Lahey Health is now part of Beth Israel Lahey Health

by Kassel K

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Image for iron Iron is a mineral found in meats, eggs, milk, vegetables, grains, and other plant foods. It exists in 2 forms—heme and nonheme. Heme iron is found in animal source. Nonheme iron comes from plant sources. The body absorbs heme iron easier than nonheme iron.

Functions

Iron plays a number of roles in the body including:

  • Carries oxygen from lungs to cells throughout the body. Called hemoglobin.
  • Holds oxygen within the cells. Very important in active cells in the heart and muscles. Called myoglobin.
  • Part of a protein called collagen. This protein makes up connective tissue, cartilage, and bone.
  • Helps to make enzymes that fight infections.
  • Changes beta carotene to vitamin A.
  • Part of amino acids. These are the building blocks of protein.
  • Helps the liver get rid of harmful drugs in the body.
  • Forms part of an enzyme that is needed to make chemicals that help to pass nerve signals.
  • Makes part of cells that help with metabolism.

Recommended Intake

Iron needs are greatest during times of rapid growth. This is common in childhood, teen years, and pregnancy. Women also have higher requirements than men. It is needed to replace the iron that is lost with monthly periods. Daily recommendations include:

Age Group Recommended Dietary Allowance (RDA)
(mg/day)
Male Female
0-6 months No RDA;
Adequate Intake (AI) = 0.27
No RDA;
Adequate Intake (AI) = 0.27
7-12 months 11 11
1-3 years 7 7
4-8 years 10 10
9-13 years 8 8
14-18 years 11 15
19-50 years 8 18
51+ years 8 8
Pregnancy n/a 27
Lactation, equal to or less than 18 years n/a 10
Lactation, 19-50 years n/a 9

Iron Deficiency

People who are at higher risk for low levels of iron include:

  • Women of childbearing years
  • Teenage girls
  • Infants (depending on their diet)
  • Children
  • Low-income groups
  • People with certain gastrointestinal conditions, such as celiac disease—can block or slow absorption of iron from food

Low iron can lead to anemia. Symptoms of anemia include:

  • Fatigue: feeling tired all the time or getting tired easily with activities you used to be able to do without difficulty
  • Pale skin, especially the pink lining to your lower eyelids, under your fingernails, or your gums
  • Glossitis (an inflamed tongue)
  • Rapid heartbeat
  • Headaches
  • A ringing in the ears known as tinnitus
  • Unusual cravings for substances like ice, dirt, etc. (called pica)

Iron can be increased with changes to the diet. Iron supplements may be needed if the diet is not enough.

Iron Toxicity

Iron is toxic at high levels. The body is not effective at getting rid of excess iron. This makes it is possible for iron to build up. Iron pills and supplements for adults can cause poisoning in children.

Symptoms of iron toxicity include:

  • Nausea and vomiting
  • Diarrhea or constipation
  • Abdominal pain
  • Fainting

Major Food Sources

Much of the iron in our diet comes from foods, such as breads and cereals that are fortified with iron.

Food Sources of Mostly Heme Iron

Food Serving size Iron content
(mg)
Beef liver, cooked 3 ounces 5
Oysters, cooked 3 ounces 8
Turkey breast, roasted 3 ounces 1
Chicken, roasted, meat and skin 3 ounces 1
Tuna, fresh bluefin, cooked, dry heat 3 ounces 1

Food Sources of Nonheme Iron

Food Serving size Iron content
(mg)
Ready-to-eat cereal, 100% iron fortified ¾ cup 18.0
Lentils, boiled ½ cup 3
Beans, kidney, mature, boiled ½ cup 2
Tofu, raw, firm ½ cup 3
Spinach, boiled, drained ½ cup 3
Whole wheat bread 1 slice 1

Tips for Increasing Your Iron Intake

Your body will absorb more iron from foods when your iron stores are low. It will also absorb less when you have enough iron in your body.

Other factors that will affect how much iron you absorb from foods include:

  • Animal source iron (heme) increases the absorption of plant source iron (nonheme).
  • Vitamin C enhances the absorption of plant source iron.
  • Some substances decrease the absorption of plant source iron:
    • Oxalic acid, found in spinach and chocolate (However, oxalic acid is broken down with cooking.)
    • Phytic acid, found in wheat bran and beans (legumes)
    • Tannins, found in tea
    • Polyphenols, found in coffee

    Note: Having meat source iron and/or vitamin C with plant source iron can help make up for these decreases.

To increase intake and absorption of dietary iron:

  • Combine meat and plant sources of iron.
  • Eat foods rich in vitamin C with plant source iron. Good sources of vitamin C include:
    • Bell peppers
    • Papayas
    • Oranges and orange juice
    • Broccoli
    • Strawberries
    • Grapefruit
    • Cantaloupe
    • Tomatoes and tomato juice
    • Potatoes
    • Cabbage
    • Spinach and collard greens
  • If you drink coffee or tea, do so between meals rather than with a meal.
  • Cook acidic foods in cast iron pots. This can increase iron content up to 30 times.

RESOURCES

Eat Right—Academy of Nutrition and Dietetics  http://www.eatright.org 

Vegetarian Resource Group  http://www.vrg.org 

CANADIAN RESOURCES

Dietitians of Canada  http://www.dietitians.ca 

Health Canada  http://www.hc-sc.gc.ca 

References

Dietary supplement fact sheet: iron. Office of Dietary Supplements website. Available at:https://ods.od.nih.gov/factsheets/Iron-HealthProfessional. Updated December 7, 2018. Accessed January 13, 2019.

Iron deficiency anemia in adults. EBSCO DynaMed website. Available at:  https://www.dynamed.com/topics/dmp~AN~T115986/Iron-deficiency-anemia-in-adults . Updated August 16, 2018. Accessed January 13, 2019.

Iron deficiency anemia in children. EBSCO DynaMed website. Available at:  https://www.dynamed.com/topics/dmp~AN~T435307/Iron-deficiency-in-children-infancy-through-adolescence . Updated December 4, 2018. Accessed January 13, 2019.

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