what is the most common nutritional deficiency
iron
what types of reactions does iron participate in
REDOX…this is irons role in the body
what are the two main ionic states of iron
oxidized: ferric Fe 3+
reduced: Ferrous, Fe2+
what is the role of iron
serves as cofactor for oxidation-reduction reactions
what factors determine iron absorption
1) iron content of diet (iron food sources)
2) bioavailability of dietary iron (heme vs non heme)
3) capacity of mucosal cells to absorb iron
heme vs non heme iron
has to do with bioavailability
Heme
- most efficient source of iron
- animal foods only
- not much of our daily intake but absorption is higher
- rate of absorption is constant/consistant///can count on getting your iron from this source
Non Heme
- from plants and animals
- most of our daily intake, but less absorption
- rate of absorption not constanta
non heme iron absorption ENHANCERS
MFP factor
- meat fish poultry factor
- provides highly absorbable iron but also promotes absorption of non heme iron from other foods eaten at the same meal
- factor is associated with the digestion process
Vit C
Gastric acid
other organic acids from food
(lactic, malic, tartaric)
how do acids enhance iron absorption
- ferrous (reduced) iron is better absorbed
- acids can donate a hydrogen to ferric iron reducing it to ferrous iron
Acids REDUCE ferric iron
non heme iron inhibitors
bind with dietary non heme iron
-phyatate
(found in seeds, nuts, beans)
-polyphenols found to markedly inhibit iron absorption
(inhibitory effects reduced by presence of Vit C)
-EDTA (food additives)
-oxalate (spinach, rhubarb)
iron biological function: iron proteins
certain proteins depend on iron for their synthesis and function
classify by the type of iron structure contain
1) heme proteins (and non heme proteins)
2) iron-sulfur cluster proteins
3) proteins with single iron atoms
4) proteins with Oxygen-bridged iron
why is iron assimilation and storage important
need to store iron bc its essential for oxygen-requiring processes, electron transfer, DNA synthesis, etc
iron can participate in free radical processes
Iron transport proteins
Transferrin
- major plasma protein for iron transport
- high affinity for ferric iron
- iron is part of the protein
- binding and release of iron result in conformational change of protein
- two domains:
- Open without iron
- closed with iron
transferrin receptor
- allows uptake of iron
- protein in cell membranes
Other iron transport proteins
haptoglobulin, hemopexin, albumin
iron storage proteins
Ferritin
- major storage protein
- can house large amount of iron in a soluble, non-toxic, bioavailable form
- single best way to assess iron stores
Hemosiderin
- increase in iron overload
- closely related to ferritin
**Iron Deficiency
important because its so common worldwide
has remarkable physical symptoms
3 stages of deficiency
physical symptoms largely due to anemia:
-decreased work capacity**
-pica (trying to get iron from non food sources)
-effects on cognitive performance in children
what are the 3 stages of Iron deficiency…describe them
stage 1-iron depletion
- depleted iron stores (ferritin)
- due to progressive reduction in amount of storage iron
- dec serum ferritin
- transport iron and hemoglobin are normal at this stage…hemoglobin delivers oxygen
Stage 2 -iron deficient erythropoiesis
- complete exhaustion of iron stores
- dec blood iron concentrations
- less iron delivered to erythropoietic cells
- inc erythrocyte protoporphyrins (accumulate in RBC when iron supply not adequate for heme synthesis)
- hemoglobin usually within a normal range
stage 3- iron deficiency anemia
- complete exhaustion of iron stores and continually declining levels of circulating iron
- reduction in blood iron
- microcytic hypochromic anemia
- MAIN FEATURE: reduction in the concentration of hemoglobin in RBS
- therefore, dec in serum hemoglobin
overview of biochemical signs of iron deficiency at VARIOUS STAGES
these signs can been seen in the blood at different stages
stage 1
-dec. ferritin
stage 2
- dec. iron
- dec. transferring saturation
- inc erythrocyte protoporphyin
stage 3
-dec hemoglobin
Iron overload
toxicity syndrome
hemochromatosis
- hereditary
- more common in males
- inc iron absorption
- transferrin hypersaturation
- can cause organ damage
- avoid large doses of Vit C bc Vit C enhances absorption of non heme iron…we dont want this
