Antioxidants Flashcards
Why is vitamin A a deficiency you do not want?
Night blindness = early symptom
Regulates gene expression, important in protein synthesis and cell differentiation - can cause tissue degeneration, impaired growth and development, decreased immune defense
How is vitamin A metabolized?
Fat-soluble, requiring digestive enzymes and bile to separate it out form food and form micelles.
Travels w/chylomicrons or in portal circulation to liver
What is vitamin A the leading cause of in developing countries?
Preventable blindness (permanent damage to the eye)
What are the degenerative changes associated with eye tissues that occur in severe Vitamin A deficiency?
Xerophthalmia and Bitot’s spots
Corneal ulceration, scarring and blindness
When is an Recommended Dietary Allowance created?
When there is abundant research/evidence existing to reach consensus on human requirement
Can you see Recommended Dietary Allowance and Adequate Intake for the same vitamin?
No, RDA means there’s sufficient evidence for adequate human consumption and AI is used instead of RDA when evidence is not sufficient to reach consensus
What is a Tolerable Upper Level of Intake?
A level that, when exceeded, may present some risk to the patient
What is the Daily Value?
On nutrition labels, it lets us know how much of a vitamin or mineral we are getting, in accordance to what we need daily… Currently based on 1968 RDAs for vitamins and minerals
What is considered the level of acute or chronic toxicity?
> 25,000 IU/day (mostly overdoing the supplements)
What are the adverse effects of lower amounts of vitamin A that are still above the RDA? (There are 2)
Risk of birth defects >10,000 IU/day
Risk of bone loss and fracture >5,000 IU/day
Can you get too much Vitamin A by taking in too much of the carotenoid source of the vitamin? (Getting vitamin A from plants)
No! They don’t pose risks
What are the toxicity symptoms for vitamin A?
Headache (intra-cerebral swelling), bone/joint pain, skin changes, liver damage, systemic symptoms
What is ascorbic acid?
Vitamin C
Can humans make vitamin C?
Nope! Have to get it in the diet
What are the functions of vitamin C in terms of the immune system?
It orchestrates function of both innate and adaptive immune system, influencing both cellular and humoral immune responses
Do we metabolize large amounts or small amounts of vitamin C best?
Small amounts! We don’t want to overwhelm our gut with too much vitamin C
What is vitamin C a coenzyme for?
Collagen synthesis **
SYnthesis of some NTs, hormones and other biomolecules
Cholesterol conversion to bile acids
Catabolism of hormones, drugs and toxins
What does vitamin C facilitate absorption of?
Iron
What are the signs of scurvy (vitamin C deficiency)?
Connective tissue pathologies
Petechial hemorrhages
Loose teeth
Bone deformities in children
What do you have to do with vitamin C and smokers?
Oxidative stress causes smokers to require 35mg more to maintain similar blood levels of vitamin C to healthy people
Where does the jury stand on vitamin C and it’s protection on the person from the common cold?
Some athletes may find vitamin C supplementation helpful for preventing colds
May be worthwhile for common cold patients to test whether it has a therapeutic effect for them
What molecule is vitamin C made from?
Glucose! (Modified corn syrup….)
True or false: Natural vitamin C is chemically identical to synthetic vitamin C
True
Is a “natural” vitamin C supplement better than synthetic or as good as eating the food it was extracted from?
Nope.. Unimpressive. Just for marketing!
What are mineral ascorbates?
Less acidic form of ascorbic acid (take off the proton and add a mineral for people who cannot tolerate excess acidity)
What is Ester-C?
An attempt at making vitamin C more fat soluble! Didn’t show evidence of superiority except reduced gastric sensitivity so don’t waste your dollars!
Is vitamin C potentially toxic in large amounts?
Nope, UNLESS you have kidney stones - “despite conflicting results, it may be prudent for individuals predisposed to oxalate kidney stone formation to avoid high-dose vitamin C supplementation”
Why would vitamin C have a tolerable Upper Limit? (It does)
Trying to prevent GI upset and diarrhea from excess absorbed vit C (excess vit C has an osmotic effect pulling water into the bowels)
How many vitamin E isoforms are there?
8 total
4 tocopherols
4 tocotrienols
What is the designation for natural vitamin E to look for on a label?
D- or RRR stereoisomer
What is the chemical designation to look for on a label for synthetic vitamin E?
Dl- or “all-rac”
How do companies protect the antioxidant effect of vitamin E?
Esterification - still allows you to use the vitamin E (look for -el at the end of the vitamin E on the label)
True or false: we are unable to get vitamin E from supplements that have gone through esterification
False - our body is able to do de-esterification of vitamin E by a digestive process before it can be absorbed and utilized
Can you absorb D-tocopheryl on your skin?
No, your skin doesn’t break down vitamin E the way your digestive system can
Rhodopsin
Facilitates vision in low light situations
Essential component of vitamin A
What do you look for when identifying an esterified vitamin E?
tocopherYL followed by “acetate” or “sulfate”
What is the vitamin E form that the liver secretes and why?
Only alpha-tocopherol
Because hepatic alpha-tocopherol transfer protein selects it for incorporating the alpha isoform into VLDL particles
What happens to gamma-tocopherol, tocotrienols and other isoforms in the body?
They’re metabolized in the liver and excreted. We aren’t 100% sure what they do in the body before being excreted, maybe have some activity in the gut
What are the functions of alpha-tocopherol?
It’s a potent anti-oxidant in lipid environments, maybe helping the immune system via membrane activity
What is the most abundant tocopherol in our diet?
Gamma-tocopherol due to its presence in plant-based oils and nuts
What is the most abundant tocopherol in body tissues?
Alpha-tocopherol!
Is vitamin E deficiency something you’ll likely see in practice?
No, it’s really rare and usually associated with impaired fat absorption or genetic defects.
May see suboptimal intake which is common! Causes increase in cardiovascular risk
Which vitamin is commonly missing from people’s diet and results in lots of people getting less than their RDA?
Vitamin E
What are the best food sources of vitamin E?
Vegetable oils, nuts, whole grains, green leafy vegetables and fortified foods
How should you take for fat-soluble supplements?
With food!
What are seeing with vitamin E in observational studies?
Those who take Vitamin E or have acceptable blood levels are linked to lower cardiovascular disease (but they may also just be HEALTHIER)
What have intervention studies shown about vitamin E and its efficacy for protecting against cardiovascular disease?
No benefit as an intervention against cardiovascular disease
What are the risks of vitamin E supplementation in very sick people?
Increased mortality in chronic disease taking large doses of synthetic or alpha-only vitamin E (natural is best)
