It is not uncommon for an endurance athlete, especially a female, to ask me about using iron to help with performance. Though it seems logical that iron, which helps carry oxygen, would serve this purpose, it is not always that straightforward.
For men, iron will most likely cause constipation without improving performance, because most men are not iron deficient. Menstruating females will benefit only if they are low in iron. Therefore, my answer is that using iron depends on: 1) whether the athlete has anemia; and 2) whether iron could treat that anemia.
So, what is anemia? Anemia is a low level of red blood cells (RBCs), which are the oxygen-carrying cells in our blood. The common reasons for anemia are genetic, nutritional, hormonal, bleeding and chronic diseases. Anemia can also develop in response to athletic training. RBCs are constantly being produced in the bone marrow, and they need iron, a mineral we get from our diet. Iron is used to make hemoglobin, the protein in the RBCs that actually carries the oxygen. Kidneys produce a hormone called erythropoietin, which stimulates the bone marrow to make RBCs.
Anemia is diagnosed by two simple blood tests: the hemoglobin (oxygen-carrying protein) and hematocrit (concentration of RBCs). Iron in the body is usually measured by the ferritin level (measuring iron stores in the body) and the transferritin level (measuring how much iron is being used to carry oxygen). Tests also measure the size of the RBCs—small, normal, or large. The size test helps to determine the type of anemia that is diagnosed.
Small RBC. Also known as microcytic anemia, this is the most common type of anemia, with iron deficiency the likely cause. Genetic causes for microcytic anemia are sickle-cell anemia (SCA), sickle-cell trait (SCT) and alpha or beta thalassemia, which are all problems with the hemoglobin. SCA and SCT are seen in African descendants, and thalassemia is seen in both African and Mediterranean descendants. Whereas iron supplementation will treat iron deficiency anemia, iron will not help with types of anemia that have genetic causes.
Normal RBC. Also known as normocytic anemia, this is seen in patients with a variety of chronic diseases. Kidney disease is one of the most common reasons, because the kidney cannot make erythropoietin. Athletes with anemia from chronic diseases should be monitored by their physicians.
Large RBC. Also known as macrocytic anemia, this is the least common type of anemia. The inability to absorb vitamin B12, called pernicious anemia, is a common cause of this type. Low folic acid, alcoholism and thyroid problems can also cause this type of anemia.
Iron deficiency anemia usually occurs in menstruating females. Diets that lack certain nutrients—e.g., vegetarian, vegan and low-caloric diets—can also cause iron-deficiency anemia, since red meat is the largest source of iron. An iron supplement is the treatment for this type of anemia. Those who exclude meat from their diets need to ensure they are getting enough iron and calories, and they should consider consulting a sports dietician. Adding vitamin C supplements to iron intake can increase iron absorption. However, other supplements that vegetarians or vegans may use (e.g., calcium and magnesium) can block iron absorption. With this in mind, take iron and vitamin C at a different time of day than other supplements. Blood tests in athletes that show anemia and ferritin levels under 12 percent or transferritin levels under 16 percent will benefit from iron supplements.
Athletic anemia occurs with low hemoglobin or hematocrit levels due to normal training adaptations, but with normal ferritin and transferritin levels. Because the ferritin and transferritin levels are normal, treatment is unnecessary. However, if a female athlete without anemia is experiencing excess fatigue and has low ferritin levels, she should consider iron supplementation, since her condition could be the precursor to actual anemia.
Athletes with sickle cell trait (SCT) or disease (SCD) can develop a "sickle cell crisis," which might require hospitalization. Dehydration and infections are common reasons for a crisis. These athletes must stay hydrated before, during and after training sessions, increase their rest periods during practice, and avoid training if they are feeling sick. They should also talk with their doctors to understand more about participation in athletics.