Nutrition - Vitamins

Front 1

What are vitamins, and what is their physiologic function? (general answer)

Back 1

necessary for metabolic fxns but can't be synthesized (or at least not in sufficient amts)

not energy sources, not used for structural purposes

Front 2

What are the 13 required vitamins?

Back 2

1) 4 fat soluble: ADEK
2) 8 B-complex
3) Vit C

Front 3

DRI stands for:

Back 3

dietary reference intakes

EAR
RDA
AI
UL

Front 4

What is EAR?

Back 4

est avg req

meets req of HALF of healthy individ in a given age/gender grp

used to plan & assess dietary adequacies

Front 5

What is RDA?

Back 5

recc dietary allowance

meets nearly all (98%) requirements in a given age/gender group

Front 6

AI

Back 6

adequate intake

recommended avg daily intake based on approximations of intake in apparently healthy people, = assumed to be adequate

used when RDA can't be determined

Front 7

UL

Back 7

tolerable upper intake level

highest dose likely to pose no risk of adverse effects for almost all in gen pop'n.

Front 8

intensive abx tx can cause a deficiency in these vitamins

Back 8

1) K
2) biotin

synth by intestinal bacteria

Front 9

kidney dz can cause a deficiency in this vitamin, leading to "renal rickets"

Back 9

vitamin D

a critical enzymatic alteration to a vit D precursor occurs in the kidney

Front 10

these vitamins have enterohepatic circulation; since they need to be absorbed > once, malabsorption rapidly leads to clinical deficiency

Back 10

folate
B12
A
D

Front 11

patients w/ roux-en-Y bariatric surgery need supplementation of these vitamins

Back 11

ALL!

most vitamin absoprtion occurs in the proximal intestine

Front 12

newborns particularly need these vitamins

Back 12

K - neonatal GI tract is sterile
E (and K) - don't cross placental membrane efficiently

D - if infant is breastfeeding

Front 13

ADRs associated w/ vitamins

Back 13

anti-convulsants interact w/ K, D, folate, biotin, B6

INH binds pyridoxine

Front 14

vitamin that mediates calcium homeostasis

Back 14

vit D

Front 15

in what situations might you see vit D deficiency?

Back 15

20 min of sun on hand is sufficient. poor exposure when:

1) winter in northern latitudes
2) elderly (esp institutionalized)
3) dark skin
4) sunscreen decreases
5) ↓ intake of fortified foods (milk, yogurt, cheeses; OJ) - esp in lactose intolerant Asians, AA

Front 16

what toxicities are associated with excess vitamin D?

Back 16

↓ appetite, nausea, thirst, stupor

Front 17

what role does vit D play in the body?

Back 17

steroid hormone acting on
1) intestines (absorption of Ca, PO3)
2) bones (mobilize Ca via PTH)
3) kidneys (reabsorption of Ca in DT via PTH)

Front 18

what is rickets?

what are sx of rickets?

what vitamin deficiency is it associated with?

Back 18

1) SOFT BONES <-> improper mineralization of cartilage in children

2) lordosis of spine, leg bowing

3) vitamin D

Front 19

what are 3 possible causes of vitamin D deficiency?

Back 19

1) inadequate synthesis (or inadquate UV exposure)

2) inadequate absorption

3) inadequate dietary supply

Front 20

what is osteomalacia?

what are the sx?

Back 20

1) demineralization of EXISTING bone (adults)

2) fx, W/O gross changes in bone contour

Front 21

what is osteoporosis?

Back 21

↑porosity b/c skeletal remodeling tips in favor of net loss of bone mass beginning in 40s.

menopause accelerates

FX common in vertebrae, femoral neck, pelvis

Front 22

which is the single mineral for which the avg US diet is most deficient?

Back 22

calcium

Front 23

should elderly or young people take Ca & Vit D supplements?

Back 23

mixed study results

ERT + Ca + vit D in post menopausaul women effective in ↓ osteoporosis

Front 24

what are tx for osteoporosis?

Back 24

biphosphonates (Fossamax)

PTH subQ injxns (teriparatide, Forteo) - ↑ osteoblast activity & bone density

Front 25

what is the difference between
1) retinol
2) retinyl esters
3) retinal
4) retinoic acid
5) B-carotene

Back 25

1) retinol: transport
2) retinyl esters: storage
3) retinal: vision
4) retinoic acid: epithelial differentiation & growth
5) B-carotene: dietary (in veggies) -> converted to retinol in intestinal mucosa

Front 26

roles of vit A in the body?

Back 26

1) vision in reduced light
2) differentiation of epithelium (mucus secretion)
3) anti-oxidant (B-carotene)
4) bone remodeling
5) enhanced immunity
6) glycoprotein, MPS synth

Front 27

foods that vit A can be obtained from?

Back 27

1) largest amts of retinyl esters from animal products (egg yolks, liver, fish oil, milk, butter)

2) B-carotene from green & orange veggies

Front 28

sx of vit A deficiency

Back 28

1) vision problems: leading cause of blindness; night blindness; xeropthalmia

2) defects in epith tissue maintainence (acne, psoriasis)

3) ↑infxns (↓immunity)

Front 29

sx of vit A toxicity?

how does it occur?

Back 29

1) bone pain, dermatities, hepatosplenomegaly, nausea, diarrhea, birth defects

2) only yellow skin w/ B-carotenes

occurs w/ high doses over mo/yrs

Front 30

what are indications for synthetic retinoids? how do they work?

Back 30

1) acne & psoriasis

2) synthetic b/c ↓ toxicity compared to vit A = ↑ doses ok

3) ↓ sebum production & assoc. inflammatory response

Front 31

differences bewteen vit K types:
1) K1
2) K2
3) K3

Back 31

1) veggies
2) intestinal bacteria
3) synthesized from synthetic precursor

Front 32

principal role of vit K?

mechanism?

Back 32

blood clotting

coenzyme for glutamic acid carboxylase -->
clotting factors need this to bind Ca -->
bind phospholipids on plts

Front 33

how do coumarin and warfarin work?

Back 33

vit K antagonists

Front 34

how *might* vit K favor calcification of bone?

Back 34

proteins like osteocalcin also undergo vit K mediated carboxylation of gla residues

Front 35

how do humans meet the bulk of vit K requirement?

Back 35

gut bacteria

K1 in plants but only a few (spinach) contain large amts

cow milk = v little;
human milk = 20% of daily req

Front 36

sx of vit K deficiency

Back 36

↑ PT

Front 37

causes of vit K deficiency

Back 37

unusual, b/c synth in gut, except in

1) newborns (poor transference across placenta, sterile GI tract) - receive injxn @ birth to prevent bleeding

2) broad spectrum abx

3) ↓ fat absorption (eg CF)

Front 38

vit K toxicity: cause & sx

Back 38

1) infants w/ prolonged administration of K3

2) hemolytic anemia & jaundice (toxic to RBCs)

Front 39

how is vit E obtained?

Back 39

vegetable oils (rich); liver, eggs (moderate) -->

GI lymphatics -->
a-tocopherol incorporated

into VLDL in liver -->

blood

Front 40

role of vit E?

Back 40

anti-oxidant: protect membranes from free radicals & lipid peroxidation

most effective of the lipid soluble

Front 41

vit E toxicity

Back 41

unlikely- least toxic of the fat soluble vits (no toxicity at 300mg/day)

Front 42

vit E deficiency
-populations affected

Back 42

1) mostly premature infants

in children or adults, assoc w/ ↓fat absoprtion
2) CF
3) chronic cholestasis ie ↓bile in duodenum
4) abetalipoproteinemia
5) transport defect (eg in a-tocopheral transport protein)

Front 43

vit E deficiency
-sx

Back 43

neuro:
1) spinocerebellar degeneration, ataxia, areflexia
2) mild-mod sensory neuropathy

(in adults, may develop 10-20yrs post-malabsorption)

Front 44

what are the major ROS?

Back 44

1) superoxide (O2-): moderately reactive; forms H2O2 via superoxide dismutase

2) h peroxide (H202): not a free radical itself, but can give rise to to OH-

3) hydroxyl radical (OH-): usu reacts w/ 1st molecule it encounters (ie, rate is diffusion controlled). Most often formed by H2O2 + Fe++ (Fenton rxn)

Front 45

how do ROS cause damage?

Back 45

1) protein oxid'n -> degradation by proteases, catalytically less or inactive, more thermo-labile

2) lipid peroxid'n: loss of membrane integrity =↓ cell fxn

3) DNA oxid'n: strand breaks, base modific'n

Front 46

types of antioxidants?

Back 46

1) enzymes:
superoxide dismutase, glut peroxidase, catalase

2) endogenous chemicals:
glutathione, ubiquinol

3) exogenous chemicals:
vit E, C, B-carotenes, phenolics, lycopenes (tomatoes)

Front 47

what are lycopenes?

Back 47

almost exclusively from tomatoes
50% of caretonids in human serum
single highest ROS quenching capacity of all dietary carotenoids

Front 48

what are potential benefits of vit E supplementation?

Back 48

1) ↓ risk of MI (obs study) b/c of ↓ LDL oxid'n

2) delay onset of cataracts (WITH vit C & B carotene; no evidence w/ pure vit E in RCT so far)

Front 49

water-soluble vitamins
1) excretion method?
2) storage amts?
3) biological fxn?

Back 49

1) urine
2) stores generally not significant
3) coenzymes (most are non-covalently bound & regenerated at end of rxn, so v. small amts required in diet)

Front 50

what are the H2O-soluble vitamins?
what are their coenzyme forms?

Back 50

Thiamine (B1) / TPP
Riboflavin (B2) / FMN, FAD
Niacin (B3) / NAD
pantothenic acid (B5) / CoA
Pyridoxine (B6) / pyridoxal phosphate
Biotin (B7) / pyruvate carboxylases (& other carboxylases)
Cobalamine (B12) / Cobalamine
Ascorbic acid (C) / prolyl OHase (& others)
Folic Acid / THF

Front 51

what is TPP?
what are its physiological fxns?

Back 51

thiamine pyrophosphate

cofactor used by many enzymes:

1) energy metabolism of most tissues (pyruvate decarboxylase, a-ketoglutarate dehydrogenase)

2) transketolase in pentose-P path

3) synthesis of ACh

Front 52

1) what are the sources of thiamine?

2) where is deficiency found?

Back 52

1) synthesized by plants or microorganisms - whole wheat, peas, beans

2) wherever polished rice is a major component of the diet

Front 53

thiamine (B1) deficieny - sx

Back 53

beriberi (wet & dry)
wernicke korsakoff

Front 54

what is wet beriberi?

Back 54

thiamine deficiency

impacts CV fxn

swelling of legs, fluid in lungs, tachycardia

Front 55

what is dry beriberi?

Back 55

thiamine deficiency

affects nerves & muscles

memory loss & confusion
pain- hands & feet
trouble standing/moving
involuntary eye movements

Front 56

what is wernicke-korsakoff?

Back 56

thiamine deficiency

chronic alcoholics: dietary insuffiency or impaired absorption

confusion, ataxia

Front 57

what is the physiologic role of riboflavin (B2)?

Back 57

synthesis of FMN, FAD =
used in NADH dehydrogenase, succinate dehyrog, methylene THF reducatse

Front 58

riboflavin deficiency - sx?

Back 58

not associated w/ major human dz, but accompanies other deficiencies (causing dermatitis, chelosis, glossitis)

Front 59

physiologic role of niacin (B3)

Back 59

NAD, NADP - coenzymes in redox rxns - esp FA, cholesterol, steroid synth

Front 60

what is pellagra?

Back 60

niacin deficiency

4D's: dermatitis, diarrhea, dementia, death (if un-tx'd)

Front 61

what is a pharmacologic use of niacin?

Back 61

to tx hyperlipidemia, along w/ statins

(↓ lipolysis in adipose, VLDL, LDL)

Front 62

where can niacin be obtained?

Back 62

esp rich in MEAT
Trp can be converted, but usu not enough for human bodies

common (along w/ other defiicencies) in roux-en-Y bypass pts

Front 63

physiologic role of pyridoxine (B6)

Back 63

many - PLP coenzyme used in:
1) AA metabolism (sythesis, catabolism, energy prodxn from AA)
2) heme catabolism
3) synth of 5HT & NE
4) synth of sphingolipids for myelinization
5) NAD synthesis
6) homocysteine metabolism

Front 64

which drug can cause B6 (pyridoxine) deficiency?

Back 64

INH

Front 65

B6 (pyridoxine) deficiency sx

Back 65

MANY - b/c involved in so many diff rxns

include
1) behavioral changes (b/c of role in NTM & myelin synth)
2) anemia

Front 66

what is the main source of biotin (B7)?

Back 66

intestinal bacterial synthesis

Front 67

physiologic fxns of biotin?

Back 67

coenzyme in carboxylase rxns:
pyruvate carboxylase (gluconeogen)
acetyl-CoA carboxylase
mt propionyl-CoA carboxylase

Front 68

biotin deficiency is caused by?

Back 68

1) long abx therapies
2) excessive consumption of raw eggs (avidin in egg whites have high affinity for biotin, preventing absorption)

Front 69

panthothenic acid (B5) fxns?

Back 69

1) coenz in CoA (fat, CHO, protein metabolism<-- transfer of acyl groups)

2) phosphopantetheine in FA synth

Front 70

B5 sources & deficiences?

Back 70

pantothenic acid deficiency rare b/c of ess nature of CoA.

eggs, liver, yeast (but widely distributed)

Front 71

cobalamin (B12) fxns?

Back 71

1) homocys Me-transferase (HCys + 5Me-THF --> Met + THF)

2) Methylmalonyl CoA mutase: isomerizes (odd # C FAs) & (methylmal CoA)

Front 72

B12 sources

Back 72

animal meat, not plants

Front 73

causes of B12 deficiency

Back 73

liver can store up to 6 years' worth- deficiencies usually result from inadequate absorption rather tahn supples (eg anti-IF)

also vegans (abstain from all animal products)

body has low requirement (small stores but small losses)

Front 74

sx of B12 deficiency

Back 74

megaloblastic anemia / pernicious
(rapidly dividing cells THF for nucleotide synthesis for DNA replication)

progressive demyelination of nerve cells (accumulation of abnormal FA & incorporation into cell membranes)

Front 75

folic acid fxn

Back 75

1 carbon metabolism
(folate conjugated to PABA --> pteroic acid)

Front 76

folic acid sources

Back 76

yeasts, leafy vegetables, liver

Front 77

describe folic acid storage & metabolism

Back 77

also reduced to THF via DHFR
<-- stored in liver in poly-glu form -->
intestinal mucosal cells remove glu -->
pass into bloodstream -->

Front 78

folate deficiency - sx

Back 78

1) megaloblastic anemia
2) NTD in fetus

Front 79

vitamin C (ascorbic acid) - fxns

Back 79

1) collagen stability (Lys, Pro -OHase
2) catabolism of Tyr
3) bile acid synth
3) absorption of Fe (reducing agent: ferric --> ferrous)
4) biosynth of cortisol, aldosterone, cholesterol --> bile acids
5) antioxidant

Front 80

what is scurvy?

Back 80

vit C deficiency

↓ collagen stability =

easily bruised skin
soft swollen gums
↓ wound healing, ↑ hemorrhaging
osteoporosis
anemia

vit C = well absorbed, so primary cause of deficiency is poor diet

Front 81

how should vitamin C supplements be stored?

Back 81

avoid long-term storage
avoid exposure to alkali

most unstable of all the vitamins