By Shawn Hueglin, PhD, RD, CSSD
Reprinted with permission from SCAN’S PULSE, Spring 2019, Vol 38, No 2, official publication of Sports, Cardiovascular, and Wellness Nutrition (SCAN), Academy of Nutrition and Dietetics, Chicago, IL.
The rigorous physical training undertaken by athletes increases the physiological demand for oxygen, as well as increases demand on the transport systems responsible for its delivery. Iron is necessary for the production of oxygen transporters—hemoglobin and myoglobin–and is an essential cofactor for energy utilizing enzymes. Blood hemoglobin carries oxygen from the lungs to all bodily tissues, and myoglobin in the muscle holds and stores oxygen for use during exercise. Because iron content of tissues is one of the factors that determines aerobic capacity, it is closely linked with sport performance.
Dietetics practitioners who have the ability to identify low serum iron levels and have an established protocol for addressing inadequacies can help prevent declines in athletic performance. This article outlines a practical approach for identifying and treating iron deficiency. It should be noted that additional micronutrients including vitamin B12 and folate are also required for healthy red blood cell production, and vitamin B6 is needed for heme synthesis.
Prevalence of inadequate iron stores
Iron deficiency anemia (IDA) is more likely to occur in athletes than in healthy, sedentary individuals. It has been demonstrated that athletic populations, especially female and adolescent athletes, have the highest prevalence of iron depletion.1 Prevalence of IDA in adult athletes is usually low (3-5%); however, National Health and Nutrition Examination Survey (NHANES) II data demonstrated a much higher rate of IDA in healthy adolescents (9-10% of girls and 1% of boys). It is suggested that 20% to 50% of female athletes and 4% to 50% of male athletes have depleted iron stores, indicating the importance of dietary intervention and blood screening protocols to prevent anemia.2,3 Higher frequency is seen among athletes participating in sports such as running, triathlon, swimming, rowing, soccer, and basketball.4 Iron depletion, if not detected and treated early enough, can develop into IDA. IDA disturbs brain and muscle metabolism, impairs aerobic processes, and impacts endurance performance and work capacity as well as immune response and temperature control.2
Because iron depletion progresses through stages, significant performance decrements can occur prior to an athlete experiencing IDA. Therefore, to prevent IDA it is critical to have a screening protocol in place to detect the early stages (see Fig. 1 for specific stages). In the early stages of depletion, an athlete who follows an appropriate dose of supplemental iron can deplete serum ferritin stores relatively quickly (in 6-12 weeks) compared with a lengthy recovery time of 6 months or longer once the IDA is reached and hemoglobin is impacted.
Symptoms of poor iron stores
Common symptoms of depleted or deficient iron stores include shortness of breath or early fatigue during exercise, decreased motivation to train, increased rating of perceived exertion (RPE), decreased aerobic capacity, decreased training adaptions, decreased time to exhaustion, koilonychias (spoon nails), glossitis, and dysphagia. However, deficiency can exist without the presence of any of these symptoms.5 Chronic fatigue is the most common clinical symptom for iron depletion, but it is a poor indicator because it can be attributed to many other conditions. Therefore, the appropriate diagnosis for iron depletion and anemia is via laboratory testing.5
