Low Iron: Why Eating More Iron Isn't Always the Whole Answer

If you've been told your iron is low, your first thought might be: I need to eat more iron.

And sometimes, improving iron intake is an important part of the solution. But low iron isn't always simply caused by not eating enough.

Iron levels can also be influenced by how well you absorb iron, how much your body needs and how much iron you're losing. Understanding why your iron is low can therefore be just as important as looking at what you're eating.

What does iron actually do?

Iron is an essential mineral involved in several important functions, including oxygen transport and energy metabolism.

Much of the body's iron is found in haemoglobin, the protein in red blood cells responsible for carrying oxygen.

Iron deficiency occurs when the body's iron stores become depleted.

Importantly, you can have iron deficiency without having iron-deficiency anaemia. Anaemia tends to occur as iron deficiency becomes more severe.

This is one reason low iron shouldn't be dismissed simply because haemoglobin is still within the normal range.

Haem vs non-haem iron: what's the difference?

There are two main forms of iron in our food.

Haem iron is found in animal foods such as meat, poultry and seafood. It is generally more readily absorbed by the body.

Non-haem iron is found in foods including legumes, tofu, nuts, seeds, grains, vegetables and iron-fortified foods. It is also present in some animal foods, but plant foods contain non-haem rather than haem iron. Its absorption is more strongly influenced by other components of the meal.

That doesn't mean plant-based iron sources aren't useful. It simply means that how we build the meal can matter too.

For example, vitamin C can improve non-haem iron absorption, while phytates and polyphenols can reduce absorption.

Practical combinations might include:

• lentils with capsicum

• iron-fortified cereal with berries

• tofu with broccoli

• chickpeas with tomato

Who is more at risk of low iron?

Some people have higher iron requirements, greater losses or other factors that make maintaining adequate iron stores more difficult.

These include menstruating women, particularly those experiencing heavy menstrual bleeding, pregnant people, vegetarians, athletes and people with impaired digestive absorption.     

Heavy menstrual bleeding is particularly important. The 2024 European Hematology Association recommendations identify it as a major cause of iron deficiency in women of reproductive age.  

This can also be relevant for people with conditions such as endometriosis when heavy menstrual bleeding is present.

Gastrointestinal conditions can matter too. Conditions such as coeliac disease can interfere with iron absorption, meaning someone's dietary iron intake may not necessarily explain their iron status.

Why does iron become low?

Broadly, there are four important possibilities:

Not enough coming in: your dietary intake isn't meeting your needs.

More being used: iron requirements increase during periods such as pregnancy and growth.

Not enough being absorbed: gastrointestinal conditions and some medications can interfere with absorption.

More being lost: blood loss, including heavy menstrual bleeding or gastrointestinal bleeding, can gradually deplete iron stores.     

And importantly, more than one of these can be happening at the same time.

This is why simply telling someone with low iron to eat more red meat or spinach can miss an important part of the picture.

Can you improve iron absorption?

Yes. If you're relying heavily on non-haem iron, pairing iron-rich foods with vitamin C is one practical strategy.

Tea and coffee contain polyphenols that can reduce iron absorption, so their timing may also be worth considering when iron status is a concern.    

Research into iron supplements illustrates how significant these interactions can be. In a small controlled study of 34 iron-deficient women, vitamin C increased absorption from an oral iron supplement, while coffee substantially reduced it. However, this study investigated a 100 mg iron supplement, so those exact effects shouldn't automatically be assumed for everyday meals.   

For most people, there's no need to become overly restrictive about meal combinations. Instead, these strategies can be used where they are actually useful.

When should you speak to your GP?

Low iron is a finding, not an explanation.

Nutrition can help improve dietary iron intake and absorption, but if your iron is low, finding out why matters too.

Current recommendations emphasise investigating the cause of iron deficiency alongside treating the deficiency itself. This becomes particularly important when iron deficiency is recurrent, unexplained or isn't responding as expected.    

If you've been told your iron is low, speak with your GP about appropriate investigation and treatment. Iron supplementation should also be discussed with an appropriate healthcare professional rather than self-prescribed based on general nutrition information.

The takeaway

Iron nutrition is about more than simply eating foods that contain iron.

Your dietary intake, the type of iron you're eating, absorption, individual requirements and iron losses can all influence your iron status.

Improving nutrition can be an important part of managing low iron. But sometimes the most important question isn't “How can I eat more iron?”

It's “Why is my iron low?”

Book a consultation today to get personalised nutrition advice tailored to your goals.

References:

1. Lolascon A, Andolfo I, Russo R, et al. (2024). Recommendations for diagnosis, treatment, and prevention of iron deficiency and iron deficiency anemia. HemaSphere, 8, e108. DOI: 10.1002/hem3.108.

2. Piskin E, Cianciosi D, Gulec S, Tomas M, Capanoglu E. (2022). Iron Absorption: Factors, Limitations, and Improvement Methods. ACS Omega, 7, 20441–20456. DOI: 10.1021/acsomega.2c01833.

3. Von Siebenthal HK, Moretti D, Zimmermann MB, Stoffel NU. (2023). Effect of dietary factors and time of day on iron absorption from oral iron supplements in iron deficient women. American Journal of Hematology, 98, 1356–1363. DOI: 10.1002/ajh.26987.

4. Kumar SB, Arnipalli SR, Mehta P, Carrau S, Ziouzenkova O. (2022). Iron Deficiency Anemia: Efficacy and Limitations of Nutritional and Comprehensive Mitigation Strategies. Nutrients, 14, 2976. DOI: 10.3390/nu14142976.