Iron supplementation maintains ventilatory threshold and improves energetic efficiency in iron-deficient nonanemic athletes.
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.
Hinton
P S
PS
Department of Nutritional Sciences, University of Missouri, Columbia, MO 65211, USA. hintonp@missouri.edu
Sinclair
L M
LM
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*
D006454:Hemoglobins; D019266:Iron, Dietary; D011990:Receptors, Transferrin; D005293:Ferritins