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. Design: Randomized, double-blind iron supplementation. Setting: University of Missouri-Columbia and surrounding community. Subjects: Twenty iron-deficient (serum ferritin, sFero16 mg/l; serum transferrin receptor, sTfR48.0 mg/l; or sTfR/log sFer index 44.5), nonanemic (hemoglobin, Hb4120 g/l, women; 4130 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 ¼ 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 postsupplementation (P ¼ 0.01); this effect was greater in individuals with lower sFer before intervention (Po0.05). Changes in sFer from pre-to post-treatment were positively correlated with changes in VT (P ¼ 0.03), independent of supplementation. The iron group significantly increased gross energetic efficiency during the submaximal test (P ¼ 0.04). Changes in sFer were negatively correlated with changes in average respiratory exchange ratio during the submaximal test (Po0.05). Conclusions: Iron supplementation significantly improves iron status and endurance capacity in iron-deficient, nonanemic trained male and female subjects.

Clinical evaluation of iron treatment efficiency among non-anemic but iron-deficient female blood donors: a randomized controlled trial

“…Overall mean changes of hemoglobin (Δ 11 g/L) and ferritin (Δ 13 ng/mL) levels between baseline and the end of the treatment were consistent with expected values. Such a biological change, induced by a comparable amount of elemental iron, was enough in some previous randomized placebo controlled trials to obtain a favorable impact on fatigue and endurance [4-6,8,9]. The degree of hypoferritinemia could also be critical.…”

“…Further studies using fatigue questionnaires and serum ferritin as a marker have confirmed this effect [2-4]. Physiological measurements have also been carried out in randomized double-blind controlled trials: aerobic capacity increases [5-8] and muscle fatigability decreases [9] among trained or untrained volunteers.…”

Reticulocyte and erythrocyte hypochromia markers in detection of iron deficiency in adolescent female athletes

“…Iron is a micronutrient involved in numerous biologic processes, many of which are vital for not only health but also athletic performance [25, 26, 27]. On the other hand, iron deficiency is the most common deficiency in the world, and some studies indicate that in athletes iron deficiency occurs more frequently than in the general population [27, 28, 29].…”

Four Weeks of IV Iron Supplementation Reduces Perceived Fatigue and Mood Disturbance in Distance Runners

“…A decrease in BLa within the IRON group was observed following the week 2 and week 6, 3000 m time trials, which is similar to previous findings [32]–[34], whilst PLACEBO recorded higher BLa for comparable run times. Hinton et al [35] report that as a result of iron deficits, the oxidative capacity of the muscle is reduced and therefore the workload at which the ventilatory threshold and blood lactate accumulation occurs is lower [35]. Some studies have reported no change in BLa following supplementation [36], [37], but discrepancies in time course of treatment and the chosen modality (most have involved oral supplementation), dosage and study design may have influenced these results.…”