Increasing Iron Status through Dietary Supplementation in Iron-Depleted, Sedentary Women Increases Endurance Performance at Both Near-Maximal and Submaximal Exercise Intensities

Abstract

Background Iron deficiency persists as the most common micronutrient deficiency globally, despite having known detrimental effects on physical performance. Although iron supplementation and aerobic exercise have been examined individually and are known to improve physical performance, the impact of simultaneous iron supplementation and aerobic training remains unclear. Objective The aim of this study was to examine the individual and combined effects of iron supplementation and aerobic training on improving maximal and submaximal physical performance in iron-depleted, nonanemic (IDNA) women. We hypothesized that women receiving iron would improve their endurance performance but not their estimated maximal oxygen consumption (eVO2max). Methods Seventy-three sedentary, previously untrained IDNA (serum ferritin <25 µg/L and hemoglobin >110 g/L) women aged 18–26 y with a body mass index (kg/m2) of 17–25 participated in a double-blind, 8-wk, randomized controlled trial with a 2 × 2 factorial design including iron supplementation (42 mg elemental Fe/d) or placebo and aerobic exercise training (5 d/wk for 25 min at 75–85% of age-predicted maximum heart rate) or no training. Linear models were used to examine relations between training, supplement, and changes in the primary outcomes of observed maximal oxygen consumption (VO2peak) and eVO2max and ventilatory threshold (absolute oxygen consumption and percentage of maximum). Re-evaluation of a published meta-analysis was used to compare effects of iron supplementation on maximal oxygen consumption (VO2max) and VO2peak. Results There were significant training-by-supplement interactions for VO2peak, volume of oxygen consumption at the ventilatory threshold, and the percentage of eVO2max where the threshold occurred, with the iron-untrained group performing better than the placebo-untrained group. There was no beneficial effect of iron supplementation for VO2max (mean difference: 0.53; 95% CI: −0.75, 1.81; P = 0.42), but a significant benefit was observed for VO2peak (mean difference: 1.87; 95% CI: 0.15, 3.60; P = 0.03). Conclusions Iron supplementation increases endurance performance at submaximal and maximal (VO2peak) exercise intensities in IDNA women. However, increasing iron status does not increase eVO2max. This trial was registered at clinicaltrials.gov as NCT03002090.

Vitamins and Minerals for Energy, Fatigue and Cognition: A Narrative Review of the Biochemical and Clinical Evidence

“…A meta-analysis on 22 studies found that iron supplementation improved both maximal exercise performance and submaximal exercise performance, demonstrated by a lower heart rate required to achieve defined workloads [132]. In a recent trial, 73 young untrained women with nonanemic iron deficiency received either a placebo or 42 mg iron daily for 8 weeks and were submitted to aerobic exercise training; iron supplementation increased endurance performance at submaximal and maximal exercise intensities; serum ferritin increased significantly in the supplemented group vs. the placebo group (46.9 µg/L vs. 21.8 µg/L) [133].…”

Iron Deficiency in Menstruating Adult Women: Much More than Anemia

“…Nonhematological manifestations of ID include fatigue, reduced physical endurance, defective structure or function of epithelial tissues, pica, restless legs syndrome (RLS), decreased cognitive performance, and behavioral disturbances. 3,4 ID impairs the health and well-being of women and increases the risk of adverse maternal and neonatal outcomes. 5,6 Our research group has observed elevated bone remodeling in IDA young adult women that improved during iron recovery, suggesting that chronic ID may be a risk factor for future osteoporosis in women.…”

The Impact of Iron Supplementation on Athletic Performance in Elite-Level Female Athletes–A Systematic Review

“…Each study identified a cutoff point that they used to define IDNA. Two studies considered that changes in physical performance could occur in women who are iron depleted but not clinically iron deficient; therefore, the cutoff score for iron depletion was set at 25 mg/L (23,24). One study used the sFer cutoff of 20.0 mg/L to identify rowers as IDNA (6).…”

“…Another study that conducted a four-day recall, including a weekend, analyzed baseline dietary iron intake using Nutritionist IV to quantify dietary iron intake (11). The other 2 studies analyzed the records for daily intakes of iron, inhibitors, and enhancers of iron absorption and macronutrient content using the Nutrition Data System for Research software (23,24). Two other studies also conducted a four-day dietary recall, but they did not specify whether it included a weekend day (3,29).…”