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Nutrition > Vitamin A > Flashcards

Vitamin A Flashcards

1
Q

T/F

Fat soluble vitamins are mostly lost when cooking with water

A

False

Little are lost

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2
Q

How many grams of fat are needed for bile secretion for absorption of fat soluble vitamins?

A

5-10g

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3
Q

Fat soluble vitamins are absorbed by what means? How are they transported?

A

Passive diffusion; transported with lipids in lipoproteins

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4
Q

Where are fat soluble vitamins found in the cell?

A

Lipid portions

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5
Q

Where are fat soluble vitamins stored?

A

Liver and adipose tissue

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6
Q

Are fat soluble vitamins toxic?

A

Yes, in large amounts they are toxic

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7
Q

What is bile, where is it made, stored and concentrated?

A

Emulsified made from cholesterol in the liver, stored and concentrated in the gallbladder.

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8
Q

What happens with fat-rich chyme enters the SI?

A

Stimulates CCK

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9
Q

What does CCK do

A

Gallbladder contraction causing bile secretion from the gallbladder through the Sphincter of Oddi to the SI

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10
Q

What should you assume when you see “cholate” in a word?

A

Bile acid

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11
Q

What are micelles?

A

Fatty acids, monoglycerides, fatsoluble vitamins, cholesterol & bile

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12
Q

What does retinol (vit A) affect?

A

Reproduction and growth

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13
Q

What does retinal (vit A) affect?

A

Vision

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14
Q

What does retinoic acid (vit A) affect?

A

Cell differentiation

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15
Q

Where is preformed vitamin A found?

A

Animal products: dairy products, liver, fish, eggs.

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16
Q

What is a retinol ester?

A

Retinol with a fatty acid attatched

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17
Q

What is proformed vitamin A?

A

Precursors to vitamin A

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18
Q

Where is proformed vitamin A found?

A

Plant products: orange, yellow, red colors.

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19
Q

T/F

Proformed vitamin A intake should equal preformed vitamin A

A

False,

Proformed vitamin A is only necessary when we don’t get enough preformed vitamin A in our diet

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20
Q

How much proformed vitamin A is necessary to equal preformed vitamin A activity?

A

12x as much proformed to equal preformed activity

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21
Q

Considering proformed vit A, how many known carotinoids are known? How many can be convered to retinol?

A

> 600

<10%

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22
Q

What is the difference between what RE and carotenoids are bound to?

A

Carotenoids are bound to a fatty acid,

RE’s are bound to a fatty acid and protein in food

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23
Q

What makes vitamin A soluble?

A

Bile

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24
Q

Free retinol and carotenoids are incorportated into…

A

Micelles

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25
Q

How much of RE are absorbed?

A

80%

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26
Q

How and where in the body is Vitamin A absorbed?

A

By passive diffusion in the duodenum and jejunum

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27
Q

What is retinol bound by?

A

Cellular-retinol-binding-protein (CRBP)

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28
Q

What happens to retinol in the enterocyte?

A

Retinol is reesterified to a RE by lecithin retinol acyl transferace (LRAT)

29
Q

What are RE incorporated into?

A

Chylomicrons

30
Q

What is step 1 to vitamin A absorption?

A

Retinol, fatty acids, and carotenoids are absorbed as part of micelles by passive diffusion in the SI. Retinol is bound by CRBP.

31
Q

What is step 2 to vitamin A absorption?

A

Fatty acids are reesterified to retinol by LRAT, reforming a RE

32
Q

What is step 3 to vitamin A absorption?

A

RE and carotenoids are packaged into chylomicros and sent through the lymph system

33
Q

What percentage of Vitamin A is absorbed from raw veggies as opposed to cooked veggies?

A

5% absorbed from raw

60% absorbed from cooked

34
Q

If retinol intake is low, what happens to carotenoids?

A

Carotenoids are metabolized to 2 retinals

35
Q

If retinol intake is low, what happens to retinals?

A

Either:

  1. Retinal is bound by CRBP, reduced to retinol, esterified via LRAT and incorporated into chylomicros.
  2. Oxidized to retinoic acid and travels to the liver bound to albumin
36
Q

What happens to retinol if intake is adequate?

A

Incorporated into chylomicrons

37
Q

How much of vitamin A is stored in the liver?

A

50-80%

38
Q

What problem with Vit A metabolism will occur with patients with a low protein status? What must be done to remediate the problem?

A

Retinol cannot be metabolized out of the liver. Must correct protein deficiency first!!!!

39
Q

What is the formula for rhodopsin?

A

Retinol -> retinal + opsin

40
Q

What is vitamin A important for vision wise?

A

Vision in dim light

41
Q

If you decrease vitamin A what else is reduced in the vision pathway?

A

Rhodopsin and night vision

42
Q

In cell differentiation, retinoic acid is important for rapidly dividing cells by directing…

A

Keratin synthesis

43
Q

Vitamin A is important for catalyzing the reaction of turning keratinizing cells into what other kind of cells?

A

Mucus-secreting cells

44
Q

What happens to mucus secreting cells, and where does it happen, when vitamin A intake is diminished?

A

Keratin producing cells replace mucus secreting cells in the respiratory, GI, and urinary tracts (process called hyperkeratinization)

45
Q

How does vitamin A affect gene expression?

A

Retinoice acid interacts with DNA in nucleus. Stimulates the production of GFs and enzymes.

46
Q

How does vitamin A intake affect bones?

A

Vitamin A deficiency stimulates osteblasts

Excessive vitamin A stimulates osteoclasts

47
Q

What are 2 major functions that carotenoids have?

A

Affect immune system and cell growth/differentiation

48
Q

Specific carotenoids may inhibit growth & proliferation of several cancer lines, but what can supplementation cause?

A

Increase risk of several cancers

49
Q

T/F

A vitamin is an inorganic compound

A

False,

Organic

50
Q

What is the most reduced for of vitamin A called?

A

Retinoic acid

51
Q

What are 3 examples of conditions associated with clinical deficiency of vitamins?

A

Pellagra
Burning feet syndrome
Keshan’s disease

52
Q

What are subclinical deficiencies of vitamins associated with?

A

Increased risk of chronic diseases

53
Q

In vitamin A digestion, what are proteins and fatty acids removed by respectively, and where?

A

Proteins removed by proteases in the stomach and SI

Fatty acids removed by lipases in SI

54
Q

What is the most reduced and most oxidized form of Vitamin A?

A

Most reduced = Retinol

Most oxidized = Retinoic acid

55
Q

What is the RDA?

A

Recommended dietary allowance. Meets nutritional need of 97.5% of the population

56
Q

What the RAE?

A

Retinol activity equivalents

57
Q

What is the RAE for men and for women respectively?

A 
Men = 900 RAE
Women = 700 RAE
58
Q

What is the #1 vitamin deficiency worldwide?

A

Hypovitaminosis A

59
Q

What are the 2 causes of hypovitaminosis A?

A
  1. Inadequate intake

2. Fatty acid malabsorption

60
Q

What are the 4 categories of symptoms associated with hypovitaminosis A

A
  1. Vision problems (e.g. night blindness, xerophlamia, dry eye, bitot’s spots, permanent blindness more common in developing countries)
  2. Reproduction problems
  3. Depressed immune system
  4. Skin problems (follicular hyperkeratosis caused by plugs of keratin).
61
Q

Who is most at risk for hypovitaminosis A?

A

Children

Fatty malabs patients

62
Q

What is a sign of fatty malabsorption

A

Steatorrhea

63
Q

How much vitamin A intake happens before symptoms of acute hypervitaminosis A happens?

A

> 200,000 RAE

64
Q

What are some symptoms of chronic hypervitaminosis A?

A

Dry lips (cheilitis), dry/itchy skin, alopecia, bone/joint pain, fx, liver damage.

65
Q

T/F

Vitamin A taken at toxic levels is a taratogen?

A

True

66
Q

What is the TUL (tolerable upper intake limit) For vitamin A?

A

3000 RAE

67
Q

What is the TUL for carotenoids?

A

None

68
Q

Chronic carotenoid consumption can lead to what condition?

A

Yellow/orange skin

69
Q

What conditions are smokers and former smokers at risk for with carotenoid toxicity?

A

Increased risk of lung cancer, heart disease, death. `

Nutrition (11 decks)

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