13 Iron Flashcards
Homeostasis of iron regulated mostly by?
Absorption
hard to excrete iron
How much iron do we need?
less than 5 grams
- trace minerals
Iron ionic states
Oxidized
- Ferric Iron Fe3+
Reduction
- Ferrous Iron Fe2+
serves as a cofactor for oxidation/reduction reactions
Absorption of iron determined by?
- “content” of diet
- “bioavailability” of dietary iron
- heme vs non-heme - capacity of mucosal cells to absorb iron (typically non heme)
- absorption enhancers and inhibitors
- iron status
Food sources of diet
red meats fish poultry eggs legumes dried fruits
heme vs non heme
Heme
- animals
- 10% daily intake
- 25-35% absorbed (constant rate)
Non Heme
- plant and animals
- 90% daily intake
- only 2-20% absorbed
- rate depends on other factors
Factors affecting non heme absorption
MFP factor (meat fish poultry) - provides heme but also promotes non heme absorption Vit C Gastric Acid lactic, malic, tartaric acid
What ionic state of iron is better absorbed?
Ferrous Acid
- acids donate hydrogen to Ferric to reduce it to ferrous
Iron absorption inhibitors
phytate (grains, beans, nuts, potatoes)
polyphenols
- fruits, veges coffee, tea, wine
- Vit C inhibits this effect***
EDTA (food additives)
oxalate (spinach, rhubarb)
4 types of proteins that require iron for their synthesis
- heme proteins (and non)
- iron sulfur cluster proteins
- proteins with single iron atoms
- proteins with oxygen bridged iron
Iron transport proteins
Transferrin
Transferrin Receptor
Others… not important
Transferin
Transport protein
- iron is part of the protein
- binding and release result of conformational change
- open without iron
- closed with iron
Transferrin Receptor
in cell membranes, allows iron intake
Iron storage proteins
Ferritin
- house large amounts of iron in soluble, non toxic, bioavailable form
- best way to assess iron stores
Hemosiderin
- increase in iron overload
% world iron deficient
30%
Symptoms of iron deficiency
anemia
- fatigue
in children
- cognative performance in children
- increase lead poisoning
Stages of iron deficiency
- iron depletion
- iron deficient erythropoiesis
- iron deficiency anemia
1st stage of iron deficiency
iron depletion
- low iron stores
- decrease serum ferratin
- normal transport iron and Hb
2nd stage of iron deficiency
Iron Deficient Erythropoiesis
- complete exhaustion iron stores
- low blood iron conc.
- less iron delivered to erythropoietic cells
- increase erythrocyte protoporphyrins
- hemoglobin usually normal
3rd stage of iron deficiency
Iron Deficiency Anemia
- complete exhaustion iron stores and declining circulating iron
- reduced HB in RBCs
Biochemical signs of iron deficiency at various stages
v ferratin v iron v transferrin saturation ^ erythrocyte protoporphryin v hemoglobin
- all blood concentration
iron overload
Hemochromatosis
- hereditary
- more prelevent in males
- increased iron absorption
- transferrin hypersaturation
- can cause organ damage
- treatment involves phlebotomy
What vitamin to avoid when have iron overload
vitamin C
