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
Where is hepcidin made?
Under what condition?
Hepcidin is produced by liver during inflammation
Kids who only drink _____ will have Fe deficiency b/c…
Kids who only drink milk will have Fe deficiency b/c Calcium interferes with its absorption
Anemia is a ______ manifestation of Fe deficiency
Anemia is a late manifestation of Fe deficiency
Body will take Fe from everywhere before stealing RBC iron
What kind of anemia occurs in fe deficiency?
Microcytic, hypochromic anemia
How does Fe deficiency affect the CNS?
- Cognitive dysfunction (eg. attention problems, cognitive lag)
- May be irreversible/permanent
Why is Fe toxic in large quantities?
What are symptoms? (3)
- Iron is an oxidizing agent
- Sx: hemorrhagic gastroenteritis, liver failure, shock
4 Functions of Zinc
- Regulates gene expression
- Cofactor for enzymes
- Stabilize membranes
- Modulate hormones
Where do you need Zn? (2)
Any tissue that’s undergoing rapid growth
Especially sexual maturation
Fe is a ___-oxidant and Zn is an ___-oxidant
Fe is a pro-oxidant and Zn is an anti-oxidant
What are two dietary sources of Zinc? (2)
Animal sources
breast milk (adequate for 6 months only)
Zinc absorption is determined by… (2)
Zn absorption is determined by
- dietary intake
- phytate
*It does NOT depend on host status like Fe does
How is Zn level regulated?
Controlling secretion of Zinc into GI tract
Which has large stores in body: Fe, Zn, both, neither?
ONLY Fe is stored
Zn does not have large stores in body
These are all symptoms of what deficiency?
- Dermatitis around mouth
- Personality change
- Immune dysfunction/delayed wound healing
- Delayed sexual maturation
Zinc deficiency
6 Sx of Zn deficiency
Dermatitis around mouth
Personality change
Immune dysfunction/delayed wound healing
Delayed sexual maturation
Anorexia
Diarrhea
What is the major sx of mild Zn deficiency?
Growth delay
Describe Zn’s toxicity
Zn is much less toxic than Fe
