Module 9

Question 1

Vitamin A

Answer 1

Carotenoids: (beta carotene) plants, pre vit A.
Retinoids: retinol, retinal, retinoic acid

Question 2

Food Sources of Vitamin A

Answer 2

RDA: 700/900 mcg RAE (women/men)
UL= 3000 mcg RAE (tight therapeutic index)
RAE= retinol activity equivalents.
Liver (retinoid) has lots
Carrots (carotenoid) or orangish colour fruits and vegetables.

Question 3

RAE Conversion

Answer 3

1 mcg RAE= 1 mcg retinol
= 2 mcg Beta-car (supplement)
=12 mcg Beta car (food)
=24 mcg non beta car
1 mcg RAE= 3.3 IU (international units)

Question 4

Functions of Vitamin A

Answer 4

Vision (retinol, retinal), Epithelial Cell Function (skin, lung, cornea, GI tract, 90% of all cancers arise in these cells), Growth, Reproduction (fertility for both men and women, retinoic acid).

Question 5

Role of retinal in the visual cycle

Answer 5

Rods of the eye- black and white vision.
The retinal form of the vitamin combines with the protein opsin to form the visual pigment rhodopsin. Helps send a nerve impulse that allows us to see.

Question 6

The visual cycle

Answer 6

1. Light strikes the visual pigment rhodopsin.
2. The retinal molecule changes from a bent (cis) to a straight (trans) configurations.
3. A nerve signal is sent to the brain, telling us that there is light, and retinal is released from opsin.
4. Some retinal is lost from the cycle.
5. Some retinal returns to its original cis configuration ands binds opsin to begin the cycle again.
6. When vitamin A status is normal, vitamin A from the blood replaces any retinal loss from the cycle.
7. When Vitamin A is deficient, little vitamin A is available in the blood, and the regeneration of rhodopsin is delayed. Until it is reformed, light cannot be percieved.

Question 7

First sign of Vitamin A deficiency

Answer 7

night blindness (normally should take less than 30 sec)

Question 8

Xerophthalmia (night blindness)

Answer 8

Deficiency of vitamin A in corneal epithelia.
Lose mucus layer: decrease nutrient absorption, lower immune system.
First night blindness (can still save eye at this point) second cornea dry and opaque.
Then scaring in deeper layers and it cant be reversed.

Question 9

Vitamin D

Answer 9

One of the few vitamins we can make.
Made in skin (Nov-Mar no vit d synthesis)

Question 10

Sources of Vitamin D

Answer 10

RDA= 15 mcg/day
Fatty fish (salmon), eggs, milk
1. Foods: naturally high in D (milk, eggs, fish), fortified with D (milk and margarine)
2. Sunlight: Nov-Mar (for where we live), caucasian 20 mins face arms and heads/day, overuse of sunscreen is associated with lack of vit D.

Question 11

Functions of Vitamin D

Answer 11

Key role: Maintain blood Ca levels. (< 1% body Ca is involved in nerve conduction, enzyme reactions, muscle contraction are priority)
Stimulate Ca absorbed from GI tract.
Draw Ca from bone (short-term response)
Reduce Ca losses from Kidney (in urine)

Question 12

Vitamin D deficiency

Answer 12

Affects bones
a) in children: lack of mineralization of bones, leads to widening of region of bones growth, RICKETS (can’t be reversed with vit D).
b) in adults: become vit D deficient, demineralization—> soft bones (osteomalacia)

Question 13

Osteoporosis

Answer 13

Lack of dietary calcium
Porus bones

Question 14

Vitamin D deficiency occurs most commonly in:

Answer 14

1. Dietary lack
2. Lack of exposure to sun or suncreen overuse.
3. Malabsorption of fat.
4. Older adults: decrease ability to activate D2/D3, decrease ability to make D3 from sun, institutions/lack of sun.
5. Infants: breastfed (need vit D supplements/drops), Babies breastfed exclusively for >6 months and or weaned to vegan diet.
6. Children 1-3: poor diet lacking vit D.
7. Preadol and adolescence: puberty through 20s (growth spurt)
8. Because bit D stored in adipose: for obesity, may need increase vit D intake.

Question 15

Vitamin D toxicity

Answer 15

RDA: 15 mg/day
UL: 4000 IU/40= 100 mcg/day
Toxicity Symptoms: hard Ca deposits in tissues/organs (kidney, heart, lung, blood vessels)

Question 16

Vitamin E

Answer 16

Antioxidant in fat soluble parts of body.
Alpha tocopherol
RDA: 15 mg/day
UL= 1000 mg/day (very wide safety range)
Food sources: seeds, nuts, oils

Question 17

Vitamin E Absorption and metabolism

Answer 17

Absorbed from GI tract, then goes to chylomicrons, then to the liver where it is not stored, then to VLDL where it is distributed to all body cells.

Question 18

Antioxidant function of Vitamin E

Answer 18

By neutralizing free radicals vitamin E guards not only cell membranes, but also body proteins, DNA, and cholesterol. Vitamin E must be regenerated by vitamin C to restore it to the form that can act as an antioxidant.

Question 19

Vitamin E deficiency

Question 20

Vitamin E toxicity

Answer 20

Very high intakes may interfere with blood clotting.

Question 21

Vitamin K History

Answer 21

1929: fat soluble factory necessary for blood clotting: Koagulation Vitamin.
1939: Vit K1- green leafies (phylloquin one), Vit K2- cheese, meat, in our colon (resident microbes).

Question 22

Vitamin K Sources

Answer 22

AI: 90/120 mcg/day (women/men)
Oils
Meats
Cheese

Question 23

Functions of vitamin K

Answer 23

Blood clotting
Bone metabolism
Kidney Function
Ca absorb from GI tract

Question 24

Role of Vitamin K in blood clotting

Answer 24

Several clotting factors include prothrombin, require vitamin K for synthesis.These are needed for fibrinogen to be converted into its active form fibrin, which is structural component of blood clots.

Question 25

Vitamin K absorption and metabolism

Answer 25

Very similar to vitamin E, not stored, and distributed throughout body.

Question 26

Vitamin K Deficiency

Answer 26

Rare
Except: long term general (broad-spectrum) antibiotics

Question 27

Vitamin K toxicity

Answer 27

Rare
No UL determined
not stored
Excess vitamin K (supplement) may interfere in anticoagulant drugs.

Question 28

K1

Answer 28

Phylloquinone

Question 29

K2

Answer 29

Menaquinone

Question 30

Lack of Vitamin E

Answer 30

Hemolytic anemia

Question 31

Vitamin E deficiency

Answer 31

Deficiency can cause membrane changes.
Nerve tissue and red blood cells are particularly susceptible.
Usually characterized by neurological problems.
Hemolytic anemia.
More symptoms include poor muscle coordination, weakness and impaired vision.

Question 32

Vitamin A absorption and metabolism

Answer 32

Vitamin A and carotenoids are bound to protein in foods. To be absorbed they must be released from the protein by pepsin and other protein digesting enzymes.
1. Preformed vitamin A is present primarily as retinol bound to fatty acids.
2. In the body, retinol and retinal can be interconverted.
3. Once retinoic acid has been formed, it cannot be converted back to retinal or retinol.
4. Beta carotene from plant foods can be converted into retinal in the intestinal mucosa and in the liver.

Question 33

Vitamin A toxicity

Answer 33

Can be toxic at extremely high doses.
Toxicity include nausea, vomiting, headache, dizziness, blurred vision, and a lack of muscle coordination.
Particular concern for pregnant women because it could contribute to birth defects.
Chronic toxicity symptoms include: weight loss, muscle and joint pain, liver damage, bone abnormalities, visual defects, dry scaling lips and skin rashes.

Question 34

Retinoids (foods or supplements) of concern:

Answer 34

Infants/Children on high doses—> vitamin supplement 1500 mcg RAE (Children 4-8: RDA-400 mcg RAE, UL 900 mcg RAE).
Multivitamin overuse.
Long Term use of Accutane for acne (teratogen, causes birth defects)

Question 35

Vitamin D Absorption and Metabolism

Answer 35

1. Enzymes in the liver add a hydroxyl group to carbon number 25.
2. Enzymes in the kidney add a hydroxyl group to carbon number 1, forming active vitamin D.
3. Low levels of active vitamin D stimulate calcium absorption from the intestine. Higher levels act with parathyroid hormone at the bone to increase bone breakdown and at the kidney to increase calcium retention.
4. Blood calcium and phosphorus are maintained at levels that support bone mineralization.

Question 36

Sources of D3

Answer 36

Eggs, milk, fish

Question 37

Sources of D2

Answer 37

(ergocalcified) (sun-dried mushrooms)