Putting the "Iron" in IRONMAN

News and Updates

by Dr. Nikita Fensham

When you think of iron, you may think of Popeye! While spinach might not be the best source, the guy certainly exuded strength and energy. In fact, iron is crucial to many of the reactions that happen in your body, including those involved in energy metabolism. It is also the centrepiece of hemoglobin, which carries oxygen around your body in red blood cells. There are plenty of other functions as well, involving bone and reproductive organ function, but for the purposes of keeping to word limits, we will stick with the ones you care about the most — the ones that are going to make you faster.

Athletes in general — and perhaps women more so because of the menstrual cycle — are more at risk for iron deficiency than the general population. This is because of increased losses that happen due to reduced blood flow to the gastrointestinal tract and subsequent temporary bleeding, with minor contributions from sweat and urine. Foot-strike breakdown of red blood cells is less likely to play a role as the iron released is taken up again. Due to the increased training demands, the risk of a mismatch in nutrition, especially in vegetarian athletes, may also contribute to the risk of iron deficiency. Finally, it is becoming increasingly recognised that a hormone released by the liver, called hepcidin, is upregulated in athletes (meaning an athlete’s cells are more sensitive to it): its role is to block iron absorption from the gut and recycling from immune cells, which further exacerbates the situation!

So how do you know if you are iron-deficient? This is where you book a doc appointment and get some blood tests.

Too often we as ambitious, perfectionist, pedantic triathletes focus on adding more “one-percenters” to our arsenal, rather than building the foundation first. The aero helmet, the [insert name brand here] running shoes, the goggles that tell you how slow you are while you’re swimming… all giving us false hope, or perhaps false ego, that we will perform better.

But while these debits to our bank accounts seem justified, we hesitate to spend extra dollars on groceries or appointments with the doc to optimise our health. Sadly too, however, is that most doctors are taught to manage your illnesses, not your health; so I acknowledge that booking an appointment with the goal of being better than good is often met with a blank face.

Nevertheless, I think you should be empowered to be a partner with your doctor, rather than a “patient”. So this article is designed to get into the weeds of iron for athletes, the testing, and what you can do if things aren’t quite right.

A blood test is the most reliable and effective way of determining iron deficiency. (Photo by ThisisEngineering RAEng on Unsplash)

Side note: some tests are unreliable in athletes even though they would be used in the general population to diagnose iron deficiency. You may be deficient in iron but your hemoglobin levels are still maintained in the meanwhile, so you would not be considered “anemic”. Because ferritin, which is the storage form of iron, is upregulated in response to inflammation (and exercise, by implication), it is not reliable on its own in athletes. Furthermore, the iron level in the blood isn’t a great marker either as it is different depending on the time of day and is affected by red blood cell breakdown.

However, if you are indeed iron deficient, evidence suggests that addressing it through food or supplementation is important for both your health and performance.

So the key markers to ask your doc for are:

1. Ferritin – although unreliable on its own, it is useful when used along with other markers to look at iron stores.

2. Hemoglobin (Hb) – this is necessary to see if you are anemic or not, and tells your doc about the severity of the iron deficiency. It can also alert the doc to other causes of anemia that do not involve iron.

3. Mean corpuscular volume (MCV) and mean cellular hemoglobin (MCH) – this is getting a bit technical but these tell us about the “quality” of your red blood cells in terms of size and how much hemoglobin is inside, and can guide your doc in determining your type of anemia, if present, or how much of an effect the iron deficiency is having on your red blood cell production in your bone marrow.

4. Transferrin saturation – transferrin is what transports iron in your blood, almost like a hiker and his backpack! So this marker gives us an idea about the number of hikers in relation to the number of backpacks – if its low, then there are too few backpacks around for the hikers to be useful.

5. Soluble transferrin receptor – this is a bit of a bonus if you can get your doc to order it as it tells us more about the “functional” pool of iron as opposed to just the stores.

A quick look at numbers: in athletes, a ferritin level less than 35ug/l is considered iron-deficient, and when it drops below 20ug/l with a transferrin saturation of less than 16% then the bone marrow red blood cell production is becoming affected. Anemia is an Hb less than 115g/l. Depending on your results and your history (e.g. sex, menses, diet, altitude training), getting tested quarterly to annually is recommended.

Great, so what do you do now? Well, if you’re iron sufficient, then keep doing what you’re doing. The recommended dietary intake is 8mg for males and 18mg for females, but these are general population guidelines to avoid deficiency and there are no athlete-specific guidelines as yet to account for the potentially increased requirements.

Green leafy vegetables are a good source of iron – but iron from meat is better absorbed. (Photo by engin akyurt on Unsplash)

Heme sources of iron, such as meat and seafood, are better absorbed than non-heme sources, which means that vegetarian athletes need to pay extra attention to getting in enough iron. Other factors such as vitamin C (enhances absorption of non-heme sources) and tea, coffee, and dairy (which inhibit absorption of iron) should also be considered. Finally, that hepcidin hormone we mentioned earlier peaks at 3-6h post-exercise, so getting in your iron in the 60min post-exercise might be a good strategy to employ.

If you are iron deficient, then you have three options: address dietary intake (I suggest working with a dietician here), oral supplementation, or intravenous supplementation. Intravenous is highly effective but you do need a doc here as it carries some risks as well. Oral supplementation with enterically coated (to avoid gastrointestinal distress) slow release ferrous sulphate is most widely tolerated. Which option applies to you depends on your lab results and history, so it is important to consult the experts.

Hopefully, you are feeling more informed and empowered at the end of this article. I’m a strong believer in taking charge of your health and becoming a partner with your healthcare team in working towards a more optimal human being, rather than only seeking help when the wheels have already come off.

But, being a partner also means respecting the boundaries of your knowledge: be engaged, ask questions, don’t be afraid to ask for testing, but be guided by professionals in the area. Just as iron deficiency will hamper your health and performance, iron overload through unnecessary supplementation is just as dangerous.

There you go folks: everyone can be an IRON(wo)man!


1.         Burden RJ, Morton K, Richards T, Whyte GP, Pedlar CR. Is iron treatment beneficial in, iron-deficient but non-anaemic (IDNA) endurance athletes? A systematic review and meta-analysis. British Journal of Sports Medicine. 2015;49(21):1389-97.

2.         Clénin G, Cordes M, Huber A, Schumacher YO, Noack P, Scales J, et al. Iron deficiency in sports – definition, influence on performance and therapy. Swiss Med Wkly. 2015;145:w14196.

3.         McCormick R, Dawson B, Sim M, Lester L, Goodman C, Peeling P. The Effectiveness of Transdermal Iron Patches in Athletes With Suboptimal Iron Status (Part 1). International Journal of Sport Nutrition and Exercise Metabolism. 2020;30(3):185-90.

4.         McCormick R, Dreyer A, Dawson B, Sim M, Lester L, Goodman C, et al. The Effectiveness of Daily and Alternate Day Oral Iron Supplementation in Athletes With Suboptimal Iron Status (Part 2). Int J Sport Nutr Exerc Metab. 2020:1-6.

5.         Peeling P, Dawson B, Goodman C, Landers G, Wiegerinck ET, Swinkels DW, et al. Effects of exercise on hepcidin response and iron metabolism during recovery. Int J Sport Nutr Exerc Metab. 2009;19(6):583-97.

6.         Sim M, Garvican-Lewis LA, Cox GR, Govus A, McKay AKA, Stellingwerff T, et al. Iron considerations for the athlete: a narrative review. European Journal of Applied Physiology. 2019;119(7):1463-78.


This article should not be considered medical advice and is instead intended to be the opinions of the author. Always seek independent medical advice before making any decisions based on your health.


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