Iron in Food and Supplements: The Complete Guide

Iron is found in food and is also often used in nutritional supplements. In this comprehensive article, you'll learn all about the benefits of iron, its effects on your body, and how to recognize a deficiency.

You will also learn which foods contain the most iron and which blood values ​​are important to determine whether you have sufficient (or too much) iron available in your body.

Iron is an essential mineral that plays a vital role in the body, particularly in the production of hemoglobin, the protein that carries oxygen in red blood cells. A dietary iron deficiency can lead to fatigue and a weakened immune system.

In this article, you'll discover the functions of iron, how the body regulates and stores iron, the recommended daily amounts, and the causes and consequences of iron deficiency.

We also discuss iron supplements and how to optimize iron absorption from your diet, as well as the risks of iron overload.

Read on to learn all about this essential mineral and how to ensure you get enough iron for optimal health.

There are two types of iron in our diet: heme iron and non-heme iron.

1. Heme iron - Found in muscles and blood, heme iron is only found in animal products , such as meat, poultry, and seafood. It is more easily absorbed by the body than non-heme iron.
2. Non-heme iron - Found in plant foods such as leafy greens, whole grains, nuts, cocoa, seeds, and legumes. Non-heme iron is also found in animal products. This is easy to remember when you consider that animals eat the plants that contain non-heme iron!

Iron supplements almost always use a form of non-heme iron. Some examples of common forms of non-heme iron are:

1. Iron fumarate (ferrous fumarate)
2. Iron bisglycinate
3. Iron citrate
4. Iron sulfate
5. Iron lactate
6. Iron gluconate
7. Iron picolinate

In general, these forms of iron differ mainly in their chemical composition, bioavailability (absorbability), and potential side effects.

It's important to choose a form of iron that is well-tolerated and effectively absorbed by your body. This can vary depending on individual factors and any specific recommendations from a doctor or nutritionist.

For supplements, iron fumarate (ferrous fumarate) is preferred for the following reasons:

1. Bioavailability - Iron fumarate generally has good bioavailability, meaning it can be easily absorbed by the body. This can result in an effective supplement for iron deficiencies.
2. Tolerability - For many people, iron fumarate is well tolerated and causes fewer side effects compared to some other forms of iron, especially with long-term use.

The best-known function of iron is the transport of oxygen, but this mineral also plays a crucial role in many other processes in our body. (2)

This is why it is so important to get enough iron:

1. Transport of oxygen - Iron is an essential component of hemoglobin, the protein in red blood cells that binds and transports oxygen from the lungs to tissues throughout the body.
2. Energy production - Iron plays a role in the production of adenosine triphosphate (ATP), the body's main energy source. It is involved in various enzymatic reactions essential for metabolism and energy production.
3. The immune system - Iron is essential for healthy immune system function. It plays a role in the production and activity of white blood cells, which protect the body from infection and disease.
4. How the brain works - Iron is involved in the synthesis of neurotransmitters, such as dopamine and serotonin, which are important for communication between nerve cells and the regulation of mood, emotions and cognitive functions.
5. DNA synthesis - Iron is essential for the synthesis of DNA, the genetic material of cells. It is necessary for the growth, development, and repair of tissues in the body.

Our body has a fascinating system for regulating iron levels. This system ensures the body has enough iron to perform essential functions and prevents excessive iron accumulation, which can be harmful to health.

1. Storage - When more iron is ingested than we immediately need, the excess iron is stored as ferritin, a protein that can bind iron and store it in cells (more on this later). This occurs primarily in the liver, spleen, and bone marrow.
2. Absorption - When iron stores in the body are low, iron absorption from the intestines increases. This is regulated by a complex system of proteins and hormones.
3. Recycling - When a red blood cell dies, it is broken down in the spleen and liver. This process releases the iron, which is then reused to make new red blood cells or stored for future use.

How much iron you need daily depends on your age and individual needs. These are the guidelines from the Health Council and the Nutrition Center.(3)

When your body doesn't have enough iron, it will first draw on its reserves. But if even those are depleted, you can develop an iron deficiency. You can recognize an iron deficiency by the following symptoms:

1. Fatigue - Iron is needed to transport oxygen. Less oxygen means you can produce less energy, which can lead to fatigue.
2. Quickly out of breath - The less oxygen your blood can carry, the faster you have to breathe and therefore quickly become out of breath.
3. Pale skin - An iron deficiency causes poor blood circulation. This can lead to pale skin.
4. Restless legs - An iron deficiency can affect dopamine production, which can trigger restless legs.

These are the most common symptoms recognized by the Nutrition Center.(4)

Because the body can recycle iron and store it relatively easily, an iron deficiency doesn't develop overnight. It's a gradual process. You're therefore at risk of a deficiency if, over a prolonged period of time, you:

1. Blood loss (menstruation, stomach ulcer, blood donation, tumors)
2. Have a higher need for iron (pregnancy, breastfeeding)
3. Reduced ability to absorb iron (intestinal problems, gastric reduction surgery)
4. Not getting enough iron (diet)

Women who experience heavy menstrual bleeding (menorrhagia) are at increased risk of iron deficiency. Iron deficiency symptoms can also occur in women with lighter periods.

Pregnant women have a increased need iron. This is because the body then produces more blood to supply the baby and placenta with sufficient oxygen and nutrients.

The iron regulation system cleverly adapts to this by absorbing more iron from your diet. However, it is important to eat extra iron-rich foods during pregnancy, because the need for iron increases even more in the 2nd ^and 3rd ^trimesters .(5)

A well-stocked iron supply is also necessary for childbirth due to the blood loss and the breastfeeding period during which the baby is dependent on breast milk for its iron supply.

Because breast milk is not very rich in iron and infants are completely dependent on milk for their iron intake, babies can also develop iron deficiency.

The same applies to older children who are still growing. During a growth spurt, more blood is needed in a short period of time to supply the growing body with sufficient oxygen.

Sometimes it is not the extra need for iron that causes an iron deficiency. The cause can also be due to a Lower or less efficient absorption of iron in the small intestine. Examples of situations in which iron absorption is less efficient include:

1. Bowel problems such as Crohn's disease or ulcerative colitis (IBD); A recent dissertation by Roberta Loveikyte (April 2024) discovered that 1 in 5 outpatients with IBD has anemia, often due to an iron deficiency. (6)
2. Gastric bypass (stomach reduction surgery)
3. Celiac disease (gluten allergy) or gluten intolerance

Because non-heme iron (plant-based foods) is less well absorbed than heme iron (animal products), it can be included in a vegetarian or vegan diet. it can be a challenge to get enough iron.

It's therefore important to eat more of these foods and pay attention to how they're eaten to improve absorption . This can be done by combining certain foods in a meal:

Vitamin C supports the absorption of non-heme iron. Combining foods rich in vitamin C, such as fruit, with iron-rich foods improves iron absorption. A glass of orange juice with a meal is a good example.(7),(8)

These substances inhibit the absorption of iron

1. Calcium (including in dairy products)
2. Phytic acid (found in grains and legumes)
3. Polyphenols (eg in tea and coffee)

That's good to know, of course, but how do you apply that in practice?

Try to eat foods rich in calcium, phytic acid, and polyphenols separately from your meal if they contain iron. For example, have your cup of coffee an hour after your meal instead of right after. Do you like a bowl of yogurt after your meal? Eat it as a snack or wait a bit longer.

To get you started, try this simple recipe . This dish will give your iron levels a significant boost. It combines foods rich in non-heme iron with ingredients rich in vitamin C.

Do you suspect your iron levels are too low? Then you can have your blood tested by your GP. These blood values ​​together provide a good picture of your iron status and help identify an iron deficiency or anemia:

1. Hemoglobin (Hb) - Indicates whether sufficient oxygen can be transported by the blood.
2. Hematocrit (Ht) - To measure the ratio of red blood cells to total blood volume.
3. Ferritin - Indicates how much iron is available for the body to use (iron stores).
4. Transferrin – To determine iron status.

You suffer from anemia if you have too little hemoglobin or too few red blood cells. in your blood. Anemia can be temporary or chronic (e.g., due to a hereditary condition).

Although iron deficiency is the most common cause of anemia, it is possible for a person to have an iron deficiency without having low hemoglobin levels.

Other factors, such as a vitamin B12 or folic acid deficiency , can also cause anemia, as can underlying conditions that break down red blood cells. Therefore, an iron deficiency is not the same as anemia!

1. Anemia: decreased hemoglobin level 
2. Iron deficiency: decreased serum* ferritin level

(*) Serum is a clear, jelly-like fluid that remains after blood has clotted and the blood cells have settled. Serum contains various components, including proteins, hormones, nutrients, waste products, and other dissolved substances.

The hemoglobin value (Hb value) indicates how much hemoglobin is present in the blood and therefore how much oxygen the blood can carry. A healthy Hb value varies by age(9)

A low Hb level can lead to anemia, which results in insufficient oxygen transport in the blood. You can increase your iron levels by taking the following steps:

1. Choose more iron-rich foods (see overview below)
2. Combine animal products (heme iron) with plant products (heme iron)
3. Mix iron-rich meals with ingredients that contain a lot of vitamin C
4. Eat calcium-rich products separately
5. Don't drink your coffee immediately after your meal

On the other hand, a high Hb level can indicate sufficient oxygen in the blood, but the blood can become thicker and more viscous than normal. You may be consuming too much iron, for example, by overdosing on iron supplements. You can lower your iron levels in the following ways:

1. Limit red meat consumption
2. Choose vegetable protein sources
3. Avoid iron-rich foods
4. Moderate the consumption of iron-rich vegetables
5. Combine meals with dairy products (or other foods rich in calcium)

Iron is stored in the body as ferritin and is distributed throughout the body by transferrin (a protein in the blood that binds to iron). Measuring your ferritin levels, therefore, provides insight into your iron stores.

Because your ferritin levels are largely genetically determined, you don't have much control over how they change. However, you can try a few things yourself to increase your ferritin levels:

1. Choose more iron-rich foods (see overview below)
2. Combine animal products (heme iron) with plant products (heme iron)
3. Mix iron-rich meals with ingredients that contain a lot of vitamin C
4. Eat calcium-rich products separately
5. Don't drink your coffee immediately after your meal

If your blood test shows high ferritin levels, this doesn't necessarily mean you have too much iron. An infection or a (hereditary) condition, for example, can increase the presence of the protein ferritin in your blood. You can try to lower your ferritin levels yourself by taking the following steps:

1. Limit red meat consumption
2. Choose vegetable protein sources
3. Avoid iron-rich foods
4. Moderate the consumption of iron-rich vegetables
5. Combine meals with dairy products (or other foods rich in calcium)

Heme iron is mainly found in (red) meat, poultry, and fish. Non-heme iron is found in whole grains, cocoa, dried fruit, nuts, and leafy greens.

These are examples of iron-rich foods that will help you get your daily iron intake:

An excess of iron, also known as iron overload (medical term: hemochromatosis) can be dangerous. However, you generally don't need to worry about eating too much iron. In most cases, the cause is one of the following:

1. Genetic factors
2. Excessive use of iron supplements
3. Repeated blood transfusions
4. Liver diseases

In the Netherlands, the upper limit for iron intake has been set at 45 mg per day for adults and 40 mg per day for children up to 14 years of age (Health Council and the European Food Safety Authority EFSA).

This means that if you consume more than 40 or 45 mg of iron per day, you will experience symptoms of iron poisoning can experience. (source)

Iron overload can lead to unpleasant symptoms. These can range from mild to severe, depending on the degree of iron accumulation and the organs affected. Common symptoms include:

1. Yield
2. Nausea
3. Stomach ache

If iron overload (hemochromatosis) is left untreated, further complications may occur including:

1. Joint pain
2. Liver function disorders (such as liver enlargement)
3. Skin discoloration (bronze or gray tint)
4. Heart problems (such as heart rhythm disturbances and heart failure)
5. Diabetes
6. Hormone disruptions

If iron overload is suspected, it is important to seek medical help for diagnosis and treatment.

Reference list

1. https://www.ncbi.nlm.nih.gov/books/NBK540969/
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9219084/
3. https://www.voedingscentrum.nl/encyclopedie/ijzer.aspx#blokhoe-neemt-het-lichaam-ijzer-op
4. https://www.voedingscentrum.nl/encyclopedie/ijzer.aspxVoedingscentrum
5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7123805/
6. https://research.rug.nl/en/publications/iron-deficiency-in-inflammatory-bowel-disease-the-underestimated
7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7607440/
8. https://www.ncbi.nlm.nih.gov/books/NBK448204/
9. https://richtlijnen.nhg.org/landelijke-eerstelijns-samenwerkingsafspraken/laboratoriumdiagnostiek#volledige-tekst-referentiewaarden