Contributed by Dr. Steven T. Devor – Director of Performance Physiology for MIT and OhioHealth, and Associate Professor of Exercise Physiology, Department of Human Sciences, and Department of Physiology and Cell Biology, The Ohio State University
The physical challenge of training and competing in long endurance races like marathons, ultra-marathons, and half- and full-ironman triathlon events is tremendous and places a number of challenges on the athlete to perform optimally over a long training season, and then peak on race day. For many, this challenge can become even more burdensome if you experience symptoms such as a lack of endurance, a higher heart rate during training sessions, persistent fatigue, irritability, and a noticeable reduction in your motivation to train.
Often endurance athletes place the blame on improper, or poorly timed, fueling with carbohydrate. Or their drop in performance and increased mental fatigue is thought to be from overtraining, which is not uncommon for endurance athletes. However, what might be the culprit is as simple as low iron stores, or inadequate dietary iron intake, that can result in iron deficiency anemia.
Iron is known as an essential nutrient, which means that your body is not able to synthesize the iron it requires for proper function and optimal health. Accordingly, iron must be obtained from either foodstuffs or as a supplement. Iron deficiency anemia develops when you do not consume enough dietary iron over time. Although there are other types of anemia, iron deficiency anemia in particular can completely sideline your ability to train and perform at your peak as an endurance athlete.
Endurance athletes and others do not develop iron deficiency anemia in a matter of days. This is an illness that develops slowly over time when the recommended daily dietary iron needs are not consistently met, and the body is forced to pull iron from the reserve it has in order to function properly. In this scenario iron stores within the body become depleted. When iron storage is very low or depleted, the red blood cells that get produced are smaller than they should be, and importantly those smaller red blood cells do not contain an adequate amount of hemoglobin.
Hemoglobin, which is found on the red blood cells, is responsible for binding oxygen. And then the red blood cells carry that bound oxygen to the skeletal muscles and allow work (i.e., exercise) to be done. Since red blood cells have a lifespan of approximately 120 days, in the presence of iron deficiency anemia the smaller red blood cells slowly begin to predominate in the blood stream. And the ability of these smaller red blood cells to carry an adequate amount of oxygen to the working skeletal muscles during exercise is severely compromised. Thus, exercise capacity, the ability to train and race hard, diminishes.
The way your body attempts to overcome the smaller red blood cell size, and their diminished ability to deliver the required oxygen, is that your heart rate will rise higher than it should during exercise. Your body is attempting to meet the metabolic demand you are placing on it during exercise in an iron deficient state. Simply put, your body will not win this battle. Your skeletal muscles and brain will not function optimally. And this smaller red blood cell-increased heart rate during exercise cycle results in decreased endurance and a lack of motivation to exercise, which can manifest as increased irritability and a sort of chronic fatigue.
The good news is that clinical iron deficiency anemia is detected by a simple blood test with your physician. So if you are having signs of increased fatigue and diminished endurance capacity, I recommend you have a blood test done by your family practice doctor. Generally, if your hemoglobin levels are low it is likely your iron storage is low, or perhaps complete iron deficiency anemia has developed.
The number one and most simple method to prevent low iron stores and iron deficiency anemia is to ensure that your diet contains adequate sources of iron. Below are five simple steps that will help keep iron levels where they need to be in your body:
With regard to iron supplementation, it is not at all curious to know that many competitive endurance athletes use iron supplements. The thought process follows that if iron is beneficial for the oxygen carrying capacity in the blood, more of it must be better. Indeed a recent scientific publication examined competitive road cyclists in France and determined that over one-third of those tested had artificially elevated levels of serum ferritin, which indicates high iron levels. Clearly, a supplement regimen that embraces an unchecked use of iron is not a plan that is consistent with sound health and wellness choices.
Dietary iron is critical for optimal health and physical function. While reversing low iron stores or iron deficiency anemia will elevate endurance performance, too much iron will likely result in unwanted gastrointestinal distress.
Finally, be aware that though relatively small, there is a percentage of the population that possesses an inherited defect that results in excessive iron absorption from food. In this small sub-set of individuals if the excessive iron absorption and storage is left untreated, liver damage can result. However, for most of us it is important for both optimal health and enhanced endurance performance to consume the recommended daily dietary intake of iron (8 – 10 mg per day for men, and 18 – 20 mg per day for women) from whole food sources and avoid over consumption.