Iron explained

Iron is an important dietary mineral that is involved in various bodily functions, including the transport of oxygen in the blood. This is essential in providing energy for daily life. Good sources of iron include red meat, offal and iron-fortified breakfast cereals.

Iron is lost from the body through shedding intestinal cells, sweat and blood loss. About one-third of the world’s population is iron deficient, with menstruating women at greater risk than men and postmenopausal women. It is thought that up to five per cent of the Australian population has iron deficiency anaemia.

Recommended dietary intakes

The average person needs to absorb just a small amount of iron each day to stay healthy (around 1mg for adult males and 1.5mg for menstruating females). To achieve this, however, we need to consume several times that amount. This is because our bodies absorb only a fraction of the iron contained in the foods we eat.

The Australian Recommended Dietary Intake (RDI) for iron is the amount of dietary iron required to meet the needs of most of the population. This amount is different for different age groups and life stages.

Recommended dietary intakes (per day)

Infants 0–6 months	0.2mg (breastfed/adequate intake; bottle-fed infants will need 5–10 times this amount)
Infants aged 7–12 months	11mg
Girls and boys aged 1–3 years	9mg
Girls and boys aged 4–8 years	10mg
Girls and boys aged 9–13 years	8mg
Boys aged 14–18 years	11mg
Girls aged 14–18 years	15mg
Women aged 19–50 years	18mg
Pregnant women	27mg
Women aged 51 years and over	8mg
Men aged 19 years and over	8mg

Roles of iron

Some of the many roles of iron include:

• Oxygen transport – the red blood cell contains haemoglobin, a complicated protein that carries oxygen. Haemoglobin is partly made from iron, and accounts for about two-thirds of the body’s iron supply.
• Myoglobin – a special protein that helps store oxygen in muscle tissue. Myoglobin contains iron and is responsible for the red colour of muscle.
• Enzymes – many enzymes throughout the body contain iron, including those involved in energy production. Enzymes are the catalysts that drive many of the cells’ functions.
• Immune system – proper functioning of the immune system relies, in part, on sufficient iron. The immune system helps us ward off illness and disease.

High-risk groups

Certain people are at increased risk of iron deficiency, including:

• Babies given cow’s milk instead of breast milk or iron-fortified formula
• Toddlers
• Teenage girls
• Menstruating women, especially those who have heavy periods
• Women using an IUD (because they generally have heavier periods)
• Pregnant women
• Breastfeeding women
• Women with more than one child
• People who repeatedly crash diet
• Vegetarians
• Athletes in training
• People with renal (kidney) failure
• People with worm infestations
• Aborigines
• Low income earners
• Regular blood donors
• People with conditions that predispose them to bleeding, such as gum disease or stomach ulcers, polyps or cancers of the bowel
• People taking aspirin as a regular medication
• People who have a lower than normal ability to absorb or use iron such as someone with coeliac disease.

Two types of iron

The two types of iron include:

• Haem iron – found in animal foods such as beef, chicken and fish. Offal products such as liver and kidney are particularly rich in haem iron. The body absorbs just under one-quarter of the iron contained in animal foods.
• Non-haem iron – found in plant foods such as beans and lentils. The body only absorbs between two and eight per cent (less than one-tenth) of the iron from plant sources. Good vegetarian sources of non-haem iron include iron-fortified breakfast cereals, flours and grains. Red meat also contains non-haem iron.

Iron stores affect absorption

The healthy body absorbs around 18 per cent of the available iron from a typical western diet (which includes animal foods) and about ten per cent from a vegetarian diet. However, you may be absorbing much less than that, even if your diet includes iron-rich foods. The most significant influence on iron absorption is the amount of iron already stored in the body. The body stores iron in various places including the liver. If your stores are high, your body absorbs less iron from the foods you eat. Conversely, low iron stores increase your ability to absorb iron.

Dietary factors that boost iron absorption

Certain foods and drinks help your body to absorb greater amounts of iron:

• Vitamin C (found in fruits and vegetables) increases iron absorption.
• Meat boosts iron absorption from plant sources.
• In most cases, cooking increases the amount of available non-haem iron in vegetables. For example, the body absorbs six per cent of the iron from raw broccoli, compared to 30 per cent from cooked broccoli.

Dietary factors that reduce iron absorption

Certain foods and drinks reduce your body’s ability to absorb iron, including:

• Soy proteins can reduce absorption from plant sources.
• Tannins from tea, coffee and wine reduce iron absorption by binding to the iron and carrying it out of the body.
• The phytates and fibres in wholegrains such as bran can reduce the absorption of iron and other minerals.
• Vitamin A helps to release stored iron, so not enough vitamin A in the diet could lead to iron deficiency.
• Calcium and phosphorus reduce the absorption of plant-sourced iron.

Iron supplements

Iron deficiency anaemia is diagnosed with a blood test. You may be advised by your doctor to take iron supplements. Points to note include:

• The most common side effect of iron supplements is dark coloured or black stools (poo), so don’t be alarmed by this change to your bowel habits.
• Other common side effects include nausea, vomiting, constipation and diarrhoea. See your doctor for advice but, generally speaking, treatment involves lowering the recommended dose for a short time to give the body time to adjust.
• Iron supplements should be taken on an empty stomach.
• Take the supplements as advised by your doctor. The human body isn’t very good at excreting iron and you could poison yourself if you take more than the recommended dose.

Too much iron can be harmful

The body stores iron very efficiently and too much iron can be toxic. Haemochromatosis is a condition characterised by excessive iron stores. Some studies suggest that haemochromatosis increases the risk of heart disease and some cancers, such as colorectal cancer. Treatment includes limiting the amount of iron in the diet and regularly removing blood until iron levels normalise.

Where to get help

• Your doctor
• An accredited practising dietitian, contact the Dietitians Association of Australia

Things to remember

• Iron is an important dietary mineral that is involved in various bodily functions, including the transport of oxygen in the blood.
• It is thought that up to five per cent of the Australian population has iron deficiency anaemia.
• The most significant influence on iron absorption is the amount of iron already stored in the body.

You might also be interested in:

• Anaemia.
  
• Haemochromatosis.
  
• Iron deficiency - adults.
  
• Iron deficiency - children.
  
• Nutrition - women's extra needs.
  
• Pregnancy and diet.
  
• Vegetarian eating.
  

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Deakin University - School of Exercise and Nutrition Sciences

Last reviewed: March 2011

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Iron is an important dietary mineral that is involved in various bodily functions, including the transport of oxygen in the blood. Good sources of iron include red meat, offal and iron-fortified breakfast cereals. Too much iron can be toxic, especially to children. Haemochromatosis is a condition characterised by excessive iron stores.

Content on this website is provided for education and information purposes only. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your qualified health professional. Content has been prepared for Victorian residence and wider Australian audiences, and was accurate at the time of publication. Readers should note that over time currency and completeness of the information may change. All users are urged to always seek advice from a qualified health care professional for diagnosis and answers to their medical questions.

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