Iron

How much iron do you need per day?

The Recommended Dietary Allowance (RDA) for iron for healthy people with normal blood iron levels ^[1]:

Chart 1. RDA for Iron
Age	Iron (mg/day)
0-6 months	Breast milk or formula*
7-12 months	11
1-3 years	7
4-8 years	10
9-13 years	8
14-18 years boys	11
14-18 years, girls	15 (26 for vegans)
19+, men	8 (14 for vegans)
19+, menstruating women	18 (33 for vegans)
Pregnant women	27
Breastfeeding women	10
Women after menopause	8 (14 for vegans)

Chart 1 source: NIH.gov, Office of Dietary Supplements ^[1]. NOTE: Cow’s milk is low in iron and it can cause gastrointestinal bleeding, so it should not be given to infants before 1 year of age ^[32,43]. Individuals regularly engaging in hard exercise may need 30% more iron than the RDA listed above ^[1].

Heme and Nonheme Iron

Dietary iron can appear as:

• Nonheme iron in plant foods, milk products, eggs and iron-fortified foods
• Heme iron in meat and fish; heme iron comes from the hemoglobin in the blood and myoglobin in the muscles.

Heme iron is about 1.8 times as bioavailable as nonheme iron, which means you need to get about twice as much iron from plant foods than from animal foods to get the same effect ^[1].

Picture 1. Foods rich in iron

Chart 2. List of Foods High in Iron
ANIMAL FOODS (heme iron)	Iron (mg)
Beef or lamb spleen (3 oz, 85 g)	33
Pork spleen (3 oz, 85 g)	19
Pork liver (3 oz, 85 g)	15
Clams (3 oz, 85 g)	12
Chicken giblets (liver, heart, kidneys) (3 oz, 85 g)	5-9
Cuttlefish, mussels, octopus, oysters, whelks (3 oz, 85 g)	2-9
Beef liver (3 oz, 85 g)	6
Beef (3 oz, 85 g)	2-5
Bison, deer, horse, moose (3 oz, 85 g)	4
Sardines and anchovies (European) with bones (3 oz, 85 g)	4
Goat (3 oz, 85 g)	3
Shrimps, canned (3 oz, 85 g)	2
Chicken, duck, turkey (3 oz, 85 g)	1-2
Fish: bass, catfish, haddock, halibut, herring, mackerel, trout, tuna (3 oz, 85 g)	1
PLANT FOODS (nonheme iron)
Cereals ready-to-eat, fortified (30 mg dry = 1 cup, prepared)	6-18
Oats, instant, prepared (1 cup, 237 mL)	6
Amaranth, teff (1 cup, 237 mL)	5
Soybeans (1/2 cup, 120 mL)	4.5
Legumes: beans, chickpeas, lentils (1/2 cup, 120 mL)	2-5
Pumpkin seeds (1 oz, 28 g)	4
Blackstrap molasses (1 tbsp, 20 g)	3.5
Bagel, biscuit (4″ dia)	3.5
Spinach, boiled (1/2 cup, 120 mL)	3
Grains: quinoa, rice, spelt, wheat kamut (1 cup, 237 mL)	3
Prune juice (1 cup, 237 mL)	3
Beets, canned (1/2 cup, 120 mL)	3
Cornflakes (1 oz dried = 1 cup prepared )	2.5
Tofu (2 oz, 57 g)	2.5
Potatoes, sweet potatoes (1 cup, 237 mL)	2
Grains: barley, bulgur (1 cup, 237 mL)	2
Figs, dried (2 oz, 57 g)	2
Sunflower seeds (1 oz, 28 g)	2
Cashew nuts (1 oz, 28 g)	2
Bread, white or whole-wheat (2 slices, 50 g)	2
Cabbage (Chinese) (1 cup, 237 mL)	2
Swiss chard, cooked (1/2 cup, 120 mL)	2
Bulgur (1 cup, 237 mL)	2
Strawberries (1 cup, 237 mL)	1.5

Chart 1 sources: USDA.gov ^[3] All listed foods are ready to eat.

Human breast milk contains about 0.3 mg iron/liter. About 50% of iron from breast milk is absorbed ^[1]. Breast milk is a sufficient source of iron for healthy infants up to their 6 months of age. The Adequate Intake (AI) for iron for 0-6 months old infants is 0.27 mg/day and for 7-12 months old infants 11 mg/day ^[1].

Iron Supplements

Oral Supplements

Without prescription (over-the-counter):

• Some multivitamin/mineral supplements contain some iron (typically 18 mg), which is Recommended Dietary Allowance for menstruating women, but is not sufficient to treat iron deficiency anemia. Before using iron supplements, speak with your doctor about the appropriate dose and form. Do not take iron supplements without doctor’s approval, if you are pregnant, have a liver or other disease, you are allergic to anything or you take other drugs or supplements.

NOTE: Heme iron supplements are more bioavailable than nonheme ones and ferrous forms more than ferric ones. Oral iron supplements are available as tablets, chewables, capsules, suspensions or solutions.

You should take iron supplements with water on an empty stomach at least 30 minutes before meals. You can take iron with a small amount of food to prevent stomach irritation. Food can decrease the absorption of iron by up to 50% ^[40].

Injections

Intravenous or intramuscular injections are intended mainly for individuals with iron deficiency who can not tolerate oral supplements.

• Iron dextran and ferumoxytol may be given in a single large dose.
• Ferric gluconate and iron sucrose are given in smaller doses.

Side effects of iron injections may include flushing, headache, dizziness, rashes, fever, pain at the injection site, and, rarely, anaphylactic shock, which may be fatal (mainly after iron dextran or ferumoxytol).

The effectiveness of iron supplements in treating iron-deficiency anemia is confirmed by increasing levels of reticulocytes (immature erythrocytes, reflecting increased erythrocyte production) in the blood few days after starting treatment and later, by increasing hemoglobin levels.

There is INSUFFICIENT EVIDENCE about the effectiveness of iron supplements in attention deficit-hyperactivity disorder (ADHD), depression, fatigue in people with normal iron levels, improving athletic performance, canker sores, Crohn’s disease, female infertility, heavy menstrual bleeding ^[1,4].

Who should NOT take iron supplements?

Adult men and women after menopause with normal blood iron levels and individuals with hemochromatosis, sideroblastic or hemolytic anemia should not take iron supplements without a doctor’s approval in order to avoid iron overload ^[1,2].

Iron Supplements Safety: Side Effects, Toxicity

The human body cannot get rid of excess iron quickly (only small amounts are lost in the urine and sweat), so taking iron supplements in absence of iron deficiency increases the risk of iron toxicity. The Tolerable Upper Intake Level (UL)–the dose that should not be toxic–for iron, is 40 mg/day before 14 years of age and 45 mg/day after 14 years of age ^[1].

Side effects of prescribed doses of oral iron supplements may include nausea, vomiting, abdominal cramps, constipation, diarrhea, temporary staining of the teeth (especially with liquid iron supplements) and black or green stool ^[1].

Iron supplements may worsen stomach ulcers or intestinal ulcers in ulcerative colitis or Crohn’s disease and may increase the risk of malaria and pneumonia in children in tropical areas ^[1,2]. To avoid or reduce iron side effects, you may initially take a half of the dose, followed by the full dose after few days, or get iron by intravenous injections. Eventual harmful effects of iron supplements taken by a mother for the unborn baby are neither confirmed, nor excluded.

Allergic reaction, mainly to iron dextran injections, may include metallic taste in the mouth, facial swelling, drop of blood pressure, or death.

Iron overdose (acute iron poisoning) my occur after ingesting 20-60 mg of iron/kg body weight. 200 mg iron taken at once can be deadly for a child. Symptoms of overdose appear within 1-6 hours of ingestion and include nausea, vomiting, abdominal pain, tarry stools, lethargy, weak and rapid pulse, low blood pressure, fever, difficulty breathing, coma and, often, death; if a victim survives, symptoms may subside for 12 to 48 hours after the iron ingestion and may include heart, kidney, liver, blood or brain damage, of which some may be permanent.

Iron overload (chronic iron poisoning) is a condition, in which, despite a normal iron intake, excess iron builds up in the internal organs and causes cirrhosis of the liver, diabetes, heart muscle damage, or joint problems. This may happen in hereditary hemochromatosis or after repeated transfusions (in sideroblastic anemia, thalassemia major). Rarely, iron overload may occur in individuals with normal blood iron levels taking high doses of iron supplements. To avoid iron overload, iron supplements should never be taken without an obvious reason – iron deficiency or a risk of developing it.

Iron Absorption, Body Stores, Interaction With Foods and Drugs

About 15-35% of heme iron from meat and fish and 2-20% of non-heme iron from plant foods, eggs and dairy products are absorbed in the small intestine–mostly in the duodenum–and, to a smaller extent, in the colon ^[1,10].

Factors that INCREASE the absorption of the nonheme iron from plant foods, milk, eggs and fortified foods:

• Meat, poultry and fish ^[1,2,9,10]
• Vitamin C from supplements, fortified foods ^[17], or fruits/juices high in vitamin C: lemon, orange or apple juice, guava, pineapple or pawpaw (Carica papaya) ^{[9,13,20,21,22]}
• Erythorbic (isoascorbic) acid, a vitamin C derivative, commonly added to processed meats, baked goods, jams and vegetable juices ^[13]
• Supplemental hydrochloric acid ^[13] (in individuals with low gastric acid)
• Low body iron (ferritin) stores ^[10,12]
• Pregnancy ^[13]
• Whisky, brandy, beer, red and white wine; alcoholics often have abnormally increased iron stores (hemochromatosis) ^[9,13,28].

Factors that DECREASE the absorption of the nonheme iron from plant foods, milk, eggs and fortified foods:

• Absent or low gastric acid (achlorhydria or hypochlorhydria) due to chronic gastritis caused by Helicobacter pylori infection ^[34,35] or autoimmune atrophic gastritis in pernicious anemia
• Tannins and polyphenols in cocoa ^[36], black and green tea ^[9,13,19,46], herbal teas (peppermint, chamomile, vervain, lime flower) ^[36], coffee ^[9,26], sorghum ^[13], chili ^[37], oregano ^[9,13], chocolate and Yod Kratin (a vegetable in South Asia) ^[38]
• Phytates in bran (wheat, oats, barley), wheat germ, whole grains, seeds, walnuts, sweet almonds, beans (except green beans), peas, lentils, soy, rolled oats, rice ^{[1,2,9,12,45]}. According to some long-term studies, phytates did not decrease the bioavailability of iron, though ^[47].
• Soy protein and proteins in milk, whey and egg whites (casein, albumin) ^[9,10,12,13]
• Maize (cornmeal, tortilla) ^[9]
• Recent iron intake ^[13]
• Calcium from dairy products ^[4,18,24] but less likely from supplements ^[11,13,41]
• Zinc supplements taken with water but not with meal ^[12]
• Drugs that lower stomach acidity (antacids, such as calcium carbonate, H2 blockers, such as ranitidine and cimetidine ^[44], proton pump inhibitors ( omeprazole ^[42]), cholestyramine (cholesterol-lowering resin), levodopa, levothyroxine, methyldopa, penicillamine, quinolones, tetracyclines, and bisphosphonates ^[1]
• Cadmium ^[31], lead ^[29], cobalt ^[13], strontium, manganese ^[13], copper ^[13,29]
• Vitamin A (retinol) and vitamin B2 (riboflavin) deficiency ^[10]
• Obesity ^[10,27]
• Hemochromatosis, alpha-thalassemia 1 and beta-talasssemia ^[10]

Once in the blood, iron binds to a protein transferrin and becomes available for the incorporation into hemoglobin in the red blood cells whenever needed. Iron in excess of immediate needs is stored as ferritin (an iron-protein compound) in the liver, spleen and bone marrow.

Allopurinol (for treatment of gout), may increase the iron storage in the liver, so it should not be used in combination with iron supplements ^[1].

Iron supplements (but not iron from foods) may decrease the absorption and thus reduce effectiveness of zinc, certain antibiotics (such as ciprofloxacin, demeclocycline, minocycline, tetracycline), or other drugs, such as bisphosphonates (alendronate, etidronate), levodopa, methyldopa, levothyroxine, mycophenolate mofetil and penicillamine ^[4].

Therefore, it is recommended to take iron supplements at least two hours apart from abovementioned foods and drugs.