More times than not, when female runners complain about feeling sluggish during workouts, it turns out that their iron is low. The loss of iron in the blood, which often occurs from menstrual bleeding, is called iron-deficiency anemia.
Since iron is an essential ingredient of the proteins hemoglobin and myoglobin that transport oxygen inside your blood and muscles, a lack of iron diminishes oxygen transport, which has obvious implications for running. Anemia can also occur from inadequate iron in the diet, the risk of which is increased with a vegetarian diet.
While you may not even notice anemia during activities of normal living (when your muscles’ demand for oxygen is relatively low), you may feel fatigue while running (when your muscles’ demand for oxygen is much greater). If you’re mildly anemic, difficulty doing intense training like interval workouts may be the only symptom you experience. With moderate or severe anemia, even easy running feels difficult.
The gold standard diagnostic test of iron-deficiency anemia is ferritin, the protein that stores iron in the blood and acts as a buffer against iron deficiency and iron overload. Blood ferritin level indicates the total amount of iron stored in the body. (A complete blood count (CBC), which includes information about hemoglobin, hematocrit, and the number and shape of red blood cells may be used together with ferritin to diagnose anemia.)
With mild anemia, you may only need to increase consumption of iron-rich foods, like lean red meat, dark poultry, and iron-enriched or fortified breads, cereals, and pastas. More severe cases may necessitate an iron supplement (e.g., ferrous bisglycinate or ferrous sulfate). When consuming iron-rich foods, consume vitamin C to increase iron absorption.