, increased risk is largely confined to very low 25(OH)D levels, with minimal health gains for 25(OH)D levels greater than 50 nmol/L. New evidence indicates that both high and low 25(OH)D levels may be associated with increased health risks. Taken together these considerations present a considerable challenge to clinical decision-making around treatment on the basis of 25(OH)D levels.
authors.affiliation: MBChB, PhD, Professor, National Centre for Epidemiology and Population Health, The Australian National University, Canberra, ACT.
authors.forename: Robyn
authors.initials: R
authors.lastname: Lucas
authors.forename: Rachel
authors.initials: R
authors.lastname: Neale
mesh_terms: D001315:Australia / Q000453:epidemiology; D019587:Dietary Supplements; D019317:Evidence-Based Medicine; D006801:Humans; D007118:Immunoassay / Q000592:standards; D015201:Meta-Analysis as Topic; D064887:Observational Studies as Topic; D012307:Risk Factors; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood* / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000175:diagnosis* / Q000188:drug therapy* / Q000453:epidemiology
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D