Iron and cognitive function – its impact on concentration and memory

In 1713, N. Lemery and E.F. Geoffroy demonstrated the presence of iron in blood after burning blood samples to ashes and observing that the remaining particles were attracted by a magnet. Today, iron is primarily associated with haemoglobin and oxygen transport, but its importance also extends to the proper functioning of the nervous system. According to an approved health claim, iron contributes to normal cognitive function, although mental performance itself depends on a number of factors.

1. Iron in the nervous system
2. Iron deficiency
3. Iron in the diet

Iron in the nervous system

The importance of iron for cognitive function stems from its role in processes that are essential for the proper activity of nerve cells. The brain consumes a large amount of energy relative to its mass, which is why it is particularly sensitive to disturbances in oxygen transport, energy metabolism and the functioning of mitochondria – the structures responsible for energy production within cells.

Iron is a component of the protein haemoglobin, which helps transport oxygen from the lungs to the tissues, and an adequate supply of oxygen to nerve cells is essential for maintaining their activity. This element is also a component of many enzymes involved in energy metabolism, so its role is not limited solely to the blood and red blood cells.

Furthermore, in the nervous system, iron is involved in the metabolism of neurotransmitters, including dopamine, serotonin and noradrenaline. Its role in myelination processes – the formation of myelin sheaths around nerve fibres – is also significant. These sheaths influence the efficiency of nerve impulse conduction. For these reasons, adequate iron intake is important both during the development of the nervous system and in adulthood.

Iron deficiency

Iron deficiency can develop gradually and does not always lead to anaemia straight away. Initially, iron stores are depleted – as assessed, amongst other things, by ferritin levels – and only later may more pronounced changes in blood count appear, such as lower haemoglobin levels, reduced red blood cell volume, or signs of iron-deficiency anaemia. At this stage, symptoms are often non-specific, as fatigue, drowsiness, weakness, reduced exercise tolerance, difficulty concentrating, or a feeling of ‘brain fog’ may also result from sleep deprivation, chronic stress, infections, thyroid disorders, insufficient energy intake, or other nutritional deficiencies.

Low iron levels in the body are of particular concern among people with increased requirements or greater losses of this mineral. This applies, among others, to women with heavy periods, children and adolescents during growth spurts, pregnant women, athletes, people following an unbalanced plant-based diet, people who have suffered from bleeding, and those with gastrointestinal diseases or malabsorption disorders.

Estimated iron content in some sources

Iron in the diet

Meat, offal and fish contain haem iron, which is more easily absorbed than the non-haem iron found in plant-based foods. Foods containing non-haem iron include pulses, whole grains, pumpkin seeds, sesame seeds, nuts, cocoa, tofu and green leafy vegetables.

Iron absorption is influenced by the composition of the entire meal. Vitamin C can enhance the absorption of non-haem iron, so it is beneficial to combine plant-based foods rich in iron with peppers, citrus fruits or pickled vegetables. The absorption of this element may be limited by phytates found in cereals and legume seeds, polyphenols in coffee and tea, and high calcium intake at the same time.

"Experts recommend consuming drinks such as coffee, tea, herbal infusions or hot chocolate 1–2 hours before or after a vegan meal, whilst washing down the meals themselves with water or fruit juice rich in vitamin C. Experts also highlight the benefits of including pickled vegetables and fermented foods in general in a vegan diet, as – as research shows – the lactic acid bacteria they contain increase the absorption of iron from the digestive tract." Sławomir Ambroziak – Pharmacologist

In dietary supplements, iron is most commonly found in the form of iron salts, such as sulphate, fumarate or gluconate, as well as in chelated forms. Preparations may be single-ingredient or combined, for example with vitamin C, folic acid, vitamin B12 or other ingredients used in products intended for women, physically active people or those at greater risk of iron deficiency.

Sources:

• Murray-Kolb L. E. (2013). Iron and brain functions. Current opinion in clinical nutrition and metabolic care, 16(6), 703–707. https://doi.org/10.1097/MCO.0b013e3283653ef8
• Cheli, V. T., Correale, J., Paez, P. M., & Pasquini, J. M. (2020). Iron Metabolism in Oligodendrocytes and Astrocytes, Implications for Myelination and Remyelination. ASN neuro, 12, 1759091420962681. https://doi.org/10.1177/1759091420962681
• Sharp, P., & Srai, S. K. (2007). Molecular mechanisms involved in intestinal iron absorption. World journal of gastroenterology, 13(35), 4716–4724. https://doi.org/10.3748/wjg.v13.i35.4716