Iron Review

Iron

SOURCES
Heme Iron

• Meat, poultry, fish

Non-Heme Iron

• Plants
• Dairy
• Influenced by enhancers and inhibitors
• Vit C enhances
• Phytates inhibit
• Polyphenols - fruits, veg, soy, coffee, tea

DIGESTION, ABSORPTION, TRANSPORT, STORAGE

Heme iron digestion:

• Proteases released from globin
• Not affected by enhancers / inhibitors

NON-Heme iron digestion:

• HCl and proteases released from food
• Affected by enhancers / inhibitors
• Enhancers
• Sugars
• Acids and acidic pH
• Mucin
• Meat & fish
• Poultry
• Inhibitors
• Alkaline pH
• Polyphenols (coffee)
• Oxalic acids (spinach, tea)
• Phytic acids (whole grains, legumes)
• Phosvitin
• Divalent cations\
• MEDICATIONS

Heme-Iron Absorption

• Absorbed intact by carrier protein (Heme Carrier Protein 1)
• Degraded in enterocyte to separate iron

NON-heme Iron Absorption

• Reductases reduce ferric iron Fe3+
• Ferrous iron Fe2+ absorbed via DMT1 transporter

Iron in the Enterocyte:

• Used for gut cell functions
• Transported into circulation
• Requires oxidation in Fe3+ state
• Requires hephaestin and ferroportin
• Hepcidin controls ferroportin
• Hepcidin made in liver 
• High iron levels trigger more Hepcidin and leads to less Iron in circulation
• Low iron levels trigger less Hepcidin and more Iron in circulation
• Stored, may be excreted
• Stored in ferritin
• Cells live 2-3 days
• Transferrin transport
• Carries iron absorbed from gut (protects body from oxidizing potential of iron)
• Carries recycled iron
• Carrier iron released from storage
• Cell membrane uptake via transferrin receptors
• Stored in liver bone marrow spleen
• Primarily as ferritin
• Hemosiderin used when iron high

TURNOVER EXCRETION

Iron is recycled extensively

• Reticuloendothelial cells take up old RBCs
• Haptoglobin and hemopexin clean up iron from hemolyzed RBCs
• Excretion via:
• Intestines
• Skin
• Kidneys
• Menses

FUNCTIONS
Oxygen transport

• Hemoglobin - 2/3rd of total body iron
• Myoglobin - capillary blood to myocytes

ETC

• Cytochromes
• moves protons
• Other enzymes
• Iron bond to sulfur

• Mono-oxygenases & Di-oxygenases
• Amino acid metabolism
• Synthesis of neurotransitters, carnitine, collagen
• Peroxidases
• Antioxidant role ~ catalase
• Immune defense
• Thyroid hormone synthesis ~ peroxidase

INTERACTIONS

• Do not take iron with calcium and zinc supplements

DEFICINIENCY

• At risk
• new borns
• Menses
• Malabsorption
• Antacids
• Vegetarian

TOXICITY

Hemochromatosis

• Genetic
• Nongenetic