Here is a question for you: as athletes, do we like to simplify things without looking at the bigger picture? Maybe some of us do, maybe some of us don’t – but how many times do we base our feelings on how well or poorly a training session went purely based on our numbers; heart rate, power or pace. If we don’t hit the exact numbers, how many of us would consider this as a session that we failed? If we think about how we respond to numbers that dictate our training, how do we perceive the numbers that dictate our physiology and health?

Now I would like to take this question and focus it a bit more on an area of science that was the focus of my PhD in exercise physiology. This area is iron status and its control and movement within our body, especially within athletes and people who regularly exercise. Returning to the initial question of this article for a moment, do we really know what the number on the blood form means when we get our iron tested? Or have you even had an iron test? What does this single blood measure tell us about our physiology at this point in time?

Iron is considered a fundamental mineral within our body: we need it for delivering oxygen to all the cells in your body, helping us to produce energy to stay alive and iron also helps with maintaining your DNA structure and immune system. Because it is so vital to our body’s normal functioning it is recommended that we ingest 10-18g of iron daily from the food that we eat. Did you know that of this 10-18g of ingested iron, only about 0.5-2g is actually absorbed in our intestines? This large difference is because our body doesn’t have any way of removing the iron that is already inside us. In fact, when it comes to iron, we can store it, absorb it and recycle it, but we cannot get rid of it very well. This means that we have to control how much iron enters our body – and to do this, we use a hormone known as hepcidin, and it helps to prevent us from having too little iron (aka deficient and tired and not able to function very well) or too much (aka toxic and a very, very bad state for the body to be in, though this tends to be a genetic issue).

Hepcidin: master controller of iron in the body

Hepcidin helps your body control its iron stores and it does this by stopping you from absorbing too much iron or limiting the movement of iron throughout your body. So, if you have normal or healthy iron levels and you go and eat a steak, your body will not need to absorb a large amount of iron. Your hepcidin levels will naturally increase and you will not absorb a lot of iron from the steak. On the other hand, if you are iron deficient and you eat a steak, your low iron levels will stop hepcidin from rising and you will absorb a lot of the iron from the steak. In this way your body is incredibly intuitive!

Now there are many situations where people will have an increased iron demand to support their physiology. This can include teenagers that are going through a growth spurt, females who regularly get their menstrual cycle and females who are pregnant. People who regularly train or exercise will also need more iron! Yes, that is right; the more you exercise, the higher your iron demand. But not many people realise this – and what we see is that, compared to the 12% of non-exercising females and maybe 2% of males who are iron deficient, the stats for iron deficiency in athletes increase to 15-35% in females and 3-11% in males! From these numbers, it seems that you are twice as likely to be iron deficient if you train regularly!

So why, when we exercise, are we more prone to iron loss and at a risk of becoming iron deficient? Well, when we exercise we can actually loose small amounts of iron through sweating, gastro-intestinal bleeds (minor chaffing in the gut) or through a process known as ‘haemolysis’ (basically, your red blood cells break and iron inside them spills out; your red blood cells are very flimsy and so the force you create with each foot strike during a run may be enough to cause this throughout your body). While each of these independently only mean tiny losses of iron, if they occur every single day (sometimes 2-3 a day) and you don’t increase you iron intake to compensate for this, then over time this can lead to a drop in your iron stores in your body.

When it comes to exercise and hepcidin (that iron hormone), this is where we can get into some juicy physiology! After exercising, our bodies produce a generally benign inflammatory response that drives our adaptation and improvement to exercise. This inflammatory response after exercise releases a number of chemical markers – and one of these chemical markers of inflammation will cause hepcidin to increase about 3 hours after your session.

So, let me put this into context: if I did a training session, my body would produce a normal increase in inflammatory markers. After finishing my training, I get in my car and drive home (then get stuck in some traffic because it is around 5:30/6pm); I eventually get home, shower, cook food and by the time I sit down to eat it is ~7:30 pm. That means when I am eating it is in that sweet spot post exercise when hepcidin is increasing in my body in response to the inflammation. This means the food that I am eating for dinner that night, that may have some iron in it, will not be absorbed very well. Remember, hepcidin stops you from moving iron into your body from your gut and moving it around your body. If you train regularly without increasing your iron intake or are not aware of how iron physiology works, then you may very well be eating your ‘iron rich’ meal but not actually absorbing the iron very effectively from that meal. Again, if this happened once it is not going to be a big deal, but if you exercise regularly and you eat your main iron rich meal at night after training, then over time you are not moving iron into your body effectively.

I should probably mention now that hepcidin like all hormones will have levels that change throughout the day. You should have the lowest levels in the morning with higher levels in the afternoon. This should give you a bit of a heads up on the best time of the day to take your iron supplement if you are on one. There is also some research that has looked at females with regular menstrual cycles and how hepcidin changes throughout the cycle. The very small amount of research in this space (and I am talking about one study that did some minor tracking of the hormone), showed that hepcidin was lowest during menses (when you have your period), and then gradually increased throughout the rest of the cycle. What does this mean for iron supplements in females? Maybe it means we need to be focusing our iron intake around our cycle and eating more iron when we get our period. I say maybe because this is my professional interpretation of what one study says on the topic; the actual data to support when to take iron supplements according to female physiology has not been done yet. But trust me, if I get the opportunity I will be gunning for this study!

Now that you know iron deficiency is fairly common in athletes (or regularly exercising people), I am in no way suggesting you go start taking iron supplements. I am a firm believer in getting tested first! Basically, test don’t guess. To get the best results from your iron blood tests, you need to have the test done in the morning, be well rested, have fasted and be well hydrated. You need to get the full iron panel and not just ferritin (ask you GP for this and they will order the full test panel).  The reason for not doing the test later in the day and after exercise is because the blood marker for iron stores (aka ferritin) will increase if there is inflammation in the body. So, if you are sick or have done exercise and then have a blood test, it may give you artificially elevated levels and then you could be mis-diagnosed.

For athletes or people who train regularly, you want to aim for iron stores (ferritin levels) of ~60 ug/L. If your iron stores drop to ~30ug/L you are technically iron depleted and may feel some effects like tiredness, poor concentration, increase effort to do normal workloads or training loads. If your levels drop to ~20 ug/L you are iron deficient, and the symptoms listed above may be a bit worse. Your GP will only ever call you about your iron levels if your ferritin levels drop to ~12 ug/L because now you are considered anaemic and you are compromising your ability to deliver oxygen around your body (really not ideal if you are trying to exercise – and trust me, your fatigue levels will reach new highs).

Always ask to see your results and investigate consulting with someone that understands that we need to take a preventative approach and start treating you when you are iron deplete and not when you reach the stage of anaemia (heavily depleted)! This is something that I am more than happy to talk about with anyone anytime!

Dr Claire Badenhorst

Every clinic needs a doctor, at Sports Lab, Claire is ours. Dr Claire Badenhorst  is our physiologist (PhD Exercise Physiology, Academic at Massey University in Auckland) with research focus areas currently in female health, iron deficiency and endurance athletes.