Other factors that prevent or enhance iron absorption might have a bigger impact on iron levels than dietary and supplemental iron. Read this post to learn about these factors, as well as iron supplements and ways to make sure you get the most of it.
This post is a continuation of a 4 Part Series
Part 4: Negative Effects of High Iron
- Sources of Iron
- Adequate Iron Intake
- Iron Supplementation
- Ways to Increase Iron without Iron Supplements
- Ways to Decrease Iron
- Interactions Between Iron and Other Substances
Sources of Iron
- meat and poultry, including organ meats like liver, heart, kidney, and blood
- fish, including shellfish and sardines
- green leafy vegetables, including broccoli and kale
Plant-based foods that are high in iron in non-heme form (but may also be high in substances that prevent iron absorption) include:
- pulses, including chickpeas, beans, peas and lentils
- seeds, including sesame and pumpkin seeds
Some (not necessarily healthy) foods are fortified with iron. These include flour, grains, cereals, pasta, rice, salt, sugar, bakery products, milk and dairy products, chocolate drinks, and infant formulas (R, R2).
A number of iron supplements are available in the form of ferrous sulfate, ferrous gluconate, ferrous fumarate, and heme iron (R).
Adequate Iron Intake
The adequate intake of iron for infants 6 months and less is 0.27 mg/day.
Older infants and children 1 to 3 years require 11 and 7 mg/day, respectively.
Children aged 4-8 and 9-13 require at least 10 and 8 mg/day, respectively, in order to prevent developmental delays and behavioral disturbances.
Adults aged 19–70 and over 70 yr require at least 8 mg/day of iron.
Women of childbearing age (19-50 yrs) should have a daily intake of 18 mg of iron.
Pregnant women should take 27 mg of iron daily to decrease the risks of preterm delivery and having a low birthweight baby.
In many populations, the amount of iron absorbed from the diet is not enough to meet most individual requirements, especially during infancy, intense exercise, and pregnancy, where biological iron needs are the highest (R, R2).
If the amount of absorbable iron in the diet cannot be readily improved, iron supplementation is required to prevent iron deficiency anemia. This is almost always the case for children 6-24 months of age and pregnant women (R, R2, R3).
Different Forms of Iron Supplements
Supplemental iron is found in ferrous (+2) and ferric (+3) forms. Since the ferric form must be converted in the body to the ferrous form for absorption, the ferrous form is more bioavailable and thus, more preferred (R).
- Ferrous citrate
- Ferrous sulfate
- Ferrous gluconate
- Ferrous succinate
- Amino acid chelates, such as iron bisglycinate and iron aspartate
- Heme iron
While the most commonly studied iron supplement is ferrous sulfate, food fortification and supplementation studies have shown that amino acid chelate forms of iron (such as glycinate) are better or equally as well absorbed as ferrous sulfate (R, R2). 25 mg of ferrous glycinate was able to bring up iron levels to the same level as did 50 mg of ferrous sulfate in pregnant women (R).
Newer formulations iron supplements like heme iron polypeptides, iron amino acid chelates, carbonyl iron, and sugar-iron complexes may be more tolerable and have fewer GI side effects than ferrous salts. However, some of these preparations are not as bioavailable and their clinical efficacy is yet to be proven (R, R2).
Parenteral iron treatment (iron delivered into the muscle or vein) require medical supervision. It can be given when oral iron supplementation is not tolerated by the patient, which is often the case for people with malabsorption from celiac disease and inflammatory bowel disease (R).
It is also recommended in cases where hemoglobin must be increased increase rapidly like after a surgery or blood transfusion (R).
Iron Supplementation Side Effects
Oral iron causes side effects in up to 60% of patients, such as constipation, diarrhea, nausea, and heartburn (R).
High doses of ferrous sulfate are associated with gastrointestinal irritability, constipation, nausea, and heartburn (R). In a case study, a patient with several chronic diseases developed stomach ulcers with iron deficits after supplementing with high dose (325 mg) of ferrous sulfate (R).
For iron infusions, severe side effects like allergy, low blood pressure, nausea, and stomach pain may develop after a rapid infusion (R).
Contraindications with Iron Supplements
Iron supplement should not be used in:
- People with normal iron balance (men, postmenopausal women) because iron will not be absorbed and will just pass through the body (R).
- People with hemochromatosis (R).
- Patients receiving repeated blood transfusions (R).
- Hemolytic anemia, which may increase blood iron levels and cause toxicity (R).
- Patients with inflammation of the digestive system (peptic ulcer, colitis, diverticular disease), because it can directly irritate gut mucosa and exacerbate the disease (R).
- Patients with systemic lupus erythematosus (R, R2).
Drug Interactions with Iron Supplements
Iron supplements may reduce the absorption and efficacy of the following medications. You should consult your physician or pharmacists to confirm that your supplements can be safely used with the medications that you are using.
- Levodopa (Sinemet®, Stalevo®), methyldopa (Aldomet®) (R, R2, R3)
- Levothyroxine (Levothroid®, Levoxyl®, Synthroid®) (R)
- Penicillamine (Cuprimine®, Depen®) (R, R2)
- Quinolones (R)
- Tetracyclines (R)
- Ciprofloxacine (R)
- Bisphosphonates (R)
- Medications that decrease stomach acidity, such as antacids, histamine (H2) receptor antagonists (cimetidine, ranitidine), and proton pump inhibitors (omeprazole, lansoprazole), may impair iron absorption (R, R2).
- Cholestyramine (Questran®) should be taken at least four hours apart from iron supplements because they may interfere with iron absorption (R).
- Allopurinol (Zyloprim®) may increase iron storage in the liver and should not be used in combination with iron supplements (R).
Iron Supplement Dosage and Recommendations
For treating iron deficiency anemia, a dose of 60-120 mg of elemental iron (amount of actual iron in the supplement) from ferrous sulfate is recommended per day for a minimum of 3 months in adolescents and adults, including pregnant women (R).
- Heme Iron: HemaMax Heme Iron
- Iron Glycinate:Thorne Research Iron Glycinate, Thorne Research Iron Glycinate (IHERB)
- Amino Acid Chelates with Vitamin C: Pure Encapsulations Iron Glycinate and Aspartate with Vitamin C
Ways to Increase Iron without Iron Supplements
Around 1-2 mg of iron is lost daily and a regular dietary intake of iron is required to replace this loss (R).
In addition, the enhancement of body mass during embryonic, childhood, and adolescent growth may transiently boost iron requirements (R).
1) Iron Rich Foods
Dietary iron is found in two forms: heme and non-heme (R).
The main sources of heme iron are hemoglobin and myoglobin from red meat, chicken, and fish, whereas non-heme iron is primarily found in cereals, fruits, legumes, and vegetables. Heme iron has high bioavailability (15%-35%) and dietary factors have minimal effects on its absorption, while nonheme iron absorption is much lower (2%-20%) and strongly affected by the presence of other food types (R).
2) Vitamin C
Vitamin C is the only nutrient that increases iron absorption in vegetarian and vegan meals (R).
Vitamin C and citric acid enhance iron uptake in a dose-dependent manner in part by acting as weak chelators to help solubilize iron in the small intestine (R).
Vitamin C intake is positively correlated with iron status in women (R).
3) Vitamin A
Vitamin A in combination with iron can reduce anemia more effectively than supplemental iron or vitamin A alone (R).
Vitamin A may also enhance the mobilization of iron from body stores to developing red blood cells for incorporation into hemoglobin (R).
4) Animal proteins (meat, poultry, and fish)
The consumption of meat, fish, and chicken alongside non-heme iron can enhance its absorption 2-3 fold (R).
Data from the National Health and Examination Survey in the US concluded that two alcoholic drinks daily may reduce the risk of iron deficiency and iron deficiency anemia in men and women (R).
Cigarette smoking was associated with higher blood iron and ferritin levels (R).
Ways to Decrease Iron
Excessive intestinal iron absorption will result in iron overload because there is no pathway for iron excretion in the body. Therefore, it is essential to monitor dietary iron intakes to prevent iron overaccumulation and toxicity (R).
Phytate decreases iron absorption at very low concentrations of 2–10 mg of phytate per meal (R).
Phytates are found in legumes, whole grains, nuts, and seeds. Phytates can inhibit non-heme iron absorption (up to 50 %) by binding to the iron atom (R).
A study in middle-aged females found that the more white and wholegrain bread, and nut and seed consumption they consume, the lower blood ferritin they have (R).
2) Polyphenols or Tannins
3) Soy Protein
Soy protein (found in tofu, texturized vegetable proteins, and some processed meat products) can reduce iron absorption because it contains phytates (R).
However, its effects are limited when one consumes a wide variety of foods with varying amounts of enhancers and inhibitors of iron absorption (R).
5) Frequent Blood Donation
6) Regular Intense Exercise
Daily iron losses are greater in athletes engaged in intense exercise, likely due to growing blood cell mass, muscle mass, and increased fragility and rupture of red blood cells (R).
8) Proteins in Milk and Eggs products
While proteins from animal flesh increase iron absorption, proteins from milk and eggs (with the exception of ovalbumin) reduces iron absorption when consumed with a low-iron food (R).
Interactions Between Iron and Other Substances
Calcium decreases iron absorption.
In order to maximize iron absorption, iron supplements should be taken two hours apart from calcium-rich foods (milk, cheese) or calcium supplements (R).
Zinc deficiency is associated with iron deficiency anemia, and it aggravates its symptoms.
Iron supplements, taken together with zinc supplements on an empty stomach, may inhibit the absorption of zinc.
3) Vitamin A
Vitamin A affects iron transport and red blood cell production directly (R).
4) Vitamin C
Vitamin C increases absorption of non-heme iron in the gut. It also influences the storage and transport of iron in the body (R).
Severe iron deficiency anemia can impair iodide metabolism and production of thyroid hormones. Correcting iron deficiency anemia improved the efficacy of iodine supplementation to treat thyroid diseases (R, R2, R3).
Iron depletion increases aluminum absorption. Susceptible individuals, such as renal failure patients, have an increased risk of aluminum toxicity if they are iron deficient (R).
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