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Part 21 deals with the major topic of iron supplementation. Iron deficiency is a well-known problem in the general population and athletes in particular. Symptoms in the latter group include decreased endurance ability, chronic fatigue and recurring illnesses such as minor infections and symptoms, which are also often prevalent in unexplained underperformance syndrome (overtraining). The review of iron, which our experts have provided, is comprehensive. In addition, two lesser topics (α-ketoglutarate (AKG) and α-ketoisocaproate (KIC)) are addressed in separate articles.
C Goodman and P Peeling
Iron deficiency is the most prevalent nutritional disorder in the world and is particularly pertinent in athletes. An altered iron status may range in severity from iron depletion (serum ferritin (SF) <35 µg/l, haemoglobin (Hb) >115 g/l, transferrin saturation >16%) to iron deficiency anaemia (SF <12 µg/l, Hb <11.5 g/l, transferrin saturation <16%).1
It is recognised that optimal physical performance is dependent on the efficient delivery and utilisation of oxygen by the exercising muscle. Iron is a fundamental element to both of these processes due to its role as the functional component of haemoglobin and myoglobin, as well as being a critical constituent of mitochondrial enzymes and cytochromes that promote oxidative phosphorylation. Insufficient iron stores may thus lead to feelings of lethargy and decrements in athletic performance.
There are several reasons why athletes may present with low iron levels, including plasma volume expansion, low dietary iron intake, low iron bioavailability and excessive iron excretion/loss. Furthermore, female athletes are at greater risk of iron deficiency, due to menstrual blood loss and suboptimal dietary intake. During exercise, iron losses can occur from several avenues such as red blood cell haemolysis, haematuria and sweating. Such iron loss mechanisms are dependent on the exercise mode, intensity and duration (for review see ref 2). Additionally, recent research has demonstrated that the hormone hepcidin may …
Competing interests None.
Provenance and peer review Commissioned; not externally peer reviewed.