Vit A Flashcards
initial transport of the fat soluble vitamins happens in the ___
chylomicron
There is no control on amount taken up for fat soluble vitamins because of ___cytosis
pino
what are the 3 forms of Vit A found in the body?
retinol, retinal, retinoic (and preformed vit A from animal foods–>retinol as retinyl ester)
only ___% of carotenes in foods are provitamin A
10; these are carotenes in plant-based foods
this provitamin A, when split in half, obtain 2 retinol
beta carotene
this provitamin A only forms one retinol
alpha-carotenes
examples of non provitamin A carotenes (provide no retinols)
lycopene (prostate cancer reduction) and lutein (role in eye)
what is the conversion factor for b-carotene –>retinol?
50 %
re-esterification prefers which fatty acid?
palmitate
what is the pathway of the chylomicron?
leave cell–>lymph–>blood–>liver
some retinal is converted to retinoic (irreversible) instead of retinol. Where does this go?
the blood
1 RAE = __ mcg retinol, ___ mcg beta carotene, __ mcg from b-carotene in supplements, ___ mcg from other provitamin carotenes
1; 12; 2; 24
holo-RBP needs ___ to transport retinol to sites of action
TTR (transthyretin)
zinc and amino acids are required to make and release this
apo-RBP
foods fortified with retinol in Canada
margarine, low fat milk, soy beverages
if the IU is from carotenes, to get RAE you divide by ___
20
if all carotene, 1 RE = ___ RAE
0.5
what is the DV of Vit A?
1000 RE
what is rhodopsin?
11-cis retinal (made from retinol) and opsin
xerophthalmia
dryness
Bitot’s spots
foamy white spots of accumulated secretions
keratomalacia
eye softens and becomes opaque
The binding of retinoic acid to RXR and RAR promotes:
DNA transcription, which leads to cell differentiation and growth–>epithelial cells
Consequences of too much retinol?
damage to bone and birth defects
what is hyperkeratosis
obstruction and enlargement of hair follicles; this looks the same as vit. C deficiency
This is the “final step” in vitamin A deficiency: the lens is covered so can’t see, ability for making tears is lost. This is irreversible
Corneal ulceration
what is a static indicator of vitamin A status?
plasma retinol, showing whether liver stores are depleted
VAD is responsible for ___ child deaths in places with Vit A deficiencies
1/4
Examples of secondary deficiency?
fat malabsorption, protein deficiency, zinc deficiency, infectious diseases
What is the EAR?
amount that meets needs of 1/2 population
what is the EAR based on for fat soluble vitamins?
maintaining sufficient liver stores, using factorial methods
EAR for women is ___ and ___ for men; only difference based on weight
500 mcg RAE; 625 mcg RAE
what is the efficiency of storage of ingested vit A?
about 40%
what is the minimum acceptable reserve of vit A?
20 mcg/g in liver
how is RDA found from EAR?
standard deviation = 20%
what is RDA for women? What about for men?
700 mcg RAE; 900 mcg RAE
acute toxicity is called:
hypervitaminosis A
what is the UL?
3000 mcg RAE (based on liver damage, alopecia, bone pain, teratogenic effect)
NOAEL is:
No observable adverse effect lvl (studies w/ high intentional intakes)
LOAEL is:
lowest observable adverse effect lvl–>look at case reports
hepatotoxicity is found at the LOAEL of ___ mcg
14000
if IU from retinol, divide by ____ to get mcg RAE
3.3333
if IU from b-carotene in a supplement, divide by ____ to get mcg b-carotene, then divide by ___
3.33; 2
supplemental b-carotene is harmful to ____
smokers (around 10 mg)
what is lycopene found in?
makes red colour in tomatoes
what is lutein found in?
yellow veg/fruit, green leafy veg
