Week 13, Vitamin A, Vitamin C, Vitamin E Flashcards
(42 cards)
_______ is/are the most active form of vitamin A and is found mostly in animal foods.
a. retinoic acid
b. retinol
c. carotenoids
b. retinol (also known as preformed vitamin A)
* Beta-carotene (a.k.a provitamin A) is the most common of the plant carotenoids, and is converted in the body to retinol. Following ingestion of beta-carotene, the body enzymatically cleaves some of theses compounds to retinol, which is esterified (combined with an alcohol or acid) in the intestinal cell to retinyl esters that, along with the remaining carotenoids, are incorporated into chylomicrons (large triglyceride rich lipoproteins produced in enterocytes from dietary lipids) for transport into the lymphatics and eventually the blood. Dietary retinyl esters (oleic acid, stearic acid, linoleic acid) follow a similar path and are likewise incorporated into chylomicrons, eventually delivering the retinyl esters and carotenoid pigments to the liver for storage.
True or False. Vitamin E refers to 8 compounds ‘vitamers’. They consist of 4 tocopherols (alpha, beta, gamma and delta) and 4 tocotrienols (alpha, beta,
gamma and delta).
True.
The Institute of Medicine deems that only alphatocopherol
meets the requirements for vitamin E intake due to insufficient
evidence of the health benefits for humans of other tocopherols and of the tocotrienols
Vitamin E is mostly found in the:
A. Cell membranes
B. Adipose Tissue
C. Skeletal Muscle
A. Cell membranes
found largely in cell membranes (plasma, mitochondrial and microsomal). Most of the vitamin is found in unesterified fat droplets in the adipose tissue, but vitamin E can also be found in the liver, lung, heart, muscle, adrenal glands, spleen, brain, plasma and skeletal muscles.
True or False. Vitamin E quenches free radicals, acting as an antioxidant.
True.
Cell membranes of the lungs, brain and red blood cells are particularly vulnerable to oxidation. Red blood cells are vulnerable as a result of being composed of high amounts of polyunsaturated fatty acids and being exposed to high amounts of oxygen. This explains why a _________ of vitamin E can result in hemolytic anemia.
A. Deficiency
B. Toxicity
A. Deficiency
Vitamin E plays a role in the following:
A. Cell signaling B. Gene Expression C. Immune Regulation D. Inflammation E. All of the above
E. All of the above
True or False. Vitamin E is found in food largely in tocopherol form and is freely absorbed.
True.
(whereas tocotrienols, synthetic esters of tocopherols and tocopherol
acetate require hydrolyzing before they can be absorbed)
Vitamin E is absorbed mainly in the:
A. Duodenum
B. Jejunum
C. Ileum
B. Jejunum
Bile salts are required to emulsify and solubilize the vitamin E and to form micelles (which can readily diffuse across the enterocyte membrane). Consuming vitamin E with food rich in lipids enhances the absorption of vitamin E.
Vitamin E deficiency is ______ .
A. Rare
B. Common
A. Rare
It can occur with severe malnutrition, genetic defects in alphaTTP
and with fat malabsorption (Cystic Fibrosis, IBD, cholestasis, pancreatic insufficiency, chronic steatorrhea and celiac disease). Marginal intakes are quite common in the U.S., however. According to the NHANES III study, over 90% of Americans do not consume enough vitamin E to meet their daily requirement.
Severe vitamin E deficiency can manifest with neurological symptoms (ataxia (impaired coordination and balance), peripheral neuropathy (injury
to sensory nerves), loss of vibratory sense) myopathy (muscle weakness), hemolytic anemia and/or pigmented retinopathy (eye (retinal)
damage). Neurological signs/symptoms may not occur until someone has been deficient for 1020
years.
Mild GI issues, nausea, diarrhea, flatulence, impaired blood coagulation, respiratory infections, muscle weakness, fatigue, and double vision are all sign of vitamin E __________.
A. Deficiency
B. Toxicity
B. Toxicity
About 70% of the vitamin E consumed in an American diet is from:
A. gamma-tocopherol
B. beta-tocopherol
C. alpha-tocopherol
A. gamma-tocopherol
Food sources of vitamin E include:
A. vegetable oils (olive, sunflower, safflower) B. egg yolks C. nuts (especially almonds) D. wheat germ and whole grains E. green leafy vegetables F. animal foods G. All of the above
G. all of the above
Plant sources are considered superior. Note that the green portion of plants contains more alpha-tocopherols and the other portions of the plant will generally have some gamma, beta, and delta-tocopherols.
Vitamin D RDA for ages 14+ are:
A. The same for men and women, 15mg
B. 15mg men, 13mg women
C. 17mg men, 15mg women
A. The same for men and women, 15mg
These vitamin and mineral complement each other when taken with vitamin E, having synergistic effects.
A. Selenium, vitamin C
B. CoQ10, iron, zinc
C. Plant sterols, selenium
A. Selenium, vitamin C
vitamin E and selenium both possess antioxidant actions and are closely tied to selenium dependent glutathione peroxidase. They share a complementary interaction in which higher levels of one can buffer the effects of lower levels of the other.
vitamin C can complement the actions of vitamin E and is required for the regeneration of vitamin E (after oxidation).
Which of the following does vitamin E interfere with or vice versa for absorption and metabolism.
A. Other fat soluble vitamins B. Iron C. Zinc D. CoQ10 E. Plant Sterols F. PUFA's G. All of the above
G. All of the above
Fatsoluble vitamins: increased intake of vitamin E can interfere with other fat soluble vitamins (inhibit betacarotene absorption and metabolism, inhibit the absorption of vitamin K and the conversion of K to menoquinone).
Iron: interferes with the absorption of vitamin E, so it is advised to take the 2 at different times of the day (if taking them supplementally)
Zinc: interferes with the absorption of vitamin E, so it is advised to take the 2 at different times of the day (if taking them supplementally)
CoQ10: vitamin E may enhance levels of CoQ10
Plant sterols: can decrease the bioavailability of vitamin E
PUFAs: requirements for vitamin E may be higher with increased PUFAs in the diet. PUFAs are generally a good source of vitamin E, so their intake may counterbalance the increased need they confer.
True or False. Mixed tocopherols is the best option when supplementing vitamin E.
True.
Supplementation of a large amount of alpha-tocopherol can deplete gamma-tocopherol.
Vitamin E has been shown beneficial in supporting and preventing which of the following diseases:
A. CVD B. Diabetes C. Cataracts D. Dementia E. Cancer F. All of the above
F. All of the above
**Although much of the evidence is still inconsistent.
Vitamin E taken with any of the following medications may increase the risk of bleeding:
A. Anticoagulants (warfarin, Coumadin)
B. Anti-platelet drugs (Plavix)
C. NSAIDs (aspirin, ibuprofen)
D. All of the above
D. All of the above
When a particular part of the body, such as the eyes, requires vitamin A, the ______ releases the retinol, bound to retinol binding protein (RBP)
a. pancreas
b. liver
c. gall bladder
d. duodenum
b. liver
Retinol is released from the liver and transported in plasma bound to retinol-binding protein (RBP), which is synthesized by hepatic parenchymal cells. Less than 5% circulates as retinyl esters. Retinol-binding protein from human plasma is a monomeric polypeptide (M.W. 21,000) that has a single binding site. Transfer of retinol into cells may be mediated by cell surface receptors that specifically recognize RBP. After binding and releasing its vitamin A, RBP appears to have decreased affinity for prealbumin and is rapidly filtered by the kidney and degraded or excreted.
Functions of vitamin A include:
a. Eye health
b. skin and tissue growth
c. antioxidant
d. all of the above
d. all of the above. Vitamin A does SO many things
* Eyes - involved in the development and maintenance of the mucus membranes, cornea, and conjunctiva. Also plays a role in phototransduction (a process by which light is converted into electrical signals in the rod cells, cone cells and photosensitive ganglion cells of the retina of the eye). All -trans retinal is linked to a protein to form rhodopsin in the rod cells and iodopsin in the cone cells of the retina. These cells are required for night vision and the perception of color in bright light. C = cone = color. Rod = reduced = dim light.
Skin and tissue cells - involved in the integrity and growth of skin and tissue cells, including the mucus membranes of the mouth, intestines, respiratory, genitals, and urinary tract. Also involved in the production of keratin (in the skin and epithelia)
Antioxidant (many carotenoids function as antioxidants).
All of the following are major functions of vitamin C except:
a. Formation of collagen
b. Synthesis of neurotransmitters
c. Antioxidant activity
d. Absorption of iron
d. Absorption of iron (vit C aids in this, but it’s not a MAJOR function)
MAIN FUNCTIONS = Formation of collagen, synthesis of neurotransmitters (i.e. norepi and serotonin; needs B6), antioxidant activity (redox recycling of other antioxidants - vit E, glutathione; reduces free radicals)
Collagen is responsible for strengthening bones and blood vessels, anchoring teeth into the gums, and forming the substances necessary for body growth, tissue repair, and wound healing – so vit C indirectly tied to all of these too!
Also involved in synthesis of carnitine (i.e. fatty acid metabolism/energy) and tyrosine (i.e. neurotransmitter precursor)
Where is vitamin C mostly absorbed?
a. duodenum
b. jejunum
c. ileum
d. b and c
e. a-c
d. b and c - The jejunum and ileum absorb vitamin C
Hark, p. 62
The amount of vitamin C in the blood is modulated by:
a. renal excretion
b. iron status
c. liver burden
d. inflammation levels
a. renal excretion - Plasma levels will increase until renal threshold is met – levels exceeding the reabsorption threshold are excreted in the urine
(Hark, p. 62)
Vitamin C is found mostly in:
a. adrenal + pituitary glands
b. liver + kidneys
c. muscles
d. heart, lungs, spleen
a. adrenal + pituitary glands
