Iron: your missing link to better running?

Iron is a mineral that plays a critical role in your body's ability to transport oxygen, making it an essential nutrient for distance runners. In this article, we'll discuss why iron is crucial for distance running and how you can maintain sufficient levels of iron in your diet.

How can iron deficiency affect health and performance?

Iron is the key ingredient in haemoglobin, a protein present in red blood cells that carries oxygen from the lungs to the rest of the body. So, if you're running low on iron, your body won't be able to transport enough oxygen to your muscles, leading to fatigue, reduced endurance, and impaired athletic performance. Additionally, low levels of iron can weaken your immune system and increase the risk of illness.

What causes iron deficiency in runners?

Approximately 15-35% of female and 3-11% male athletes have depleted iron stores. Causes of iron deficiency in runners include:

• Low energy intake, overly restrictive diets and/or lack of iron-rich foods
• Reduced iron absorption due to inflammation post-exercise
• Red blood cell breakdown from ground impact forces (foot strike) and eccentric muscle contraction (eg. downhill running)
• High volume endurance training
• Gastrointestinal bleeding
• Sweat losses
• Urine losses
• Menstrual losses
• Regular blood donation

What are the symptoms of iron deficiency?

Symptoms of iron defiency include lethargy, fatigue, and negative mood. Some athletes may not notice any symptoms of iron deficiency, especially in its early stage. In severe cases, your ability to train and perform can be significantly reduced.

How do I know I'm iron deficient?

There are many reasons why you may feel tired, moody or perform poorly. Only a blood test can confirm if iron deficiency is the cause of your symptoms. Iron deficiency occurs in three stages, from depleted iron stores through to iron deficiency anaemia. Inflammation and abnormal hydration can make interpretation of iron studies difficult, hence blood tests for iron deficiency should ideally be performed after a rest or light training day, in the morning, in a well-hydrated state and without any signs of illness or infection.

How is iron deficiency managed?

Get advice from your sports physician or dietitian on the best ways to improve iron levels, depending on the severity of the deficiency, cause and time frame iron levels need to be restored. Iron supplements are effective for improving iron levels and performance in iron deficiency anaemia and may be warranted to prevent progression of iron deficiency in its earlier stages. Iron supplementation is provided either orally or intravenously and it's effectiveness should be followed up via a repeat blood test within 3 months. It is important not to take high dose iron supplements without medical advice, as excessive iron can be build up in your organs and cause toxicity.

Some runners end up on a relentless cycle of iron depletion and supplementation. Poor dietary iron intake and absorption is often a contributing factor to recurrent iron deficiency. Incorporating strategies to increases iron in your diet and enhance its absorption are important aspects of managing iron deficiency.

How do I improve my dietary iron and absorption?

Ensuring adequate fueling, including iron rich foods and foods that maximise iron absorption and avoiding iron inhibitors with iron-rich foods will help reduce your risk of iron deficiency.

Eat enough calories: Avoid fad diets, skipping meals and snacks and frequent fasted training. Increase your energy intake during times of high training load and fuel well before, during and after exercise.

Include iron-rich foods every day: Iron-rich foods include red meat, sardines, eggs, poultry, tuna, iron-fortified cereals (e.g. Weet-Bix, Wonder White bread), lentils, spinach, tofu, chickpeas, cashews, almonds, dried apricots and fortified beverages (e.g. Milo and Sustagen). Animal-derived iron (haem iron) is more easily absorbed than plant-derived (non-haem iron).

Pair iron-rich foods with those that enhance iron absorption: Vitamin C-rich foods such as citrus fruits, red capsicum, kiwi fruit, strawberries and broccoli improve iron absorption by up to 400%. Vitamin C can also help reverse the effect of iron inhibitors. Foods rich in vitamin A also improve iron absorption, such as sweet potatoes, carrots, spinach, and kale.

Limit iron inhibitors when eating iron-rich foods: Iron inhibitors include calcium in dairy foods, tannins in tea and coffee, phytates in wholegrains, nuts, seeds and legumes. Sprouting or cooking foods high in phytates can reduce iron inhibition.

Summary

Iron is a critical nutrient for runner's health and performance. If you notice prolonged fatigue, poor performance or low mood, check in with your sports physician or GP to understand whether iron deficiency may be the cause. Iron supplementation should only be taken on medical advice. Optimising dietary iron is important to avoid recurrent iron deficiency. Incorporate iron-rich foods into your diet every day alongside foods that enhance their absorption. Minimise iron inhibitors consumed with iron rich foods. Don't let iron deficiency hold you back from reaching your running goals. Incorporate these strategies into your diet and training, and you'll be on your way to better performance and overall health.

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References

https://www.ais.gov.au/nutrition/supplements/group_a#iron

Desbrow, Slater & Cox 2020, Sports nutrition for the recreational athlete, The Royal Australian College of General Practitioners, vol. 49, no.1-2, pp. 17-22.

Sim M et al 2019, Iron considerations for the athlete: a narrative review, European Journal of Applied Physiology, vol. 119, pp. 1463-1478.