Iron and the Endurance Athlete (1)

Is iron really that important for endurance athletes? How can you tell if you may have an iron deficiency, and what are some sources of iron?

This article was written by James L. Weinstein, MS, RD

It’s true, Iron Deficiency is the world’s most common nutritional disorder—and it’s also one of the most abundant metals on earth.  Oh, and iron is also one of the most common substances that children accidentally overdose on! So what is it about iron that has endurance athletes in a trance?  Some tout its potential ergogenic benefits, the solution to my fatigue, the answer to improving hemoglobin, the cure for lagging performance.  Others throw around words like hemochromatosis and iron overload syndrome.  My aim in this short article is to debunk some of the myths of iron, but also to give you, the athlete and coach, some tools to help make better educated decisions regarding taking iron—after all, you can buy it in the grocery store so it must be good right?

The Story of Iron

The story of iron begins with its purpose in the human body.  Iron is an essential component of hemoglobin, the protein that carries oxygen and carbon dioxide in the blood; iron also plays a role in the transfer of oxygen in the muscle cell.  Without iron, you cannot efficiently produce ATP, the body’s primary energy source.  Yet despite its clear importance and relevance to an endurance athlete, the human body has a sophisticated mechanism for minimizing absorption of iron and for ensuring that iron is not floating around free in your blood stream.  The primary way your body stores and transports iron is as ferritin.  Remember this word.  When your ferritin levels are adequate, you have enough iron in your body.  If ferritin levels are too low, you are short on iron.

Many people throw the word anemia around without ever understanding what it means.  Anemia is simply having a low hemoglobin level.  Hemoglobin carries oxygen—thus low is not so good, and very low is just downright bad and.  Hemoglobin could be low for many reasons—it just so happens that the most common reason is inadequate iron.  Essentially, when your body is making hemoglobin, it needs iron—it’ll take it from storage (ferritin) if it’s available, if not, then hemoglobin levels drop.  If Iron is the reason for the low hemoglobin (which is most often) then you have Iron Deficiency Anemia.  However, if you have a low ferritin, but your hemoglobin is still normal, you only have iron deficiency.  The difference is important as anemia is certainly more severe, but research clearly shows that having iron deficiency without anemia can lead to fatigue, lower productivity, and ultimately could lead to reduced endurance.  In athletes, Iron Deficiency Anemia can lead to dramatic and measureable decrease in athletic performance, work capacity, reduced VO2max—and this effect is reversed when iron supplements are taken.  But here is where the message of iron seems to get confused to the point that athletes now often wonder if taking iron can improve performance regardless of current iron status.  Unfortunately taking iron if you are not deficient is completely unhelpful, and in fact, may be dangerous.   About 1 in 250 people of Northern European descent have a disease where they absorb too much iron, hemochromatosis, which can be deadly.

Measuring Iron Levels

Measuring iron levels requires a simple blood test, ferritin, is the key.  If you are going to get your iron checked, remember to ask your doctor to check the ferritin along with your hemoglobin.   There are a couple of problems with ferritin—first, it goes up, falsely, when you are under stress (i.e. sick, asthma, surgery, injury, infection, etc…), so make sure you are relatively healthy when you get it checked.  Second, there is no “agreed” upon definition for a “low-ferritin” in endurance athletes.  If this subject interests you, there is a nice review in Rodenberg and Gustafson (2007)—essentially, a good bet is if ferritin is less than 30-35  ng/mL then Iron Deficiency treatment needs to be discussed and if it’s between 35-60 ng/mL  increasing iron in your diet is a prudent step.

Although Iron Deficiency Anemia seems to be prevalent in athletes in about the same rates as the general population, iron deficiency (without anemia) seems to be higher, especially in women.  So, given the importance of iron to an athlete, how do you know if you are deficient?  If you are a serious endurance athlete, it’s probably a good idea to get your ferritin checked periodically, or at a minimum, you should get your iron checked if you are having an extended period (> 7 days) where you are not recovering well, performing subpar for where you expect to be, are feeling lethargic, or are in a higher risk group to include: females endurance athletes and male and female vegetarian athletes.   The next question is how do you treat iron deficiency and the more severe anemia.

Let me start by saying Popeye was wrong.  Don’t expect to get some killer forearms every time you eat a can of spinach!  In fact, the iron in spinach is very poorly absorbed.  There are two forms of iron that you can consume, heme iron and non heme iron.  Heme iron comes from meats, fish, poultry, and about 25% of the heme iron you eat is absorbed.  All other iron, including iron from supplements, vegetables (like spinach and other dark green leafy vegetables), is absorbed at a rate between 3-15%.  Now, you may have heard that some things like orange juice can help you absorb more iron—and this is a half truth.  The reality is that Heme Iron absorption (the iron from meat) is always around 25% but the iron from the non-heme sources, well, that depends on other things in your diet.  Certain items enhance non-heme iron absorption like Vitamin C (ascorbic acid) and some things inhibit non-heme iron absorption like coffee/tea, alcohol, and the fiber found in whole grains. 

Dietary Guidelines to Increase Iron Intake and Absorption:

  1. Eat lean meats
  2. Be creative about adding high Vitamin C foods to your non-heme iron foods (add mandarin oranges, green peppers, and tomato’s to your salad of dark green vegetables)
  3. Use a cast iron pot (a little of the iron from the pot/pan ends up in the food!)
  4. Eat foods that are higher in iron.  A good source from the USDA:
  5. Reduce coffee, tea, and alcohol intake 

Although iron supplements are available over-the-counter, they should only be used in conference with your medical provider.  You need to have a legitimate reason to take iron because there is no evidence that if you are not iron deficient, that iron will help, in fact, without iron deficiency, iron may have more risk than benefit.

In Summary:

  1. Iron is important for many biological processes that are essential to an endurance athlete
  2. An athlete in a high risk group or an athlete with an unexplained drop in performance or increase in fatigue (lasting more than 7 days) should consider getting screened for Iron Deficiency and Anemia (with a test for Ferritin and Hemoglobin)
  3. Iron Supplementation should be done in consult with a trained medical provider and not without first checking your Ferritin levels.
  4. Eating a diet rich in iron will help ensure you do not become deficient
  5. Remember that a dietitian is a great source for getting reliable nutrition information
Tp Twitter Logo
About TrainingPeaks 

The staff at TrainingPeaks includes passionate athletes, coaches and data enthusiasts. We’re here to help you reach your goals through deliberate practice, innovative training and tools to keep you achieving.