Iron: the key to athletic performance

by Dr Andrew Klein

by Dr Andrew Klein

Andrew Klein

Iron is a critical nutrient involved in a number of metabolic reactions in the body, including oxygen delivery to the tissues, energy metabolism, and thermoregulation. Iron is found in every living cell in the body. Iron’s main role is to transport oxygen in red blood cells and tissues, and it does so mainly through haemoglobin. 

Iron is absorbed from our diet and is contained in meat (especially red meat), fish, eggs and cheese, as well as leafy vegetables and nuts and seeds. You can absorb iron from food in two different forms: haem and non-haem. Foods of animal origin have haem iron because these foods while dietary iron from plant foods is called non-haem iron. Haem iron is absorbed better than non-haem iron because haem iron can be absorbed directly into the small intestine, whereas non-haem iron requires a carrier. 

Iron rich foods:

Iron is co-absorbed with Vitamin C, D and E. Factors that reduce iron absorption include consuming tea or coffee with a meal, some antacids (use to treat heartburn/indigestion) and milk or other alkaline substances at mealtimes. People who have had surgery on their stomach or who suffer from Irritable Bowel Syndrome, Coeliac disease or lactose intolerance, and people with inflammatory bowel disease (Crohn’s or Ulcerative Colitis) cannot absorb much iron from their diet.

Oxygen is absorbed from the air we breathe via our lungs and pumped around our body by our heart in our blood, attached to haemoglobin in red blood cells. Oxygen is actually attached to the haemoglobin via iron (haem) molecules. Iron is required to build new red blood cells and for binding to oxygen when transporting oxygen around.

When we exercise, our muscles use oxygen for aerobic metabolism. As we exercise more, our heart beats faster and harder, and more oxygen is transported to our muscles. At some point, our muscles can’t get enough oxygen and they start to metabolise anaerobically and build up an oxygen debt. Anaerobic metabolism is not very efficient and can be viewed as a last resort to keep muscle contraction going when there is not enough oxygen. After exercise, the body has to pay back the oxygen debt, and the muscles have to recover.

Iron deficiency, when we don’t have enough iron in our body, is very common and affects up to 1 billion people throughout the world. It is the commonest nutrient deficiency. In the UK, it affects 2% of adult men and 10% of adult women. Women need more iron because they have periods and also when they get pregnant. People who eat a vegetarian or especially a vegan diet are more likely to become iron deficient. Athletes who exercise heavily (e.g. longer-distance running, triathlons, iron man/woman races) also require more iron in their diet and are more likely to become iron deficient.

When you develop iron deficiency at first, you still carry on making red blood cells, but these contain less iron, are thinner and can’t carry as much oxygen. The body keeps making the same numbers of red blood cells, but these are not as effective. After you have had iron deficiency for a long time, the body can no longer make enough red blood cells and you become anaemic, which is a more severe form of the condition.

Iron deficiency – thin red blood cells:

People with iron deficiency can’t carry as much oxygen around their body in their red blood cells. That means that when they exercise, they become anaerobic more quickly because of a lack of oxygen. Their heart rate also goes up more quickly because the heart beats faster in trying to compensate. Therefore, the maximal amount of exercise is limited, and a greater oxygen debt is built up more quickly, making recovery take longer and also making injury more likely. If you have anaemia, this is even more pronounced, and exercise is severely limited.

People with iron deficiency experience the following symptoms, all due to reduced oxygen delivery around the body:

  • Reduced exercise performance (getting tired more quickly)
  • Fatigue / tiredness / exhaustion
  • Brain fog
  • Palpitations (feeling that your heart is racing)
  • Shortness of breath with minimal exercise (such as going up the stairs)
  • Hair falling out (alopecia)
  • Brittle or rigid nails
  • Headaches
  • Anxiety
  • Depression
  • Pica (food or ice cravings)

People at greater risk of Iron deficiency:

  • Women (especially after heavier periods or during / after pregnancy)
  • Athletes
  • Vegetarian / Vegan diet
  • People with stomach or bowel conditions or diseases

Treatment of iron deficiency:

  • Nutrition. Optimising what you eat and when you eat it. Good nutritional advice is key
  • Oral supplements. Supplements containing a small amount of active iron are best, 15-25mg per tablet (e.g. Pregnacare). Take one supplement once a day between meals with Vitamin C containing drink (e.g. orange juice).

If nutritional advice and changes to your diet and oral supplementation (for at least three months) don’t work, an intravenous iron infusion may be necessary. The Cambridge Iron Clinic can advise you if an intravenous iron infusion is indicated.

So, in summary, iron in our diet is critical for oxygen transport around the body, and iron deficiency is associated with reduced performance when exercising, as well as fatigue and muscles pain and injury. Nutrition is key, and iron supplementation is important in female athletes, vegans and vegetarians and pregnant women. Understanding your iron levels can improve athletic ability significantly.

Dr Andrew Klein

The Cambridge Iron Clinic