Trace Elements Flashcards
Bioavailability
the extent to which other dietary constituents affect the absorption and retention of a nutrient
trace mineral are especially susceptible to interference with absorption
Iron - what does it do?
Tissue oxygenation
- O2 transport
- Electron transport
- Enzymes for O2 activation
CNS myelination: dopamine synthesis
Iron - where do we get it?
Heme - meat/liver
Non-heme - legumes, whole grains, nuts
fortified
Iron absorption form?
Heme Fe»Non heme (>30% vs <10%)
Calcium is the only dietary factor that can decrease heme iron absorption!
which dietary factor can decrease heme iron absorption?
calcium
Positive factors affecting non-heme iron absorption
Vitamin C
Meat/fish
Negative factors affecting non-heme iron absorption
PHYTATES!! (bran / oat / beans / rye) calcium polyphenols fiber soy
Phytate (phytic acid)
binds zinc / iron / calcium - in gut lumen
humans dont have phytases
high in grains and legumes (maize/wheat>legumes>rice)
major cause of dietary deficiency
Despite the absolute amount of iron in food, the bioavailability markedly influence absorption
meat - high kidney bean - low bread - low human milk - high formula - low
What is iron’s main point of regulation?
Amount absorbed (mostly proximal duodenum)
deficiency - increased abs
inflammation - decreased abs
What is iron’s main loss?
Loss not regulated
Bleeding / cell sloughing
Hepcidin?
Blocks transport of iron - binds ferroportin (by regulating ferroportin, hepcidin controls entry of iron into plasma)
- decreased in iron deficiency
- increased in inflammation
what is it? antimicrobial peptide synthesized in enterocytes
what form of iron is absorbed?
Fe2+
ferritin
storage form of iron
liver
bone marrow
spleen
during inflammation, hepcidin increases and iron uptake decreases but what happens to ferritin levels?
they may be normal or high - always obtain inflammtory markers with ferritin levels
tranferrin
transports in blood
iron deficiency -etiology
poor bioavailability dietary iron dietary inadequacy high demand - hemolysis / helminths pregnancy / infancy / growth chronic immuno-stimulation (increased hepcidin)
what is the most common micronutrient deficiency in world and us
iron
iron deficiency
at risk?
BF infants Premature Young children Adolescent girls Preg Blood loss Obese / sp BS
Iron deficiency effects?
Anemia (microcytic, hypchromic) - reduced O2 carrying capacity
Impaired cognitive function in Developing brain - irreversible, even w/ correction of deficiency anemia
Iron is prioritized to erythrocytes - so if see anemia likely fucking up earlier cascade
Iron deficiency - don’t be fooled
Lab values may all be normal in earlier stages when brain stores are depleted an you will only have low ferritin
Effect of Iron deficiency in early infancy on cognitive function
even in absence of anemia can impair behavioral and cognitive development
Iron toxicity
Potent pro-oxidant
But normal individuals are able to REGULATE ABSORPTION
Overdose - hemorrhagic gastroenteritis, shock, liver fialure
Hereditary hemochromatosis
defect in hepcidin
absorption excessive - accumulate iron - liver damage
