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Iron is an essential trace mineral in the body, associated with numerous processes relevant to athletic performance (e.g. oxygen transport, energy production). Despite its importance, athletes (particularly females and adolescents) tend to present with a greater incidence of iron depletion than the general population, likely a result of the increased iron requirements resulting from exercise-related mechanisms. Left untreated, iron depletion may develop into iron deficiency anaemia (IDA), whereby haemoglobin production becomes compromised, negatively impacting an individual’s exercise capacity. Accordingly, maintaining adequate iron stores appears essential for athlete cohorts, and should be a priority consideration in the context of athlete nutrition.
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Despite the importance of iron to numerous essential exercise relevant processes, the body cannot make its own iron, and is dependent on iron derived from food sources. Although iron is widely distributed in many food types, inappropriate food combinations can compromise absorption. The natural presence of phytates, tannins and, to a lesser extent, calcium in food inhibits iron absorption from iron-rich plant food. This inhibition can be partly negated by consuming foods and/or beverages with specific chemical properties that enhance absorption. Furthermore, exercise itself has been shown to transiently elevate the iron regulatory hormone, hepcidin, which is responsible for the homeostatic regulation of intestinal iron absorption. Therefore, individualised dietary intervention in conjunction with the training program in high-risk individuals is critical to help prevent iron depletion, particularly during peak periods of altered iron metabolism. Early detection of depleted iron stores and dietary intervention are warranted, since depleted or exhausted iron stores recover slowly and may take months to be replenished.
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DEFINING THE STAGES OF IRON DEFICIENCY
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Several common haematological markers are used to categorise an individual’s iron status in the general population, with each marker assigned a reference range and threshold value that is associated with healthy iron status. Of note, these general population reference points are also applied to the athlete population, given the absence of sport-specific standardised values. Within the scope of these reference ranges, it is generally accepted that there are three stages of iron deficiency, distinguished according to the combined interpretation of the haematological markers shown in Table 11.1.
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