What is iron?

Iron is an essential trace element that plays a central role in oxygen transport, energy metabolism, the immune system, and cell formation. It is a component of the red blood pigment hemoglobin, which picks up oxygen from the lungs in red blood cells and transports it to the body's cells. Without iron, cells could not receive enough oxygen, and energy production would break down.

About two-thirds of the body's iron is found in hemoglobin, with the rest in muscles (as myoglobin) and in enzymes involved in energy and cellular processes. The body contains around 3–5 grams of iron in total and can store only a limited amount, so a continuous supply through the diet is necessary.

There are two forms of iron in food:

  • Heme iron (from animal sources such as meat, fish, and poultry) – is absorbed especially well.

  • Non-heme iron (from plant sources such as legumes, whole grains, nuts, and spinach) – is absorbed less efficiently, but its absorption can be significantly improved by vitamin C.

How does iron work?

Iron is involved in a wide range of essential processes that keep the body and mind functioning.

Oxygen transport and energy production:
Iron's most important function is the transport and storage of oxygen. Hemoglobin in the blood and myoglobin in the muscles need iron to bind oxygen. At the cellular level, iron is part of numerous enzymes that produce energy (ATP) in the mitochondria—the cells' “powerhouses.”

Blood formation:
Iron is essential for the formation of new red blood cells. If iron intake is insufficient, the body cannot produce enough hemoglobin, resulting in iron-deficiency anemia, which can cause fatigue, paleness, shortness of breath, and reduced physical performance.

Immune system:
Iron supports the activity of immune cells (especially lymphocytes and macrophages) and helps defend against pathogens. A deficiency can weaken immune function, while adequate iron levels strengthen the body's defenses.

Brain and nervous system:
Iron plays an important role in the production of neurotransmitters such as dopamine, serotonin, and noradrenaline. It therefore affects mood, concentration, memory, and mental performance. Adequate iron intake is especially important for brain development in childhood.

Hormones and metabolism:
Iron is a component of enzymes involved in the synthesis of hormones, DNA, and collagen. It also helps with detoxification in the liver.

Benefits of iron

  • Enables oxygen transport in the blood

  • Supports energy production and reduces fatigue

  • Promotes the formation of red blood cells and hemoglobin

  • Supports concentration, memory, and mental performance

  • Strengthens the immune system

  • Contributes to hormone and DNA synthesis

  • Supports skin, hair, and nails through improved cell regeneration

Possible side effects and interactions

Iron is essential, but balance is key: both deficiency and excess can cause health problems.

Iron deficiency:
The most common nutrient deficiency worldwide. Causes include blood loss (e.g., menstruation or surgery), an unbalanced diet, or impaired absorption in the intestines. Symptoms include exhaustion, paleness, brittle nails, hair loss, dizziness, and difficulty concentrating.

Iron overload:
Excessive intake—especially from high-dose supplements—can cause nausea, stomach discomfort, or constipation. Chronically elevated iron stores (e.g., with hemochromatosis) can damage the liver, heart, and pancreas.

To improve absorption, iron should ideally be taken with vitamin C and not together with coffee, tea, milk, or calcium, as these substances inhibit absorption.

Conclusion

Iron is an indispensable trace element for energy, blood, the immune system, and the brain. It ensures that every cell receives enough oxygen—the foundation for vitality, concentration, and performance. Women, athletes, vegetarians, and vegans in particular have increased needs. A balanced diet or targeted supplementation—ideally in a well-tolerated form such as iron bisglycinate or iron(II) gluconate—helps maintain optimal iron levels and restore energy to both body and mind.

Sources

  1. Abbaspour N, Hurrell R, Kelishadi R. (2014): Review on iron and its importance for human health. J Res Med Sci, 19(2), 164–174.

  2. Ganz T, Nemeth E. (2012): Iron metabolism: interactions with normal and disordered erythropoiesis. Cold Spring Harb Perspect Med, 2(5), a011668.

  3. Beard JL, Connor JR. (2003): Iron status and neural functioning. Annu Rev Nutr, 23, 41–58.

  4. Zimmermann MB, Hurrell RF. (2007): Nutritional iron deficiency. Lancet, 370(9586), 511–520.