Week 13, Vitamin A, Vitamin C, Vitamin E

Question 1

_______ is/are the most active form of vitamin A and is found mostly in animal foods.

a. retinoic acid
b. retinol
c. carotenoids

Answer 1

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.

Question 2

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).

Answer 2

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

Question 3

Vitamin E is mostly found in the:

A. Cell membranes
B. Adipose Tissue
C. Skeletal Muscle

Answer 3

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.

Question 4

True or False. Vitamin E quenches free radicals, acting as an antioxidant.

Answer 4

True.

Question 5

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

Answer 5

A. Deficiency

Question 6

Vitamin E plays a role in the following:

A. Cell signaling
B. Gene Expression
C. Immune Regulation
D. Inflammation
E. All of the above

Answer 6

E. All of the above

Question 7

True or False. Vitamin E is found in food largely in tocopherol form and is freely absorbed.

Answer 7

True.

(whereas tocotrienols, synthetic esters of tocopherols and tocopherol
acetate require hydrolyzing before they can be absorbed)

Question 8

Vitamin E is absorbed mainly in the:

A. Duodenum
B. Jejunum
C. Ileum

Answer 8

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.

Question 9

Vitamin E deficiency is ______ .

A. Rare
B. Common

Answer 9

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.

Question 10

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

Answer 10

B. Toxicity

Question 11

About 70% of the vitamin E consumed in an American diet is from:

A. gamma-tocopherol
B. beta-tocopherol
C. alpha-tocopherol

Answer 11

A. gamma-tocopherol

Question 12

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

Answer 12

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.

Question 13

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

Answer 13

A. The same for men and women, 15mg

Question 14

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

Answer 14

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).

Question 15

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

Answer 15

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.

Question 16

True or False. Mixed tocopherols is the best option when supplementing vitamin E.

Answer 16

True.

Supplementation of a large amount of alpha-tocopherol can deplete gamma-tocopherol.

Question 17

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

Answer 17

F. All of the above

**Although much of the evidence is still inconsistent.

Question 18

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

Answer 18

D. All of the above

Question 19

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

Answer 19

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.

Question 20

Functions of vitamin A include:

a. Eye health
b. skin and tissue growth
c. antioxidant
d. all of the above

Answer 20

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).

Question 21

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

Answer 21

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)

Question 22

Where is vitamin C mostly absorbed?

a. duodenum
b. jejunum
c. ileum
d. b and c
e. a-c

Answer 22

d. b and c - The jejunum and ileum absorb vitamin C

Hark, p. 62

Question 23

The amount of vitamin C in the blood is modulated by:

a. renal excretion
b. iron status
c. liver burden
d. inflammation levels

Answer 23

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)

Question 24

Vitamin C is found mostly in:

a. adrenal + pituitary glands
b. liver + kidneys
c. muscles
d. heart, lungs, spleen

Answer 24

a. adrenal + pituitary glands

Question 25

True or false? Vitamin C is the least stable of all the vitamins?

Answer 25

True: It is the least stable of all the vitamins, and is easily destroyed during cooking and processing.

(Hark, p. 62)

Question 26

Absorption of vitamin C is 70-90%. Absorption_______ with higher doses.

a. increases
b. decreases

Answer 26

b. decreases

Higher doses decrease absorption; for example, doses > 1g/d results in about 50% absorption

Question 27

Vitamin C deficiency can lead to which of the below:

a. scurvy
b. tuberculosis
c. rheumatic fever
d. Cushing’s syndrome

Answer 27

a. scurvy

• Acute vit C deficiency: total body Vit C = <300mg and plasma <0.2mg/dL
• Signs can appear in as little as 1 mo with little/no vit C intakes (i.e. < 10mg/day) – think of sailors

Question 28

True or false - vitamin A is ingested either as pre-formed vitamin A (retinol or retinyl ester), or a beta-carotene that can be split into retinol in the intestine.

Answer 28

True.

Question 29

What are the classic manifestations of scurvy?

a. Hemorrhage, hyperkeratosis, hypochondriasis, hematologic abnormalities
b. Hypoxia, hypokalaemia, hypothermia, hypovolaemia
c. Extreme lethargy, slow wound healing, hair loss, cold intolerance
d. Vomiting, abdominal pain, seizures, peripheral neuropathy

Answer 29

a. 4 H’s = Hemorrhage, Hyperkeratosis, Hypochondriasis, Hematologic abnormalities

Hemorrhage - d/t connective tissues weakening - petechiae (tiny round brown-purple spots due to bleeding under the skin), bruising, purpura (rash of purple spots d/t small blood vessels leaking into skin, joints, intestines, etc.), bleeding gums

Hyperkeratosis - d/t impaired collagen synthesis (thickening of the outer layer of the skin - which is made of keratin)

Hematologic abnormalities (i.e. iron deficiency anemia) - d/t increased bleeding, decreased non-heme iron absorption

Hypochondriasis - assoc. w/ psychological changes (also incl. hysteria, depression)

• Initial symptoms = fatigue (probably the result of impaired carnitine biosynthesis), malaise, inflammation of the gums
• Disease progression = impaired collagen synthesis and weakened connective tissues > leading to bleeding
• Additional signs include depression, loosening/loss of teeth due to tissue/capillary fragility, joint pain, poor wound healing, corkscrew hairs
• Scurvy is fatal if left untreated

Question 30

All of the following populations have increased requirements for vitamin C except:

a. cigarette smokers
b. alcoholics
c. clients w/ recent surgery
d. elderly
e. SAD diet
f. hyperthyroidism

Answer 30

f. hyperthyroidism

Alcohol - decreases vit C absorption
Cigarette smoking - depletes vit C tissue levels
Surgery - for healing
Elderly - decreased food consumption, insufficient food preparation practices
SAD diet - diets devoid of fresh fruits and veg

Also - Individuals with severe burns, fractures, pneumonia, rheumatic fever, tuberculosis, malabsorption, some cancer patients, end-stage renal disease

Question 31

All of the following tactics help reduce symptoms of excess vitamin C except:

a. Dividing dosages
b. Taking w/ food
c. Using buffered forms
d. Take w/o food

Answer 31

d. Take w/o food

Question 32

Which of the following are risk factors of excess vitamin C supplementation? Choose all that apply:

a. oxalate kidney stones
b. iron toxicity
c.

Answer 32

a. oxalate kidney stones
b. iron toxicity

Iron toxicity - risk w/ high dosage in those with Fe disorders / excess Fe (i.e. hemochromatosis, sideroblastic anemia, etc.)

Question 33

Beta carotene is the most abundant carotenoid present in ______ fruits and vegetables (select all that apply):

a. green
b. yellow
c. orange

Answer 33

a-c. Clorophyll blocks the orange pigment for green produce.

*Due to inefficient conversion, 12 micrograms of beta-carotene in food yields only about 1 microgram of retinol (a.k.a. - retinol activity equivalent). Other carotenoids are even less efficiently converted to retinol. 100 IU of retinol in supplements translates to 30 micrograms RAE, while 100 IU of beta-carotene equates to 5 micrograms RAE.

Question 34

What is the TUL of vitamin C:

a. 2,000mg
b. 3,000mg
c. 4,000mg
d. 5,000mg

Answer 34

a. 2,000mg

Since vitamin C is water-soluble, the body excretes the excess when intake exceeds the body’s requirements. However, because vitamin C is metabolized to oxalic acid, consuming too much may cause increased excretion of oxalate, which suggests that patients with a history of forming oxalate kidney stones should avoid high doses of this vitamin. Doses in excess of the TUL (2000 mg/day) can have other side effects including nausea, diarrhea, and abdominal cramps.

Ab pain + osmotic diarrhea can present when bowel tolerance is reached d/t unabsorbed vit C being metabolized by large intestine bacteria

Question 35

Vitamin A deficiency is one of the most common forms of malnutrition worldwide in ______:

a. infants and young children
b. pregnant women
c. post menopausal women
d. elderly

Answer 35

a. infants and children

Primary deficiency - inadequate intake of vitamin A and its precursors.
Secondary deficiency - poor absorption of fat soluble vitamins (CF, Crohn’s, tropical sprue or liver disease, or those with excessive alcohol intake).

Question 36

Vitamin A toxicity occurs with :

a. intake of 30mg/day (100,000 IU/day)
b. acute doses of 150mg (500,000 IU/day)
c. a + b

Answer 36

c. a + b
* Do not supplement in pregnant women. This can cause birth defects. No retinol on face either.

Symptoms of toxicity include: bone and skin changes, liver abnormalities (hepatomegaly), headache, nausea, vertigo, blurred vision, and lack of muscle coordination.

Because only limited amounts of carotenoids are converted to vitamin A, excessive intake of beta-carotene has not been shown to produce toxic effects. May develop yellow tinge to the skin - this carotenosis - commonly seen in babies whose caretakers give them squash and sweet potatoes (not harmful).

Question 37

Symptoms of vitamin A deficiency include:

a. perifollicular hyperkeratosis
b. night blindness
c. xerophthalmia
d. immune impairment
e. all of the above

Answer 37

e. all of the above

• xerophthalmia - can progress from conjunctival thickening to corneal ulceration and eventual irreversible blindness
• Immunity - impairment of both humoral and cell-mediated immunity; the latter effect known to increase mortality from certain infectious diseases, such as measles, in developing countries.

Question 38

The RDA for vitamin C for adults ≥19 yo is:

a. 90 mg/day for men; 75 mg/day for women
b. 100 mg/day for men; 80 mg/day for women
c. 150 mg/day for men; 130 mg/day for women
d. 100 mg/day for men & women

Answer 38

a. 90 mg/day for men; 75 mg/day for women

These values are based on the intake of vitamin C observed to preserve high neutrophil concentrations without great urinary losses to provide antioxidant protection.

Question 39

True or false? The RDA for smokers is 35 mg/day higher than for nonsmokers.

Answer 39

True - because smokers are under increased oxidative stress from the toxins in cigarette smoke and generally have lower blood levels of vitamin C.

Question 40

All of the following drugs reduce vitamin C status except:

a. aspirin
b. proton pump inhibitors
c. contraceptives w/ estrogen
d. chemotherapy drugs
e. SSRIs

Answer 40

e. SSRIs

Chemotherapy Drugs (e.g., cisplatin): Antioxidants such as vitamin C aid the body in neutralizing reactive oxygen species that are otherwise harmful to DNA, lipids and proteins. Antineoplastic agents (e.g., cisplatin) induce irreversible cellular injury by releasing free radicals; therefore, significant quantities of endogenous antioxidants, like vitamin C, are depleted. There is ongoing debate about whether supplementation with ascorbic acid or other antioxidants is beneficial or harmful during chemotherapy.

Question 41

Which of the following does not interact with vitamin C?

a. copper
b. aluminum
c. vitamin E
d. selenium
e. vitamin K

Answer 41

e. vitamin K

Iron: Vit C enhances absorption of non-heme Fe + reverses effects of some foods on non-heme Fe absorption; Vit C supp may exacerbate Fe overload in some cases

Copper: ⬆️ Vit C intake inhibits Cu absorption + ⬇️ Cu tissue levels; high dose Vit C can accelerate development of Cu def. (~2mg/d Cu supp reco’d)

Flavonoids: quercitin + rutin have been shown to inhibit oxidation of Vit C in vitro; thought that flavonoids may have a sparing effect on Vit C when levels are low

Vit E: high dose of one can ⬆️ needs for the other (work together as antioxidants)

Selenium: may ⬇️ absorption of Se (sodium selenite form)*

Aluminum: may ⬆️ absorption of aluminum (reco’d to separate supp from aluminum containing antacids, food, bevs)

Niacin + thiols: help regenerate Vit C if ascorbic acid doesn’t re-form from ascorbyl radicals

Question 42

The RDA for vitamin A for men 19 and older is:

a. 400 mcg /day
b. 500 mcg/day
c. 800 mcg/day
d. 900 mcg/day

Answer 42

d. 900 mcg/day (equivalent to 3,000 IU)

*700 for women (2,333 IU)
The UL for vitamin A from retinol is 3,000 micrograms of preformed vitamin A.