Iron Deficiency in Runners

iron deficiency runners
56% of runners suffer from an iron deficiency. That's almost 2.5 times more prevalent than issues of low iron in non-runners!

Did you know that 56% of runners suffer from an iron deficiency? That’s almost 2.5 times more prevalent than issues of low iron in non-runners!

In fact, outside of training deficiencies, low iron is one of the most common reasons for poor results during workouts and races.

So, why are iron deficiencies so common in runners and why is iron so important?

That’s what we are going to discuss in this article. You’ll learn…

  • Why exactly runners are so prone to issues of low iron
  • The impact low iron has on your training and overall health
  • Why it’s so difficult to absorb iron (and what to do about it)

Why are runners so prone to iron loss?

The research has shown that runners lose more iron than non-runners for a multitude of reasons. Here’s a look at some of the big reasons why…

1. You lose iron with each step.

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.

Since runners are taking thousands of extra steps per day, the extra loss of iron compared to non-runners is significant.

2. You lose iron through sweat

According to a study published in the American Journal of Clinical Nutrition, iron loss is directly related to the volume of sweat lost and has been calculated at 22.5 micrograms iron per liter of sweat.

Perhaps another way to phrase the calculation to make it more relatable is that studies suggest that runners may lose about 1.2 milligrams of iron with each gallon of sweat, making up a loss of about 0.3 milligrams of iron per liter of sweat.

It may not seem like much, but daily runs in hot and humid weather have a big impact on your iron levels.

3. Loss of iron from GI tract

Third, 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.

4. Loss of iron from menstruation

Finally, female runners have an especially difficult time maintaining proper iron levels since they also lose iron during menstruation.

The impact of low iron on training and performance

Now that we know why runners have such prevalent issues with low iron, it’s time to look at what this means for your training.

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.

A 2011 study by Diane DellaValle and Jere Haas investigated the relationship between serum ferritin levels and performance in rowers.

After comparing the rowers best times 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.

A 2007 study by P.S. Hinton and L.M. Sinclair at the University of Missouri followed twenty male and female athletes who had low serum ferritin levels

The researchers 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).

This is just a cursory look at the many studies that directly link low iron with a decline in training and racing performance. Suffice it to say the evidence is overwhelming.

Will eating more iron-rich foods solve the problem?

One of the major issues with getting enough iron is that it’s been shown to be notoriously difficult for the body to absorb and utilize.

In fact, iron bioavailability is estimated to be only 14% to 18% for those consuming animal products and as low as 5% to 12% for plant-based eaters.

This is the result of many factors, including…
  • Iron-rich plant foods often contain phytates, compounds that bind to iron, rendering it inaccessible to the body as it travels through the digestive tract.
  • Many common foods such as calcium, protein and caffeine have all been shown in research to inhibit the absorption of iron.
  • There are also the polyphenols (which include tannins), as well as certain micronutrients and proteins in our foods that inhibit absorption.

This is why it’s usually recommended runners be on an iron supplement unless they’ve had their levels tested and they know they are above normal.

The really cool thing about iron supplementation is that it’s one of the few supplements you can directly measure through blood work.

I saw a huge impact in my iron levels when I switched and they’ve got lots of data from InsideTracker and other blood-monitoring companies showing the difference in ferritin levels.

I definitely encourage you to check out the research and results. 

I’ll follow-up with an article on iron-rich foods you can add to your diet, what foods to avoid and the best times to consume iron for maximum results.

Don't let low iron slow you down

MAS Iron was developed for a single purpose: to be the most well-absorbed, cutting-edge iron supplement for runners who want to ensure they have the iron they need to perform their best.


Risser, W. L.; Lee, E. J.; Poindexter, H. B.; West, M. S.; Pivarnik, J. M.; Risser, J. M.; Hickson, J. F., Iron deficiency in female athletes: its prevalence and impact on performance. Medicine & Science in Sports & Exercise 1988, 20 (2), 116-121.

Hinton PS, Giordano C, Brownlie T, Haas JD. Iron supplementation improves endurance after training in iron-depleted, nonanemic women. J Appl Physiol (1985). 2000 Mar;88(3):1103-11

DellaValle DM, Haas JD. Impact of iron depletion without anemia on performance in trained endurance athletes at the beginning of a training season: a study of female collegiate rowers. Int J Sport Nutr Exerc Metab. 2011 Dec;21(6):501-6

Hinton PS, Sinclair LM. Iron supplementation maintains ventilatory threshold and improves energetic efficiency in iron-deficient nonanemic athletes. Eur J Clin Nutr. 2007 Jan;61(1):30-9.

Dellavalle, D. M.; Haas, J. D., Iron Supplementation Improves Energetic Efficiency in Iron-Depleted Female Rowers. Medicine & Science in Sports & Exercise 2014, 46 (6), 1204-1215.

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Waalen, J.; Felitti, V. J.; Gelbart, T.; Beutler, E., Screening for hemochromatosis by measuring ferritin levels: a more effective approach. Blood 2008, 111 (7), 3373-3376.