title: Iron supplementation maintains ventilatory threshold and improves energetic efficiency in iron-deficient nonanemic athletes.
abstract: OBJECTIVE
  To determine the effect of iron supplementation on iron status and endurance capacity.
  
  
  METHODS
  Randomized, double-blind iron supplementation.
  
  
  METHODS
  University of Missouri-Columbia and surrounding community.
  
  
  METHODS
  Twenty iron-deficient (serum ferritin, sFer<16 microg/l; serum transferrin receptor, sTfR>8.0 mg/l; or sTfR/log sFer index >4.5), nonanemic (hemoglobin, Hb>120 g/l, women; >130 g/l, men) men and women (18-41 years) were recruited via fliers and newspaper advertisements; 20 of 31 eligible subjects participated.
  
  
  METHODS
  A 30 mg measure of elemental iron as ferrous sulfate or placebo daily for 6 weeks.
  
  
  RESULTS
  Dietary iron intake and physical activity did not differ between groups before or after supplementation. Iron supplementation significantly increased sFer compared to placebo (P=0.01), but did not affect Hb or hematocrit. Iron supplementation prevented the decline in ventilatory threshold (VT) observed in the placebo group from pre- to post-supplementation (P=0.01); this effect was greater in individuals with lower sFer before intervention (P<0.05). Changes in sFer from pre- to post-treatment were positively correlated with changes in VT (P=0.03), independent of supplementation. The iron group significantly increased gross energetic efficiency during the submaximal test (P=0.04). Changes in sFer were negatively correlated with changes in average respiratory exchange ratio during the submaximal test (P<0.05).
  
  
  CONCLUSIONS
  Iron supplementation significantly improves iron status and endurance capacity in iron-deficient, nonanemic trained male and female subjects.
authors.affiliation: Department of Nutritional Sciences, University of Missouri, Columbia, MO 65211, USA. hintonp@missouri.edu
authors.forename: P S
authors.initials: PS
authors.lastname: Hinton
authors.forename: L M
authors.initials: LM
authors.lastname: Sinclair
mesh_terms: D000293:Adolescent; D000328:Adult; D019587:Dietary Supplements; D004311:Double-Blind Method; D005080:Exercise Test; D005260:Female; D005293:Ferritins / Q000097:blood*; D006400:Hematocrit; D006454:Hemoglobins; D006801:Humans; D000090463:Iron Deficiencies; D019266:Iron, Dietary / Q000008:administration & dosage*; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000187:drug effects* / Q000502:physiology; D011990:Receptors, Transferrin / Q000378:metabolism*
chemical_list: D006454:Hemoglobins; D019266:Iron, Dietary; D011990:Receptors, Transferrin; D005293:Ferritins