Iron and Athletes Part I: The Role of Iron in Athletic Performance
The Importance of Iron to Athletic Performance
Iron is a trace mineral that plays a large, multifaceted role in the sports performance picture. It is a component of hemoglobin, so it is crucial to getting enough oxygen to the lungs and tissues. It is also a component of myoglobin, which acts as an oxygen acceptor in the muscles, and is a readily available source of oxygen for energy-producing mitochondria. Finally, it is a key component of cytochrome enzymes that are involved in the production of ATP or, in simpler terms, energy production (Mahan).
Deficiency, Depletion and Sub-Optimal Levels
Iron deficiency anemia limits an athlete’s capacity for work and, thus, performance. Anemia also impairs immune and cognitive function (Rosenbloom). Iron depletion, marked by low serum ferritin levels or iron stores (<20ng/mL [Mayo Clinic]), can also be detrimental to athletic performance. Some studies also suggest that sub-optimal ferritin levels (i.e. within laboratory reference range, but on the low end [i.e. ferritin of <40ng/mL]) may be a limiter to athletic performance (Rosenbloom). However, with regards to sub-optimal levels of ferritin, the research around effects on performance is mixed and more studies are needed to draw a true conclusion. If you fall in the sub-optimal range, seek the opinion of a physician who works with athletes before supplementing, work with a dietitian to add more dietary sources of iron, and look for other potential culprits for fatigue if it is present. For example, are you getting enough calories and sleep? Are you drinking excessive amounts of coffee and tea (coffee and tea can inhibit iron absorption by as much as 50% [Mahan])? Are you over trained?
A Quick Disclaimer
Yes, I just spoke about how important iron is to athletic performance. But before you go out and buy iron supplements, which can contain levels of iron that far exceed daily needs, please understand that iron levels are a little like the story of Goldilocks and the Three Bears: you want to get it just right. Too much iron can be dangerous, can compromise health and can cause unpleasant side effects. According to the NIH, acute intakes of more than 20 mg/kg iron from supplements or medicines can lead to stomach upset, constipation, nausea, abdominal pain, vomiting, and fainting. Taking supplements containing 25 mg elemental iron or more can also reduce zinc absorption and plasma zinc concentrations (zinc supports immunity, so it is important to have a physician help you make the decision to add a supplement). In severe cases (e.g., one-time ingestions of 60 mg/kg), iron overdose can result in multisystem organ failure and even death (NIH). It is best to go to a doctor who regularly works with athletes, and get an iron panel done to see where your levels actually are. Let your physician look at your bloodwork and make the final decision about intervention or lack thereof.
Athletes Most At-Risk for Iron Deficiency?
Several groups of athletes are at higher risk of iron deficiency. Endurance athletes, particularly elites, are one such group. One study found that 60% of elite female triathletes and 55.6% of elite female runners in their cohort had experienced at least one incidence of iron deficiency during the study’s six year period, while 25% of elite male triathletes and 6.3% of elite male runners experienced iron-deficiency anemia (Coates). Collegiate, female athletes are also at-risk, with one study finding that 60% of female college athletes were affected by iron deficiency (Eichner). Other at-risk athletes include: the rapidly growing male adolescent athlete, the female athlete with heavy periods, athletes with energy-restricted diets, athletes with GI bleeding (generally runners), vegetarian athletes, athletes with hemolysis caused by foot impact and athletes with heavy sweat losses (Rosenbloom).
Why is Iron a Problem in Athletes?
Athletes are particularly vulnerable to iron issues for several reasons. First, many athletes do not consume sufficient dietary iron particularly when they are trying to achieve body composition goals. Some athletes are also moving to more of a plant-based diet, which can certainly be healthy if done correctly, but can lead to iron issues without careful attention. Other factors that contribute to iron deficiency in athletes include: heavy sweat losses (iron is lost in sweat), gastrointestinal bleeding (known to occur in runners), heavy menstruation in female athletes, hemolysis caused by foot impact, and training stress, which increases energy needs and can lead to myoglobinuria due to muscle stress (Rosenbloom).
Maintaining proper iron levels is not a huge obstacle. Proper diet and supplements (if necessary and recommended by a physician) are easy to incorporate into your day. If you are an athlete who is serious about performance, you do need to be concerned with getting the correct amount of iron in your diet. If you are an athlete that is at higher risk of iron deficiency, visit your doctor and get his or her recommendation on how many times per year you need to do bloodwork. For all athletes, if you are feeling abnormally fatigued, it would be prudent to make an appointment with your doctor to evaluate what might be going on and if low iron is the culprit. These strategies in addition to good nutrition and a balanced, thoughtful training plan will help you to stay on the podium rather than on the sidelines.
Coates, A., Mountjoy, M., & Burr, J. (2016). Incidence of iron deficiency and iron deficient anemia in elite runners and triathletes. Clin J Sport Med.
Eichner R. Anemia and female athletes. Sports Med. Dig. 2000; 22:57.
Mahan, L. Kathleen, Escott-Stump, Sylvia, Raymond, Janice L. (2012). Krause’s Food and the Nutrition Care Process, Edition 13. Elsevier Saunders.
Mayo Clinic. Ferritin Test. Feb.10, 2017. Retrieved from: http://www.mayoclinic.org/tests-procedures/ferritin-test/details/results/rsc-20271960.
NIH. Iron Dietary Supplements Factsheet for Health Professionals. (Feb. 11, 2016). Retrieved from: https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/.
NIH. Iron Fact Sheet For Consumers. (Feb 17, 2016). Retrieved from: https://ods.od.nih.gov/pdf/factsheets/Iron-Consumer.pdf.
Rosenbloom, C., & Coleman, E. (2012). Sports Nutrition: A Practice Manual for Professionals. (5th ed.). Chicago, Illinois: Academy of Nutrition and Dietetics.