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.

For serving size for specific foods, see Nutrient Rating Chart below at the bottom of this page.

Description Function Deficiency Symptoms Toxicity Symptoms Cooking, storage and processing Factors that affect function

Drug-nutrient interaction Nutrient interaction Health conditions Supplements Food Sources Public Recommendations References

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 can be decreased by caffeine and by tannins found in coffee and tea. Recent research on tea, however, has repeatedly shown that individuals with healthy iron status need not worry about the impact of tea tannins on their iron absorption. These same studies advise individuals who are iron deficient, however, to wait at least one hour after a meal before drinking green or black tea. Phosphates found in carbonated soft drinks can also decrease iron absorption.

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 Parkinson's 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?

The most advantageous nutrient for helping you increase your absorption of plant-food iron is vitamin C. A meal that contains about 25 milligrams of vitamin C may as much as double your absorption of plant food iron from that meal. Copper is another key nutrient for supporting your iron metabolism. In this case, it is transport of iron around the body that relies in many ways on the presence of copper. So important is this relationship that iron-deficiency anemia may sometimes reflect the more basic underlying problem of copper deficiency. Vitamin A may also help improve iron status, and perhaps because of their relationship to stomach acidity levels, so might amino acids and organic acids (like citric acid or malic acid). There might also be better absorption of some plant iron from a meal when animal foods containing heme iron (the primary form of iron in animals) are present.

Research is less clear on the relationship between iron and calcium, although most studies show problems with iron absorption when too much calcium is present. Since too much calcium in this case usually means 300 milligrams or more, this iron-calcium interaction is not likely to cause practical problems in most food situations. But it might come into play if a person had high iron requirements and was drinking a full glass of cow's milk (containing about 300 milligrams of calcium) along with an iron-rich meal. In this kind of circumstance, it might make sense to cut meal-time consumption of the milk in half and hold the other half for a between-meal snack. The ability of calcium to block iron absorption has led some researchers to recommend that individuals with high iron requirements avoid taking calcium supplements alongside of meals. Other nutrients that can lower absorption of plant iron include phytic acid (found in grains and legumes), certain plant food polyphenols (like tannins), and soy proteins. However, we are still able to absorb helpful amounts of iron from plant foods that contain any or several of these nutrients, and foods like whole wheat, whole grain rice, soybeans or other legumes are still very much worth including in the diet, even when iron absorption from these foods is moderate to low.

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

What foods provide iron?

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

Very good sources of iron include romaine lettuce, blackstrap molasses, tofu, mustard greens, turnip greens, string beans, and shiitake mushrooms.

Good sources of iron include beef tenderloin, lentils, Brussel sprouts, asparagus, venison, garbanzo beans, broccoli, leeks, and kelp.

 

Introduction to Nutrient Rating System Chart

In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the World's Healthiest Foods that are either an excellent, very good, or good source of iron. Next to each food name, you'll find the serving size we used to calculate the food's nutrient composition, the calories contained in the serving, the amount of iron contained in one serving size of the food, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling." Read more background information and details of our rating system.

World's Healthiest Foods ranked as quality sources of: iron
Food	Serving Size	Cals	Amount (mg)	DV (%)	Nutrient Density	World's Healthiest Foods Rating
Thyme, dried, ground	2 tsp	7.9	3.56	19.8	44.9	excellent
Dill weed	2 tsp	5.1	0.98	5.4	19.4	very good
Cumin seeds	1 tsp	7.5	1.32	7.3	17.6	very good
Parsley, fresh	2 tbs	2.7	0.46	2.6	17.0	good
Basil, dried, ground	2 tsp	7.5	1.28	7.1	17.0	very good
Spinach, boiled	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, dried, ground	2 tsp	9.2	1.32	7.3	14.4	very good
Turmeric, powder	2 tsp	16.0	1.88	10.4	11.7	excellent
Black pepper	2 tsp	10.9	1.24	6.9	11.4	very good
Swiss 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
Romaine lettuce	2 cup	15.7	1.23	6.8	7.8	very good
Blackstrap molasses	2 tsp	32.1	2.39	13.3	7.4	very good
Tofu, raw	4 oz-wt	86.2	6.08	33.8	7.1	very good
Kelp (sea vegetable)	0.25 cup	8.6	0.57	3.2	6.6	good
Coriander seeds	2 tsp	9.9	0.56	3.1	5.6	good
Mustard greens, boiled	1 cup	21.0	0.98	5.4	4.7	very good
Shiitake mushrooms, raw	8 oz-wt	87.2	3.59	19.9	4.1	very good
Turnip greens, cooked	1 cup	28.8	1.15	6.4	4.0	very good
Green 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, boiled	1 cup	36.4	1.17	6.5	3.2	good
Broccoli, steamed	1 cup	43.7	1.37	7.6	3.1	good
Shrimp, steamed/boiled	4 oz-wt	112.3	3.50	19.4	3.1	good
Brussel 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	1 cup	154.6	4.44	24.7	2.9	good
Lentils, cooked	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, raw	0.25 cup	186.7	5.16	28.7	2.8	good
Sesame seeds	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, uncooked	0.25 cup	158.9	3.93	21.8	2.5	good
Fennel, raw, sliced	1 cup	27.0	0.64	3.6	2.4	good
Chili pepper, dried	2 tsp	25.5	0.60	3.3	2.4	good
Kidney beans, cooked	1 cup	224.8	5.20	28.9	2.3	good
Mustard seeds	2 tsp	35.0	0.76	4.2	2.2	good
Tomato, ripe	1 cup	37.8	0.81	4.5	2.1	good
Lima beans, cooked	1 cup	216.2	4.49	24.9	2.1	good
Pinto beans, 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
Crimini mushrooms, raw	5 oz-wt	31.2	0.57	3.2	1.8	good
Summer squash, cooked, slices	1 cup	36.0	0.65	3.6	1.8	good
Beets, Boiled	1 cup	74.8	1.34	7.4	1.8	good
Garbanzo beans (chickpeas), cooked	1 cup	269.0	4.74	26.3	1.8	good
Collard greens, boiled	1 cup	49.4	0.87	4.8	1.8	good
Navy beans, 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
Black beans, cooked	1 cup	227.0	3.61	20.1	1.6	good
Calf's liver, braised	4 oz-wt	187.1	2.97	16.5	1.6	good
Sweet potato, 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 2003.
• Beard JL. Iron biology in immune function, muscle metabolism and neuronal functioning. J Nutr 2001 Feb;131(2S-2):568S-79S; discussion 580S 2001. PMID:15700.
• Chiueh CC. Iron overload, oxidative stress, and axonal dystrophy in brain disorders. Pediatr Neurol 2001 Aug;25(2):138-47 2001. PMID:15600.
• Emerit J, Beaumont C, Trivin F. Iron metabolism, free radicals, and oxidative injury. Biomed Pharmacother 2001 Jul;55(6):333-9 2001. PMID:15640.
• Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism. West Publishing Company, New York, 1995 1995.
• Hallberg L. Perspectives on nutritional iron deficiency. Annu Rev Nutr 2001;21:1-21 2001. PMID:15670.
• 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 2001.
• Leung AK, Chan KW. Iron deficiency anemia. Adv Pediatr 2001;48:385-408 2001. PMID:15630.
• 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 2001. PMID:15690.
• Lininger SW, et al. A-Z guide to drug-herb-vitamin interactions. Prima Health, Rocklin, CA, 2000 2000.
• Rouault TA. Systemic iron metabolism: a review and implications for brain iron metabolism. Pediatr Neurol 2001 Aug;25(2):130-7 2001. PMID:15610.
• 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 2001. PMID:15590.
• Thompson KJ, Shoham S, Connor JR. Iron and neurodegenerative disorders. Brain Res Bull 2001 May 15;55(2):155-64 2001. PMID:15650.

Send this page to a friend...