iron

What can high-iron foods do for you?

  • Enhance oxygen distribution throughout your body
  • Keep your immune system healthy
  • Help your body produce energy

What events may indicate a need for more high-iron foods?

  • Fatigue and weakness
  • Decreased ability to concentrate
  • Increased susceptibility to infections
  • Hair loss
  • Dizziness
  • Headaches
  • Brittle nails
  • Apathy
  • Depression

Excellent food sources of iron include chard, spinach, turmeric and thyme.

 

Description

What is iron?

Iron is vital to the health of the human body, and is found in every human cell, primarily linked with protein to form the oxygen-carrying molecule hemoglobin. The human body contains approximately 4 grams of iron.

Dietary iron comes in two forms: heme iron and non-heme iron. Heme iron is found only in animal flesh, as it is derived from the hemoglobin and myoglobin in animal tissues. Non-heme iron is found in plant foods and dairy products.

How it Functions

What is the function of iron?

Oxygen Distribution

Iron serves as the core of the hemoglobin molecule, which is the oxygen-carrying component of the red blood cell. Red blood cells pick up oxygen from the lungs and distribute the oxygen to tissues throughout the body. The ability of red blood cells to carry oxygen is attributed to the presence of iron in the hemoglobin molecule.

If we lack iron, we will produce less hemoglobin, and therefore supply less oxygen to our tissues. Iron is also an important constituent of another protein called myoglobin. Myoglobin, like hemoglobin, is an oxygen-carrying molecule, which distributes oxygen to muscles cells, especially to skeletal muscles and to the heart.

Energy Production

Iron also plays a vital role in the production of energy as a constituent of several enzymes, including iron catalase, iron peroxidase, and the cytochrome enzymes. It is also involved in the production of carnitine, a nonessential amino acid important for the proper utilization of fat. The function of the immune system is also dependent on sufficient iron.

Deficiency Symptoms

What are deficiency symptoms of iron?

Although the human body conserves iron very well by reusing iron from old red blood cells to make hemoglobin for new red blood cells, iron deficiency is one of the most common nutrient deficiencies in the United States and around the world. Poor iron status may be caused by inadequate dietary intake, poor absorption, parasitic infection, and/or medical conditions that cause internal bleeding.

People who donate blood regularly, women with excessive menstrual bleeding, those who use medications (for example, antacids) that interfere with the absorption of iron, and pregnant and lactating women may be at risk for iron deficiency. In addition, the elderly, vegetarians, and children often have inadequate intake of this mineral.

Iron deficiency causes microcytic and hypochromic anemia, a condition characterized by underdeveloped red blood cells that lack hemoglobin, thereby reducing the oxygen carrying capacity of red blood cells. But even before iron deficiency anemia develops, people with poor iron status may experience a variety of symptoms including fatigue, weakness, loss of stamina, decreased ability to concentrate, increased susceptibility to infections, hair loss, dizziness, headaches, brittle nails, apathy, and depression.

Individuals with poor iron intake may also demonstrate an unusual eating behavior called pica, in which they eat unsuitable and/or inedible materials such as dirt, clay, laundry starch, charcoal, and/or lead paint chips. In children, iron deficiency is associated with learning disabilities and a lower IQ.

Toxicity Symptoms

What are toxicity syptoms for iron?

Iron poisoning, caused by acute ingestion of large quantities of iron-containing supplements, causes nausea, vomiting, damage to the lining of the intestinal tract, shock, and liver failure, and is a leading cause of death among children.

Chronic iron overload, or excessive iron storage, can cause a variety of symptoms including loss of appetite, fatigue, weight loss, headaches, bronze or gray hue to the skin, dizziness, nausea, and shortness of breath. It is generally believed that chronic iron toxicity occurs only in people who require regular blood transfusions, take iron supplements, or in those with a genetic iron storage disorder called hemachromatosis. With hemochromatosis, iron is deposited in tissues throughout the body, most notably the liver, pancreas, and heart, potentially causing cirrhosis, diabetes, or cardiac insufficiency.

Although iron overload is not likely to develop from food sources alone, men, because they do not experience iron losses, may be at greater risk for the problems associated with excessive iron. In recent years, excess iron intake and storage, especially in men, has been implicated as a cause of heart disease and cancer. In addition, iron has been found in increased levels in the joints of people with rheumatoid arthritis.

Impact of Cooking, Storage and Processing

How do cooking, storage, or processing affect iron?

Much of the iron in whole grains is found in the bran and germ. As a result, the milling of grain, which removes the bran and germ, eliminates about 75% of the naturally occurring iron in whole grains. Refined grains are often fortified with iron, but the added iron is less absorbable than the iron that naturally occurs in the grain. Cooking with iron cookware will add iron to food, a practice that can eventually lead to iron toxicity.

Factors that Affect Function

What factors might contribute to a deficiency of iron?

Iron absorption is increased when there is an increased physiological need for iron, as occurs in children during rapid growth periods and during pregnancy and lactation.

Iron absorption is decreased in people with low stomach acid (hypochlorhydria), a condition that is common in the elderly and those who use antacids frequently. In addition, iron absorption is decreased by caffeine and tannic acid found in coffee and tea and by phosphates found in carbonated soft drinks.

Phytates, found in whole grains, and oxalates, found in spinach and chocolate, may also decrease iron absorption by forming complexes with the mineral that cannot be absorbed through the digestive tract.

Drug-Nutrient Interactions

What medications affect iron?

Use of the following medications may increase the amount of iron you need in your diet:
  • Aspirin and non-steroidal anti-inflammatory medications (for example, ibuprofen) may cause gastrointestinal bleeding. Over the long term this can cause iron deficiency anemia.
  • Histamine blockers (Tagamet and Tagamet HB, Pepcid and Pepcid AC, Axid and Axid AR, Zantac) prevent the release of stomach acid and are used in the treatment of ulcers, heartburn, and acid reflux. These drugs reduce iron absorption by decreasing the acidity of the stomach. For this same reason, antacids (for example, Tums and Rolaids) reduce iron absorption.
  • Neomycin, an antibiotic, reduces iron levels.
  • Stanozolol, a synthetic anabolic steroid related to the natural hormone testosterone, is associated with iron depletion.
  • Iron binds with warfarin (Coumadin), which may decrease the absorption or activity of iron.

Pencillamine and Deferoxamine (Desferal) are chelating agents used to treat iron intoxication and chronic iron overload. The use of oral contraceptives reduces the amount of blood lost in the menstrual cycle. As a result, women who take oral contraceptives may have high blood levels of iron, presuming they consume a sufficient amount of iron in their diet.

Dietary iron, especially from iron-containing supplements, may impact the absorption of the following medications:
  • Iron binds with sulfasalazine, decreasing sulfasalazine absorption.
  • Iron decreases the absorption of tetracycline.
  • Iron supplements may decrease absorption of thyroid hormone medications.
  • Iron supplements may interfere with the action of carbidopa, a drug used in the treatment of Parkinsonís disease.
  • Iron supplements decrease the absorption of methyldopa, a drug used to lower blood pressure in people with high blood pressure.

Nutrient Interactions

How do other nutrients interact with iron?

Several nutrients increase iron absorption including ascorbic acid (vitamin C), copper, cobalt, and manganese. Amino acids also improve iron absorption by stimulating the secretion of hydrochloric acid in the stomach. High dietary intake of calcium may decrease absorption of dietary iron.

Health Conditions

What health conditions require special emphasis on iron?

Iron may play a role in the prevention and/or treatment of the following medical conditions:
  • Alcoholism
  • Attention deficit disorder
  • Colitis
  • Diabetes
  • Excessive menstrual blood loss
  • Iron deficiency anemia
  • Leukemia
  • Parasitic infections
  • Restless leg syndrome
  • Stomach ulcers
  • Tuberculosis

Form in Dietary Supplements

What forms of iron are found in dietary supplements?

Most dietary supplements contain ferrous sulfate, a source of non-heme iron. Iron is also available in supplemental form as ferrous fumarate and ferrous succinate

Food Sources

Introduction to Nutrient Rating System Chart

The following chart shows the foods which are either excellent, very good or good sources of this nutrient. Next to each food name you will find the following information: the serving size of the food; the number of calories in one serving; DV% (percent daily value) of the nutrient contained in one serving (similar to other information presented in the website, this DV is calculated for 25-50 year old healthy woman); the nutrient density rating; and the food's World's Healthiest Foods Rating. Underneath the chart is a table that summarizes how the ratings were devised. For more detailed information on our Nutrient Rating System, please click here.

 

Foods Ranked as quality sources of:
iron
Food Serving
Size
Cals Amount
(mg)
DV
(%)
Nutrient
Density
World's
Healthiest
Foods Rating
Thyme, Ground 2 tsp 7.9 3.56 19.8 44.9 excellent
Cumin, Seeds 1 tsp 7.5 1.32 7.3 17.6 very good
Parsley, Fresh 1 oz-wt 10.2 1.76 9.8 17.2 very good
Basil, Ground 2 tsp 7.5 1.28 7.1 17.0 very good
Spinach (boiled, with salt) 1 cup 41.4 6.43 35.7 15.5 excellent
Cinnamon, Ground 2 tsp 11.8 1.72 9.6 14.5 very good
Oregano, Ground 2 tsp 9.2 1.32 7.3 14.4 very good
Turmeric, Ground 2 tsp 16.0 1.88 10.4 11.7 excellent
Pepper, Black 2 tsp 10.9 1.24 6.9 11.4 very good
Chard, Boiled 1 cup 35.0 3.96 22.0 11.3 excellent
Rosemary, Dried 2 tsp 7.3 0.64 3.6 8.8 good
Lettuce, Romaine 2 cup 15.7 1.23 6.8 7.8 very good
Blackstrap Cane Molasses 2 tsp 32.1 2.39 13.3 7.4 very good
Peppermint Leaves, Fresh 1 oz-wt 19.9 1.44 8.0 7.3 very good
Tofu, Raw 4 oz-wt 86.2 6.08 33.8 7.1 very good
Coriander, Seeds 2 tsp 9.9 0.56 3.1 5.6 good
Dill Seed 2 tsp 13.4 0.72 4.0 5.4 good
Greens, Mustard, Boiled 1 cup 21.0 0.98 5.4 4.7 very good
Mushrooms, Shiitake, Raw 8 oz-wt 87.2 3.59 19.9 4.1 very good
Greens, Turnip, Cooked 1 cup 28.8 1.15 6.4 4.0 very good
Green Snap/String Beans, Boiled 1 cup 43.8 1.60 8.9 3.7 very good
Leeks, Boiled 0.50 cup 16.1 0.57 3.2 3.5 good
Kale, Fresh, Boiled 1 cup 36.4 1.17 6.5 3.2 good
Broccoli (pieces, steamed) 1 cup 43.7 1.37 7.6 3.1 good
Shrimp, MixedSpecies, Steamed, Boiled 4 oz-wt 112.3 3.50 19.4 3.1 good
Brussels Sprouts, Boiled 1 cup 60.8 1.87 10.4 3.1 good
Asparagus, Boiled 1 cup 43.2 1.31 7.3 3.0 good
Soybeans, Cooked 1 cup 297.6 8.84 49.1 3.0 good
Olives, Ripe 1 cup 154.6 4.44 24.7 2.9 good
Lentils, Boiled 1 cup 229.7 6.59 36.6 2.9 good
Venison 4 oz-wt 179.2 5.07 28.2 2.8 good
Pumpkin Seeds, Dried 0.25 cup 186.7 5.16 28.7 2.8 good
Seeds, Sesame 0.25 cup 206.3 5.24 29.1 2.5 good
Celery, Raw 1 cup 19.2 0.48 2.7 2.5 good
Quinoa, Dry 0.25 cup 158.9 3.93 21.8 2.5 good
Fennel Bulb, Sliced, Raw 1 cup 27.0 0.64 3.6 2.4 good
Chili Peppers, Red, Dried 2 tsp 25.5 0.60 3.3 2.4 good
Beans, Kidney, Cooked 1 cup 224.8 5.20 28.9 2.3 good
Seeds, Mustard 2 tsp 35.0 0.76 4.2 2.2 good
Tomato, Red, Raw, Ripe 1 cup 37.8 0.81 4.5 2.1 good
Beans, Lima, Cooked 1 cup 216.2 4.49 24.9 2.1 good
Beans, Pinto, Cooked 1 cup 234.3 4.46 24.8 1.9 good
Green Peas-Boiled 1 cup 134.4 2.46 13.7 1.8 good
Mushrooms, Crimini, Raw 5 oz-wt 31.2 0.57 3.2 1.8 good
Squash, Summer, All Varieties 1 cup 36.0 0.65 3.6 1.8 good
Beets, Boiled 1 cup 74.8 1.34 7.4 1.8 good
Beans, Garbanzo, Cooked 1 cup 269.0 4.74 26.3 1.8 good
Collard Greens, Boiled, Drained 1 cup 49.4 0.87 4.8 1.8 good
Beans, Navy, Cooked 1 cup 258.4 4.51 25.1 1.7 good
Beef Tenderloin, Lean Broiled 4 oz-wt 240.4 4.05 22.5 1.7 good
Beans, Black, Boiled 1 cup 227.0 3.61 20.1 1.6 good
Liver, Calf 4 oz-wt 187.1 2.97 16.5 1.6 good
Sweet Potato (small, baked with skin) 1 each 95.4 1.46 8.1 1.5 good
World's Healthiest
Foods Rating
Rule
excellent DV>=75% OR Density>=7.6 AND DV>=10%
very good DV>=50% OR Density>=3.4 AND DV>=5%
good DV>=25% OR Density>=1.5 AND DV>=2.5%

Public Health Recommendations

What are current public health recommendations for iron?

In 2000, the Institute of Medicine at the National Academy of Sciences established an Adequate Intake level for infants up to 6 months old and Recommended Dietary Allowances for all other age categories. The recommendations appear below:

  • 0-6 months: .27 mg
  • 7-12 months: 11 mg
  • 1-3 years: 7 mg
  • 4-8 years: 10 mg
  • Boys 9-13 years: 8 mg
  • Boys 14-18 years: 11 mg
  • Girls 9-13 years: 8 mg
  • Girls 14-18 years: 15 mg
  • Men 19-30 years: 8 mg
  • Men 31-50 years: 8 mg
  • Men 51-70 years: 8 mg
  • Men greater than 70 years: 8 mg
  • Women 19-30 years: 18 mg
  • Women 31-50 years: 18 mg
  • Women 51-70 years: 8 mg
  • Women greater than 70 years: 8 mg
  • Pregnant women 14-50 years: 27 mg
  • Lactating women 14-18 years: 10 mg
  • Lactating women 19-50 year: 9 mg

Due to the fact that iron status is influenced by the type of diet consumed and by oral contraceptives(see Drug-Nutrient Interactions above), the Institute of Medicine established additional recommendations for vegetarians and for women taking oral contraceptives. These recommendations are as follows:

  • Adult men following a vegetarian diet: 14 mg
  • Adult, premenopausal women following a vegetarian diet: 33 mg
  • Adolescent girls following a vegetarian diet: 26 mg
  • Adolescent girls taking oral contraceptives: 11.4 mg
  • Adult, premenopausal women taking oral contraceptives: 10.9 mg

References

  • Arezzini B, Lunghi B, Lungarella G et al. Iron overload enhances the development of experimental liver cirrhosis in mice. Int J Biochem Cell Biol 2003 Apr;35(4):486-95.
  • Beard JL. Iron biology in immune function, muscle metabolism and neuronal functioning. J Nutr 2001 Feb;131(2S-2):568S-79S; discussion 580S.
  • Chiueh CC. Iron overload, oxidative stress, and axonal dystrophy in brain disorders. Pediatr Neurol 2001 Aug;25(2):138-47.
  • Emerit J, Beaumont C, Trivin F. Iron metabolism, free radicals, and oxidative injury. Biomed Pharmacother 2001 Jul;55(6):333-9.
  • Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism. West Publishing Company, New York, 1995.
  • Hallberg L. Perspectives on nutritional iron deficiency. Annu Rev Nutr 2001;21:1-21.
  • Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press: Washington DC, 2001.
  • Leung AK, Chan KW. Iron deficiency anemia. Adv Pediatr 2001;48:385-408.
  • Lieu PT, Heiskala M, Peterson PA, Yang Y. The roles of iron in health and disease. Mol Aspects Med 2001 Feb-2001 Apr 30;22(1-2):1-87.
  • Lininger SW, et al. A-Z guide to drug-herb-vitamin interactions. Prima Health, Rocklin, CA, 2000.
  • Rouault TA. Systemic iron metabolism: a review and implications for brain iron metabolism. Pediatr Neurol 2001 Aug;25(2):130-7.
  • Roy CN, Andrews NC. Recent advances in disorders of iron metabolism: mutations, mechanisms and modifiers. Hum Mol Genet 2001 Oct 1;10(20):2181-6.
  • Thompson KJ, Shoham S, Connor JR. Iron and neurodegenerative disorders. Brain Res Bull 2001 May 15;55(2):155-64.

This page was updated on: 2004-11-21 11:23:24
© 2002 The George Mateljan Foundation