Quick summary

Iron is an essential mineral crucial for oxygen transport, energy metabolism, and various enzymatic processes in the human body. It plays a key role in hemoglobin formation and is necessary for normal growth and development.

What is it?

Iron is a vital mineral involved in many biological functions in humans. Chemically known simply as iron, it is a metallic element that the body requires to support health and physiological processes. Iron does not belong to a distinct mineral subgroup in this classification but is fundamental due to its role in oxygen transport and metabolism. It is found in various dietary sources, both animal- and plant-based.

Main functions in the body

  • Oxygen transport as a component of hemoglobin and myoglobin
  • Supports cellular energy metabolism
  • Contributes to various enzymatic reactions

Recommended intake and upper limit

Recommended Dietary Allowances (RDAs) or Adequate Intakes (AIs) for iron vary by age, sex, and life stage. These levels are set to meet the nutritional needs of nearly all healthy individuals. Tolerable upper intake levels (ULs) are established to reduce the risk of adverse effects from excessive consumption, with limits also varying depending on age group.

For detailed, official recommended intakes and ULs, consult authoritative sources such as the NIH Office of Dietary Supplements fact sheet for iron.

Best food sources

  • Red meat
  • Poultry
  • Seafood
  • Legumes
  • Fortified cereals
  • Dark leafy green vegetables

Deficiency: causes, symptoms and risk groups

Iron deficiency is considered one of the most common nutritional disorders worldwide. It is also the leading cause of anemia, a condition characterized by insufficient healthy red blood cells.

Risk groups include:

  • Infants and young children
  • Women of reproductive age, especially pregnant women
  • Individuals experiencing chronic blood loss
  • People with inadequate dietary intake or malabsorption issues

Signs and symptoms may include:

  • Fatigue
  • Weakness
  • Paleness
  • Impaired cognitive function
  • Reduced immune function

Supplement forms

The evidence reviewed does not specify particular iron supplement forms or recommend one form over another. Common supplement forms available generally include ferrous sulfate, ferrous gluconate, ferrous fumarate, and others; however, differences in absorption or clinical effectiveness are not detailed here.

Absorption and bioavailability

Iron absorption is influenced by the form of iron and the presence of dietary factors that may enhance or inhibit uptake. There are two main dietary types:

  • Heme iron: Found in animal sources, this form is generally absorbed more efficiently by the body.
  • Non-heme iron: Found in plant sources and fortified foods, this form has lower bioavailability.

Enhancers of absorption include:

Inhibitors of absorption include:

  • Phytates
  • Polyphenols
  • Calcium
  • Certain plant compounds

The presence of these factors in meals can substantially impact how much dietary iron enters the bloodstream.

Potential benefits: what does the evidence say?

Correction of iron deficiency anemia:

The strongest evidence supports the use of iron supplementation for treatment of iron deficiency anemia. Supplementation typically improves symptoms related to anemia such as fatigue and cognitive impairment in those diagnosed with deficiency.

Limitations: Benefits have only been demonstrated in individuals with iron deficiency. Supplementation in people who already have adequate or high iron stores is not beneficial and may pose risks.

Side effects and toxicity

There are no commonly noted side effects reported for iron at typical dietary levels; however, excessive iron intake can lead to toxicity. Iron overdose may cause gastrointestinal distress and, in severe cases, more serious outcomes, especially in children.

Respecting established upper intake levels is important to minimize the risk of toxic effects. Particular caution is advised for individuals with iron overload disorders such as hemochromatosis and for young children, who are more vulnerable to iron poisoning.

Drug and nutrient interactions

The supplied evidence does not include specific drug–nutrient interaction data. Nonetheless, it is known that iron absorption can be decreased or impaired by certain medications and other nutrients, which emphasizes the importance of medical advice when combining iron supplements with other treatments.

Who should be careful?

  • Individuals with genetic or acquired iron overload disorders, such as hemochromatosis
  • Young children, due to the risk of iron poisoning
  • Pregnant and breastfeeding women, who should consult healthcare professionals regarding iron needs
  • Those with kidney disease, thyroid disease, or other medical conditions
  • People using medications potentially interacting with iron absorption or metabolism

Frequently asked questions

1. Can taking iron supplements help if I do not have iron deficiency?
Supplementing with iron without a diagnosed deficiency is generally not recommended and may be harmful. Iron supplements are typically reserved for those with confirmed low iron status.

2. What foods improve iron absorption?
Vitamin C-rich foods, such as citrus fruits or bell peppers, can enhance iron absorption when consumed alongside iron-containing foods.

3. Can I get enough iron from a vegetarian diet?
Iron from plant-based sources is less well absorbed, but careful dietary planning including legumes, fortified foods, and vitamin C can support adequate intake. Some people, especially women with higher iron needs, may require monitoring.

4. How do I know if I am iron deficient?
Iron deficiency is diagnosed through clinical evaluation including blood tests measuring hemoglobin, ferritin, and other iron markers. If symptoms or risk factors exist, consult a healthcare professional.

Evidence limitations

  • The evidence reviewed does not supply data on differences among iron supplement forms nor clinical outcomes beyond the correction of deficiency.
  • There are no EU-authorized health claims for iron presented in this summary.

References

Disclaimer: This page provides an evidence-based overview of iron from reputable sources but does not constitute medical advice. Individuals who are pregnant, breastfeeding, have medical conditions such as kidney disease or iron overload disorders, or take medications should consult a healthcare professional before starting any iron supplementation.

Last reviewed

June 2024