Correcting Iron Deficiency to Increase Performance

by Rachelle Viinberg, ND

Although you’ve recently been training hard for an upcoming competition, you’ve struggled to complete workouts. You’re getting enough sleep and your diet is clean, but even walking up the stairs causes dizziness and fatigue. Is this what being in shape feels like?

Some of the tell-tale symptoms of iron deficiency include loss of endurance, chronic fatigue, high exercise heart rate, low power, frequent injuries, low immunity, and irritability.  As a female Olympic rower, I observed that iron deficiency was one of the most common causes of exertional fatigue on my team. With eighteen practices per week, correcting this deficiency was paramount for performance.

Dietary iron recommendations are 1.3 to 1.7 times higher for athletes than non-athletes. Low iron appears more pronounced in endurance sports. The body adapts to training load by increasing the total amount of red blood cells and need for iron. In other sports, such as long distance running, a phenomenon called, “foot-strike hemolysis” can occur. This is due to repeated jarring foot-strikes, which physically break red blood cells. Heavy sweating, minor gastrointestinal bleeding from intestinal lining damage (a common phenomenon during strenuous exercise), and menses are particular risks for low iron stores.

Before going further, it’s important to understand the difference between anemia, low iron stores and iron deficiency anemia. Anemia simply means having a low hemoglobin level, which is a protein in red blood cells. It is responsible for carrying oxygen from your lungs to your body’s tissues and returning carbon dioxide from the tissues back to the lungs. However, anemia is not necessarily caused by low iron, which is an essential component of hemoglobin. There are a handful of chronic and genetic diseases that can have the same effect. To determine the cause of anemia ferritin, a marker of total body iron stores, must be tested as well. If hemoglobin and ferritin are low, the individual likely has iron deficiency anemia. The interesting part is that many people can have all the symptoms of anemia without low hemoglobin. This means that low ferritin (insufficient iron), but normal hemoglobin can produce symptoms that can be corrected once iron levels are increased.

Insufficient iron is common not only in athletes. In my practice, I see people with a primary concern of “fatigue” almost daily. Of particular interest are women with menorrhagia (heavy menses), which compounds the problem of iron deficiency. Often this is an estrogen dominant picture, which is a whole other article in itself.  After a full diagnostic workup, including assessments for nutrient deficiencies, thyroid dysfunction, hormone imbalances, and food intolerance, I often find these women to be low in iron. A global perspective of the results should be taken, as many of the findings can impact each other. For instance, food intolerances can impede iron absorption and anemia is often the first indicator of hypothyroidism.

It’s important to get thorough lab testing to find the cause of fatigue and treat accordingly. That said, there are a few things people should keep in mind when testing ferritin. Firstly, it can falsely increase with stress, surgery, infections, injuries, and asthma (to name a few). Being tested while healthy will help ensure adequate results. Note also that supplementing with iron when there is no deficiency is unhelpful, if not harmful. Too much iron can increase inflammation, raise cholesterol, decrease cardiovascular health, and may even predispose one to cancer.

So what’s the best source of iron if iron insufficiency or iron insufficiency anemia is detected? In addition to dietary recommendations, ferrous sulfate, gluconate or fumarate are typically recommended. Often these forms of iron have low bioavailability as minerals, in their ordinary form, are difficult for the body to absorb through the intestine. Compounding the problem, are undesirable side effects like constipation, diarrhea, nausea and vomiting.

Fortunately there is another alternative.  Ferrous bisglycinate chelate is a low molecular weight mineral compound in which the minerals are bound to amino acids to produce a natural organic chelate that can pass easily through the intestinal wall. In addition to increased absorption, it does not react with other nutrients and has less gastric side effects (1). In fact, absorption of iron in this form has been found to be 2.6 times safer than common dietary iron supplements like ferrous sulfate (2). Absorption is controlled by body iron stores with greater amounts generally being absorbed by individuals with lower iron status. This means that someone suffering from iron-deficiency anemia may uptake 90 percent of the iron, while someone who is not iron deficient may only take up 10 percent (3). Despite this phenomenon, individuals are still encouraged to have their ferritin tested before beginning supplementation.

In summary, it is important to do a thorough medical history and lab work-up when chronic fatigue or exertional fatigue is a complaint. If iron deficiency or iron deficient anemia is found to be a contributing cause, correcting iron stores can have an enormous impact on performance. Along with dietary recommendations, one of the best iron supplements is in the bisglycinate chelate form due to its absorption and lack of side effects. As with many situations, in treating iron deficiency, one answer does not solve all.



  1. Pineda, O. et al. 2001. Effectiveness of treatment of iron-deficiency anemia in infants and young children with ferrous bis-glycinate chelate. Nutrition, 17: 381-384.
  2. Szarfarc, S. et al. 2001. Relative effectiveness of iron bis-glycinate chelate (Ferrochel) and ferrous sulfate in the control of iron deficiency in pregnant women. National University of Cajamarca, Vol. 51, No. 1.Borzele
  3. Borzelleca, J. and Jeppsen, R. 1999. Safety evaluation of ferrous bisglycinate chelate. Food and chemical toxicology, 37: 723-731.


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