For athletes, proper nutrition is not just fuel but the foundation of their athletic performance. A crucial element for athletes is iron, which plays a key role in energy production and is part of:

  • Hemoglobin is the protein that transports oxygen to the body’s tissues;
  • Myoglobin is a cardiac and skeletal muscle tissue protein responsible for muscle oxygen reserves.

Female athletes often experience iron deficiency due to dietary characteristics, menstruation, and intensive training, which increases iron loss.

Treatments for Iron Deficiency:

  • Diet: Increase the intake of iron-rich foods such as red meat and liver, seafood, lentils, and beans. Avoid pairing these with foods that inhibit iron absorption, such as calcium, zinc, polyphenols, dietary fibers, and caffeine.
  • Injections
  • Oral Supplements: These can improve iron status in athletes but often cause side effects, including abdominal discomfort, constipation, and nausea. Uncontrolled use increases the risk of iron overload.

Ferritin Analysis: Iron Deficiency Possible Even at Levels Above 15 µg/L

Ferritin is a blood protein considered a vital indicator of the body’s iron stores. The physiological range of serum ferritin for adult women is between 15 and 200 µg/L. However, the exact ferritin level indicating iron deficiency remains a subject of scientific debate.

The WHO sets a critical ferritin level of 15 µg/L for diagnosing iron deficiency. However, even with ferritin levels above 15 µg/L, one can experience iron deficiency due to many conditions, such as intensive physical activity and inflammatory processes, which can artificially raise ferritin levels.

Iron Deficiency Progresses in Three Stages:

  1. Depletion of Iron Stores in Liver, Spleen, and Bone Marrow Cells: Ferritin levels drop during this stage, but hemoglobin levels remain sufficient.
  2. Latent Iron Deficiency / Iron Deficiency Without Anemia: Iron delivery to cells and erythrocyte production decrease, manifesting as low blood iron levels.
  3. Iron Deficiency Anemia: Insufficient iron intake decreases hemoglobin synthesis, leading to anemia.

Iron Deficiency and Performance

Iron Deficiency and Performance

Athletes’ performance suffers primarily at the stage of iron deficiency anemia when oxygen transport is significantly reduced. However, even latent iron deficiency can manifest as impaired function of oxidative enzymes, respiratory proteins, immune function, and feelings of fatigue, all of which can also reduce performance. Early detection and correction of depleted iron stores can prevent further development of iron deficiency.

Important Note: Iron supplements do not improve performance in individuals without iron deficiency. Excess iron in the body is toxic.

How Iron is Absorbed: Ferritin and Hepcidin

When iron stores decrease, the body absorbs iron from food more actively, which is related to reduced hepcidin synthesis in the liver, a protein that regulates iron absorption. Low hepcidin levels in the blood increase iron absorption from food. It is important to note that iron absorption increases even when liver iron stores are reduced but before blood iron levels drop.

Optimal Ferritin Level: Study on Healthy Women Aged 18-50

Swiss scientists from the Human Nutrition Laboratory proposed a new method for assessing iron deficiency based on the ferritin level at which iron absorption from food begins to decrease, which could help more accurately diagnose iron deficiency and prevent its consequences.

Study Results:

  • Hepcidin levels increased linearly with increasing ferritin across nearly the entire ferritin range.
  • Iron absorption increased when hepcidin levels dropped below 3.09 nmol/L. Above this threshold, iron absorption remained stable.
  • Iron absorption increased when ferritin levels fell below 51.1 µg/L. Above this threshold, iron absorption remained stable.
  • A hepcidin level of 3.09 nmol/L corresponded to a 51.1 µg/L level of ferritin.

Conclusion and Clinical Application

Iron absorption increases in the state of “latent” iron deficiency—a condition where decreased iron stores have not yet led to a drop in blood iron levels.

Iron deficiency begins at the threshold ferritin level at 50 µg/L. This value suits young women but may differ for men, children, and older adults.

In healthy individuals without recent iron supplement intake, ferritin levels reflect the body’s iron stores. Ferritin concentration is directly proportional to the amount of stored iron: 1 µg/L of ferritin corresponds to 8-10 mg of stored iron.

A threshold ferritin level of 50 µg/L suggests that young women need at least 400-500 mg of stored iron. Interestingly, this value was previously estimated as the minimum iron reserve necessary for pregnancy. When iron stores drop below 400-500 mg, hepcidin synthesis in the liver decreases, and blood hepcidin levels fall. Iron absorption is activated when hepcidin levels fall below ~3 nmol/L, corresponding to a ferritin level of ~50 µg/L.

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