Iron, The Athlete, and Food
It is easy to forget about the little guys in sports nutrition. Sure, calories and macronutrients provide the energy and building blocks for training, performance and life. And supplements come with a great tag line. But vitamins and minerals make everything in our body work. And iron is a key example of this. So, in this blog we look at iron considerations for the athlete.
Why should we care about iron as an athlete (and a human!)?
Iron has many roles in the body. But to draw out ones that will peak the interest of most athletes …
Iron has a fundamental role in aerobic energy production in the body. It is what carries oxygen in red blood cells to the muscles and all the other tissues in the body, so they can produce energy aerobically. And it is needed to produce energy efficiently in the cells once that oxygen has been delivered.
Iron is also necessary for proper functioning of the immune system. And health is the first principle of sports nutrition. A sick athlete misses more training days, can’t train to their full potential and / or can’t recover effectively. And ultimately this can impact performance in competition.
In addition, iron has a role in cognitive development and performance. So, when you need to be top of your game with fast reaction times, iron may have a role.
Athlete’s may be at higher risk of iron deficiency
Athletes and the recreationally active may have higher iron requirements than their sedentary counterparts. This is because training causes adaptations that increase total blood volume and red blood cell count in order that more oxygen can be delivered to working muscles. And more red blood cells = more iron needed. This is going to be most significant in sports requiring a big aerobic ‘engine’, like middle distance and endurance sports.
In addition, athletes typically experience higher iron losses through sweat. Runners and other sports where the body ‘pounds’ against a surface can also lose more iron through the damage to red blood cells on impact. And endurance athletes may lose iron through bleeding in the gut that happens as the gut stops functioning as effectively in long duration exercise.
And if that wasn’t enough, athletes may not absorb iron from the diet as effectively in the hours after exercise: the inflammatory response that occurs after exercise increases the levels of an inhibitor of iron absorption in the gut.
Within athletes, at particular risk are:
Female athletes with a menstrual cycle, because of monthly blood losses during menstruation
Vegetarian or vegan athletes, as plant derived iron (non-haem iron) is not absorbed or utilised as effectively as animal derived (haem) iron. Also, omniverous athletes who don’t eat sufficient haem iron. More information on this in the final section of this blog
Endurance athletes, as gut function and the inflammatory response is typically highest the longer the duration of exercise
Calorie restricted athletes, if intake of dietary iron is inadvertently reduced along with calorie intake and low carbohydrate intake increases the inflammatory response following exercise
Extended use of non-steroidal anti-inflammatories, as these can cause bleeding in the gut similar to long duration exercise
What is iron deficiency?
These days we typically define three stages of iron deficiency. These are:
Iron depletion: this is where iron stores are depleted, but the ‘functional’ levels of iron remain sufficient
Iron deficient erythropoiesis: iron stores are depleted and normal red blood cell production has started to fall, but the existing ‘functional’ levels of iron remain sufficient or thereabouts
Iron deficient anaemia: iron stores are depleted, red blood cells are no longer produced at sufficient frequency, and ‘functional’ iron levels in red blood cells are no longer sufficient for the individual’s needs. This is where symptoms typically manifest, including fatigue, shortness of breath, headaches and dizziness.
So, what can you do? If you experience symptoms of iron deficiency, or you are a high risk athlete, you may want to consider getting a blood test to assess your iron status (or speak to a qualified professional if you are unsure).
It is worth knowing that with most medical and commercial iron status blood tests, it is recommended to test multiple markers of iron status. This is because simply testing something like haemoglobin (the component of red blood cells that contains iron) would not identify if you are iron depleted … as at this stage functional iron levels are still normal.
Typical markers that may be tested are:
Ferritin: this is what iron is stored in
Transferrin: this is what iron is transported in (we can test total transferrin and how much of this is actually carrying iron)
Haemoglobin: the functional iron containing component of red blood cells
Iron: free levels of the good stuff itself!
If you are getting a test for iron status, a few words of advice:
Do not undertake high intensity or long duration exercise in the 24 hours before the test, as this can cause temporary fluctuations that don’t represent the ‘true’ iron status
Ensure you are hydrated, as dehydration reduces blood volume and that can make levels of the markers appear higher than they really are
Don’t get a test when you are sick, as iron is mobilised through the body as the immune system fights the infection and so, like with heavy exercise, the results may not represent the ‘true’ iron status
How can we maintain iron levels …
We obtain iron in the diet. There are two types of iron: haem iron (derived from animal sources) and non-haem iron (derived from plant sources). Haem iron is absorbed and utilised by the body more effectively than non-haem iron. As we currently understand it, up to about 40% of haem iron consumed may be absorbed. In contrast, only about 5% of non-haem iron may be absorbed.
The richest sources of haem iron are typically red meats, and then other meats, egg yolks and fish such as sardines are also sources. Non-haem iron is richest in dark leafy greens, legumes, wholegrains and fortified food products.
It is worth being conscious of what is eaten alongside the iron rich food too, as this can impact how much of the iron is absorbed. Vitamin C helps transport iron across the gut. This would be foods such as oranges, peppers, potatoes, Brussel sprouts. However, on the flip side fibre can trap iron and inhibit transport across the gut (non haem iron containing foods are typically high fibre and this is part of the reason this iron is less well absorbed). Therefore, it is recommended to avoid eating vegetables with seeds and skin still on alongside the iron rich food, and to cook vegetables well (although this destroys some of the vitamin C). An alternative is to have a glass of fresh orange with it, or an orange as dessert after! Tannins, found in things like tea and red wine, can also inhibit iron transport.
When iron rich food is eaten may also be important. In the first section of this blog I explained how after exercise iron absorption may be inhibited in the gut. Therefore, it might be advisable to consume iron as far after heavy or long duration exercise as possible. For example, for dinner or breakfast the morning after a long run.
If an individual simply cannot maintain their iron levels through diet then iron supplements may be considered. And if these are not sufficient, then iron injections may even be considered. However, both should be done under medical supervision and regular blood tests for iron status. Although iron deficiency is not good for health or performance, excess levels are also toxic. It is a case of staying within just the right range!
Find out more:
The IOPN Podcast, with guest Dr. Pete Peeling: “Iron Considerations for the Athlete”: https://www.wedoscience.com/126-iron-considerations-for-the-athlete-with-pete-peeling-phd/
Review article, Sims et al 2019: “Iron Considerations for the Athlete: A Narrative Review”: https://pubmed.ncbi.nlm.nih.gov/31055680/