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NFS284 > Section 3-5: Vitamins > Flashcards

Section 3-5: Vitamins Flashcards

1
Q

What are the B vitamins?

A 
B1 Thiamin
B2 Riboflavin
B3 Niacin
B6 
B12
Biotin
Pantothenic acid
Folate
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2
Q

Water-soluble vitamins

A

B, C

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3
Q

Fat-soluble vitamins

A

ADEK

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4
Q

Which group has the highest vit C requirement?

A

smokers

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5
Q

What is used in assessment of nutrient intake studies?

A

24h recall

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6
Q

Which is the vit that we are getting the least of?

A

Vit C

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7
Q

Why are most Canadians not getting enough vitamins?

A

due to lack of fruits & veggies in diet

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8
Q

how can we get all required vitamins?

A

eat a variety of foods from different food groups

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9
Q

if a nutrient has been added to a food, it has to be listed in the ____

A

nutrition facts table

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10
Q

Enriched pasta has which vitamins?

A
  • vit A
  • vit C
  • calcium
  • iron
  • thiamine
  • riboflavin
  • niacin
  • folate
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11
Q

define: bioavailability

A

how much of a nutrient can be absorbed and used in the body

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12
Q

digestion & absorption of water-soluble vitamins

A

1) digestive enzymes help release vitamins from food
2) some niacin absorbed in stomach
3) absorbed in small intestines → blood stream
4) bacteria of large intestines synthesize some vitamins → some absorbed

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13
Q

digestion & absorption of fat-soluble vitamins

A

1) digestive enzymes help release vitamins from food
2) gall bladder release bile → emulsify
3) incorporated into micelles → diffuse across epithelial layer
4) packaged into chylomicrons
5) lymph → bloodstream

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14
Q

which type of vit can be stored? where can it be stored?

A

fat soluble – in adipose tissue

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15
Q

which soluble vit can stay in the body for a long time?

A

B12 (several years; body recycles it)

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16
Q

Mechanism of vit action

A

1) vit + chemical group → functional enzyme
2) functional enzyme + incomplete enzyme → active enzyme
3) active enzyme bind to molecules to speed up reaction
4) enzyme & coenzyme can be reused or seperated

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17
Q

what are vit used for in the body?

A

coenzymes for…

  • energy metabolism
  • single carbon metabolism
  • antioxidants
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18
Q

B vit function as ____

A

coenzymes in energy metabolism

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19
Q

which vit are used for energy metabolism?

A
  • Thiamin
  • Riboflavin
  • Niacin
  • Pantothenic acid
  • Biotin
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20
Q

which vit are used for single carbon metabolism?

A
  • B6
  • Folate
  • B12
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21
Q

single carbon metabolism

A

transfer of methyl groups

  • synthesis of DNA components
  • DNA methylation (control gene expression)
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22
Q

which vit act as antioxidants?

A

C

E

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23
Q

antioxidants

A

protection from oxidative damage or oxidative stress

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24
Q

disease associated with thiamine

A

Beriberi: caused by thiamine deficiency

Wernicke-Korsakoff Syndrome: alcohol causing thiamine deficiency

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25
Q

Symptoms of beriberi

A
  • weakness
  • nerve tingling
  • poor coordination
  • paralysis
  • death
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26
Q

beriberi is a problem at which places?

A

populations with unenriched white rice

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27
Q

Wernicke-Korsakoff syndrome

A
  • thiamine needed for alcohol metabolism
  • excess alcohol deplete thiamine
  • impacts cognitive functions
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28
Q

best source of riboflavin

A

milk

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29
Q

riboflavin is sensitive and will be destroyed by…

A

light

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30
Q

disease associated with niacin

A

Pellegra: niacin deficiency

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31
Q

symptoms of pellegra

A

4Ds: Dermatitis, diarrhea, dementia, death

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32
Q

pellegra is caused by…

A

diets high in corn

  • niacin is bound to a protein in corn, making it not bioavailable
  • tryptophan is low in corn (precursor for niacin)
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33
Q

Where was pellegra common? How was it treated?

A

S. USA

Now, S. USA corn is treated with lime → break covalent link between niacin and protein → bioavailable

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34
Q

niacin can be synthesized from…

A

tryptophan

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35
Q

2 forms of niacin found in the body

A

1) nicotinic acid

2) nicotinamide

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36
Q

niacin in ___ doses is used to treat ____ disease

A 
50 mg (higher than UL);
cardiovascular disease
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37
Q

why does high doses of niacin work for treating cardiovascular disease? What is the consequence of going over the UL?

A
  • lower LDL
  • raise HDL
  • lower serum TG

side-effects: burning, tingling sensation in skin (face, chest)

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38
Q

function of B6

A

1) transaminatin: make non-essential AA
2) deamination: make ATP & glucose
3) decarboxylation: make NT

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39
Q

homocysteine hypothesis

A
  • homocysteine is toxic to blood at high levels → increased risk of cardiovascular disease
  • B6, B12, folate reduce levels of homocysteine in the blood → reduce risk of cardiovascular disease
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40
Q

mechanism for homocysteine hypothesis

A

(slide 20)

1) B6 convert homocysteine → cysteine
2) methyl-B12 convert homocystein → methionine
3) methyl folate gives B12 methyl group → methyl B12
4) B6 gives folate methyl group → methyl folate

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41
Q

relationship between folate & homocysteine & cardiovascular disease

A

folate → less cardiovascular disease (observational studies)

folate → decrease serum homocysteine (intervention trials)

lower homocysteine → lower cardiovascular disease ??

  • confirmed by observational studies
  • not confirmed by intervention trials (doesn’t work)
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42
Q

difference between folate vs. folic acid

A

folic acid:

  • used in fortified food
  • more stable
  • only 1 attached glutamate

folate:

  • found naturally in food
  • have many glutamates attached
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43
Q

function of folate in the body

A
  • Single carbon metabolism
  • Formation of RBC
  • neural tube formation
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44
Q

Folate deficiency results in…

A

megaloblastic / macrocytic anemia

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45
Q

megaloblastic / macrocytic anemia

A

RBC unable to divide → larger than normal RBC

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46
Q

when does neural tube form?

A

20-28 days after conception

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47
Q

how to prevent NTD?

A
  • fortification of food with folate

- all women who might get pregnant should take multivitamin with at least 400 ug of folate

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48
Q

how does B12 prevent NTD?

A

1) folate makes methyl B12, which converts homocysteine → methionine
2) methionine → methionine derivative
3) methionine derivative → DNA methylation → neural tube closure

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49
Q

possible causes of NTD

A
  • genetics

- dietary (folate & vit B12)

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50
Q

since fortification of foods with folate, what has happened?

A
  • 50% reduction in NTD

- reduction in childhood cancers

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51
Q

a common example of a NTD

A

spina bifida

52
Q

what is a good biomarker for measuring folate?

A

amount found in RBC

53
Q

are people getting enough folate in Canada?

A

Yes!

  • no one is getting 0 folate
  • 22% getting less than recommended
  • 40% are getting too much
54
Q

Why is folate from food intake low, but RBC folate levels are adequate?

A
  • over-fortification

- supplements

55
Q

can too much folate cause cancer?

A

human observational studies: more folate = less cancer

animal studies:

  • more folate (with predisposition to cancer) = increased risk of cancer
  • more folate (healthy) = decreased risk of cancer
56
Q

“secondary folate deficiency”

A

lack of B12

57
Q

lack of B12 causes…

A
  • megaloblastic anemia
  • pernicious anemia
  • less myelin sheath formation
58
Q

B12 is biosynthesized by ____ and is concentrated in ____

A

micro-organisms;

animal tissue

59
Q

which vit does vegetarians have trouble getting enough of without supplements?

A

B12, since it is only found in animal tissue

60
Q

Pernicious anemia is due to…

A
  • inability to absorb B12

- autoimmune disease that destroy parietal cells (secrete intrinsic factor)

61
Q

how to distinguish between megaloblastic anemia & pernicious anemia?

A

Both caused by B12 deficiency, but pernicious anemia will not respond to treatment that supplements iron because it is problem with intrinsic factor

62
Q

Absorption of B12

A

1) stomach enzymes break covalent bond with food
2) combines with IF in duodenum
3) absorbed in ileum (receptor for IF-bound B12 and passive diffusion for unbound)
4) B12 synthesized by colon bac’t cannot be absorbed

63
Q

B12 is required for the formation of ____, explaining why there are neurological symptoms when there is not enough B12

A

myelin sheath

64
Q

atrophic gastritis & how it relates to B12

A

inflammation of stomach lining that results in reduced secretion of stomach acid & bacterial overgrowth

  • can’t break covalent bond b/t B12 and food
  • interfere with IF production
65
Q

Causes of B12 deficiency

A

atrophic gastritis (common cause in older people)

66
Q

Treatment for atrophic gastritis / B12 deficiency

A
  • B12 injections (initially)
  • B12 supplements (later on)

These work because supplement B12 is not bound to protein, so would not require acid to break it apart

67
Q

what may mask B12 deficiency?

A

excessive intake of folic acid

68
Q

what happens when B12 deficiency is masked?

A
  • no anemia

- neurological damage

69
Q

What is the UL for folate? How was it determined?

A

1000 ug

Higher than this will mask B12 deficiencies

70
Q

Vit C is an antioxidant that counterbalances ____

A

oxidative stress

71
Q

Oxidative stress damages…

A
  • protein
  • DNA
  • membranes
  • LDL cholesterol (go inside arterial walls)
72
Q

Oxidants are…

A

very reactive O containing compounds that will damage the body unless neutralized by antioxidants

73
Q

sources of oxidants

A

1) dropped electrons in ETC → superoxide (O2-)

2) superoxide → H2O2

74
Q

Mechanism of vit C acting as antioxidant

A

Donate e- to O2- → O2

Ascorbic acid → dehydroascorbic acid

75
Q

why is vit C requirement for smokers higher?

A

smoking generates free radicals in lung tissue

76
Q

each vit C can neutralize ____ free radicals

A

2

77
Q

Can Vit C be reused? How?

A

dehydroascorbic acid → ascorbic acid when given electrons / H+ by other antioxidants

78
Q

What happens when we don’t get enough vit C? Why?

A

scurvy (disease);
Breakdown of organs (!!)

Vit C is needed to make strong, cross-linked connective tissue. Without it, connective tissue is week. Connective tissue is found in every organ of the body.

79
Q

Symptoms of scurvy

A
  • excessive bruising

- bleeding gums around teeth (caused by stress when chewing)

80
Q

forms of vit A

A

1) retinol →
2) retinal →
3) retinoic acid
4) B-carotene (→ retinol)

81
Q

retinol = ___

sources?

A

pre-formed vit A;

animal sources

82
Q

B-carotene is made up of…

A

retinol + retinal

83
Q

which two forms of vit A is inter-convertible? which cannot be converted to any other forms once formed?

A

retinol retinal;

retinoic acid

84
Q

is B-carotene a good way to get retinol?

A

No, conversion is very inefficient

85
Q

main function of B-carotene

A

circulates in blood as antioxidant

  • observational studies show it may reduce risk of lung cancer in smokers
  • intervention trial: extremely high doses of B-carotene did not reduce risk of lung cancer
86
Q

axis of Kaplan-Meier plot

A 
x = years
y = incidence of disease
87
Q

What happens when you eat too much vit A?

A

Hypercarotenemia

  • B-carotene accumulates in fat deposits in blood
  • skin turns orange
  • result in pre-cancer lesions (animal studies)
  • make other conditions worse
88
Q

What if there is too little vit A?

A

Night blindness

89
Q

Mechanism: vit A leading to night blindness

A

1) cis-retinal + opsin = rhodopsin (cis → trans retinal)
2) rhodopsin sends light signals to brain
3) retinal seperate from opsin
4) some retinal is lost
5) normally, vit A replaces lost retinal
6) if not enough vit A, rhodopsin can’t form → less sensitive to light

90
Q

what is night blindness?

A

After destroying all retinal/opsin at retina (sudden bright light), how fast you can recover and see in the dark again. Very slow = night blindness

Rate at which vit A can be converted to retinal.

91
Q

General term for vitamins & things that do similar things @ the cellular level

A

Ligand

92
Q

How does vit A regulate gene expression?

A

retinoic acid → nuclear receptor → act as TF to alter gene expression

93
Q

Vit A is involved in cell differentiation. It allows epithelial cells at the ____ to ______. What is the consequence of this? Give one specific example.

A

eyes, intestines, lungs;
differentiate into mucus secreting cells;
dry, hard keritin (no mucus) → increased risk of infection;
Xerophthalmia

94
Q

Xerophthalmia

A

dry eyes caused by lack of vit A;

may cause blindless if condition worsens

95
Q

Vit A differentiation is responsible for the formation of…

A

cells responsible for defense

  • WBC
  • mucus secreting cells
96
Q

who is at risk for vit A deficiency?

A

children < 5 y.o.

pregnant women

97
Q

1 vitamin deficiency in the world

A

vit A

98
Q

getting enough vit A prevents…

A
  • infection

- blindness

99
Q

____ based in ___ provides 75% of the worl’d vit A capsules

A

Micronutrient Initiative;

Ottawa

100
Q

Excess vit A causes…

A

Teratogen → birth defects

101
Q

Prenatal supplements prevents Teratogen by…

A
  • B-carotene → 375 ug
  • vit A (as acetate) → 300 ug
    = total dose < RDA (700 ug)

More B-carotene because it has not been associated with causing Teratogen

102
Q

Prenatal supplements contain which major vit?

A

B-carotene & vit A
Folic acid
B12

103
Q

How much folic acid is in prenatal supplements? why?

A 
1000 ug (1 mg) → UL
This is high, but won't mask B12 deficiency if present
104
Q

biosynthesis of vit D3 from cholesterol

A

cholesterol → 7-dehydrocholesterol →(UV)→ vit D3 → converted to more bioactive forms in the body

105
Q

in winter, which areas are at risk for vit D deficiency?

A

+40 or -40 latitude due to lack of sun exposure

106
Q

function of vit D

A
  • increase Ca absorbed from intestines
  • increase Ca reabsorbed from kidneys
  • Bone reabsorption (with PTH)
  • Bone formation when there is enough Ca
107
Q

How is Ca absorbed?

A

1) passive diffusion → bloodstream

2) active transport by binding to Ca transport protein → Ca pump at basolateral end

108
Q

How does vit D increase Ca absorption?

A

regulate gene expression to produce more Ca transport protein, which increases absorption amount and efficiency

109
Q

Vit D deficiency causes which diseases?

A

1) rickets → loss of mineral component of bone (children)

2) osteomalacia→ loss of mineral component of bone (adults)

110
Q

what vit cannot be found in breast milk? What must be done to treat this?

A

vit D;

babies must be supplemented with vit D if exclusively breast fed

111
Q

rickets // osteomalacia can be cured if caught in time

A

rickets

112
Q

RDA for vit D is based on…

A

requirement needed for bone health

113
Q

RDA for vit D from 1997 → 2010

A

increased for every age group

114
Q

Vit D has been linked to…

A

reduced cancer risk

→ not proven though

115
Q

men and women over the age of 50 need which supplement? why?

A

vit D;

  • need for vit D increases after age 50
  • biosynthesis of vit D in skin declines with age
116
Q

__ different compounds make up vit E. What are they?

A

8

  • tocopherols (4 compounds)
  • tocotrienols (4 compounds)
117
Q

main form of vit E in blood

A

a-tocopherol

118
Q

which form of vit E is found in supplements?

A

a-tocopherol

119
Q

function of vit E

A
  • antioxidant

- anti-coagulant

120
Q

vit E is linked to ____ by observational studies, but not by intervention trials

A

reduced risk of cardiovascular disease

121
Q

where is vit E located in the cell?

A

embedded in cell membrane (because fat soluble)

122
Q

How does vit E act as antioxidant?

A

vit E donate e- to free radicals that target the cell membrane
- antioxidant function restored by getting e- from other antioxidants

123
Q

what happens when vit E is missing an e-?

A

if it cannot be restored to vit E, it will become a free radical itself

124
Q

___ spares vit E by…

A

selenium

  • neutralize H2O2 → H2O
  • less vit E used to neutralize free radicals because there is less free radicals
125
Q

plant form of vit K. it is found in…

A

phylloquinone;

leafy greens

126
Q

supplement form of vit K

A

menaquinones

127
Q

vit K is responsible for…

A
  • blood clotting

- proteins that regulate bone metabolism

NFS284 (16 decks)

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