Met 2: Micronutrients/Trace Elements Flashcards
Why do we get micronutrient deficiencies when we need so little?
Bioavailability problems! The absorption of micronutrients is heavily affected by what other substances are present in the GI tract.
So, micronutrients are susceptible to poor absorption
What are sources of heme iron?
Non-heme iron?
Heme iron: meat, liver
Non-heme iron: beans/legumes, whole grains, nuts, fortified grains
Function of Fe in body (2 CNS, 3 Metabolic)
- Part of electron transport chain
- Enzyme cofactor
- Carrying O2
- CNS myelination
- Dopamine synthesis
Which is better absorbed: heme Fe or non-heme Fe?
What is the one thing that can affects its absorption
Heme Fe is much better absorbed (less affected by bioavailability)
Calcium inhibits Heme Fe absorption
What is phytate?
Where is phytate found? (3)
Phytate: storage form of phosphorous for plants. serves as anti-oxidant
Found in grains, legumes, rice
How does phytate affect Fe absorption?
Can we break down phytate?
It binds cations such as Fe and prevents their absoprtion (chelator).
We lack the enzymes needed to degrade phytate.
How does inflammation affect Fe absorption?
Inflammation decreases Fe absorption
How are Fe levels regulated?
How is Fe excreted?
Fe is regulated via absorption in the duodenum
Fe can only be excreted by bleeding and cell sloughing (no good way to get rid of excess iron)
Describe Fe absorption and delivery to liver (4 steps)
- Fe is absorbed by enterocyte
- Fe can be stored in cell as ferritin
- Or, Fe can be pumped across basolateral side by ferroportin
- In the blood, Fe binds transferrin
- Transferrin binds to its receptor on hepatocyte cell surface and Fe can be delivered to hepatocyte
Where is most of Fe delivered to?
Bone marrow (for erythropoiesis)
How does Vitamin C affect Fe absorption?
Vitamin C increases Fe absorption
elevated _____ is evidence of increased Fe absorption
elevated TIBC is evidence of increased Fe absorption
What are the two sources of Fe in our blood?
Dietary absorption and degradation of RBCs in spleen
What cation state is Fe in when best absorbed?
What nutrient helps with this?
Fe is better absorbed if reduced to 2+ (ferrous state)
Vitamin C helps with this
How does Hepcidin affect Fe absorption?
What is one thing seen on labs?
- It binds and inhibits ferroportin, so Fe can’t be pumped out of enterocytes or hepatocytes
- Labs will show normal or elevated ferritin b/c iron is building up in enterocytes even though there may be deficiency
