There are countless reasons for being unable to handle your normal training load—sleep deprivation, illness, stress—but if you just can’t seem to shake the fatigue, you could be dealing with a deficit of red blood cells, or anemia.
“If athletes are anemic, they won’t function optimally,” says Janis Abkowitz, head of hematology at University of Washington School of Medicine. “Red cells bring oxygen to [your muscles and other tissues]. If there are too few of them, normal [daily] activities—walking, climbing stairs—get more difficult. You can’t exercise to the level that you had before.”
There are several types of anemia, which affects a quarter of the world’s population. The list includes sickle cell anemia and anemias associated with other diseases and conditions, but iron-deficiency anemia is by far the most common. It disproportionately affects endurance athletes, especially women who menstruate. It comes on slowly, which makes it tricky to catch, particularly because research suggests athletes might just chalk up the symptoms to personal shortcomings. Fortunately, it’s easy to cure. (If you’re concerned that you might be anemic, the first step is a visit to your doctor.)
What Causes Anemia
Iron is crucial to our bodies’ ability to intake, transport, and process oxygen. Our red blood cells transport oxygen throughout the body via hemoglobin, a protein molecule that the body can’t create without iron.
“Iron is a balance,” Abkowitz says. We build up our iron stores through our diet, and we lose it primarily via bleeding and urination. Our body first responds to an iron deficiency by making smaller cells. Then, if the problem persists, it makes fewer cells, she explains. An iron deficiency alone won’t typically be symptomatic. A patient will notice the effects when their body has been iron deficient long enough to cause a meaningful dive in red blood cell count.
Athletes are especially prone to iron-deficiency anemia because intense training increases the body’s need for iron. High-altitude training and endurance training have particularly high oxygen demands. Any physical exertion stimulates increased red blood cell production; you need to transport more oxygen to perform at a high level. Exercise-induced sweating and muscle inflammation slowly eat away at iron stores as well. The other major factor behind anemia is diet—not eating enough iron-rich foods like red meat may lead to a deficiency.
What the Symptoms Look Like
The most common symptoms of iron deficiency anemia are fatigue and loss of endurance. You might find that your heart rate increases with activity more dramatically than in the past, and you might have more frequent dizzy spells, Abkowitz explains.
A handful of tests can determine whether you have iron-deficiency anemia. Abkowitz starts with a full blood count, which measures hematocrit (red blood cell count) and hemoglobin (the iron-containing molecule within the red blood cells). If those numbers are low, she’ll look at mean cell volume, which is smaller than normal with iron-deficiency anemia. Then she’ll check the reticulocyte count, or the number of new cells your body makes each day. Finally, a serum ferritin test will measure the amount of iron stored in your body.
How to Treat Anemia
After a proper diagnosis, your doctor may recommend a tailored dose of supplemental iron, which is the most surefire way to rebuild depleted stores. Though uncommon, it’s possible to overdo it with supplemental iron—and there’s no reason to take it if you aren’t iron deficient—so be sure to get a legitimate diagnosis and a prescribed dose.
Pills can’t fully replace an iron-rich diet. There are two types of dietary iron: heme iron (the type that comes in red blood cells) and nonheme iron. Our body has an easier time absorbing heme iron—red meat is a great source—but it can absorb nonheme iron, found in foods like spinach, eggs, rice, and fortified cereal, as well as most iron supplements. Eating plenty of vitamin C—via whole foods or a vitamin supplement—can help the body better absorb nonheme iron.
While you’re busy replenishing your iron stores, you should also dial back your training. Greg McMillan, a coach based in Flagstaff, Arizona, who works with some of the world’s best runners, requires athletes diagnosed with anemia to stop all intense, long-duration workouts. For two to three weeks, he advises short, low-intensity exercise. McMillan typically sees his athletes return to full training capacity after four to six weeks of iron supplementation and an iron-heavy diet.