Dietary Supplement Fact Sheet: Iron

Written by National Institutes of Health

Iron is an important component of good health. Detailed information on iron intake, iron deficiency and iron supplements.

Table of Contents

• Iron: What is it?
• What foods provide iron?
• What affects iron absorption?
• What is the recommended intake for iron?
• When can iron deficiency occur?
• Who may need extra iron to prevent a deficiency?
• Does pregnancy increase the need for iron?
• Some facts about iron supplements
• Who should be cautious about taking iron supplements?

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• What are some current issues and controversies about iron?
• What is the risk of iron toxicity?
• Selecting a healthful diet
• References

Iron: What is it?

Iron, one of the most abundant metals on Earth, is essential to most life forms and to normal human physiology. Iron is an integral part of many proteins and enzymes that maintain good health. In humans, iron is an essential component of proteins involved in oxygen transport [1,2]. It is also essential for the regulation of cell growth and differentiation [3,4]. A deficiency of iron limits oxygen delivery to cells, resulting in fatigue, poor work performance, and decreased immunity [1,5-6]. On the other hand, excess amounts of iron can result in toxicity and even death [7].

Almost two-thirds of iron in the body is found in hemoglobin, the protein in red blood cells that carries oxygen to tissues. Smaller amounts of iron are found in myoglobin, a protein that helps supply oxygen to muscle, and in enzymes that assist biochemical reactions. Iron is also found in proteins that store iron for future needs and that transport iron in blood. Iron stores are regulated by intestinal iron absorption [1,8].

What foods provide iron?

There are two forms of dietary iron: heme and nonheme. Heme iron is derived from hemoglobin, the protein in red blood cells that delivers oxygen to cells. Heme iron is found in animal foods that originally contained hemoglobin, such as red meats, fish, and poultry. Iron in plant foods such as lentils and beans is arranged in a chemical structure called nonheme iron [9]. This is the form of iron added to iron-enriched and iron-fortified foods. Heme iron is absorbed better than nonheme iron, but most dietary iron is nonheme iron [8]. A variety of heme and nonheme sources of iron are listed in Tables 1 and 2.

Table 1: Selected Food Sources of Heme Iron [10]

References