Iron Supplementation Improves Energetic Efficiency During Submaximal Exercise in Iron Deficient Non-anemic Women (P24-042-19)

It has been estimated that 37–50% of anemia in non-pregnant women of reproductive age (WRA) is associated with iron deficiency (ID). Some of the highest rates of anemia associated with ID have been found in Latin American and Caribbean countries including Mexico. It has been well established that iron deficiency anemia (IDA), characterized by a reduced concentration of hemoglobin, results in a decline in muscular work capacity exhibited by a decrease in aerobic capacity and the ability to perform physical exercise. There is conflicting evidence on the impairment of physical work capacity in the iron deficient non-anemic (IDNA) state that is characterized by low serum ferritin but normal hemoglobin. The purpose of this study was to determine if iron status influences physical work capacity during submaximal exercise in Mexican women 18- to 45-year-old who are marginally iron depleted but not anemic. Thirty-three iron-depleted (serum ferritin < 20 μg/L), non-anemic (hemoglobin > 120 g/L) women (age: 26.5 ± 6.4 yr) received either 10 mg elemental iron as FeSO4 daily (Fe: iron-supplement group, n = 18) or an identical placebo capsule (P: placebo group, n = 15) for 6 wk in a randomized, double-blind controlled trial. The energy cost of performing work during cycle ergometry at 25 and 50 watts were determined from indirect calorimetry at baseline and following the supplementation period. We observed increased serum ferritin (P = 0.035) and total body iron (P = 0.001), and decreased serum transferrin receptor (P = 0.028) in the Fe group compared with the P group. Based on mixed model ANOVA for a time-by treatment interaction, at end line participants in the Fe group performed work at both 25 and 50 W with lower mean energy expenditures (EE) compared to the P group (difference in EE at 25 W = 0.28 kcal/min, P = 0.036; difference in EE at 50 W = 0.41 kcal/min; P = 0.017). Findings suggest that marginally iron depleted but non-anemic Mexican women improved their iron status and physical work efficiency following the consumption of supplemental iron. These results are important for WRA whose social, economic and dietary circumstances increase their risk for IDNA and suggest that a large proportion of these women who rely on physical labor as a livelihood may be working harder to achieve the same amount of work output as individuals with normal iron levels. Funding provided by The College of Human Ecology and Agricultural & Life Sciences, Cornell University.