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All About Iron

From being a crucial building block of steel, to nourishing plants and helping carry oxygen in our blood, iron is always busy helping sustain life on Earth. Read on to learn about the many different functions of iron, what foods you can find iron in, and how to get the most out of dietary iron.

What is iron?

Iron is the most abundant of all metals; it is the fourth most common element in the Earth’s crust by weight and much of the Earth’s core is thought to be composed of iron, too. On the periodic table, iron is the 26th element and part of the transition metals group, expressed as Fe.

What does iron do?

Iron plays many roles in human and plant health. In humans, iron is a component of haemoglobin, the protein in our blood that carries oxygen from the lungs to the tissues. In plants, iron plays a role in the production of chlorophyll, the green pigment responsible for photosynthesis. Just like iron carries oxygen in human blood, it also does the same in plants – it helps to transport enough oxygen through a plant’s circulatory system for survival.

Let’s get into the details of what iron does in the human body:

Immune System Health

Iron is necessary for the proliferation and maturation of white blood cells, particularly lymphocytes, which in turn helps support a healthy immune system response to infections.

Red Blood Cell Health

Iron is an essential component of haemoglobin, a red blood cell protein that transfers oxygen from the lungs to the tissues.
Fun fact: Blood is thought to be red because of the interaction between iron and oxygen – blood looks red because of the way in which chemical bonds between the two elements reflect light.

Muscular Health

Iron is a component of a protein called myoglobin. Myoglobin provides oxygen to our muscles, supporting muscle metabolism and healthy connective tissue. Iron is also the reason why muscles are red, due to its chemical bonds with oxygen (as mentioned above).

Thyroid Health

Did you know that iron is required for the synthesis of thyroid hormones? The thyroid is the butterfly shaped organ in our neck that impacts our metabolism, energy levels and more. An enzyme called thyroid peroxidase (TPO) depends on the haeme component of iron to convert T4 (thyroxine) into T3 (triiodothyronine) – this conversion is crucial as the body uses the T3 form of thyroid hormone to function at its best.

During Pregnancy & Infant Growth

During pregnancy, a woman’s blood volume and red cell mass increase due to the dramatic surge in maternal blood production, therefore the amount of iron that women need increases during pregnancy. Iron is also crucial for the healthy development of the foetus and, to keep up with their rapid growth and development, iron demands are increased for infants.

Which foods are rich in iron?

Iron is an essential mineral – our bodies don’t make iron, so we need to obtain it through our diet or via supplementation. Iron is naturally present in foods like red meat and seafood and is also added to some food products like cereals and sliced bread. Dietary iron has two forms, haeme (from animal products) and non-haeme (from plants and iron-fortified foods). Here is a list of the top haeme and non-haeme food sources of iron:

HAEME IRON: Beef and lamb liver, beef steak, oysters, mussels, sardines.

NON-HAEME IRON: Dried apricots, tofu, spinach, parsley, green peas.

Foods rich in haeme iron are typically absorbed better than non-haeme iron foods due to specific receptors in our intestine. The bioavailability, or amount of iron absorbed, is approximately 14-18% from mixed diets that include substantial amounts of meat, seafood and vitamin C. About 5-12% of iron is absorbed from vegetarian diets.


Is there a way to increase iron absorption?

Certain foods and nutrients can help our bodies absorb iron, so to ensure your iron is being absorbed as best it can:

  • Consume foods high in vitamin-C alongside foods that contain iron (squeezing lemon juice over your iron-rich meals is the easiest way to do this)
  • Cook plant foods to improve the amount of available iron

Other foods and nutrients can interfere with iron’s absorption, so it is best to:

  • Avoid drinking tea and coffee during or directly after having iron-rich foods
  • Avoid eating foods like lentils, chickpeas and beans with your iron-rich foods (these legumes contain compounds called polyphenols that can inhibit the absorption of iron)

Speak to your health professional before making any significant changes to your diet or if you suspect you are iron deficient. Do not take iron supplements unless prescribed by your doctor.


- Blaszczak-Boxe, A. (2017), Facts about Iron, Live Science, cited on 1.10.19, <>

- Murray, M.T & Pizzorno, J.E (1998), The Encyclopedia of Natural Medicine (3rd Ed.), Chapter: Anemia, pp.292-300, Atria Paperback

- National Institutes of Health, (2019), Iron Fact Sheet for Professionals, cited on 24.9.19, <>

- Nutrient Reference Values for Australia and New Zealand (2014), Iron, cited on 24.9.19, <>

- Soyano, A & Gomez, M. (1999), Role of iron in immunity and its relation with infections, Archivos latinoamericanos de nutricion, 49(3): 40S-46S