Why iron is essential for runners

Illustration by Joshua Simson

Why is iron important?

A trace element in the body, iron is involved in the function of the immune system, but its most critical role is in getting oxygen to your muscles. So iron is needed for the body’s metabolism and oxygen transport system to function properly – and this is especially important in physical activity. However, iron deficiency is common – according to the World Health Organisation, it’s the most widespread nutritional disorder in the world, affecting people in the industrial world as well as developing countries.

How much do I need?

Men need 8.7mg per day; women need 14.8mg daily (NHS figures).

Does running make me more likely to be anaemic?

Anaemia is a deficiency of red blood cells (RBC) in the body. There are many causes, with iron deficiency being the most common. As a rule, exercise does not predispose a person to anaemia, but the symptoms associated with anaemia – usually excessive fatigue – may become apparent earlier in an athletic person. Iron-deficiency anaemia is more common in women of childbearing age, due to loss during menstruation, and vegetarians are at increased risk if they are not careful about their intake because less iron is absorbed from non-meat food sources.

What are the best food sources of iron?

Liver (although pregnant women should avoid it), red meat, dark poultry (e.g. chicken thighs), beans, nuts, dried fruit, wholegrains, fortified breakfast cereals and most dark-green leafy vegetables (such as kale). Heme iron, found in red meat and dark poultry, is a more readily available source of iron (18 per cent absorbed from these foods). Our bodies absorb about 10 per cent of non-heme iron from vegetables and grains. Vitamin C, taken in conjunction with a meal, improves the absorption of non-heme iron, as does meat protein. Tannins (found in tea) and calcium can decrease absorption.

Does running cause red blood cell or iron loss?

Foot-strike haemolysis causes red blood cells to be destroyed during exercise. This was initially thought to be caused by compression of capillaries in the feet while running, but the damage has also been noted in swimmers, weightlifters and rowers. This blood-cell loss is typically not significant enough to be detected in a blood test. We all lose iron every day through the gastrointestinal tract, and trace amounts are lost in sweat.

Should I get checked out?

If you’re healthy and training is going well, you’re probably fine. But if you’re experiencing unexplained fatigue and/or a decline in your performance that has persisted for weeks, it’s worth getting checked out. Vegetarians and women with heavy periods are at greater risk of low iron and anaemia, and so screening may be justified.

What about a supplement?

Discuss this with your doctor. A supplement (such as Blueiron, £14.99 for 330ml) can top up dietary intake and is safe in the absence of a condition such as haemochromatosis, a disorder in which iron is absorbed too efficiently and excess amounts are deposited in the organs – about one person in 250 of Northern European descent carries the gene for this.