Iron Supplementation is Beneficial for Female Athletes
Iron is an essential nutrient, especially for athletes. Iron’s most important role is to transport oxygen through the body via the blood protein hemoglobin. When iron intakes and absorption are inadequate to meet needs, the hemoglobin molecule that contains iron at its core cannot be produced. Symptoms such as fatigue, weakness and dizziness relate to the reduced ability of the body to transport oxygen. Iron deficiency in athletes reduces oxygen uptake and the output of muscles, impairing performance. Female athletes are at additional risk of iron deficiency. As women, they have high blood losses due to menstruation. The World Health Organization reports that one in two women worldwide are iron deficient. Athletes also have higher iron needs: high-impact sports such as running causes blood cells in the foot to burst, athletes may have unbalanced diets when they attempt to achieve a certain body weight or body composition, and the inflammation caused by constant exercise can also prevent efficient iron uptake from food (see the section on iron in the Position Statement on Nutrition and Athletic Performance from the American Dietetic Association for more background). Women who are athletes are therefore at a higher risk of iron deficiency anemia than either women or athletes in general.
Recently, Pasricha and co-workers conducted a systematic review and meta-analysis on the effect of iron supplementation in female athletes. They selected 22 publications that represented the results of supplementing over 900 women randomly to iron supplements or a control treatment. The iron supplementation dose and varied widely, from amounts that can be easily reached by the diet (10 mg) to very high doses given to women with clear iron deficiency (325 mg). Most trials used elemental iron as Fe2SO4 as the intervention. The authors were interested in trials that reported on both maximal and sub-maximal exercise performance, normally expressed as peak oxygen uptake (VO2max) and heart rate during exercise.
The authors found that iron supplementation improved maximal and submaximal exercise performance. Relative and absolute VO2max was improved in the supplemented group in trained women, and the effect was seen in women regardless of whether they were iron deficient at baseline or not. This reflects improvements in the oxygen-carrying capacity of the body. Heart rate decreased during submaximal exercise for the supplemented group, showing that oxygen transportation is more efficient with iron supplementation.
This study is important as it shows a functional benefit to iron supplementation that goes beyond merely correcting clinical deficiency. Improvements were seen both in women who were iron deficient, and those who were not. Ultimately, the aim behind taking micronutrient supplements is not to avoid deficiency, but to improve quality of life, or that of another important and tangible outcome. For female athletes, their training regimen is intended to improve their physical performance. It is clear here that iron supplementation can help.
Sant-Rayn Pasricha, Michael Low, Jane Thompson, Ann Farrell, and Luz-Maria De-Regil. Iron Supplementation Benefits Physical Performance in Women of Reproductive Age: A Systematic Review and Meta-Analysis. J. Nutr. 2014 jn.113.189589; first published online April 9, 2014. doi:10.3945/jn.113.189589
Rodriguez NR, Di Marco NM, Langley S. American College of Sports Medicine position stand. Nutrition and athletic performance. Med Sci Sports Exerc. 2009;41:709–31. http://journals.lww.com/acsm-msse/Fulltext/2009/03000/Nutrition_and_Athletic_Performance.27.aspx