Iron deficiency is rather common among people active in sports. Iron deficiency (low ferritin level) and iron deficiency anemia (low hemoglobin and ferritin levels) are common among men and women, but more common among women athletes. Menstruation increases the risk for iron deficiency (anemia). High intensity training and endurance sports increase iron demand up to 70% compared to armchair athletes, therefore athletes are one risk group for iron deficiency. Iron is excreted with sweat, urine, skin, blood and gastrointestinal tract. Athletes experience also faster decomposition of red blood cells, e.g. by feet´s mechanical force during running decomposition of red blood cells may increase .
HOW DOES IRON DEFICIENCY AFFECT ENDURANCE ATHLETES?
The most well-known task for iron is oxygen transport in our bodies. In case of iron deficiency oxygen transport is weaker, oxygen transport to muscles decreases during physical activity, which decreases the maximum physical capacity and physical endurance is weaker.
Symptoms of iron deficiency are tiredness, powerlessness, decline in physical endurance, shortness of breath, headache, ringing in the ears, palpitations, paleness, odd appetite (urge to eat chalk, ice etc), fragile nails and hair, cracks in the corners of the mouth and loss of appetite. Odd appetite is not a rare symptom, therefore if you feel the need to eat snow or nice, it is worth checking your iron levels.
There are different signs for iron deficiency and having any of the symptoms does not imply that you must have iron deficiency. People experience iron deficiency differently – a lot of people have symptoms when iron levels have declined but there are also people, who don´t experience any symptoms even in case of very low ferritin levels. Iron deficiency develops to iron deficiency anemia in which case symptoms are more common.
WHAT IS PSEUDOANEMIA?
Iron deficiency anemia should not be mixed with pseudoanemia. Pseudoaneemia is a situation, when blood´s hemoglobin level has decreased but this is not due to lack of iron but instead due to increase in blood plasma volume. Blood plasma increases in athletes (especially among endurance athletes) up to 20% that leads to decrease in hemoglobin level. A person benefits from iron supplements in case of anemia, when blood hemoglobin level increases. In case of pseudoanemia, no benefit is achieved from iron supplements. E.g. in a research made among swimmers it was found that during intense training periods, blood´s hemoglobin and hematocrit (volume of red blood cells in plasma) levels decreased, but increased during non-intense periods, mainly before big competitions .
Diagnosing iron deficiency and iron supplementation
Iron deficiency (anemia) is diagnosed by blood test. Ferritin test is used to evaluate a person´s iron stores and basic blood test is used to diagnose anemia. Iron deficiency without anemia can be diagnosed already with ferritin level <30 μg/L, although the lower limit for ferritin among men and women is only 10 and 28, respectively (can differ a bit among different labs). Different other tests can also be used to diagnose iron deficiency, more information from your doctor. The first thing to do in case of iron deficiency (anemia) is to find out the cause. When women offer suffer from iron deficiency due to menstruation, there can be also other reasons, e.g. internal bleeding or iron absorption disorders. Some drugs, e.g. medicines that reduce stomach acid, also increase absorption disorders for many vitamins and minerals.
Shoud athletes use iron supplements to prevent iron deficieincy? Rather not. For a healthy person, extra iron is not absorbed. Therefore a person does not benefit from iron supplementation. Iron supplements are, however, needed in case of diagnosed iron deficiency (anemia), because with just iron-rich food, increasing ferritin level is impossible. The level of iron stores, i.e. ferritin, should be at least 50–70 μg/L, but can also be higher. Iron has many different important tasks in addition to oxygen transport. For instance, iron is needed for optimal thyroid function. Iron supplementation also helps to increase physical endurance in case of deficiency. Symptoms of iron deficiency start to fade away after couple of weeks of iron supplementation.
 Bärtsch P, Mairbäurl H, Friedmann B. Pseudoanämie durch Sport [Pseudo-anemia caused by sports]. Ther Umsch. 1998 Apr;55(4):251-5. German. PMID: 9610226.
 A. Aro, M. Mutanen, M. Uusitupa. Nutrition Science, 4.–7.volume, 2017.