Symptoms of Iron Deficiency in Runners
Determining if you have an iron deficiency can be somewhat difficult if you’re a runner.
The main symptom is fatigue and a slight shortness of breath. You can appreciate the dilemma here if you’re a runner – you’re always tired after a workout and shortness of breath defines our preferred mode of transportation. I remember training for my first marathon and walking around like a zombie most of the day – it wasn’t iron related, but kick me if it didn’t feel that way.
However, it is best to get your levels checked by your physician if you’re worried.
It’s a very simple and quick blood test that most doctors would be willing to provide if you tell them you’re running a lot of miles and feeling more fatigued than usual.
Even if you are not iron deficient, you can establish a good baseline for your iron levels, which could help you identify an iron problem down the road.
If you do get your iron levels tested, always go before running. Dehydration will make your iron levels appear higher than they are. Likewise, don’t drink a gallon of water before you head to the lab or your levels will be artificially low.
What Do The Numbers Mean
The major iron status tests of interest to runners are: hemoglobin, hematocrit, red blood cells (rbc) and ferritin.
In my experience coaching elite runners, a ferritin level less than 30 ng/ml in women and less than 40 ng/ml in men is often enough to reduce performance.
While these numbers are not considered low by medical professionals, they can impact your running.
If I am Iron Deficient, Does That Mean I Have Anemia?
There is some disagreement in the world of sports medicine over whether low ferritin levels by themselves can impair your performance, and whether runners need more ferritin than the general population.
A substantial number of athletes are iron-deficient without being anemic—i.e. their serum ferritin levels are low, but their hemoglobin levels are still normal. Historically, most doctors and researchers have argued that it’s not possible for performance to be impaired if you are iron deficient but non-anemic (normal hemoglobin).
If your hemoglobin levels are normal, you shouldn’t suffer any negative effects from an inability to get oxygen to your muscles.
How Runners Lose Iron
Runners lose more iron than non-runners for a multitude of reasons.
Through your feet – First, a process called foot strike hemolysis occurs in runners, especially those who run high mileage. Foot strike hemolysis is a process where red blood cells are damaged when the foot hits the ground, thus reducing your hemoglobin levels.
Through Sweat – Iron is lost through sweating. While the amount of iron loss isn’t staggering, for a runner working out in hot and humid conditions, the losses can easily add up.
Through the intestines – Loss of iron through the GI tract (primarily the stomach or large intestine) is a problem for some athletes. Iron loss through the GI tract is fairly minor, but there may be a cumulative effect over months of running that leads to iron deficiency.
Female Runners – Finally, female runners have an especially difficult time maintaining proper iron levels since they also lose iron during menstruation.
Why Is Iron Important for Runners
Red blood cells, which contain hemoglobin (an iron-containing protein), transport oxygen to your working muscles when you run.
If you have low iron levels, you will generate fewer red blood cells and your hemoglobin levels will decline. Therefore, less oxygen will be transported to your muscles, and running performance will suffer.
In addition, another part of the iron equation are your ferritin levels.
Ferritin is an iron storage protein; your body uses it to hold on to iron atoms until they’re needed, whether that’s for making hemoglobin or any of the other proteins in your body that include iron.
How Does a Low Ferritin Level Impact Performance?
New research has has indicated that low ferritin levels have a persistent, performance-inhibiting effect even when hemoglobin levels are normal.
A 2011 study by Diane DellaValle and Jere Haas investigated the relationship between serum ferritin levels and performance in rowers.1 After conducting blood tests on 165 female collegiate rowers, DellaValle and Haas determined that 10% were anemic (low ferritin and low hemoglobin), 30% had low ferritin but normal hemoglobin, and the rest had normal values for both. The threshold for what constituted “low ferritin” was set at 20 ng/mL (or µg/L; these units are identical).
After comparing self-reported best time over 2 km in the past six months, the researchers found that the low ferritin/normal hemoglobin group was 21 seconds slower than the rowers with normal ferritin.
By using a technique called multiple regression analysis, DellaValle and Haas were able to demonstrate that the difference in 2 km time between the groups remained statistically significant even when the boundary defining “low ferritin” was raised to 25 ng/mL. This is more than twice the traditional boundary of 12 ng/mL that is used for the general population.
Will an iron supplement improve performance in non-anemic, low ferritin runners?
A 2007 study by P.S. Hinton and L.M. Sinclair at the University of Missouri followed twenty male and female athletes who had serum ferritin levels lower than 16 ng/mL—somewhat lower than DellaValle and Haas’s threshold.2 The athletes were split into two groups; one got an iron supplement; the other got a placebo. After six weeks of training, individual responses were all over the board, but they did have some interesting findings.
Hinton and Sinclair were able to show that the subjects who increased their ferritin levels the most experienced an increase in their ventilatory threshold (they got more fit), and the people who experienced a decrease in ferritin saw their ventilatory threshold drop (they lost fitness).
Another study by DellaValle and Haas, published in 2014, provides further evidence that iron supplements can boost fitness in people with low ferritin but normal hemoglobin.3 The structure of this study was very similar to Hinton and Sinclair’s: forty female rowers were split into two groups; one received an iron supplement, while the other received a placebo. The rowers underwent a 4 km time trial, trained for six weeks, then completed another 4 km time trial.
Though there was no difference in time trial performance between the two groups, the iron supplement group improved their rowing efficiency more than the placebo group, and had lower lactate levels during the first few minutes of the time trial as well.
Why does low ferritin appear to impair performance slightly even when hemoglobin levels are normal?
Some scientists hypothesize that low ferritin levels can cause a drop in your body’s ability to process lactate, since some of the proteins that are important for lactate metabolism use iron too, but there isn’t any solid evidence on this as of right now.
Regardless, these studies indicate that ferritin levels can play a role in performance, even when hemoglobin levels are normal.
DellaValle and Haas’ work also indicates that endurance athletes should probably shoot for a serum ferritin level of at least 20-25 ng/mL.
What’s the bottom line?
If you’ve been feeling like your performances in workouts and races aren’t quite where they should be, think about getting your serum ferritin checked, and if it’s below 25 ng/mL, talk to your doctor about taking an iron supplement.
How to Supplement
As you can see, the cards are stacked against you as a runner when it comes to maintaining your iron levels. Therefore, it is important that you consciously monitor your iron intake through your diet and with supplements if you already have low levels.
Iron rich foods
Good food sources of iron include: lean meat, oysters, egg yolk, dark green leafy vegetables, legumes, dried fruit, and whole grain or enriched cereals and bread.
If you are worried about your iron levels, avoid drinking coffee, milk, or tea with iron-rich meals, as calcium inhibits iron absorption.
In addition, you should drink vitamin c with your iron rich foods since vitamin c aids in absorption.
Supplementation
I suggest most runners be on an iron supplement unless their iron levels have tested high in the past.
- When you go to buy an iron supplement, make sure it’s in the form of ferrous sulfate. Usually, you can find iron at a health store like vitamin world or a GNC. You can take iron in a pill or liquid form, whichever works best for you. Pills are often easier to find, but liquid absorbs better.
- Like when you’re eating, avoid calcium an hour before and an hour after taking your iron. Likewise, take with vitamin c (a pill or orange juice) and a b-complex supplement to aid absorption.
- I suggest taking your supplement before bed. Iron supplements can sometimes cause minor stomach issues and gas. If you take them at night, it probably won’t bother you.
- If you’re just looking to maintain your iron levels, supplement with 30mg. If you have tested for low iron, supplement with 60mg.
Can Your Iron Levels be Too High?
Now we know that your ability to run fast times in a race can be inhibited when your ferritin is low, even if your hemoglobin levels are normal.
You might be wondering:
“Well, why doesn’t everyone just take an iron supplement? Better safe than sorry!”
Not so fast. In addition to the problems of iron deficiency, distance runners also need to be aware of iron overload. Though rare, iron overload—more properly referred to as hemochromatosis—can cause serious health problems. Getting overloaded on iron isn’t simply a function of getting too much iron in your diet; typically your body is pretty good at regulating its iron levels automatically.
Hemochromatosis and the risk of long term health damage
When your body’s iron levels are high, your intestines absorb less iron from the foods in your diet, keeping your overall iron stores from getting too high, and the converse happens when iron levels are low.1
However, in people with hemochromatosis, a genetic mutation turns off this self-regulating mechanism, and your body absorbs an abnormally high amount of iron from your diet all the time. This can lead to very high blood ferritin levels, and eventually organ damage.
The genetic mutation associated with hemochromatosis is relatively common as far as genetic disorders go; one scientific paper estimates that as many as one in 100 people of Northern European descent could carry the genes for hemochromatosis.2 The mutation is virtually unknown in non-Europeans.
Historically, doctors recommended genetic screening for hemochromatosis among people of European ancestry, given how common the genetic mutation is. However, more recent research has demonstrated that the proportion of people who actually exhibit symptoms of hemochromatosis is lower—somewhere around 2 to 5 percent of the gene-carrying population, according to a study by Jull Waalen and colleagues at The Scripps Resaerch Institute in California.3
Here’s the deal:
Instead of an expensive and complicated genetic test, Waalen et al. recommend testing ferritin levels to screen patients for hemochromatosis, since one of the hallmark signs of the problem is sky-high ferritin levels. This works out conveniently for runners who are considering whether or not they need to be on an iron supplement too, since you’ll want to get your iron checked regardless.
In a 2004 article, medical doctors Heinz Zoller and Wolfgang Vogel caution that iron supplements should be used only after confirming that an athlete really does have iron-deficiency anemia.2 And of course, the best way to do this is with a complete blood count (to find hemoglobin levels) and a ferritin test.
The laboratory-normal range for ferritin is around 12-300 ng/mL for men and 12-150 ng/mL for women—the exact numbers depend on which reference you consult—but recall that new scientific research has shown that distance runners ought to have a minimum of 25 ng/mL to prevent poor performance.4
Conclusion
Fortunately, it’s hard to miss iron overload—according to Waalen et al., real problems only arise when ferritin levels are over 1000 ng/mL. If this is the case, your doctor will talk with you about how to manage your condition.
Iron supplements can do you a lot of good, but only if you need them. The fastest, cheapest, and easiest way to find out if you should be taking an iron supplement is by getting your serum ferritin levels checked.
If they’re low, or borderline-low, an iron supplement is a good idea. If your ferritin is normal, great! You’re getting enough iron in your diet already and you don’t need to bother with the trouble and expense of taking a supplement. Finally, if your ferritin is abnormally high, make sure you talk to your doctor.
Remember to listen to our podcast episode with one of the researchers of iron studies, Pam Hinton, who shared even more detail on iron supplements, and how to make sure you include enough.
By paying attention to your iron levels, getting tested if you think you may be low, and increasing your iron intake through diet or supplements, you can avoid lulls in your training and boost performance.
Do You Absorb More Iron Cooking in a Cast Iron Pan?
One method you might have heard about to increase the amount of iron in your diet is cooking your food using cast iron cookware. Absorbing iron from your pots and pans sounds completely crazy—is there any truth to this, or is it just a running old-wives’ tale?
Putting this “myth” to the test
Conceptually, the proposed process for iron from your cookware ending up being absorbed by your body as a nutrient is as follows: individual atoms of iron either flake off or are chemically absorbed by the food you’re cooking, which makes its way to your stomach where the iron gets absorbed and eventually put to use making hemoglobin, ferritin, and other iron-containing proteins.
Fortunately, testing out whether this actually happens pretty easy. All we’d need to do is cook some food in cast iron cookware, check its iron content, and compare this to the same meal cooked in non-iron cookware.
This exact experiment was described in a 1991 article in the Journal of Food Science by Y.J. Cheng and H.C. Brittin.2 An initial experiment, published in 1984, had confirmed that some iron is transferred to food cooked in cast-iron cookware, and that more acidic foods have a greater propensity to absorb iron.3
Cheng and Brittin’s study set out to get a more accurate picture of exactly how much iron is absorbed by two commonly-eaten and fairly acidic foods: applesauce and spaghetti sauce.
Using standard ingredients from a supermarket, Cheng and Brittin cooked up one hundred batches of applesauce and one hundred batches of spaghetti sauce. Fifty batches of each were cooked in cast-iron pots, and fifty were cooked in CorningWare glass dishes, which of course do not contain iron.
A small sample of each batch was analyzed for its moisture content and iron content—it was important to control for moisture content because one cooking method might drive off more water, making it appear as though there was more iron in the food, when really it was merely a concentrating effect.
Cheng and Brittin’s data confirmed that both applesauce and spaghetti sauce pick up a measurable amount of iron after being cooked in cast iron cookware.
When the foods were cooked in the glass dishes, their iron content was negligible: less than one milligram of iron per 100 grams of food (about 3.5 ounces). But when the foods were cooked in cast-iron pots, the spaghetti sauce picked up about 2 mg of iron per 100g of sauce, and the applesauce picked up 6 mg per 100g.
For reference, a typical serving of each of these—about one cup—would be around 250 g, and the recommended daily intake of iron is 8 mg for men and 18 mg for women. A typical iron supplement contains 45 mg of iron.
The moisture content of the dishes did not differ between the cookware, meaning the increase in iron content represents a true transfer of iron from the cast iron pot into the food.
The ability of cast iron cookware to impart just a little bit of iron to foods cooked in it is very convenient if you’re looking to boost your iron intake.
The amount of iron transferred to the food happens to be just enough to be a significant source of dietary iron, but not enough to pose any risk of iron overload in healthy people.
Conclusion
If you are trying to increase your intake of iron, try doing some of your cooking in cast iron pots and pans. You’ll get best results by cooking moist, acidic foods like applesauce, chili, tomato sauce, stew, and scrambled eggs.
As a rough rule of thumb, one cup of these foods will gain about six to eight milligrams of iron after being cooked in cast iron cookware.
Dry, non-acidic foods like pancakes, rice, and green beans don’t pick up much iron from a cast iron pot. Of course, your diet should also contain plenty of foods that naturally contain iron, like red meat, beans, lentils, and spinach.
Recent Research on Iron Deficiency in Runners and Impact on Performance
In this in-depth podcast episode, we talk with Pam Hinton, associate professor and director of graduate studies, along with being in the Department of Nutrition and Exercise Physiology at the University of Missouri.
Pam has recently covered an amazing study about iron and endurance athletes, the potential negative consequences, and how it can affect your health and endurance.
Surprisingly, even if you’re only mildly iron deficient, it still negatively affects your performance. So what can you do? Listen and see for yourself! We include:
- What numbers to look out for when checking for iron deficiency
- How to avoid iron toxicity
- The best foods to eat to increase your iron uptake
- Why endurance athletes are at increased risk for iron deficiency
- What signs to watch out for in iron deficiency
Besides iron, there are other vitamins and minerals that are crucial to your bodies well-functioning. Pam shares her top supplement recommendations for endurance athletes, and the best sources of minerals and vitamins you may not be getting enough of.
Coaches Answer Your Questions About Iron for Runners
The following are episodes from our daily coaching podcast, where our expert team of coaches answers your questions.
These bite-sized, 10-min podcasts are filled with amazing training and nutrition nuggets that you can consume on your run or in the gym.
We’ve included all of our iron supplementation for runners episodes below, but you can also subscribe to get your daily dose of running guidance.
Foods that Help You Absorb More Iron
Why iron is so important for runners? Which foods increase or hinder iron absorption? What is the difference between heme and non-heme iron? Coach Claire explains in today’s episode.
Ideal Iron Levels For Runners, Why It's Important and How to Supplement
Coach Jeff is back on the daily podcast and today he talks about iron deficiency in runners. Why iron is so important for runners? What are the symptoms of low iron levels? How to supplement properly and which form is best? Find out in today’s Extra Kick podcast episode.
What should you do when your iron (ferritin) levels are low and you can't seem to get them up while you continue running?
What should you do when your iron (ferritin) levels are low and you can’t seem to get them up while you continue running?
Should you rest? If so, what happens to your fitness?
If you try to train through, how long will it take your iron levels to return to a healthy level?
Coach Claire helps you figure out this complex issue in today’s daily podcast episode.
