Iron - what it does and why you need it

Written by Catherine Saxelby on Tuesday, 16 April 2013.
Tagged: balanced diet, dieting, diets, dinner, energy, exercise, health, meal planning, supplements, vegetables, vegetarian

Iron - what it does and why you need it

Our bodies need iron. Not the sort used in barbells, weights and stream trains but the essential mineral we get from our food. And especially so if you're a teen, an athlete or a woman — even more so if you are pregnant. Read on for my outline of what iron does in the body, how much you need and where can you get it.

Iron's role in the body

Iron is a key component of haemoglobin, the protein in red blood cells that gives them their red colour and (along with vitamin B12 and folate) carries oxygen to every part of the body. If your body iron store or haemoglobin count is low, you will feel chronically tired and unable to exercise and you will have little energy (a common complaint for women).

Iron is needed for many enzymes and co-enzymes, especially ones involved with the immune response. A lack of iron can lower your immunity and leave you prone to frequent infections.

Iron forms part of the muscle protein myoglobin, which explains why athletes need to have good iron stores for peak performance.

How much do you need?

The recommended intake for women is 18 mg a day, but this increases to 27mg during pregnancy. Men need only 8 mg a day. Teenagers need 11-15 mg per day. See below.

Iron requirements have not been established for endurance athletes such as marathon runners (ordinary runners only need about as much iron as non-athletes).

As with most things in nutrition, prevention is the best strategy so aim to avoid getting low in iron in the first place. Make sure you're getting your recommended intake of iron, especially if you're a female athlete. For those who are concerned about iron deficiency, a good first step is to get a blood test at your doctor's.

CHILDREN
0.2 mg for babies (0 to 6 months)  AI
 7 mg for babies (7 to 12 months)  EAR
 9 mg for toddlers (1 to 3 years)
10 mg for schoolchildren (4 to 8 years)
 8 mg for girls and boys (9 to 13 years)
15 mg for teenage girls (14 to 18 years)
11 mg for teenage boys (14 to 18 years)

ADULTS
18 mg for women (18 to 50 years)
 8 mg for women (51 to 70+ years)
 8 mg for men (18 to 70+ years)
27 mg for pregnant women
 9 mg for breastfeeding women
      (from NHMRC Australia & New Zealand 2006) AI = Adequate Intake, EAR = Est Average Requirement

What foods give you iron?

You get iron from two key groups of food and they're very different:

1. Lean red meats, fresh not processed

Red meats are hard to beat when it comes to iron. Lean red meats like beef, lamb, venison and kangaroo are the best sources of iron not only because they are they rich in iron but also because the iron is well-absorbed by the body. Around 40 per cent of meat's iron is in the form of bio-available haem iron.

Red meat has twice as much iron as chicken and three times as much as fish. Generally the redder the meat, the richer it is in iron. In the average Australian diet, meat, chicken and fish account for around 20 per cent of all iron eaten.

I know many dislike the taste but liver and organ meats (including foie gras, chicken livers and lambs fry) boast an impressive concentration of iron – see table. Just a small amount spread on toast or crackers can make a big difference to getting in the iron. Processed meats like salami, sausages, bacon and hot dogs aren't as healthy for you as fresh cuts of meat due to their salt and nitrites.

2. Non-meat sources of iron

Whole grains, iron-enriched breakfast cereals, vegetables, legumes (beans and lentils), nuts and eggs contain iron, but the iron is non-haem or inorganic iron and is not absorbed as well as that found in meat.

Why? Vegetables contain fibre and oxalates while bran and wholegrains contain phytates, which both bind and hold iron, so the full quota cannot be properly absorbed.

Of the foods listed, grains make the greatest contribution to our diet, with around 30 per cent of iron coming from fortified breakfast cereals, bread and brown rice or pearl barley.

Foods for iron

Food

Amount

Iron (mg)

Well-absorbed iron sources (haem iron)

   

Lean lamb, grilled

125g

6.8

Pâté, chicken liver

60g

5.3

Lean beef mince, cooked

125g

4.3

Lean beef sirloin, grilled

125g

3.9

Pork leg steak, grilled

125g

1.5

Salmon, canned, drained

125g

1.5

Chicken breast, skinless, roasted

125g

0.9

Bream, grilled

125g

0.6

     

Less well absorbed iron sources   (non-haem iron) *

 

 

Whole wheat breakfast biscuits

2 biscuits

3.0

English spinach, cooked

½ cup

3.0

Muesli, natural

½ cup

2.3

Baked beans

½ cup

2.2

Milo powder

1 tablespoon

1.7

Egg, boiled

1 whole

1.1

Brown rice, boiled

1 cup

0.9

Wholemeal bread

1 slice

0.7

Dried apricots

6 halves

0.7

Peanut butter

1 tablespoon

0.5

      *  Consume with a food high in vitamin C eg orange juice to aid absorption

 

Spinach and Popeye

Spinach was once recommended as a rich source of iron. This, now out-of-date belief, is nevertheless still held by many. Popeye was wrong! Spinach does contain a lot of iron - but it is not well absorbed. Its naturally-occurring fibre and oxalates bind most of the iron so it cannot pass into the body.

Look at this comparison:

  • A small, 100g, beef or lamb steak contains 4.1mg of iron. As around only 20% of this will ultimately be absorbed, the true iron contribution from this steak is only 0.8mg of iron.
  • In contrast, a serve of spinach contains a much larger 6.4mg, but at only 5% absorption, a tiny 0.06mg actually ends up inside our body.

Iron helpers

Even small amounts of meat (like a few strips of beef in a vegetable stir-fry) improve iron absorption. Something in meat known simply as the "meat factor" works to make the iron in vegetables more available.

For vegetarians, iron is improved with the help of vitamin C. A glass of fruit juice or some vitamin C-rich vegetables with a meal increase the amount of iron from grains or lentils.

What you drink with your meal also plays a part. Orange juice doubles iron intake relative to water, while milk decreases it by 50% and tea by 75%.

Who can run low on iron?

Vegetarians tend to have a lower iron status than meat-eaters, because the iron in vegetables and grains is not well absorbed - although a well-planned vegetarian diet can meet iron needs. See my suggestions on how to combine grains, vegetables and legumes with vitamin C.

Athletes miss out on iron as the heavy pounding of running or exercising can prematurely destroy blood cells (known as haemolysis). Greater muscle mass means more myoglobin is produced, which further raises iron needs. "Sports anaemia" is well documented in professional female athletes and can affect their capacity to train to peak levels.

Young children under the age of two are at risk of iron deficiency as they are growing fast and can be fussy eaters. In children, signs of iron deficiency are delayed psychomotor development and poor capacity for exercise. Low birth weight and preterm delivery are things that further put babies at risk.

Teenage girls require more iron to meet the demands of rapid growth and the onset of menstruation with its loss of blood.

What are the first signs of iron deficiency?

Running low on iron can cause a number of health problems such as:

  • tiredness
  • lack of energy
  • poor stamina
  • little ability to do physical work or exercise
  • frequent infections
  • feeling the cold more than usual.

A blood test measuring the markers of iron - your serum ferritin (a measure of your body's iron stores) or serum transferrin (the main iron transporting protein in the circulation) - will help your doctor diagnose whether or not you have iron deficiency anaemia. Talk to your doctor about arranging a blood test.

Catherine Saxelby

About the Author

Catherine Saxelby knows nutrition! She is an accredited nutritionist, food commentator, blogger and award-winning author. Her latest book Catherine Saxelby's Food and Nutrition Companion answers all those tricky questions on healthy eating, diets and supplements. It draws together a lifetime of advice and gives you all you need to know to eat right! It's a complete A to Z. A handy desk go-to reference.