As runners, we usually like to pay attention to how we feel when we run and we may even track our performance by using a GPS running watch or record how far we ran and how long it took.
As long as you are following a good training plan, you should be improving, feeling stronger and running faster in your workouts.
If you start to feel sluggish, unusually tired, or start to struggle to hit the paces you were previously running with ease, it should be a red flag that something’s up.
One of the most common causes of fatigue in runners or performance declines is from runner’s anemia or iron deficiency.
In this article, we will discuss anemia and running, iron deficiency in runners, and the association with running and iron deficiency.
We will cover:
- Why Is Iron Important for Runners?
- Anemia and Running: What Is Runner’s Anemia?
- What Are Signs of Iron Deficiency In Runners?
- Iron Deficiency vs. Anemia
- Why Are Runners Prone to Iron Deficiency?
- 7 Tips to Increase Iron Levels In Runners
Let’s get started!
Why Is Iron Important for Runners?
Iron is an essential mineral that plays several key roles in the body, several of which are vital to running well.
Iron is important for runners because it is part of the hemoglobin molecule in red blood cells. Hemoglobin is a protein that carries the oxygen in your blood.
Because all of your tissues need oxygen, including your muscles when you run, it’s crucial that you have enough iron to have adequate, healthy hemoglobin molecules.
Iron is also part of the myoglobin molecule, which is a protein found in muscles that plays the crucial role of extracting the oxygen from the hemoglobin molecules once it is delivered to the muscle.
Iron deficiency limits the ability of the body to transport oxygen to your muscles when you’re running and to use the oxygen.
Finally, iron also assists in the energy-generating pathways in your muscles that convert carbohydrates and fats into ATP, or usable cellular energy.
Taken together, it can be seen why iron deficiency in runners causes feelings of fatigue and energy depletion.
What Is Runner’s Anemia?
Runner’s anemia is defined as a reduction in the concentration of iron in a runner’s blood caused by running or other strenuous endurance exercise.
It is also sometimes referred to more broadly as athlete’s anemia, though it’s most common in endurance athletes. Runner’s anemia may also be referred to as macrocytic anemia.
Runner’s anemia and iron deficiency in runners are unfortunately common.
One study that looked at the iron and hemoglobin status in 113 recreational and competitive runners found that 56% of the runners (63 in total) had systemic iron deficiency.
What Are Signs of Iron Deficiency In Runners?
One of the challenges of runner‘s anemia or iron deficiency in runners is that there are sometimes no signs or symptoms, at least for quite some time while the deficiency continues to progress in severity.
Unless low ferritin levels are picked up on a routine lab exam, runners may not know they are iron deficient until their iron stores are very low.
This is problematic because it takes quite a long time to restore iron levels to a healthy level.
Most research suggests that it can take at least three months or more to reverse runner’s anemia or iron deficiency in runners, depending on the athlete’s nutritional status, training, and ferritin levels.
The classic signs and symptoms of iron deficiency in runners, with or without concurrent anemia, include fatigue, malaise, lethargy, pallor, depressed mood and energy, difficulty concentrating, breathlessness during exercise, and reduced performance.
Another challenge with properly diagnosing iron deficiency in runners or runner’s anemia is that many of the common signs and symptoms can easily be blamed on training hard, or even just overtraining syndrome.
In addition to the feeling of fatigue and other signs of iron deficiency in runners, you may also notice the following sequela:
- Poor recovery during workouts (such as between intervals) and between workouts
- Increased heart rate during exercise
- Frequent injury
- Frequent illness
- Hair loss
- Premature fatigue in your runs relative to your fitness level
- Irritability
Iron Deficiency vs. Anemia
There’s a lot of confusion about anemia and iron deficiency in runners, and many runners who are told they have low iron aren’t sure if that’s the same thing as anemia.
Anemia is the general term for a condition in which your red blood cell count is abnormally low.
There are several types of anemia, with iron-deficiency anemia being one of them.
However iron deficiency doesn’t necessarily result in a diagnosis of anemia or iron-deficiency anemia.
If iron deficiency is caught early enough, iron stores in the body, known as ferritin levels, can be replenished. This will prevent the progression to iron-deficiency anemia.
Research suggests that runner’s anemia and iron deficiency in endurance athletes progresses through three stages of increasing severity:
Stage 1: Iron Depletion or Mild Iron Deficiency
In the first stage of iron depletion, ferritin levels in endurance athletes drop to below 35 µg/mL, but hemoglobin and transferrin levels are normal.
The athlete will still feel normal, but efforts should be made to increase ferritin levels above the 35 µg/mL mark.
Stage 2: Iron Deficient
In the second stage, the athlete is iron deficient but does not have anemia.
Blood work will reveal ferritin levels below 20 µg/mL, and although hemoglobin will still be normal, transferrin levels will be low.
Runners with iron deficiency may start to feel more exhausted while running, or as if they are not recovering well between workouts.
Stage 3: Iron-Deficiency Anemia
If efforts are not made to consume more iron and restore ferritin levels, iron deficiency can escalate to iron deficiency anemia.
Ferritin levels will drop below 12 µg/mL, and transferrin and hemoglobin levels will be low.
In this stage, anemic runners will notice signs and symptoms of anemia, such as exhaustion, breathlessness during exercise, and poor endurance.
Why Are Runners Prone to Iron Deficiency?
Runner’s anemia wasn’t so named by accident; it points to the fact that runners are prone to iron deficiency and possibly anemia from running.
Intense endurance exercise increases the excretion of iron through sweat, urine, and feces, because red blood cells are lost through these means.
Running Causes Foot-Strike Hemolysis
Distance running can cause foot-strike hemolysis, which refers to damage to red blood cells (which carry iron) from the impact of landing on your feet with each running step.
Essentially, every time your feet strike the ground during your running stride, some number of red blood cells are damaged due to the shock and impact.
Foot-strike hemolysis reduces viable red blood cells, placing runners at a higher risk of becoming an anemic runner.
Running Increasing the Excretion of Iron and Red Blood Cells
A study looking at the iron status of 45 male distance runners found that 23 out of 45 runners had low serum ferritin values (< 35 ng/mL).
The study revealed that the main reason for iron deficiency in these runners was due to blood loss in stool.
When the runners were not training, they had 1.5 mL blood loss per day in their stool, which is normal iron excretion.
However, under intensive training conditions, fecal stool blood loss increased up to 4.9-6.6 mL per day, which is roughly 3-5 times more blood loss.
Running Increases the Production of Hepcidin
Another factor that causes low ferritin levels in endurance athletes is that vigorous exercise increases the body’s production of hepcidin, a molecule that blocks the absorption of iron.
One study found that hepcidin levels were increased for up to 24 hours in endurance athletes after a strenuous workout. These factors makes anemia from running is a possibility.
Other Risk Factors for Iron Deficiency in Runners
Female runners who menstruate are at an increased risk of iron deficiency or runner’s anemia due to the monthly loss of blood through menstruation.
Note that in addition to the blood loss through menstruation, women are at a greater risk of iron deficiency because they tend to not consume as many iron-rich foods, especially heme sources of iron.
Vegetarian and vegan runners are also at an increased risk of iron deficiency because the richest and most readily-absorbed sources of iron are from animal meats.
Iron from animal sources is called heme iron, while iron from plant sources is called non-heme iron.
According to the National Institutes of Health, the bioavailability of heme iron is about 14-18% compared to 5-12% for non-heme iron.
Many non-heme sources of iron are high in phytates, fiber, and certain polyphenols, which can interfere with iron absorption, which is partially attributable to this difference in bioavailability of iron from plant-based foods.
7 Tips to Increase Iron Levels In Runners
If you have been diagnosed with runner’s anemia, or iron deficiency, it is important to work with your doctor to find an effective treatment plan.
Recovery can take up to six months or more, depending on the severity of your condition.
Runners with iron deficiency that has not progressed to iron deficiency anemia are typically able to recover faster, provided they still take aggressive measures to increase iron levels.
The following are a few tips to increase iron levels:
#1: Eat Foods High In Iron
Aim for foods high in heme iron such as red meat and organ meats, though plant-based sources like lentils, iron-fortified cereals, and dark, leafy greens are good for vegetarians.
#2: Take an Iron Supplement
Iron supplements are usually necessary to reverse runner’s anemia. Speak with your doctor about the dosage you need.
#3: Cook In Cast-Iron Pans
Cooking in cast-iron skillets and cookware has been shown to increase serum ferritin levels because microscopic flecks of iron come off the cast-iron cookware and get absorbed into your food.
#4: Don’t Forget Micronutrients
Certain micronutrients can enhance the absorption of iron, particularly vitamin C and to a lesser extent, vitamin A.
Therefore, pair your iron-rich foods with foods high in vitamin C and A.
For example, have red and orange bell peppers with steak or lentils, or a glass of orange juice with iron-fortified breakfast cereal.
#5: Rest or Cross Train
One of the ways that runners lose iron is through footstrike hemolysis.
Switching to a lower-impact and lower-intensity type of exercise, such as swimming or cycling, can reduce blood loss.
It often makes sense to back off the intensity of your training as well.
Not only is this usually mandated by your body because of low energy and poor oxygenation of your tissues, but it also slows the rate of iron deficiency if you can ease up on your workouts.
Vigorous exercise causes a greater excretion of blood in the stool and sweat, and increases the production of hepcidin, which blocks iron absorption.
#6: Cut Out Coffee and Tea
The tannins in coffee and tea inhibit iron absorption, so it’s important to avoid drinking these beverages at the same time that you take your iron supplements or eat iron-rich foods.
#7: Time Your Supplements
As mentioned, vitamin C enhances the absorption of iron, so take your iron supplement at the same time as a vitamin C supplement.
On the other hand, calcium inhibits the absorption of iron, so spread out these supplements by at least four hours, and avoid eating calcium rich foods at the same time as taking supplementary or dietary iron.
A diagnosis of runner’s anemia or iron deficiency for runners doesn’t have to be a death sentence, but it’s important to work diligently to restore iron levels if you do find yourself dealing with low iron.
If you would like to take your training down a notch and switch out some of those runs for a lower impact cardio, check out our low-impact cardio ideas for runners.
