What is iron and why is it important?

Iron is an important mineral required by the body; its main function is to help haemoglobin (red blood cells) carry oxygen around the body.

Carrying oxygen around the body is essential for our body to produce the energy we require to complete our daily activities. Iron also plays an important role in supporting our immune system, muscle function and cognition.

Meeting our daily iron requirements is important to prevent conditions such as iron deficiency and iron deficiency anaemia. These conditions can result in reduced oxygen being carried around the body, leading to symptoms such as fatigue, weakness, dizziness and headaches. 

 

Haem iron vs Non haem iron

Iron can be found in two different forms within food, these are known as haem iron and non-haem iron sources. 

Haem iron is found in animal food sources such beef, lamb, kangaroo, chicken and fish. This form of iron is easily absorbed by the body compared to non-haem iron sources which are predominantly found in plant-based foods such as wholegrain breads and cereals, beans and legumes, dried fruits, nuts and seeds. 

Challenges arise when trying to meet adequate iron intakes on plant-based diets, since the body isn’t as effective at absorbing non-haem iron sources in the small intestine. 

Therefore, individuals following a vegan/vegetarian diet are at a much greater risk of developing iron deficiency and iron deficiency anaemia compared to individuals who follow a meat-based diet. 

 

Iron Requirements

Iron requirements vary between males and females and throughout different stages of life. The table below displays the recommended daily intake (RDI) for iron at different ages for both male and females:

 

Age group RDI
Infants (7-12m) 11mg/day
Girls and boys 1-3m 9mg/day
Girls and boys 4-8yrs 10mg/day
Girls and boys 9-13yrs 8mg/day
Girls and boys 14-18yrs 15mg/day (girls) and 11mg/day (boys)
Women 19-50yrs 18mg/day
Women 51+ yrs 8mg/day
Men 19+ yrs 8mg/day
Pregnant women 27mg/day
Breast feeding women 18+ yrs 9mg/day
Breast feeding women 14-18 yrs 10mg/day

The current Australian RDI also advises that individuals following a vegan/vegetarian diet, increase their iron intake to 1.8 times more than the recommended daily intake for each age bracket. This increased requirement for iron is aimed to help with the poor absorption of non-haem iron in the body. However, studies that determined this increased requirement did not investigate the effects of iron-enhancing nutrients such as vitamin C, which may be consumed in larger amounts on a plant-based diet from fruit and vegetables.

 

High FODMAP iron sources

When following a low FODMAP diet, it is important to avoid high FODMAP food sources to prevent any gastrointestinal issues. Some high FODMAP food sources of iron to avoid include:

  •     Marinated meats such as kangaroo (4.1mg per 100g) and beef (3.3mg per 100g)
  •     Iron fortified wheat breads (4.2mg per 2 slices) and cereals (1.2-3.0mg per serve)
  •     Wheat germ (1mg per 10g or 1 tbsp)
  •     Cashews (2.6mg per 50g or 25 nuts)
  •     Dried apricots (1.6mg per 50g or 10 halves)
  •     Soybeans (1.8mg per 90g or ½ cup)
  •     Baked beans (1.8mg per 140g or ½ cup)

Low FODMAP iron sources

Meeting your recommended daily iron requirements while following a low FODMAP diet is still achievable by consuming low FODMAP iron sources such as:

Animal sources:

  • Plain meats such as kangaroo (4.1mg per 100g) and beef (3.3mg per 100g)
  • Salmon
  • Eggs
  • Chicken thigh

Vegetarian & vegan sources:

  • Firm tofu (2.9mg per 100g or ½ cup)
  • Cooked tempeh (2.2mg per 100g)
  • Iron fortified corn flakes/rice bubbles (3.0mg per 35g)
  • Quinoa (1.4mg per ½ cup)
  • Almonds* (1.1mg per 30g) – note larger portions of almonds would be considered high FODMAP
  • Lentils* (1.9mg per ½ cup)
  • Pepitas (3mg per 30g)

Enhancers and inhibitors of iron absorption  

Non-haem Iron absorption can be enhanced or inhibited by a variety of foods. One of the main inhibitors of non-haem iron is a chemical called phytate or phytic acid, which is commonly found in foods such as legumes, nuts, wholegrain cereals and unprocessed bran. A tip for reducing the phytate levels within legumes, grains and seeds is to soak or sprout these foods. Sourdough bread can also be a good option to choose as the fermentation process involved in making sourdough can lower phytate levels as well as the FODMAP levels.

Other inhibitors of non-haem iron absorption include polyphenols, which are found in beverages such as teas, herbal teas, coffee, cocoa and red wines. Animal proteins such as milk proteins and egg proteins can also have an inhibitory effect. 

Separating tea and coffee from iron-rich meals by about 1 hour can help mitigate the effects of these iron inhibitors..

Research has also suggested consuming high sources of calcium foods/drinks at mealtimes can also reduce non-haem iron absorption.

Vitamin C is the most significant enhancer of iron absorption and can increase iron absorption by up to sixfold in individuals with low iron. Vitamin C helps to convert iron into a form that is readily absorbed by the body and can be found in a variety of fruits and vegetables such as oranges and broccoli.

Other enhancers of iron absorption include animal meats, citric acid found in citrus foods like lemons and limes as well as vitamin A and B-carotene, which are found in carrots and sweet potatoes.  

 

An iron-rich day on the plate

An example of what a day on the plate my look like for an individual looking to meet their recommended daily intake of iron, while following a vegan/vegetarian diet is shown below:

Breakfast: A serve (35g) of iron fortified corn flakes or rice bubbles with lactose free milk and 1/2 cup strawberries = 3.0mg of iron

Morning Tea: A serve (30g) of almonds = 1.1mg of iron

Lunch: A tofu (100g), lentil (1/2 cup) salad with spinach, tomatoes and a lemon & olive oil dressing = 4.8mg of iron

Afternoon Tea: A lactose free yoghurt mixed with pepitas (30g) and a mandarin = 3.0mg of iron

Dinner: Cooked tempeh (100g) with brown rice and low FODMAP vegetables (bok choy, broccoli heads, capsicum) and a soy sauce & sesame oil dressing = 2.2mg of iron   

 

Written by Luke Jackson, Master of Dietetics student, Deakin University

Edited by Rebecca Ponsford, APD

Meeting your iron need on the low FODMAP diet – a guide for vegan & vegetarian diets
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