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Basic Human Nutrition > Chapter 8-9: Vitamins > Flashcards

Chapter 8-9: Vitamins Flashcards

0
Q

List the Water-Soluble Vitamins.

A

1) B vitamins

2) Vitamin C

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1
Q

What is the shape of the curve on a graph representing the bodily harm in relation to the amount of a nutrient that is absorbed?

A

U-shape

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2
Q

List the fat-soluble vitamins.

A

1) Vitamin A
2) Vitamin D
3) Vitamin E
4) Vitamin K

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3
Q

List the different types of B vitamins.

A 
Thiamin (B1)
Riboflavin (B2)
Niacin (B3)
Biotin
Pantothenic acid
Vitamin B6
Folate
Vitamin B12
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4
Q

Smokers have a higher requirement of which vitamin?

A

Vitamin C

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5
Q

What are fortified foods?

A

Foods to which nutrients have been added to…

i) replace nutrients lost during processing (enrichment)
ii) increase the amount of a nutrient in the food supply

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6
Q

When does a nutrient HAVE to be listed in the nutrients facts table?

A
  • when it has been added to a food
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7
Q

What is the UL for Vitamin C?

A

2,000mg

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8
Q

What is bioavailability?

A
  • how much of a nutrient can be absorbed and used in the body
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9
Q

How are fat-soluble and water-soluble vitamins absorbed differently in the body?

A

i) fat-soluble vitamins are incorporated into micelles in the small intestine and then absorbed by simple diffusion
- once inside the mucosal cells, they are packaged in chylomicrons, which enter the lymph before passing into the blood
ii) water-soluble vitamins are absorbed directly from the small intestine into the blood

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10
Q

How are water-soluble vitamins stored and excreted?

A
  • they are not stored (w. exception of B12 which can stay in body for yrs)
  • excess excreted through urine
  • deplete more quickly than fat-soluble
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11
Q

How is an active vitamin created?

A

when the vitamin combines with a chemical group to form the functional coenzyme

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12
Q

How is an active coenzyme created?

A

when a functional coenzyme combines with an incomplete enzyme

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13
Q

Which vitamins help with energy metabolism function?

A 
Thiamin
Riboflavin
Niacin
Pantothenic Acid
Biotin
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14
Q

Which vitamins help with single carbon metabolism function?

A

B6
Folate
B12

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15
Q

What is an antioxidant?

A
  • nutrient that protects from oxidative damage/stress
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16
Q

Which vitamins function as antioxidants?

A

Vitamin C

Vitamin E

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17
Q

What disease is attributed to a deficiency in Thiamine? Where is it most common?

A

BERIBERI

- common in pop’ns where unenriched white rice is a staple

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18
Q

What are some of the symptoms of Beriberi?

A
  • weakness
  • nerve tingling
  • poor co-ordination
  • paralysis
  • death
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19
Q

____ depletes thiamine.

A

Alcohol

- Wernicke-Korsakoff syndrome

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20
Q

What is the best source of riboflavin in the Canadian diet? How can it be destroyed?

A
  • milk

- riboflavin can be destroyed by light

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21
Q

Which disease is caused by a deficiency in niacin? In which diets is it most common and why?

A

Pellegra

  • diets high in corn –> niacin is bound to protein (not bioavailable)
    note: in S America, corn is treated w. lime, which releases bound niacin
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22
Q

What are the symptoms of pellegra?

A

The 4 D’s:

1) Dermatitis
2) Diarrhea
3) Dementia
4) Death

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23
Q

From which amino acid can niacin be synthesized from?

A

Tryptophan

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24
Q

What is the UL of Niacin?

A

35mg

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25
Q

Which disease is niacin used to treat? Why?

A

Cardiovascular Disease (in doses of 50mg –> side effects)

  • lowers LDL cholesterol
  • raises HDL cholesterol
  • lowers serum triglycerides
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26
Q

What is homocysteine?

A
  • an amino acid that is toxic to blood vessels

- high levels increase the risk of cardiovascular disease

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27
Q

What is the homocysteine hypothesis?

A
  • increasing intake of B6, B12, and folate keeps homocysteine levels in the blood low
  • reduces risk of cardiovascular disease
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28
Q

How does vitamin B6 lower homocysteine levels?

A
  • by helping to convert homocysteine to cysteine
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29
Q

How do folate and vitamin B12 lower homocysteine levels?

A
  • by converting homocysteine to methionine

- achieved by transfer of a methyl group from methyl folate to B12, forming methyl-B12

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30
Q

What function does folate serve in the body?

A

single carbon metabolism

  • synthesis of the components of DNA
  • DNA methylation (controls gene expression)
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31
Q

What may a folate deficiency result in?

A

Megaloblastic/Macrocytic Anemia

32
Q

What may a folate deficiency result in for a pregnant woman? Why?

A

Neural tube defects in their child

- folate needed for neural tube closure, which develops into the brain & spine

33
Q

Why is a folate deficiency so risky for women who are at childrearing age?

A

neural tube closure occurs between day 20-28 after conception - a time before many women know that they are pregnant
- thus, food is often fortified w. folate to help prevent this; also recommended to take at least 400ug of folate/day

34
Q

What is pernicious anemia?

A
  • caused by an inability to absorb sufficient B12
  • due to autoimmune disease which destroys the cells that produce IF (intrinsic factor)
  • symptomatically same as megaloblastic anemia but does not respond to iron supplementation
35
Q

B12 is required for the formation of which part of the cell?

A

MYELIN SHEATH

36
Q

What is atrophic gastritis?

A
  • inflammation of stomach lining that results in reduced secretion of stomach acid & bacterial overgrowth
  • prevents release of protein bound B12
  • severe cases interfere with production of IF
37
Q

What is the UL for folate?

A

1,000ug

38
Q

What may mask a vitamin B12 deficiency? Why is this dangerous?

A
  • excessive in take of folic acid may mask a B12 deficiency

- dangerous b/c although anemia does not develop, the neurological damage continues

39
Q

What is oxidative stress?

A
  • when there are more reactive oxygen species than can be neutralized by antioxidants in the body
  • damage to protein, DNA, membranes, LDL cholesterol
40
Q

What are some sources of reactive oxygen species?

A

1) Mitochondrial energy metabolism
2) Dropped electrons
3) Superoxide conversion to hydrogen peroxide

41
Q

How do antioxidants neutralize free radicals?

A

by donating electrons

42
Q

Why is the vitamin C requirement for smokers higher than for non-smokers?

A
  • smoking generates free radicals in lung tissue

- Vitamin C neutralizes these free radicals

43
Q

Which disease is caused by a vitamin C deficiency?

A

scurvy

44
Q

What are the 3 main functions of vitamin A?

A

1) Visual cycle
2) Gene expression
3) Cell differentiation

45
Q

How are Canadians doing with respect to their intake of Vitamin A (from food)?

A

not good - high prevalence of inadequate intake

46
Q

What is retinol?

A

pre-formed vitamin A

  • from animal sources
  • interconvertable with retinal
47
Q

Can retinoic acid be converted back to other forms once converted?

A

NO

48
Q

____ can be converted into retinol. Is this conversion efficient?

A

Beta-carotene

  • conversion is inefficient b/c (i) not all beta-carotene is absorbed, and (ii) not al beta-carotene is converted to retinol
  • 1ug RAE = 12ug beta-carotene from food
49
Q

Beta-carotene acts as a(n) ______.

A

ANTIOXIDANT

  • circulates in the blood
  • observational studies suggest that high levels of beta-carotene reduce risk of lung cancer in smokers
  • intervention trial suggests the opposite –> may have given too high of a dose of beta-carotene (hypercarotenemia) –> could be indicative of the U-shaped curve
  • in animal models, when given a more moderate dose, it is shown to benefit, but very high dose showed pre-cancerous lesions
50
Q

What is hypercarotenemia?

A
  • too much beta-carotene in the blood, which concentrates in the fat levels of the skin
  • literally turn orange
  • people who take a lot of supplements or drink 1 gallon of carrot juice/day
  • an example of the U-shaped curve
51
Q

Which vitamin is the visual cycle highly dependent on?

A

Vitamin A - specifically, retinal

52
Q

What happens to the visual cycle when deficient in vitamin A/retinal?

A
  • visual cycle cannot regenerate as well

- regeneration of rhodopsin is delayed –> until it is reformed, light cannot be perceived

53
Q

What is the relationship between nightblindness and vitamin A?

A

1) in dim light, can make out the details of a room
2) a flash of bright light momentarily blinds you as the pigment in the retina is bleached
3) quickly recover and can see the details again in a few seconds
* *when vitamin A deficient, do not recover, but remain blind for many seconds –> this inability to recover = nightblindness

54
Q

What role does vitamin A play in gene expression?

A

In transcription factor (vitamin-protein receptor), which initiates gene expression

  • when transcription of a gene is turned on, it increases the amount of mRNA made
  • if you don’t have the vitamin (a.k.a. ligand) to bind with the protein receptor, then the rest of the gene expression pathway does not work
55
Q

What role does Vitamin A play in cell differentiation?

A

1) Aids in barrier functions of epithelial tissue in eyes, intestine, lungs, etc…
- a deficiency leads to an increased risk of infection
- moist & lubricated (mucus) tissue vs. hard & dry (keratin)
2) Immune system
- vitamin A req’d for the differentiation of precursor cells (white blood cells)

56
Q

What is xerophthalmia?

A

Dry eyes

- vitamin A deficiency

57
Q

What does Vitamin A supplementation help prevent?

A

1) infection

2) blindness

58
Q

In what instance can Vitamin A be toxic?

A

Retinol can be toxic at high doses

- can become a teratogen that causes birth defects

59
Q

What is Vitamin D synthesized from on the skin? How?

A

formed from cholesterol through sun exposure

cholesterol –> dehyrdrocholesterol – (sun on skin) –> Vitamin D3 (cholecalciterol)

fact check this

60
Q

Where/when does no synthesis of Vitamin D occur?

A

during the winter at latitudes greater than 40 degrees north/south

61
Q

Where do the main functions of Vitamin D lie?

A

1) Bone health
2) Gene expression
3) Calcium absorption (bone health..?)

62
Q

What role does Vitamin D play in bone health?

A

Maintains calcium levels in the blood by…

  • increasing calcium absorption in intestine
  • increasing reabsorption of calcium from kidneys
  • increasing calcium resorption (breakdown) from bone
  • stimulating bone formation when calcium is adequate
63
Q

What role does Vitamin D play in gene expression?

A

In transcription factor (vitamin-protein receptor), which initiates gene expression

  • if you don’t have the vitamin (a.k.a. ligand) to bind with the protein receptor, then the rest of the gene expression pathway does not work
  • just like Vitamin A*
64
Q

What role does Vitamin D play in calcium absorption?

A

Vitamin D turns on the synthesis of calcium transport proteins

65
Q

What is rickets?

A
  • result of vitamin D deficiency in children

- loss of mineral component of bone

66
Q

What is osteomalacia?

A
  • rickets in adults

- loss of mineral component of bone; vitamin D

67
Q

Who in particular must be supplemented with Vitamin D? Why?

A

1) babies that are exclusively breastfed (breast milk is low in vitamin D)
2) men & women over 50yrs should take 10ug/400IU daily (biosynthesis of vitamin D in skin declines w. age)

68
Q

Vitamin D has been linked to reduced risk of _____.

A

cancer

69
Q

What are the two main compounds of Vitamin E?

A

1) Tocopherols

2) Tocotrienols

70
Q

What is the main form of Vitamin E in the blood?

A

alpha-tocopherol

- also the main form used in supplements

71
Q

What are some of the health benefits of Vitamin E?

A

1) Antioxidant

2) Blood thinner (reduces blood clotting; cardiovascular disease)

72
Q

Does Vitamin E have a causal relationship with reduced cardiovascular disease?

A

NO

- linked to prevention of cardiovascular disease in observational studies, but not intervention trials

73
Q

What is the relationship between vitamins E & C as antioxidants?

A

the antioxidant function of vitamin E can be restored by another vitamin (such as vitamin C, which gives an electron back to vitamin E)

74
Q

How does vitamin E work as an antioxidant?

A

neutralizes free radicals in the cell membrane by donating one of its electrons

75
Q

What are the two different forms of vitamin K?

A

1) phylloquinone (plant form) - green leafy vegetables

2) menaquinones (synthesized in supplements)

76
Q

What are the main functions of Vitamin K?

A

1) blood clotting - for damaged tissue (i.e. a cut), or if on blood thinning meds, vit K should be taken consistently
2) bone metabolism - vit K is req’d for proteins in bone that regulate bone metabolism

77
Q

What do fibrin threads do?

A

form the webbing of a blood clot

Basic Human Nutrition (6 decks)

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