The importance of iron to the endurance athlete


Running with Us coaches explain the importance of monitoring iron levels in endurance athletes.


Running With Us coaches
Nick Anderson and Tom Craggs

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We have often mentioned the importance of healthy iron levels within runners and its relevance to aiding performance. Too often runners concentrate on the training itself rather than the surrounding factors that could be contributing to your running having hit a ceiling or even gone backwards. 

Why is iron important for endurance athletes? 

Iron is essential for the transportation of oxygen to aerobically exercising muscles. It is an important element of haemoglobin, the oxygen carrying protein in red blood cells and is also an essential constituent in myoglobin which transports oxygen within the muscle cells to the mitochondria, the energy producer of the muscle cell. Within cells, iron is an important component in the enzymes and proteins involved in the breakdown of glycogen and other fuel sources to produce energy. 

How would I know if my iron levels are low?

The main symptoms of iron deficiency in athletes are fatigue and poor or reduced performance. You may notice your training times are slightly slower than you would expect. If the iron deficiency is not treated it can lead to anaemia. Anaemia is a condition that arises when there are a low number of red blood cells or if there isn’t enough haemoglobin within the red blood cells. Symptoms of anaemia include extreme fatigue, lethargy, feeling faint, pale skin and excessive shortness of breath on exertion.

Both men and women can be deficient in iron, but female runners are at particular risk of depleting their iron stores as their iron requirements are higher. Blood lost through menstruation needs to be replaced and iron is required for new red blood cell production. Endurance exercise by itself stimulates red blood cell production and the iron requirements go up accordingly. Low dietary iron intake is the most common cause of iron deficiency, so a focus on quality of food is of the greatest importance. Vegetarians and those who eat little red meat are particularly at risk of having low iron levels. Iron rich foods include red meat, turkey meat, leafy green vegetables, lentils and chickpeas.

Other common causes for iron deficiency in runners include coeliac disease, foot strike haemolysis where red blood cells travelling through the vessels on soles of the foot get squashed with each foot strike, altitude / hypoxic tent use and inappropriate anti-inflammatory use.

We would recommend all runners with fatigue or reduced performance to consider taking a Medichecks Iron Deficiency Check blood test to see whether low iron levels are to blame for reduced performance. This check looks at your ability to store and transport iron as well as the actual level of iron in your blood. 

If I have low iron levels can they be improved? 

Although an iron deficiency can be treated through taking supplements, the starting place must always be through dietary review and ensuring you are getting enough iron intake through the food you eat. The body absorbs two to three times more iron from animal sources than from plants and inclusion of vitamin c with meals helps with absorption of iron. Some of the best animal sources of iron include:

  • Lean beef
  • Eggs
  • Tuna
  • Chicken
  • Turkey

Vegetarians are at greater risk of iron deficiency due to the lower iron absorption rates from plant-based sources of iron but some of the best sources of iron are:

  • Beans and lentils
  • Tofu
  • Cashews
  • Dark green leafy vegetables such as spinach
  • Whole-grain and enriched breads

Typically, a runner with iron deficiency without anaemia, (with no other cause for fatigue) will start to feel better within 2 - 3 weeks of taking regular iron supplementation but this varies depending on how low the iron levels are and how well the person can absorb iron. Taking vitamin C alongside an iron supplement helps absorption and some iron supplements eg. ferrograd C have vitamin C in the same tablet. Be careful to avoid ‘slow release’ iron preparations as your body absorbs iron from the first part of the gut. Caffeine, dairy products and calcium supplements can inhibit iron absorption so iron supplements should be taken 1-2 hours either side of these. Iron absorption can also be reduced immediately after a run, so time your supplementation or dietary intake away from training sessions. 

Medicheck your iron levels

The best way to prevent iron deficiency is to make sure you have adequate iron rich foods in your diet as outlined in this article. Ideally, monitor and track your iron levels with an Iron Deficiency Check every 4 - 6 months to make sure you are providing your body with what it needs.

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