Following on from last week’s blog about the role of zinc, Dr Klaudia Raczko explores the role of another crucial mineral within the body – iron.

Why is Iron so important?

Iron is the most abundant microelement and it has multiple metabolic functions in the human body. It forms the centre of haemoglobin, which is the substance that gives red blood cells their colour and allows them to carry oxygen around the body. Iron is also involved in the oxygen storage in muscle cells and is a component of important tissue enzymes and cytochrome P450, which play a role in the detoxification process.

Most of the iron in the body is bound to proteins. Around 67% is found in the aforementioned haemoglobin, in the form of haem or heme. Haem is a ring-shaped molecule made of porphyrin with an iron ion in the centre. Iron is transported and delivered to different tissues with the help of transferrin, a protein that regulates the absorption of iron into the blood, while ferritin is the protein which stores iron and releases it when it is needed.

Iron differs from other microelements because it lacks efficient ways of excretion. This means that it’s difficult for the body to get rid of excessive iron and, as a result, any excess is stored in the body.

Iron overload or the build up of iron in the tissue of joints or major organs such as the liver or heart is a disorder known as ‘Haemochromatosis’. This condition can run in families and the risk of haemochromatosis can be tested on the genetic test (HFE gene).

Iron Dietary Sources and Absorption

There are two main forms of iron: haem, found in animal sources and non-haem found in plant-based food. Good vegetarian sources of iron include spinach, lentils, beans, seaweed, and dark chocolate. For non-vegetarians, red meat, poultry, liver and fish are good examples of iron-rich foods.

Another inexpensive and somewhat unconventional way to add increase iron intake is to cook using cast iron pots and pans, as iron from these is released into food during cooking. It should be noted that while the haem form of iron found mostly in animal food products is well absorbed, absorption of non-haem iron depends widely on enhancing and inhibiting factors as well as dietary components of the meal. The non-haem iron, which usually occurs in its oxidised form (Fe3+), needs to be reduced to Fe2+ in order to be absorbed by intestinal cells (enterocytes). This process only takes place in the presence of adequate stomach acid and ascorbic acid (vitamin C), which is why the intake of food high in vitamin C can improve the absorption of iron.

Foods that Affect Iron Absorption

Microelements such as calcium and certain polyphenols such as tannins, found in black tea decrease iron bioavailability. Though there are a number of high-iron foods available to non-meat eaters, vegetarian diets which consist mostly of non-haem iron and are rich in phytate, carry an increased risk of poor iron absorption. The Scientific Advisory Committee on Nutrition advises that processes such as soaking, milling or cooking foods such as whole grains, beans and legumes may increase the absorption of iron by the degradation of phytates and other iron inhibitors. It’s also important to acknowledge that iron is strictly conserved and where there’s a deficiency, the body increases its absorption from the gut.

Iron Testing

Iron levels can be tested in the blood. To gain a better picture of what’s happening in our body, transferrin, ferritin and TIBC (total iron binding capacity) levels should be checked.

Where there is an iron deficiency, the serum level of iron will be low and transferrin levels will be high as the body tries to increase the transport of the iron to the places it’s needed. Ferritin levels will, in contrast, be low as this is proportional to the level of stored iron.

In cases where there is a more significant iron deficiency, lower levels of haemoglobin (Hb) suggesting anemia and a lower than normal MCV (mean cell volume – which describes the size of the red cell) will be detected in the blood tests. If the blood tests show a low MCV, this would suggest that the anaemia is caused by an iron deficiency. If MCV is higher than normal, then it’s likely that the anaemia is caused by a vitamin B12 or folate deficiency instead.

High ferritin levels can also indicate increased inflammation which should be addressed. And if the iron levels are too high, the simplest way to decrease this is to donate blood – which has the added bonus of helping others in the process.

The Three Stages of Iron Deficiency

Iron deficiency can be divided into 3 stages: depletion of iron stores, decreased iron transport and iron deficiency anaemia (IDA). The latter of these is the most serious.

Iron Deficiency Anaemia

Prevalence of anaemia is high worldwide and it imposes the greatest risk on the most vulnerable groups of population such as young children and both premenopausal and pregnant women.

Bleeding from the gastrointestinal tract is a common cause of iron deficiency anaemia – which may itself be the result of chronic inflammation, ulceration or varices. Some medications such as aspirin, warfarin, steroids or NSAIDs such as ibuprofen or naproxen are associated with increased risk of bleeding and can have a negative impact on the gut lining.

Another common and recurring cause of blood loss is menstruation and so premenopausal women should ensure adequate iron intake during this time.

Other less common causes are things like parasitic infections (particularly hookworm) and small intestinal bacterial overgrowth (SIBO). Bacteria like iron and so use it for their metabolism before it can be absorbed. In cases of chronic low iron or low ferritin levels and no other obvious issues, SIBO may be the underlying cause.

Symptoms of Iron Deficiency

Iron deficiency can present in many different ways. Fatigue, immune system impairment, poor brain function and neurocognitive decline are just some symptoms of iron deficiency. This is because iron plays an important role in oxygen transport and the successful delivery of oxygen to the different parts of the body.

Some clinical signs include pallor (a term used to describe a pale skin tone), glossitis (which presents as a red painful tongue), angular stomatitis (painful inflammation at the corners of the mouth) and koilonychia (also known as ‘spoon nails,’ where nails look scooped out).

How to Deal With Iron Deficiency

Iron deficiency is quite common and can be easily tested from a blood sample. When detected and treated, the risk of developing iron deficiency anemia and its significant consequences, can be prevented. Considering that iron supplements are usually not well tolerated by most people and should only be taken under the supervision of a healthcare professional, ensuring adequate iron intake from those dietary sources mentioned above (especially those from animal sources) is the best way to protect the body from an iron deficiency.

If you’d like to speak more with Dr Klaudia Raczko about a possible iron deficiency or related issues, please book an appointment with her here.

Written by Dr Klaudia Raczko


Lopez, A., Cacoub, P., Macdougall, I. C. and Peyrin-Biroulet, L. (2016) ‘Iron deficiency anaemia’, The Lancet, 387(10021), pp. 907–916.

SACN (2011) Iron and Health Report. Available at:

Sharp, P. A. (2010) ‘Intestinal Iron Absorption: Regulation by Dietary and Systemic Factors’, International Journal for Vitamin and Nutrition Research, 80(45), pp. 231–242.

Strain, J. (Sean) and Cachman, K. D. (2009) ‘Minerals and Trace Elements’, in Gibney, M. J., Lanham-New, S. A., Cassidy, A., and Vorster, H., Introduction to Human Nutrition. 2nd ed. Willey-Blackwell, pp. 188–227.