Iron Deficiency and Iron Deficiency Anemia in Adolescent Athletes: A Systematic Review

IntroductionMost athletes are in excellent health with lifestyles combining regular exercise with a nutritious diet (1,2). However even the healthiest athletes are at risk for iron deficiency and iron deficiency anemia. Athletes subjecting themselves to prolonged strenuous exercise, and daily endurance training risk developing anemia. Iron deficiency can occur with or without the development of anemia and may be symptomatic or asymptomatic (3). The laboratory parameters of the same are seen in table 1.Anemia is present when red cell mass is reduced below normal limits. Measuring red cell mass directly is uncommon. Instead, the hemoglobin level and hematocrit are commonly used (see table 1). The clinical presentation and management of anemia varies according to the mechanism of red cell mass loss. The mechanism of anemia can be classified using three broad categories: hypoproliferation, ineffective erythropoiesis, and blood loss or hemolysis.Iron deficiency can result in a hypoproliferative anemia. Iron is a key component of hemoglobin and key to the molecule's ability to carry oxygen. A lack of iron impairs hemoglobin synthesis and ultimately results in hypoproliferation of red cells in the marrow. While iron stores are depleted by erythropoiesis transferrin saturation decreases, total iron binding capacity (TIBC) increases, and ferritin levels decrease. Transferrin is a protein that transports iron in plasma while ferritin is the predominant storage form of iron. The increase in TIBC reflects decreased saturation of transferrin as iron stores are depleted. A microcytic, hypochromic anemia emerges once iron stores are completely depleted and hemoglobin synthesis is consequently impaired.Exercise performance is dependent on the capacity of the body to transport oxygen. Thus a shortage of hemoglobin in the athlete due to iron deficiency will cause the body to work slower and affect performance negatively (4). Lower levels of stored iron, principally ferritin, can negatively affect aerobic training (5). Decreased energy efficiency and increased muscle fatigue and cramping are manifestations of diminished iron reserves.Several studies have reported that athletes are prone to iron deficiency, which can lead to iron deficiency anemia (5,6). This article provides an overview of iron deficiency and iron deficiency anemia in athletes.Search strategyA MEDLINE search was conducted in the PUBMED directory for articles relating to anemia in athletes in month of January 2013. The keywords 'anemia' and 'athletes' were used. After applying limits for articles addressing human subjects and published in English, 200 articles were located. Articles unrelated to adolescent athletes (>18 years) or published before 1985 were excluded. The abstracts of the remaining articles were read and evaluated for relevance to the topic. . Bibliographies were cross-referenced to locate articles missing from the literature search. A summary of articles reviewed is presented in table 2 (7-52).DiscussionBetween 1993 and 2005, the World Health Organization (WHO) estimated that nearly two billion people worldwide were anemic, i.e. about 25% of the world population (3). The prevalence of iron deficiency anemia in developed countries is around 20% and may be as high as 65% in developing countries (3). Given the prevalence of iron deficiency anemia that the first article published in Sports Medicine examined, iron binding capacity and hemoglobin is unsurprising (36). Even as early as 1925, an article published in Science dealt with absence of fatigue in athletes who consumed a healthy diet. This article served as the foundation for the emerging relationship between iron deficiency and anemia (37).PrevalenceIn the reviewed studies, the prevalence of iron deficiency anemia was not found to be different in athletes compared to non-athletic controls. Though the absolute hemoglobin value was lower in athletes, this difference was not statistically significant. …