Diet for Marathon Runners – Iron

Why do you need iron?

Iron is an essential element with many roles in the body. You need iron to:

  • Carry oxygen around the body.
  • Make sure your immune system works well.
  • Enable the enzymes involved in energy production to work.
  • Develop and maintain normal brain function.


Iron deficiency and iron deficiency anaemia

Iron deficiency occurs when:

  • You do not eat enough foods containing iron, for example, fad diets, low-energy diets, poorly balance vegetarian diets and fast food diets.
  • You have increased iron needs, for example, to replace blood loss (menstruation, injury), in times of growth (childhood, adolescence) and increased physical activity (excessive sweating, bleeding in the gut, breakdown of red blood cells).


How do I know if I have iron deficiency?

You may feel tired and lethargic, you won’t have the same amount of stamina to train and you may become ill often. Performance does not seem to be affected in earlier stages of iron deficiency. If the deficiency is not treated, it can lead to iron deficiency anaemia, which does impair performance. Once you have iron deficiency anaemia it may take months to get back to your normal health and fitness. Clearly prevention of iron deficiency and iron deficiency anaemia is the best goal. Ask your doctor to check your blood iron levels if you think you may have an iron deficiency. Your dietitian and doctor are the best people to work with to treat the iron deficiency.

How can I prevent iron deficiency?

You can prevent iron deficiency by ensuring you get enough iron from the food you eat.

The recommended daily intake of iron is:

  • Adolescents (12-18 yrs): 10-13 mg/day
  • Women (19-54 yrs): 12-16 mg/day
  • Pregnant women: 22-36 mg/day
  • Women (54 + yrs): 5-7 mg/day
  • Men (19 + yrs): 7 mg/day

Marathon runners may have higher iron needs due to blood losses from bleeding in the gut and red cell destruction. Athletes, especially females, should aim for the upper range of the recommended daily iron intake, and have their blood iron levels checked regularly.

Which foods contain iron?

Dietary iron occurs in two forms; haem iron and non-haem iron.
Haem iron is a rich source of iron easily absorbed by the body. Haem iron is found only in animal foods such as meat, fish, shellfish and poultry. The redder the meat the higher the iron content.
Non-haem iron is found in plant foods. Non-haem iron is not as readily absorbed as haem iron due to the following inhibiting factors:

  • Phosphoric acid (found in legumes, wholegrains and soy products).
  • Phytic acid (found in unprocessed bran, oatmeal and wholegrains).
  • Oxalic acid (found in spinach, silverbeeet, rhubarb and soybean products).
  • Tannic acid (found in tea and, to some extent, coffee).

The absorption of non-haem iron can be improved by the following enhancing factors:

  • Ascorbic acid (vitamin C). You can improve iron absorption by eating iron-containing foods with foods containing vitamin C.
  • Meat (meat contains a factor which boosts iron absorption). You can improve iron absorption by eating meat with non-haem iron sources.


Practical tips to improve iron absorption:


  • Include lean red meat in your meals three to five times each week (the red meat provides iron and increases the absorption of haem and non-haem iron in the meal).
  • If you are not having a haem iron-containing food in your meal, include a good source of non-haem iron.
  • Include foods containing vitamin C with your meal, for example, have a drink of fruit juice or piece of fruit. Examples of food containing vitamin C include: citrus fruit, (oranges, mandarins, grapefruit, lemon), fruit juice, kiwifruit, feijoas, cauliflower and broccoli, green peppers, tomatoes.
  • Avoid tea and coffee in the one or two hours around meals.
  • Look for foods fortified with additional iron, for example, some breads and cereals (look at the list of ingredients to see if processed foods contain iron).


The facts about iron supplementation

  • Iron supplements should only be taken under medical supervision, to reverse a diagnosed deficiency. Even under medical supervision iron supplements should only be used in the short term.
  • In the long term, food is the safest and healthiest way to maintain iron status.
  • Frequent use of iron supplements can have adverse effects.


What could happen if you use iron supplements all the time?

  • You could reduce the absorption of zinc, copper and calcium, increasing the risk of deficiencies.
  • You may get iron build-up in your tissues, leading to toxicity.
  • You may get greater free radical damage.
  • You may experience diarrhoea or constipation, stomach discomfort, nausea and an increased risk of infection.


The fallacies about iron supplementation

Iron supplementation will not make up for an inadequate diet!
Iron supplementation will not improve your performance unless you have iron deficiency anaemia.