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

• Published in: European journal of clinical nutrition Vol. 61; no. 1; pp. 30 - 39
• Main Authors: Hinton, P S, Sinclair, L M
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.01.2007; Nature Publishing; Nature Publishing Group
• Subjects: administration & dosage; Adolescent; Adult; anthropometric measurements; Athletes; athletic performance; Biological and medical sciences; blood; blood sampling; breathing; Clinical Nutrition; Complications and side effects; dietary mineral supplements; dietary minerals; Dietary Supplements; Double-Blind Method; drug effects; Energetics; energy intake; Epidemiology; Exercise; Exercise Test; Female; Females; ferritin; Ferritins; Ferritins - blood; Food and nutrition; Health aspects; Hematocrit; Hemoglobins; Humans; Influence; Internal Medicine; Iron; Iron - deficiency; Iron Deficiencies; iron deficiency anemia; Iron deficiency diseases; Iron in the body; Iron, Dietary; Iron, Dietary - administration & dosage; Male; Medical sciences; Medicine; Medicine & Public Health; men; Metabolic Diseases; metabolism; nutrient intake; nutrient reserves; Nutrition; nutrition assessment; nutritional status; original-article; Oxygen Consumption; physical activity; Physical Endurance; Physical Endurance - drug effects; Physical Endurance - physiology; Physiological aspects; physiology; Public Health; randomized clinical trials; Receptors, Transferrin; Receptors, Transferrin - metabolism; Respiratory system; Sulfates; women; United States; serum transferrin receptor; ferritin; endurance capacity; Human; Transferrin; Nutrition; Deficiency; Ferritin; Iron; Athlete; Inorganic element; Improvement; Efficiency; Serum; Endurance; Supplementation; Threshold
• ISSN: 0954-3007; 1476-5640
• DOI: 10.1038/sj.ejcn.1602479

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  μ g/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.