Original Article

European Journal of Clinical Nutrition (2007) 61, 30–39. doi:10.1038/sj.ejcn.1602479; published online 12 July 2006

Iron supplementation maintains ventilatory threshold and improves energetic efficiency in iron-deficient nonanemic athletes

Guarantor: PS Hinton.

Contributors: PSH contributed to the design of the experiment, analysis of the data and assisted with writing and editing the manuscript. LMS collected and analyzed the data and contributed to the writing of the manuscript.

P S Hinton1 and L M Sinclair1

1Department of Nutritional Sciences, University of Missouri, Columbia, MO, USA

Correspondence: Dr PS Hinton, Department of Nutritional Sciences, 106 McKee Gym, University of Missouri, Columbia, MO 65211, USA. E-mail: hintonp@missouri.edu

Received 17 October 2005; Revised 22 March 2006; Accepted 5 May 2006; Published online 12 July 2006.

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Abstract

Objective:

 

To determine the effect of iron supplementation on iron status and endurance capacity.

Design:

 

Randomized, double-blind iron supplementation.

Setting:

 

University of Missouri-Columbia and surrounding community.

Subjects:

 

Twenty iron-deficient (serum ferritin, sFer<16 mug/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.

Interventions:

 

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.

Sponsorship:

 

Missouri University Alumni Association, by the Elizabeth Hegarty Foundation and by the Department of Nutritional Sciences.

Keywords:

ferritin, serum transferrin receptor, endurance capacity

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