Why Every Athlete / Active Individual Should Be Thinking About Iron
If you're training hard and not paying attention to your iron status, you could be leaving performance (and health) on the table without realising it. Iron is one of the most common nutrient deficiencies in athletes, particularly women, and it's often overlooked until performance or energy has already declined.
What Does Iron Actually Do?
Iron has two jobs which supports exercise:
Oxygen transport - iron is a core component of haemoglobin, the protein in red blood cells that carries oxygen from your lungs to your working muscles.
Aerobic energy production - iron is also needed to make the enzymes involved in the electron transport chain, which is how your cells generate energy aerobically.
Put simply, without enough iron, your body cannot deliver or use oxygen as efficiently. That has knock-on effects for almost every aspect of training and performance.
Why Athletes Are at Greater Risk
It would be understandable to assume that if you eat a varied diet, you shouldn't need to think about iron at all. Unfortunately, training itself increases your iron requirements and losses in a few different ways.
Increased iron losses
Athletes lose more iron than the general population through gastrointestinal losses, sweat, and urinary losses. Endurance training in particular increases these losses over time.
Haemolysis from running
Repeated foot strike during running can damage red blood cells as they pass through capillaries in the feet, a process known as foot-strike haemolysis. This breaks down red blood cells faster than normal, releasing their iron content, some of which is lost from the body rather than recycled.
Reduced absorption post-exercise
Intense exercise triggers an inflammatory response, which raises levels of a hormone called hepcidin. Hepcidin is produced by the liver and acts as the body's gatekeeper for iron, blocking iron absorption in the gut and limiting the release of iron from body stores. Hepcidin rises in response to exercise, inflammation, and illness, meaning the very training sessions designed to make you fitter can temporarily reduce how much iron your body takes up.
Dietary inadequacy
Many athletes, particularly those restricting energy intake, following plant-based diets, or simply not prioritising iron-rich foods, may not be consuming enough iron to keep up with these increased demands.
How Iron Deficiency Affects Performance
Iron deficiency has a direct, measurable impact on the things that matter most to athletes:
Decreased VO2 max and endurance performance - without adequate iron, oxygen delivery to working muscles is compromised, reducing aerobic capacity.
Increased fatigue and reduced training adaptation - low iron limits the energy production processes your cells rely on, making sessions feel harder and blunting the adaptations you're training for.
Poor recovery and immune function - iron plays a role in immune cell function and tissue repair, so deficiency can leave you more susceptible to illness and slower to bounce back between sessions.
A 2025 systematic review by Pengelly and colleagues looked specifically at iron deficiency and supplementation in female athletes. It found that iron supplementation meaningfully improved endurance performance when athletes had severely low iron stores (below roughly 16 µg/L), but offered little to no benefit once iron stores were above 25 µg/L. This matters because it shows supplementation only works when there's a genuine deficiency to correct.
Top Tips to Maximise Iron Absorption
Getting enough iron isn't just about eating iron-rich foods, it's about how and when you have them.
Combine iron with vitamin C. Vitamin C significantly enhances the absorption of iron. Pairing lentils or spinach (plant foods containing iron) with peppers, oranges, or a squeeze of lemon can make a real difference.
Avoid tea, coffee, and calcium-rich foods around iron-rich meals. Tannins in tea and coffee, along with calcium, can inhibit iron absorption.
Space iron intake 3-6 hours after intense training. Because hepcidin rises in response to exercise and peaks a few hours afterwards, having your main iron-rich meal or supplement too soon after a hard session may mean less of it gets absorbed. Timing it a little later in the day can help.
Prioritise iron-rich foods regularly. Red meat, poultry, beans, lentils, and dark leafy greens are all good sources. Haem iron (from animal sources) is more readily absorbed than non-haem iron (from plants), so those following plant-based diets may need to be more deliberate about intake and pairing with vitamin C.
Symptoms to Look Out For
Iron deficiency can develop gradually, so it's easy to put the signs down to "just being tired from training." Keep an eye out for:
Persistent fatigue, even with adequate sleep
Reduced performance or feeling like sessions are getting harder for no clear reason
Breathlessness during exercise that feels disproportionate to effort
Frequent illness or slow recovery from colds and infections
Pale skin, brittle nails, or hair loss
Dizziness or headaches
Restless legs, particularly at night
When to Speak to Your GP
If you recognise several of these symptoms, particularly alongside a drop in performance, it's worth requesting a blood test rather than self-diagnosing or reaching for an iron supplement. This will give a much clearer picture than symptoms alone, and your GP can rule out other causes.
Final Thoughts
Iron directly underpins your ability to transport oxygen, produce energy aerobically, recover between sessions, and stay well enough to keep training consistently. Athletes and active individuals, females in particular, are at genuinely higher risk because training itself increases losses and temporarily blocks absorption.
If you're training hard and notice your performance or energy dipping without an obvious explanation, iron status is a sensible place to start looking.
If you have any questions or want nutrition support to help you think about your iron intake, book an appointment above :-)