Why Runners are at Risk of Low Iron Levels
Why Runners are at Risk of Low Iron Levels

Is fatigue creeping in earlier and earlier on your run? Has your performance dropped off for no apparent reason? The culprit could well be low iron levels. 

High intensity exercise increases iron loss by as much as 70%. Runners are particularly at risk - a 2003 study showed runners were four times more prone to red blood cell breakdown than cyclists. Iron deficiency is a prevalent yet significantly under-diagnosed problem in runners, especially in those running longer distances.

What does iron do?

Your bone marrow needs iron to make hemoglobin which is the oxygen carrying protein within red blood cells. Without adequate iron your body can't produce enough hemoglobin and without hemoglobin it can’t build enough red blood cells. Low levels of hemoglobin in the blood, or low levels of the iron storage protein ferritin, can have a significant negative effect on your ability to perform exercise due to your body’s decreased oxygen carrying ability.


How am I losing iron?

There are multiple mechanisms through which iron loss in runners occurs, including sweating (iron is a constituent of sweat), blood loss in the urine and gastrointestinal tract* and foot strike hemolysis. 

Bleeding from the GI tract during running is believed to either be caused by decreased blood flow to the GI tract or increased acidity directly breaking the GI tract down and causing bleeding. Whereas iron loss through urine is largely due to the mechanical trauma in the kidney or bladder wall in addition to breakdown of red blood cells in the bloodstream (hemolysis). 


Foot strike hemolysis is caused by the repeated impact of feet hitting the ground and has been demonstrated in multiple studies to lead to the destruction of oxygen carrying red blood cells which the body will need to replace - requiring iron to do so.


Other causes of iron loss are muscle building or bleeding in the stomach or intestines due to frequent use of NSAIDs such as ibuprofen or aspirin. Haemorrhoids or piles can also impact your iron levels. Menstruating women need to pay extra care to their iron levels due to the blood lost during periods. 

What are the symptoms of low iron levels? 

The classic signs of iron deficiency, with or without anaemia, include lethargy, fatigue, low mood, and difficulty concentrating. Runners may notice symptoms that present as overtraining, reduced performance during training, impaired response to training, and ultimately poor performance. Other common signs and symptoms of low iron include 

  • pale skin
  • feeling short of breath
  • headaches
  • palpitations
  • dry and damaged hair and skin.  

Iron supplementation in pill or capsule form has been found to increase aerobic capacity (specifically VO2 max) in non-anaemic but iron-deficient runners. 

The iron in RunStrong

RunStrong contains 5mg of Iron Bisglycinate - known as the 'gentle iron' as it is kinder on the stomach and easier for the body to absorb. Iron Bisglycinate has around 90% bioavailability and is 2-4 times better absorbed by the body than the iron sulphate and fumarate which may be used in other supplements, where bioavailability is only around 27-28%.

*Your GI tract may also bleed from regular pain relievers, especially NSAIDs such as high dose aspirin or ibuprofen (see our article on Curcumin on how it can help). Blood loss in urine and stool should not be visible. If you see blood in your waste products, please make an appointment with your doctor. 

Here's the terminology to help you decipher the science behind iron and iron deficiency:

Iron is an essential element for blood production. About two thirds of the iron in your body is found in hemoglobin.

Hemoglobin, or red blood cells, is the oxygen carrier in your blood and hence essential for your muscles to function properly. It's also what gives blood its red colour. Iron is a building block of hemoglobin, so when you don’t have enough iron, you won’t be able to produce enough hemoglobin and your muscles and other tissues will not receive enough oxygen to work effectively. 

Red blood cell is a type of blood cell that is made in the bone marrow and found in the blood. Red blood cells contain a protein called hemoglobin, which carries inhaled oxygen from the lungs to all parts of the body. They then return to the lungs with carbon dioxide to be exhaled.

Ferritin is the storage protein for iron in your body. It plays a vital function in the absorption, storage and release of iron. Ferritin levels are directly proportionate to the stored iron in your body and hence are used as an indicator when testing for iron levels. Low ferritin levels indicate your body’s iron stores are low and could be a sign of iron deficiency anaemia. 

Anaemia is a condition in which you lack enough healthy red blood cells to carry adequate oxygen to your body’s tissues. There are various types of anaemia but the most common one is Iron deficiency anaemia.

Iron deficiency anaemia is caused by a lack of iron in your body. Iron is required for the body to make red blood cells (which carry oxygen to the body’s tissues). As a result, a deficiency can leave you tired and short of breath. 




Clénin, G., Cordes, M., Huber, A., Schumacher, Y. O., Noack, P., Scales, J., & Kriemler, S. (2015). Iron deficiency in sports - definition, influence on performance and therapy. Swiss medical weekly, 145, w14196. https://doi.org/10.4414/smw.2015.14196

Parks, R. B., Hetzel, S. J., & Brooks, M. A. (2017). Iron Deficiency and Anemia among Collegiate Athletes: A Retrospective Chart Review. Medicine and science in sports and exercise, 49(8), 1711–1715. https://doi.org/10.1249/MSS.0000000000001259

Halvorsen, F. A., Lyng, J., & Ritland, S. (1986). Gastrointestinal bleeding in marathon runners. Scandinavian journal of gastroenterology, 21(4), 493–497. https://doi.org/10.3109/00365528609015168

Telford, R. D., Sly, G. J., Hahn, A. G., Cunningham, R. B., Bryant, C., & Smith, J. A. (2003). Footstrike is the major cause of hemolysis during running. Journal of applied physiology (Bethesda, Md. : 1985), 94(1), 38–42. https://doi.org/10.1152/japplphysiol.00631.2001


Burden, R. J., Morton, K., Richards, T., Whyte, G. P., & Pedlar, C. R. (2015). Is iron treatment beneficial in, iron-deficient but non-anaemic (IDNA) endurance athletes? A systematic review and meta-analysis. British journal of sports medicine, 49(21), 1389–1397. https://doi.org/10.1136/bjsports-2014-093624

Bagna, R., Spada, E., Mazzone, R., Saracco, P., Boetti, T., Cester, E. A., Bertino, E., & Coscia, A. (2018). Efficacy of Supplementation with Iron Sulfate Compared to Iron Bisglycinate Chelate in Preterm Infants. Current pediatric reviews14(2), 123–129. https://doi.org/10.2174/1573396314666180124101059

Previous post Next post