--> Unexplained pain
--> Persisting injuries
--> Unusual fatigue
--> Weakness
--> Decreased endurance
--> Decreased performance
These symptoms can have devastating consequences for athletes. Yet they are relatively common, with a simple, under-recognized and often under-appreciated cause: iron deficiency (ID). ID is one of the most prevalent nutritional deficiency in the world (WHO, 2010). Studies have demonstrated that 10–20% of menstruating women have an iron deficiency, and 3–5% of them are also anemic. ID is most common in female athletes however; it is important to note that this problem also affects male athletes (up to 11% in some studies) (Sim, et al., 2019).
The prevalence of iron deficiency is especially concerning when we consider that iron is needed by every cell and organ in the body to function properly and to sustain life. Iron plays a role in oxygen transportation, cellular repair, tissue healing and energy production, making it essential in achieving optimal performance (Sim, et al., 2019).
Ferritin is the best measure of the amount of iron stored in the body and can be measured with a simple blood test. Serum ferritin concentration is the most sensitive and specific test used for identification of iron deficiency. Recommended cutoffs for serum ferritin are highly varied. Many observational studies use <30ng/mL as a cutoff however some sources recommend serum ferritin be between 50-200ng/mL (Briden, 2018).
Interestingly, the cutoff for “normal” ferritin can be as low as 5 ng/mL depending on the lab used and the age of the client (LifeLabs, 2020). For example, the reference range for a female >18 years of age is 5-247ng/mL. That is a large range with an incredibly low cutoff for flagging those with deficiency. This happens because the “normal” ranges given on a standard laboratory report are not representative of the requirements needed for optimal health and instead, are constructed based on range in which 95% of the population would fall. That is 95% of the population in which, as we have already established, many are deficient. Therefore, even if a lab printout reads that ferritin is ‘normal’, it may in fact be too low to support the individual’s physiological needs.
One of the most recognized roles of iron in the body is its function in the formation of hemoglobin (in the blood) and myoglobin (in the muscle). Hemoglobin is a protein found in the blood that is essential for the transport of oxygen from the lungs to the various tissues of the body. If iron stores become chronically low, hemoglobin levels can decline, leading to less oxygen transport capacity (UCSF Health, 2019). Normal hemoglobin levels are 120-160g/L for females and 140-180g/L for males (LifeLabs, 2020). Reference ranges vary slightly for younger athletes.
There is no real consensus about the optimal ferritin level. Instead, some health care professionals recommend using an individualized approach to determining optimal ferritin levels by taking into consideration: the type of exercise the athlete performs (endurance versus short-duration), their training intensity and their current physical symptoms.
There are 2 main types of iron deficiency.
1. Iron deficiency (ID) without anemia: sub-optimal serum ferritin with normal hemoglobin levels.
2. Iron deficiency anemia (IDA): a later manifestation of ID in which there are sub-optimal serum ferritin levels AND low hemoglobin (≤ 130 g/L in males and ≤120 g/L in females)
While some sources may lead you to believe that only IDA is relevant, both types of iron deficiency can affect performance. Both ID and IDA have been demonstrated to negatively affect physical and cognitive function in athletes (Camaschella, 2015). With either presentation (ID with or without anemia), athletes may suffer from fatigue, low energy availability, poor recovery, chronic injuries and declining cognitive and physical performance (Camaschella, 2015) (Lopez, Cacoub, Macdougall, & Peyrin-Biroulet, 2016). When an iron deficient athlete attempts to train at their typical intensity, despite being in a deficient physiological status (i.e. not having enough gas (iron) in the tank), it can set the stage for developing an overuse injury. If an athlete is lacking a nutrient that is essential for full recovery between training sessions, injury may ensue.
Iron deficiency occurs due to a discrepancy between utilization and intake of iron. We lose and utilize iron on a daily basis through normal physiological processes (e.g. metabolism and digestive processes). Females lose additional iron through menstruation and athletes lose additional iron through processes related to exercise and inflammation. Additionally, young athletes have higher iron requirements as they expand their blood volume as a requirement for normal growth (Sim, et al., 2019).
To account for loses, athletes need an appropriate intake of iron. Dietary iron comes in one of two forms. Iron that comes from meat, poultry and fish, called heme iron, is the easiest for the body to absorb and utilize. Some plant products and fortified foods also contain iron, called non-heme iron, but this type of iron is harder for the body to absorb and utilize. Since non-heme iron is more difficult for the body to absorb and utilize, the recommended daily intake of iron for vegetarians is almost two times what is recommended for athletes who eat meat (NIH, 2019).
When iron losses exceed absorption or absorption falls below demand, iron stores become depleted, resulting in a reduced ferritin level. Eventually, the stored iron is too low to provide the tissues with sufficient iron and symptoms arise. Figure 1 below shows many of the factors that impact iron status.
Figure 1: Factors influencing iron stores
* Metabolic processes: refers to the various chemical processes that occur within your body in order to sustain life.
The International Olympic Committee recommends elite, endurance athletes, undergo routine hematological screening for iron deficiency based on the “higher than expected presence of decreased iron stores in [these] athletes” (Ljungqvist, et al., 2009). Healthcare practitioners should familiarize themselves with the role of iron, signs of low iron stores and refer to a doctor when indicated. A family doctor or naturopathic doctor can order bloodwork however; it is still important to help athletes find practitioners who are familiar with functional medicine and experienced in working with female athletes.
Replenishing iron stores may require supplementation, dietary modification, temporary activity modification, strategies to optimize gut health, treatment to improve menstrual function and other strategies. An experienced practitioner will ask questions about each of the contributing factors listed in this article and work to create a comprehensive and individualized plan. In cases where ferritin levels are extremely depleted, or where iron deficiency does not respond to dietary changes, training modifications and supplementation, injections may be required to replenish iron stores.
Iron deficiency is common and most prevalent in female athletes. A “normal” level on a laboratory report may not be sufficient to sustain optimal health and performance in athletes. Symptoms may include fatigue, low energy, poor recovery, unexplained pain and/or persisting injuries. Iron deficiency is all too common, under recognized and has huge implications, especially for female athletes.
References:
Briden, L. (2018). Period repair manual: natural treatment for better hormones and better periods. United States: Createspace Independent Publishing Platform.
Camaschella, C. (2015). Iron-Deficiency Anemia. New England Journal of Medicine, 372(19), 1832–1843. doi: 10.1056/nejmra1401038
WHO. Chapter 4: Childhood and maternal undernutrition. (2010, November 2). Retrieved August 5, 2019, from https://www.who.int/whr/2002/chapter4/en/index3.html.
Ljungqvist, A., Jenoure, P. J., Engebretsen, L., Alonso, J. M., Bahr, R., Clough, A. F., … Dubi, C. (2009). The International Olympic Committee (IOC) Consensus Statement on Periodic Health
Evaluation of Elite Athletes, March 2009. Clinical Journal of Sport Medicine, 19(5), 347–365. doi: 10.1097/jsm.0b013e3181b7332c
Lopez, A., Cacoub, P., Macdougall, I. C., & Peyrin-Biroulet, L. (2016). Iron deficiency anaemia. The Lancet, 387(10021), 907–916. doi: 10.1016/s0140-6736(15)60865-0
NIH. Office of Dietary Supplements - Iron. (2019, October 19). Retrieved November 5, 2019, from https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/.
LifeLabs. Reference Ranges SECTION (HCP- Reference Ranges Page). (n.d.). Retrieved from https://www.lifelabs.com/page-section/reference-ranges-section-hcp-reference-ranges-page/.
Sim, M., Garvican-Lewis, L. A., Cox, G. R., Govus, A., Mckay, A. K. A., Stellingwerff, T., & Peeling, P. (2019). Iron considerations for the athlete: a narrative review. European Journal of Applied Physiology, 119(7), 1463–1478. doi: 10.1007/s00421-019-04157-y
UCSF Health. (2019, November 6). Hemoglobin and Functions of Iron. Retrieved January 9, 2020, from https://www.ucsfhealth.org/education/hemoglobin-and-functions-of-iron.
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About the author: Kristin is a Registered Physiotherapist and the Owner of East Mill Physio in Elora, ON. She has a special interest in Neurofunctional Acupuncture and Sports Performance. She enjoys pushing the boundaries of what we traditionally believe to be possible with respect to injury rehabilitation and performance optimization by using a holistic treatment style.