Iron Deficiency in Runners
56% of runners suffer from an iron deficiency. That’s almost 2.5 times more than non-runners! Let’s look at the research on why this happens and how to fix it.
- Deep Dive
- Research
Evidence-Based
- 9 references on this page
- Expert fact-checked
- Last updated: April 29, 2025
Written by Jeff Gaudette
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?
As with most things when it comes to training, 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…
Loss of Iron With Each Step
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.
Loss of Iron Through Sweating
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.
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.
Loss of Iron from Menstruation
Finally, female runners have an especially difficult time maintaining proper iron levels since they also lose iron during menstruation
As you can see, while low iron is a health concern for a vast majority of the population, runners and endurance athletes are at a much greater risk due to these factors.
But, now the question has to be asked: how does iron deficiency impact training and performance?
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.
Unfortunately, even a cursory look at the many studies conducted on how iron levels impact training and racing are demonstrate overwhelmingly how negative it can be.
Here’s a brief breakdown of some of this research…
low iron levels Result in fewer red blood cells to transport oxygen
Red blood cells, which contain hemoglobin, 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.
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 iron levels.
The researchers were able to show that the subjects who increased their iron levels the most experienced an increase in their ventilatory threshold (they got more fit), and the people who experienced a decrease in iron levels saw their ventilatory threshold drop (they lost fitness).
low iron stores result in significant declines in lactate threshold
Ferritin is an iron storage protein; your body uses it to hold on to iron atoms until they’re needed
New research has has indicated that low ferritin levels have a persistent, performance-inhibiting effect even when hemoglobin levels are normal.
In fact, 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.
iron deficiency increases mental & physical fatigue from TRAINING
Iron deficiency has been shown in research to be directly responsible for increased levels of physical and mental fatigue from training.
This effect may be linked to an alteration of mitochondrial metabolism in the muscle that reduces physical capacity.
In fact, a 2023 study directly correlated increasing low iron levels with...
1. Overall fatigue reduction from training.
2. Improvements in mood, included reduced stress levels.
3. Reduced physiological stress responses in the iron group.
But won't simply 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 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…
Common iron-rich foods contain compounds that bind to iron
One reason is that 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.
There are also the polyphenols (which include tannins), as well as certain micronutrients and proteins in our foods that inhibit absorption.
It adds up to a broad range of foods and food ingredients that have the potential to inhibit absorption.
Consuming iron alongside other nutrients inhibits absorption
It’s not only the iron in your foods that make absorption difficult; all the foods you eat at your meal impact absorption.
Calcium, protein and caffeine have all been shown in research to inhibit the absorption of iron.
Therefore, even when trying to eat a healthy, iron-rich diet, you still may not be getting the iron you need to support your training.
Generic Iron Supplements Use the Least Effective Ingredients
Most generic iron supplements use cheaper forms of iron because they know many consumers won’t know the difference.
These cheaper forms of iron have been shown in research to be less effective than more expensive forms of iron, such as ferrous bisglycinate.
Moreover, if you’re using a multivitamin to try and increase your iron uptake, almost nothing is absorbed by the body due to the interference from the other vitamins and minerals found in multivitamins.
So what's the solution? What is the best way to increase my iron levels?
Luckily, you can put the science on your side with the cutting-edge iron supplement MAS Iron.
MAS Iron combines the most efficiently absorbed form elemental iron with clinically proven ingredients to aid in absorption.
Each ingredient tested alone with iron demonstrated the ability to enhance absorption by 30% to 400%. This is why MAS Iron performs like no other iron product on the market.
Here’s a quick look at how and why works so much better than anything else on the market…
4x Better Absorption
The addition of Alpha GPC when taking an iron supplement has been shown to increase absorption up to four times compared with taking iron alone.
Alpha GPC has also been shown to increase the absorption of nonheme iron from food sources.
30% Increase in Bioavailability
Clinical research on BioPerine has made it clear that black pepper increases the uptake of iron supplements as much as 30%.
Researchers believe this is because BioPerine enhances the bioavailability of iron supplements.
50% Fewer GI Side Effects
Not only is iron bisglycinate better absorbed than all other forms of iron, but research has shown using iron bisglycinate resulted in 50-percent fewer GI side effects compared to the same dose of iron sulfate.
Mas Iron: The scientifically recommended way to elevate your iron levels
INGREDIENTS CLINICALLY SHOWN IN OVER 75 STUDIES TO INCREASE IRON MORE THAN GENERIC IRON
All of MAS Edge’s products are made in the USA, cGMP-certified, and lab-tested for quality and transparency.
If you’re skeptical, I understand.
That’s why the results are backed with data…
What's the catch? Is it more expensive?
MAS Edge is committed to making this cutting-edge product accessible to everyone.
That’s why they’re offering a special limited-time offer of up to 20% off.
Here’s the best part—they also offers a 60-day money-back guarantee.
That means you can try it, and if you don’t see any results, you can return it for a full refund. No returns needed, no hassle, no risk.
If you’ve been suffering from low iron this is a game-changer that will finally help you get your iron levels where they need to be!
- Important Update
Since writing this article demand for MAS Iron has never been higher.
Endurance athletes who have suffered for years with low iron are sharing their experiences on social media, and stock is running low.
If you want to try this cutting-edge supplement, be sure to place your order without delay.
References
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.
McKie, A. T.; Barrow, D.; Latunde-Dada, G. O.; Rolfs, A.; Sager, G.; Mudaly, E.; Mudaly, M.; Richardson, C.; Barlow, D.; Bomford, A.; Peters, T. J.; Raja, K. B.; Shirali, S.; Hediger, M. A.; Farzaneh, F.; Simpson, R. J., An Iron-Regulated Ferric Reductase Associated with the Absorption of Dietary Iron. Science 2001, 291 (5509), 1755-1759.
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.