Physiology behind Iron status

As athletes do we focus on numbers too much without seeing the bigger picture?

An interesting question, maybe some of us do and maybe some of us don’t. Honestly I think I am quite guilty of this- seriously ask my coach. If he saw this question I am 99.9% sure he would be doubled over with of laughter. I think a few of us may focus on numbers to tell us how well we performed during a training session or competition, but my question to you is how often do we focus on a single number or outcome and how often do we let this define our health? If we think about how we respond to numbers and how we let this dictate our training, then how often do we let numbers dictate our physiology and health?

Now I would like to take this idea on how we interpret numbers on our health and focus it a bit more on an area of science that has dominated much of my research, essentially the last 6 years of my life (crazy right?!?!). This area is iron status and its control and movement within our body. Some of you may know and some may not know; but my PhD research looked at iron deficiency in endurance athletes and how different diets, mainly high carb vs high fat, would change or alter iron levels.

Constantly asking questions- in this case: when does it stop raining in Auckland?

Usually when I start to talk about iron I find that some people will have an idea on what I am talking about. Now I am hoping that you guys and girls, especially the females (athlete or not) would have had an iron blood test done in their life. I really hope this is the case, especially if you have felt quite flat, tired, maybe had difficulty concentrating at work, and well overall just felt mediocre. Your local GP/doctor may send you off for a blood test, and once they get the results back the doctor will typically look at your ferritin levels and classify you as healthy or iron deficient. If you haven’t been for a blood test or check up recently and you are feeling flat and tired – then go pay your doctor a visit, ASAP please!!!

  • But what exactly do these ferritin levels mean?
  • Do we ever consider our physiology when we interpret these results?

Ok let’s start at the beginning (usually the best place). So starting with the guys: you usually have around 4 g of iron in your body. Girls we have around 2.5 g. This iron in our body can be found in a couple of places and these places include:

  • in our iron stores (aka ferritin),
  • or as part of haemoglobin (part of your red blood cells that transports oxygen around our body)
  • or as enzymes (chemical messengers in the body that increase chemical reaction rates. Enzymes are like corn starch to gravy, add corn starch and the gravy will thicken quickly or more quickly than if you didn’t add it. So add an enzyme to a chemical reaction and the speed of the reaction will increase.)

We need iron for quite a few important things in our body like delivering oxygen to all the cells in your body and this oxygen along with enzyme activity helps your body to produce energy to stay alive. Iron also helps with maintaining your DNA structure. Because it is so vital to our body’s normal functioning it is recommended that we ingest 10-18 g of iron daily from the food that we eat. BUT did you know that of this 10-18 g of ingested iron only about 0.5-2 g is actually absorbed in our intestines. This large difference is because we actually don’t have any way of purposely removing the iron that is already in our body. In fact when it comes to iron we can store it, absorb it and recycle it, but we cannot remove it very well. This means that we have to control how much iron enters our body and to do this we use a hormone. This hormone is known as hepcidin and it helps to prevent us from having too little iron (aka deficient, tired and not functioning very well) or too much (aka toxic and a very very bad state for your body to be in).

Out of interest when measuring your iron levels (without paying extra for blood tests) you need to have ALL of this information:

  1. Haemoglobin: Women > 120g/L, Men > 140 g/L
  2. Ferritin: > 30 mcg/L (for athletes aim for ~60 mcg/L)
  3. C-reactive protein: < 3 mg/L
  4. Transferrin Saturation: >20% (< 20% indicated iron deficiency)

You will need all of these markers because some of them will react to inflammation in the body, and when you have inflammation it can artificially elevated some of the above values. For example ferritin (your marker of iron stores) is very reactive to inflammation, so much so that if I measured your levels before and then after exercise I would see an increase in ferritin after exercise. Transferrin saturation will also be affected with inflammation and so after exercise the correct range to use may be between 10-20%. So to get accurate information about the state of your iron levels in the body you have to get more than a single blood marker, in this case more is better.

For the best and most reliable indication of your iron levels you need to do the blood test:

  1. In the morning,
  2. You need to be well hydrated
  3. Have had 24 hours of low-moderate activity before the blood test (high intensity exercise will elevate your levels and not give the correct baseline levels) and
  4. You must not be sick or have signs of infection (again another inflammatory state).
  5. For females I would suggest you get tested in the first 14 days of your menstrual cycle and at least 4-5 days after the end of your period. During this time of your menstrual cycle you are typically in an anabolic (building) state and you have low inflammatory levels that will not affect your baseline iron status. Also after your period you will need to allow your body to recover from losing iron. I have seen far too many females claim to be iron deficient and after some follow through questions I have found that they are in the middle of their period or have just finished. Girls you iron levels will naturally decline after your period, so test 3-5 days after to see what your actually levels are. Females on the pill I would suggest getting tested 3-5 days after your hormone free period. The pill provides a smaller dose of oestrogen compared to natural cycle levels, during your hormone free (sugar pill) time you have a withdrawal bleed and your natural oestrogen levels may increase/ rebound. You are still loosing blood and iron during this bleed even though it is not a natural period, so best to let you body recover and then test iron levels when rested and in the morning.

In the next post I will do my best to explain the action of hepcidin (iron hormone) and try help you understand how your body’s physiology allows you to move and use iron. But for now I think I have talked for quite a while on iron status in the body, so I am going to leave it here for today and pick it up again in the next post. Hopefully you got something out of this and enjoyed learning about your iron levels.

Thanks from Me

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