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
2
Q
Water-soluble vitamins
A
B, C
3
Q
Fat-soluble vitamins
A
ADEK
4
Q
Which group has the highest vit C requirement?
A
smokers
5
Q
What is used in assessment of nutrient intake studies?
A
24h recall
6
Q
Which is the vit that we are getting the least of?
A
Vit C
7
Q
Why are most Canadians not getting enough vitamins?
A
due to lack of fruits & veggies in diet
8
Q
how can we get all required vitamins?
A
eat a variety of foods from different food groups
9
Q
if a nutrient has been added to a food, it has to be listed in the ____
A
nutrition facts table
10
Q
Enriched pasta has which vitamins?
A
- vit A
- vit C
- calcium
- iron
- thiamine
- riboflavin
- niacin
- folate
11
Q
define: bioavailability
A
how much of a nutrient can be absorbed and used in the body
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
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
14
Q
which type of vit can be stored? where can it be stored?
A
fat soluble – in adipose tissue
15
Q
which soluble vit can stay in the body for a long time?
A
B12 (several years; body recycles it)
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
17
Q
what are vit used for in the body?
A
coenzymes for…
- energy metabolism
- single carbon metabolism
- antioxidants
18
Q
B vit function as ____
A
coenzymes in energy metabolism
19
Q
which vit are used for energy metabolism?
A
- Thiamin
- Riboflavin
- Niacin
- Pantothenic acid
- Biotin
20
Q
which vit are used for single carbon metabolism?
A
- B6
- Folate
- B12
21
Q
single carbon metabolism
A
transfer of methyl groups
- synthesis of DNA components
- DNA methylation (control gene expression)
22
Q
which vit act as antioxidants?
A
C
E
23
Q
antioxidants
A
protection from oxidative damage or oxidative stress
24
Q
disease associated with thiamine
A
Beriberi: caused by thiamine deficiency
Wernicke-Korsakoff Syndrome: alcohol causing thiamine deficiency
25
Symptoms of beriberi
- weakness
- nerve tingling
- poor coordination
- paralysis
- death
26
beriberi is a problem at which places?
populations with unenriched white rice
27
Wernicke-Korsakoff syndrome
- thiamine needed for alcohol metabolism
- excess alcohol deplete thiamine
- impacts cognitive functions
28
best source of riboflavin
milk
29
riboflavin is sensitive and will be destroyed by...
light
30
disease associated with niacin
Pellegra: niacin deficiency
31
symptoms of pellegra
4Ds: Dermatitis, diarrhea, dementia, death
32
pellegra is caused by...
diets high in corn
- niacin is bound to a protein in corn, making it not bioavailable
- tryptophan is low in corn (precursor for niacin)
33
Where was pellegra common? How was it treated?
S. USA
Now, S. USA corn is treated with lime → break covalent link between niacin and protein → bioavailable
34
niacin can be synthesized from...
tryptophan
35
2 forms of niacin found in the body
1) nicotinic acid
| 2) nicotinamide
36
niacin in ___ doses is used to treat ____ disease
```
50 mg (higher than UL);
cardiovascular disease
```
37
why does high doses of niacin work for treating cardiovascular disease? What is the consequence of going over the UL?
- lower LDL
- raise HDL
- lower serum TG
side-effects: burning, tingling sensation in skin (face, chest)
38
function of B6
1) transaminatin: make non-essential AA
2) deamination: make ATP & glucose
3) decarboxylation: make NT
39
homocysteine hypothesis
- 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
40
mechanism for homocysteine hypothesis
(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
41
relationship between folate & homocysteine & cardiovascular disease
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)
42
difference between folate vs. folic acid
folic acid:
- used in fortified food
- more stable
- only 1 attached glutamate
folate:
- found naturally in food
- have many glutamates attached
43
function of folate in the body
- Single carbon metabolism
- Formation of RBC
- neural tube formation
44
Folate deficiency results in...
megaloblastic / macrocytic anemia
45
megaloblastic / macrocytic anemia
RBC unable to divide → larger than normal RBC
46
when does neural tube form?
20-28 days after conception
47
how to prevent NTD?
- fortification of food with folate
| - all women who might get pregnant should take multivitamin with at least 400 ug of folate
48
how does B12 prevent NTD?
1) folate makes methyl B12, which converts homocysteine → methionine
2) methionine → methionine derivative
3) methionine derivative → DNA methylation → neural tube closure
49
possible causes of NTD
- genetics
| - dietary (folate & vit B12)
50
since fortification of foods with folate, what has happened?
- 50% reduction in NTD
| - reduction in childhood cancers
51
a common example of a NTD
spina bifida
52
what is a good biomarker for measuring folate?
amount found in RBC
53
are people getting enough folate in Canada?
Yes!
- no one is getting 0 folate
- 22% getting less than recommended
- 40% are getting too much
54
Why is folate from food intake low, but RBC folate levels are adequate?
- over-fortification
| - supplements
55
can too much folate cause cancer?
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
"secondary folate deficiency"
lack of B12
57
lack of B12 causes...
- megaloblastic anemia
- pernicious anemia
- less myelin sheath formation
58
B12 is biosynthesized by ____ and is concentrated in ____
micro-organisms;
| animal tissue
59
which vit does vegetarians have trouble getting enough of without supplements?
B12, since it is only found in animal tissue
60
Pernicious anemia is due to...
- inability to absorb B12
| - autoimmune disease that destroy parietal cells (secrete intrinsic factor)
61
how to distinguish between megaloblastic anemia & pernicious anemia?
Both caused by B12 deficiency, but pernicious anemia will not respond to treatment that supplements iron because it is problem with intrinsic factor
62
Absorption of B12
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
B12 is required for the formation of ____, explaining why there are neurological symptoms when there is not enough B12
myelin sheath
64
atrophic gastritis & how it relates to B12
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
Causes of B12 deficiency
atrophic gastritis (common cause in older people)
66
Treatment for atrophic gastritis / B12 deficiency
- 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
what may mask B12 deficiency?
excessive intake of folic acid
68
what happens when B12 deficiency is masked?
- no anemia
| - neurological damage
69
What is the UL for folate? How was it determined?
1000 ug
| Higher than this will mask B12 deficiencies
70
Vit C is an antioxidant that counterbalances ____
oxidative stress
71
Oxidative stress damages...
- protein
- DNA
- membranes
- LDL cholesterol (go inside arterial walls)
72
Oxidants are...
very reactive O containing compounds that will damage the body unless neutralized by antioxidants
73
sources of oxidants
1) dropped electrons in ETC → superoxide (O2-)
| 2) superoxide → H2O2
74
Mechanism of vit C acting as antioxidant
Donate e- to O2- → O2
Ascorbic acid → dehydroascorbic acid
75
why is vit C requirement for smokers higher?
smoking generates free radicals in lung tissue
76
each vit C can neutralize ____ free radicals
2
77
Can Vit C be reused? How?
dehydroascorbic acid → ascorbic acid when given electrons / H+ by other antioxidants
78
What happens when we don't get enough vit C? Why?
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
Symptoms of scurvy
- excessive bruising
| - bleeding gums around teeth (caused by stress when chewing)
80
forms of vit A
1) retinol →
2) retinal →
3) retinoic acid
4) B-carotene (→ retinol)
81
retinol = ___
| sources?
pre-formed vit A;
| animal sources
82
B-carotene is made up of...
retinol + retinal
83
which two forms of vit A is inter-convertible? which cannot be converted to any other forms once formed?
retinol retinal;
retinoic acid
84
is B-carotene a good way to get retinol?
No, conversion is very inefficient
85
main function of B-carotene
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
axis of Kaplan-Meier plot
```
x = years
y = incidence of disease
```
87
What happens when you eat too much vit 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
What if there is too little vit A?
Night blindness
89
Mechanism: vit A leading to night blindness
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
what is night blindness?
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
General term for vitamins & things that do similar things @ the cellular level
Ligand
92
How does vit A regulate gene expression?
retinoic acid → nuclear receptor → act as TF to alter gene expression
93
Vit A is involved in cell differentiation. It allows epithelial cells at the ____ to ______. What is the consequence of this? Give one specific example.
eyes, intestines, lungs;
differentiate into mucus secreting cells;
dry, hard keritin (no mucus) → increased risk of infection;
Xerophthalmia
94
Xerophthalmia
dry eyes caused by lack of vit A;
| may cause blindless if condition worsens
95
Vit A differentiation is responsible for the formation of...
cells responsible for defense
- WBC
- mucus secreting cells
96
who is at risk for vit A deficiency?
children < 5 y.o.
| pregnant women
97
#1 vitamin deficiency in the world
vit A
98
getting enough vit A prevents...
- infection
| - blindness
99
____ based in ___ provides 75% of the worl'd vit A capsules
Micronutrient Initiative;
| Ottawa
100
Excess vit A causes...
Teratogen → birth defects
101
Prenatal supplements prevents Teratogen by...
- 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
Prenatal supplements contain which major vit?
B-carotene & vit A
Folic acid
B12
103
How much folic acid is in prenatal supplements? why?
```
1000 ug (1 mg) → UL
This is high, but won't mask B12 deficiency if present
```
104
biosynthesis of vit D3 from cholesterol
cholesterol → 7-dehydrocholesterol →(UV)→ vit D3 → converted to more bioactive forms in the body
105
in winter, which areas are at risk for vit D deficiency?
+40 or -40 latitude due to lack of sun exposure
106
function of vit D
- increase Ca absorbed from intestines
- increase Ca reabsorbed from kidneys
- Bone reabsorption (with PTH)
- Bone formation when there is enough Ca
107
How is Ca absorbed?
1) passive diffusion → bloodstream
| 2) active transport by binding to Ca transport protein → Ca pump at basolateral end
108
How does vit D increase Ca absorption?
regulate gene expression to produce more Ca transport protein, which increases absorption amount and efficiency
109
Vit D deficiency causes which diseases?
1) rickets → loss of mineral component of bone (children)
| 2) osteomalacia→ loss of mineral component of bone (adults)
110
what vit cannot be found in breast milk? What must be done to treat this?
vit D;
| babies must be supplemented with vit D if exclusively breast fed
111
rickets // osteomalacia can be cured if caught in time
rickets
112
RDA for vit D is based on...
requirement needed for bone health
113
RDA for vit D from 1997 → 2010
increased for every age group
114
Vit D has been linked to...
reduced cancer risk
| → not proven though
115
men and women over the age of 50 need which supplement? why?
vit D;
- need for vit D increases after age 50
- biosynthesis of vit D in skin declines with age
116
__ different compounds make up vit E. What are they?
8
- tocopherols (4 compounds)
- tocotrienols (4 compounds)
117
main form of vit E in blood
a-tocopherol
118
which form of vit E is found in supplements?
a-tocopherol
119
function of vit E
- antioxidant
| - anti-coagulant
120
vit E is linked to ____ by observational studies, but not by intervention trials
reduced risk of cardiovascular disease
121
where is vit E located in the cell?
embedded in cell membrane (because fat soluble)
122
How does vit E act as antioxidant?
vit E donate e- to free radicals that target the cell membrane
- antioxidant function restored by getting e- from other antioxidants
123
what happens when vit E is missing an e-?
if it cannot be restored to vit E, it will become a free radical itself
124
___ spares vit E by...
selenium
- neutralize H2O2 → H2O
- less vit E used to neutralize free radicals because there is less free radicals
125
plant form of vit K. it is found in...
phylloquinone;
| leafy greens
126
supplement form of vit K
menaquinones
127
vit K is responsible for...
- blood clotting
| - proteins that regulate bone metabolism
