Q & A Thursday: Getting the most out of the iron in your diet

Posted by kathryn in The Micronutrients and Q & A Thursday

You have about 3 – 4 grams of iron in your body at any one time.

Much of this is in the haemoglobin molecules in your red blood cells. A smaller amount forms part of certain enzymes, while the rest is in transit, bound to a protein called transferrin. Transferrin manoeuvres iron around your body to wherever it’s needed.

Every day we lose a small amount of iron. Simple bodily functions like sweating, the shedding of skin and cells in the digestive tract, lead to iron loss. Women also lose more iron each month, during their period.

On average men lose 1mg per day, while women lose 1.5 – 2mg per day, averaged over a month.

Because you are continually losing iron, you need to replace it through your diet.

Iron intake vs absorption

Those of you who know your Recommended Daily Intakes will be thinking I’ve gone crazy at this point. Here in Australia the RDI is 8mg of iron per day for men and 18mg for women. Which is quite different from the 1 – 2mg I mentioned above.

This discrepancy is because you don’t absorb all the iron from the food you eat. So you have to eat more iron than you need, to get enough into your actual bloodstream and tissue.

How much iron do you absorb?

There are two types of iron found in food and they have slightly different chemical structures:

• Haem iron is found in meat and meat products
• Non-haem iron is in plant foods

Haem iron is much more easily absorbed than non-haem iron. Which means while plants can contain significant amounts of iron (think spinach and chickpeas), it’s harder to absorb.

However, haem or non-haem, we only absorb a fraction of the iron in the food we eat:

• 15 – 25 percent of the iron from animal sources
• 2 – 5 percent of the iron from plants.

And this accounts for the discrepancy between the RDI and what your body actually needs.

Non-haem iron is important for all

While haem iron is much more easily absorbed, the iron in plant food is an important dietary source, even for non-vegetarians. We simply eat more non-haem iron, because we eat more plant based foods during the day. They are a significant source of iron in all our diets.

How to get the most out of the iron you eat:

• eat plant sources with small amounts of vitamin C foods, as this enhances iron absorption.
• phytates are compounds found in high-fibre cereals which inhibit iron absorption. Limit cereals to breakfast and have them with some fruit (for the vitamin C)
• compounds in tea, coffee and cocoa also limit the absorption of iron, so avoid drinking these with meals
• when you’re low in iron the body is able to compensate to some extent – by absorbing more of the non-haem iron.
• If you eat red meat 2 – 3 times a week, you are almost certainly getting enough iron.

I’ve written about iron sources before in this post, while this post has more about vegetarians and iron.

What is Q & A Thursday?

This post is part of Q & A Thursday – a monthly burst of blogging, where you get to dictate the subject matter. Q & A Thursday is all about simple, practical answers to food and diet dilemmas sent in by readers.

If you have a question you’d like answered send me an email. For more information you can take a look at the Q & A Thursday archives.

08 May, 2008