Iron and Athletic Performance

Iron is a key factor in endurance, recovery, and training development that often doesn't get the attention it deserves. Iron deficiency is common among athletes, particularly when facing high training loads, low energy availability, and altitude training. Intense training can also temporarily reduce iron absorption due to the hormone hepcidin. The right level is crucial: too little hampers performance and recovery, but more isn't necessarily better. In this article, we'll explore how to optimize your iron intake, when supplementation is warranted, and how to ensure iron doesn't become a factor that limits your performance.

Iron might not be something you think about every day, but for those of you who train regularly or focus on performance, it's a crucial nutrient. Iron is needed to form hemoglobin – the protein in red blood cells that transports oxygen from the lungs to the muscles. Without enough iron, delivering oxygen where it's needed becomes more challenging.

But iron does more than that. It also plays a central role in energy metabolism in the muscles, where it is part of several enzymes required to form adenosine triphosphate (ATP), the body's energy currency. In short: without iron – less oxygen, less energy, and poorer stamina.

Iron deficiency is significantly more common among athletes than in the general population. Studies show that about 15–35% of woman athletes and 5–10% of male athletes have some form of impaired iron status. Particularly vulnerable groups include endurance athletes, active youngsters, vegetarians, and individuals with high training volumes.

There are several reasons for this:

• Increased iron needs during training
• Losses through sweat, gastrointestinal tract, and (in women) menstruation
• Mechanical breakdown of red blood cells during running
• Reduced absorption of iron after training

Combine a high training load with sometimes insufficient energy intake, and it's easy to understand why iron stores can deplete.

Not all iron deficiencies are the same. It is common to distinguish between three conditions:

In this situation, the body's ferritin levels are low, but hemoglobin remains normal. The effect on performance might be subtle, yet there's an increasing risk of deterioration. Even with adequate hemoglobin levels, a decline in metabolism and movement efficiency can be observed.

Now the iron deficiency is beginning to impact the formation of new red blood cells. You may feel tired, sluggish, and find it harder to recover—even with “normal” blood levels. The stores of ferritin are low and the transport protein transferrin is low.

In this case, both iron stores, the transport protein transferrin, and hemoglobin are low. This clearly impairs oxygen transport and significantly reduces performance capacity.

The takeaway? Don't wait until it becomes serious. Early intervention is crucial.

When you train hard, levels of the hormone hepcidin increase, which regulates the body's iron metabolism. Hepcidin acts as a brake: it reduces the absorption of iron from the stomach and its release from the body's stores.

After a workout, hepcidin can be elevated for 3–6 hours, which means that iron consumed during this period is absorbed less effectively. The effect is strongest after intensive or long sessions and is further intensified by low carbohydrate availability or high inflammation. It seems to be the inflammatory process that particularly enhances the production of hepcidin and thus inhibits the reabsorption and absorption of iron. Typically unfortunate for those of us who love to train hard and long.

Iron is important for:

• Oxygen transport (hemoglobin and myoglobin)
• Aerobic energy production in the mitochondria
• Efficient recovery and training adaptation

When there's an iron deficiency, the body is compelled to depend more on anaerobic energy, which results in quicker fatigue, elevated lactate levels, and decreased endurance. In cases of significant iron deficiency (iron deficiency anemia), the impact on performance is evident and well-documented.

However, research indicates that iron supplements do not enhance performance in individuals with normal iron levels. More is not better—it's all about maintaining the correct balance.

Iron comes in two forms in food:

• Heme iron – from meat, fish, and poultry (absorbed effectively)
• Non-heme iron – from plants and grains (lower absorption)

Absorption is also influenced by what you eat alongside it. Vitamin C, meat, and fish can enhance absorption, while coffee, tea, calcium, and whole grains might inhibit it.

Another crucial factor is energy balance. With low energy availability (LEA), both iron intake and absorption tend to decrease, connecting iron deficiency to the broader syndrome of Relative Energy Deficiency in Sport (RED-S).

There's substantial evidence indicating this. Studies reveal that even athletes who meet their recommended daily iron intake can experience a decline in iron stores during intense training periods. This is largely because athletes typically metabolize nearly double the recommended daily iron intake (+70%). The body's demand increases — both to compensate for losses and to support training adaptations.

This underscores the importance of regular blood tests and an individualized diet strategy, especially if you have a history of iron deficiency. Often, a modified diet with increased food intake suffices, but endurance athletes remain at risk of iron deficiency for the reasons mentioned above.

For confirmed iron deficiency, there are three main strategies:

1. Adjustment of diet – always the first step.
2. Oral iron supplement – common and effective, but can cause gut issues at high doses
3. Intravenous iron – used in specific cases under medical supervision

Timing is also crucial: iron is often absorbed better in the morning and far from training sessions.

Yes, it's possible – but it usually requires prolonged and unnecessary overdosing.

The body has an efficient defense system where the hormone hepcidin automatically reduces iron absorption when the stores become sufficient. In most healthy individuals, this regulation functions very well, and it's difficult to overdose on iron through normal supplements.

The risk of iron overload (with potential liver impact) mainly arises if you take high doses (60–100 mg of elemental iron per day) over extended periods (often 6–12 months or more) without actually needing it. This is especially true for supplements like Niferex and Duroferon, both of which contain 100 mg of elemental iron per tablet/capsule.

Do not use high-dose iron supplements like Niferex or Duroferon without a doctor's recommendation and always follow up with blood tests (ferritin and transferrin saturation). For most athletes, significantly lower doses, such as 20–40 mg of elemental iron per day, are sufficient to correct or prevent deficiency. If this isn't enough, it's important to investigate why the iron levels aren't being regulated. Is there an underlying bleeding or issue with absorption?

When training at altitude, the need for iron significantly increases. Your body stimulates the production of red blood cells to compensate for lower oxygen pressure—a process that requires large amounts of iron.

Without sufficient iron stores, altitude training risks providing poor or no effects. Therefore, iron status checks and frequent supplementation are recommended before and during altitude stays.

Iron isn't a quick fix, but it's a fundamental requirement for training to deliver results. Too little iron can hamper performance, recovery, and long-term development—often without clear warning signs at first.

For those of you who train seriously, keep in mind:

• Regularly monitor your iron levels
• Ensure adequate energy and iron intake
• Adjust timing of meals and supplements around training
• Address deficiency early – before it becomes a problem