In trained athletes practicing predominantly aerobic physical activity, it is quite common to observe lower hemoglobin and hematocrit levels in the absence of pathology. This condition, common while performing particularly intense physical activity, is called “sports anemia”. Attempts to classify the condition and to study its incidence and etiology are complicated by the lack of a precise definition. For this reason, amongst the forms of sports anemia, we must include also a condition referred to as “pseudo anemia”, a consequence of training. In presence of pseudo anemia, the plasma volume is expanded without a corresponding increase of cellular components: this situation can simulate the anemic state, with a slightly reduced hemoglobin concentration, red blood cells of normal color, normal ferritin levels and MCV values above the normal range.
Athletes can develop two more types of anemia:
- Acute anemia, with a sudden onset and a reduction in hemoglobin concentration and hematocrit due to a drastic increase of the physiological amount of intravascular hemolysis. This phenomenon causes a release of free hemoglobin that can result in the loss of hemoglobin in urine.
- Anemia with a gradual onset, which starts with a negative iron balance and lower iron levels depleting the stored form of iron, and which eventually can develop into iron deficiency anemia.
For an early diagnosis, in addition to the usual laboratory investigation, it has been proposed to test for protoporphyrin levels. Protoporphyrin is the last stage of the biosynthetic pathway that leads to the formation of the heme group, after binding an atom of iron. If body iron levels are low, protoporphyrin begins to accumulate in the red blood cells in its free form, as an insufficient quantity of the ion makes the completion of the synthesis of heme impossible. This phenomenon has been observed in marathon runners, both during training and during race, with significant increases of protoporphyrin in the free form. Since it has been proven that exercises results in enhanced work capacity and respiratory quotient, it is believed that well-trained athletes should have higher concentrations of hemoglobin than sedentary subjects. As a matter of fact, it has been repeatedly observed that after an intense physical activity session, the circulating hemoglobin values are higher in subjects practicing a variety of sports. In contrast, a reduced concentration of hemoglobin has been found in the majority of athletes who practice endurance sports.
A reduction in circulating hemoglobin, associated with an increase in plasma volume that becomes unsaturated during the training period, may be a favorable factor for an improved cardiac output.In addition, a lower concentration of hemoglobin reduces blood viscosity; as a consequence, blood becomes more fluid, the flow at muscular level is enhanced and the transport of oxygen to the tissues is facilitated. Therefore, we can say thatduring training the body makes a better use of the heme group to ensure a greater availability of O2 in peripheral tissues.
Sometimes the athlete does not show any symptoms at rest, but his/her efficiency in training and during races drops, he/she feels tired for the whole day and recovers very slowly, both during the workout session and between one session and the next. Often this is accompanied by sore muscles, which would suggest problems of muscular origin.So, if in athletes a condition of anemia with low hemoglobin count is rare, iron deficiency is much more common and manifests itself as follows:
• lower ferritin levels
• a reduction in serum iron
• a reduction in the percentage of saturation of transferrin
• an increase in the total amount of transferrin (TIBC)
Iron deficiency is often the result of an inadequate nutrition, which depletes iron in the stored form. It is customary for athletes, especially in the pre-race period, to reduce their caloric intake in order to lose weight, which has a negative impact on the body iron balance. This bad habit has more evident effects in women athletes, because of the additional iron loss occurring during the menstrual cycle (an of 0.5-0.6 mg per day). Multiple studies have shown that after a period of sustained high- intensity workout a loss of blood occurs from the digestive tract in absence of disease, both in athletes and in sedentary subjects. This loss is generally not visible but can be easily detected through microscopic examination.
The reduction of iron is also exacerbated by perspiration. Sweat contains on average 300-400 g/l of iron per day; intense physical activity can cause up to 3l of perspiration with a consequent loss of 1-2 mg of iron per day. Another factor that characterizes “sports anemia” is hematuria, namely loss of blood in the urine. Hematuria is a transient phenomenon that disappears within 24-72 hours after the workout session; its temporary nature allows distinguishing it from hematuria caused by renal diseases.
Prevention helps to maintain an acceptable iron balance. For example, it is advised to check ferritin values and the degree of transferrin saturation at the end of the training period. It is a good practice to take in at least 20 mg of iron per day, and this is particularly important for women. It is recommended to reduce foods that can lower iron absorption: tannins in wine, tea, coffee and drinks that contain caffeine.
Training at high altitudes stimulates erythropoiesis, with an increase in blood red cells and hemoglobin which boosts the capacity to transport oxygen (this happens because at high altitudes there is a situation of hypoxia, due to a lower amount of available oxygen, and the kidneys respond by secreting increased amounts of EPO). Athletes at risk of anemia often have to resort to iron supplementation, always to be recommended by a doctor, for a period of maximum 1-3 months. Finally, we can establish that anemia in athletes is not determined by a real iron deficiency but by a discrepancy between the rate of formation of protoporphyrin and the availability of iron: with greater reserves, there is less risk of the onset of the disease.