title: Intravenous iron supplementation in distance runners with low or suboptimal ferritin.
abstract: OBJECTIVE
  Iron deficiency is prevalent in distance runners and may impair endurance performance. The current practice of oral supplementation is slow and often not well tolerated. The aim of this study was to assess the efficacy of intravenous (IV) iron supplementation (ferric carboxymaltose) compared with oral supplementation (ferrous sulfate) on iron status, hemoglobin mass (Hbmass), and physiological indices of running performance in distance runners.
  
  
  METHODS
  Twenty-seven highly trained distance runners with low (LOW) (ferritin <35 μg·L(-1) and transferrin saturation <20%, or ferritin <15 μg·L(-1)) or suboptimal (SUB) iron status (ferritin <65 μg·L(-1)) were supplemented with either IV iron (Ferinject®) or oral (ORAL) supplements (Ferrogradumet) for 6 wk. Iron status and Hbmass were assessed before supplementation and at 1, 2, 4, 6, and 8 wk in the four groups (IV LOW, IV SUB, ORAL LOW, and ORAL SUB). In addition, athletes completed a treadmill running test for running economy, lactate threshold, and V˙O2max before and after supplementation.
  
  
  RESULTS
  Both forms of supplementation substantially increased ferritin levels in all four groups. IV supplementation resulted in higher ferritin in both IV groups compared with both ORAL groups from week 1 onward. Hemoglobin concentration did not change substantially in any group. Hbmass increased in IV LOW (mean = +4.9%, 90% confidence interval [CI] = 1.1%-8.9%) and was accompanied by an increase in V˙O2max (mean = +3.3%, 90% CI = 0.4%-6.3%) and run time to exhaustion (mean = +9.3%, 90% CI = 0.9%-18.3%.
  
  
  CONCLUSIONS
  IV supplementation can effectively increase iron stores in iron-deficient runners within 6 wk and, if Hbmass is compromised, may enhance endurance capacity by facilitating erythropoiesis. Hbmass appears a more sensitive tool for measuring changes in whole body hemoglobin than hemoglobin concentration and may be useful in the diagnosis and follow-up for iron deficiency.
authors.affiliation: 1National Institute of Sports Studies, University of Canberra, Canberra, AUSTRALIA; 2Australian Institute of Sport, Canberra, AUSTRALIA; and 3King's College Hospital, London, UNITED KINGDOM.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Garvican
authors.forename: Philo U
authors.initials: PU
authors.lastname: Saunders
authors.forename: Tanusha
authors.initials: T
authors.lastname: Cardoso
authors.forename: Iain C
authors.initials: IC
authors.lastname: Macdougall
authors.forename: Louisa M
authors.initials: LM
authors.lastname: Lobigs
authors.forename: Ruth
authors.initials: R
authors.lastname: Fazakerley
authors.forename: Kieran E
authors.initials: KE
authors.lastname: Fallon
authors.forename: Bev
authors.initials: B
authors.lastname: Anderson
authors.forename: Judith M
authors.initials: JM
authors.lastname: Anson
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Thompson
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Gore
mesh_terms: D061605:Administration, Intravenous; D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D015308:Anaerobic Threshold; D019587:Dietary Supplements; D005260:Female; D005290:Ferric Compounds / Q000008:administration & dosage*; D005293:Ferritins / Q000097:blood* / Q000172:deficiency; D006397:Hematinics / Q000008:administration & dosage*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D008320:Maltose / Q000008:administration & dosage / Q000031:analogs & derivatives*; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000187:drug effects*; D012420:Running / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult
chemical_list: D005290:Ferric Compounds; D006397:Hematinics; D006454:Hemoglobins; C522335:ferric carboxymaltose; D008320:Maltose; D005293:Ferritins