What Is Iron & The Health Benefits?

Article by Emilia Fish

Did you know, the average human adult contains approximately 2-4 grams of iron, the majority of which is in our red blood cells (1, 2)? And that anaemia affects around 33% of the world's population, and that half of those cases are a result of iron deficiency (3)?

The role of iron and its interplay with oxygen.

Iron is a very important mineral in human biology as it plays a key role in oxygen utilisation. In fact, almost all our body iron requirements are exclusively involved with some aspect of oxygen use (4,5).

Some of irons roles include:

Making energy. You may have heard of the different states of iron, Fe2+ and Fe3+. Well, being able to exist in two different states means that iron can donate or accept electrons. This ability of iron means that it plays a fundamental role in our electron transport chain – basically the production of energy using oxygen. Without iron, our ability to use oxygen to make ATP (the primary energy carrying molecular) disappears (4, 6, 7).

Oxygen transport. Iron is also important in the storage and transport of oxygen. For example, haemoglobin is a protein found in the red blood cells. Each haemoglobin molecule contains iron which gives it the ability to “carry” oxygen in the blood (4).
Muscles. Our bodies require iron for muscle development during growth. Further, within our non-smooth muscles (those found in our heart and skeletal muscles) is a protein called myoglobin. It contains iron, which binds oxygen allowing the cells to produce energy required for our muscles to move (4, 8).
Supporting our immune system. The cross-talk between our immune system and iron homeostasis has long been appreciated. Iron is necessary for the development of our immune cells. Equally, iron is necessary for the growth of bacteria and parasites. Therefore, both iron deficiency and iron excess can affect our immune system and infection risk (9, 10).

Iron recommendations:

Related to its uses, and losses, different individuals require different amounts of iron. Specifically, we may require more iron during periods of fast growth (during our childhood years), during pregnancy, and if you menstruate. This is reflected in the recommendations (5):

Adolescent males (11-18) - 11.3mg/ day

Adult males (19+) - 8.7mg/ day
Females 11-50 years (pre-menopause) - 14.8mg/ day
Adult females (post-menopause) - 8.7mg/ day

Animal vs plant iron sources:

As mentioned before, iron exists in two states -- you may know these better as haem iron (Fe2+), and non-haem iron (Fe3+) (11).

Haem iron comes from animal sources such as meat (in particular red meat), and seafood (5, 12).

Non-haem iron comes from plant-based sources such as dark leafy green vegetables like kale or spinach, beans, grains, nuts, and seeds (5, 12).

Haem vs non-haem iron absorption:

Haem iron is absorbed much more readily than non-haem iron. The reason that plant-based sources of iron are less bioavailable to us is because before they are absorbed in our gut, they first need to be reduced from Fe3+ to Fe2+ (13). Vitamin C reduces Fe3+ to Fe2+. Therefore, consuming a source of vitamin C such as orange juice with a plant-based source of iron, can aid its absorption (14). Non-haem iron absorption is also enhanced when consuming it with animal protein foods. On the opposite side, some foods contain molecules known as “anti-nutrients” which reduce the bioavailability of iron. For example, bran containing cereals which contain phytates, while tea and coffee contain tannins (15, 16).

Tips to get enough iron when following a plant-based dietary pattern:

Include a diverse range of plant-based sources of iron.

Choose foods fortified with iron, such as some breakfast cereals. A food declaring iron in the nutrition label, needs to contain at least 15% per 100g = 2.1mg. Many fortified foods will contain higher amounts (5).
Eat vitamin C rich foods or drinks with meals.
Avoid drinking tea and coffee during, just before and after our main meals.

Iron overload:

Unlike most other nutrients, we do not actually have an excretory pathway for iron (17). Instead, our body controls how much it absorbs (18). This was an evolutionary advantage because iron sources were so scare, we needed to hang on to it. Today, a large proportion of individuals globally remain iron deficient. During times where we require more iron, our bodies can absorb more from our food! For example, people who menstruate or are pregnant have higher iron requirements, and therefore often will absorb more iron from their food (19, 20)!

However, there are cases where we can get ill due to consuming too much iron and our inability to excrete it. Iron overload complications include infertility, growth failure, type 2 diabetes, liver, and heart complications (21, 22).

There is also a genetic condition called haemochromatosis. This leads to too much iron in the body and requires support from your doctor to treat (5, 23).

Iron deficiency and anaemia:

Iron deficiency is defined as low body iron levels, with or without anaemia (24). It affects approximately 2 billion individuals globally (25). Iron deficiency is more common in children, young women, individuals living in low- and middle- income countries, consuming a vegetarian or vegan diet, conditions which effect iron absorption from the gut or cause chronic blood loss, and the elderly (26-28).

Mild iron deficiency symptoms include looking pale, feeling tired and lacking energy (5).

Iron deficiency anaemia is characterised by a red blood cell count below that seen in healthy individuals. Symptoms may be more severe, and include increased infection susceptibility, heart palpitations, brittle hair and nails, itchy skin, and mouth sores (5).

Supplementation

In some situations, your doctor will measure how much iron you have in your body and may recommend iron supplements if there is a risk of anaemia (5).

Other types of anaemia

Other nutritional anaemias can be a result of vitamin B12 or folate (Vitamin B9) deficiencies (29).

There is also haemolytic anaemia. It can be a result of nutritional causes sauch as a deficiency in Vitamin E, or C and selenium (30, 31). Or may be a result of non-nutritional causes including inherited blood disorders such as sickle cell disease and thalassemia, autoimmune disorders, bone marrow failure, or infections (32).

Summary

Iron and oxygen use in our body are inevitably intertwined.

Our iron requirements are affected by many individual factors including our life stage, sex, and dietary choices.
It is possible to consume our iron recommendations when following a plant-based diet but may require some additional planning.
While we cannot excrete iron, our body can change how much we absorb, depending on its needs.
Problems can arise from both excess and lack of iron in our diets.

This blog post was written by Emilia Fish, a Registered Associate Nutritionist with a BSc in Food Science and Nutrition, and MSc in Clinical and Public Health Nutrition. She is a Dietetic Assistant who has worked with several accredited Nutritionists and Dietitians, and enjoys sharing evidence-based nutrition, and recipes on @nutritionnourishment. Emilia shares others nutrition journeys and expertise on her podcast, The Nutrition Nourishment Podcast.

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