Iron (Fe)

What is iron?

Iron is a mineral required by every organ system in our bodies.¹ Most of the body’s iron is found in hemoglobin, a protein in red blood cells.² Iron is also stored within tissues and used for other essential processes. Since our bodies cannot produce iron, we must get it through our diet.

Why we need it

As a required component of hemoglobin, iron allows red blood cells to carry oxygen throughout the body. This means that without iron, our cells would not get the oxygen they need to function.

Iron is also crucial for growth and development, especially in the brain. It helps form myelin, a protective layer that coats our brain cells.³ Iron also helps synthesize neurotransmitters and regulate genes involved in brain development.³ Our immune system also requires iron to develop properly.¹ This means getting enough iron (especially early in life) helps us fight off illness and infection.

Iron has many other miscellaneous functions. It is involved in energy production, muscle function, oxygen sensing, and drug detoxification, among other things.²

Where it’s found

Iron is found in two forms in food: heme iron and non-heme iron. Heme iron, which is in animal-based foods, is more easily absorbed by the body.⁴ Non-heme iron, found in plant-based foods, is more difficult to absorb.⁴

Examples of iron-rich foods include:

Red meat
Fish and seafood
Poultry
Beans
Lentils
Tofu
Fortified cereal
Spinach
Nuts

Iron is also available as a supplement, usually in the form of non-heme iron.⁴ It’s available as a standalone supplement, or as part of a multivitamin.⁴

Daily requirements

The Recommended Dietary Allowance (RDA) for iron, or the daily amount that is likely to meet the needs of most healthy people, is 7 milligrams (mg) for children aged 1-3 years, 10 mg for children aged 4-8 years, 8 mg for children aged 9-13 years, 11 mg for males aged 14-18 years, 15 mg for females aged 14-18 years, 8 mg for men aged 19 years and up, 18 mg for women aged 19-50 years, and 8 mg for women over the age of 51.2 The RDA values for pregnant and breastfeeding women are 27 mg and 9-10 mg, respectively.²

Iron deficiency

Iron deficiency is the most common worldwide nutrient deficiency.¹ There are many possible causes of iron deficiency, including insufficient iron intake, excessive iron losses through the blood, and iron malabsorption. Groups that may be at a higher risk for iron deficiency include vegetarians and vegans, pregnant women, young children, and people with malabsorptive disorders.

Iron deficiency can lead to anemia, a condition characterized by low levels of red blood cells. Symptoms of iron deficiency anemia include fatigue, pale skin, shortness of breath, and heart palpitations.³

Iron deficiency during pregnancy can increase the risk of low birth weight, preterm delivery, and other complications.² In infants and children, iron deficiency can cause abnormal brain development and impaired immune function. It can also compromise cognitive, social, and psychological development.¹ These consequences can be irreversible in severe cases.¹

Can you get too much iron?

Iron can have negative effects if consumed in excessive amounts. Too much iron can cause gastrointestinal issues like nausea, vomiting, and diarrhea.² Prolonged iron toxicity can damage the heart, central nervous system, liver, kidney, and blood.² Iron toxicity from food is extremely rare. Instead, it’s usually due to excessive supplementation or genetic conditions.²

To prevent toxicity, a Tolerable Upper Intake Level (UL), or a maximum daily amount that is considered safe, has been established for iron. The UL for iron is 40 mg per day for infants and children aged 1-13 years, and 45 mg per day for anyone over the age of 14.²

Fun facts

Vitamin C can help us absorb non-heme iron, by promoting the conversion of ferric non-heme iron to ferrous non-heme iron (the form that can be taken up by intestinal cells).⁵ That said, pairing plant-based iron sources with vitamin C (e.g., pairing a grain with a citrus fruit) can help us maximize our iron absorption.

In order to be taken up by our tissues, iron must be oxidized (converted back to its ferric state). This process is carried out by the enzyme ceruloplasmin, which requires copper (another essential mineral) to function.² This means that if we don’t have enough copper, we can’t utilize iron. This may lead to what is called a secondary iron deficiency.

References