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NUTR207 (Nutrition and Health) > Micronutrients (Ca,Vit D) and bone health > Flashcards

Micronutrients (Ca,Vit D) and bone health Flashcards

1
Q

describe bioavailability of minerals

A

varies with need (different than vit)

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2
Q

what are binders

A

combines chemically with minerals which prevents their absorption and carries them out of the body with other wastes

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3
Q

describe nutrient interactions of minerals

sodium and calcium

phosphorus and magnesium

A

presence/absence of a vit/min can affect another’s absorption, metabolism and excretion

high sodium intakes cause both sodium and calcium to be excreted

P binds with Mg in GI tract. High P = limited Mg absoprtion

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4
Q

example of binders

A

phytates and oxalatates

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5
Q

definition of bioavailability

A

rate and extent to which a nutrient is absorbed and used

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6
Q

difference between major and trace minerals

A

major minerals are present in the body in larger amounts. Also needs to be consumed in larger amounts

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7
Q

examples of trace minerals

A

Iron zinc copper manganese iodine selenium

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8
Q

6 major minerals

A

calcium phosphorus potassium sulfur sodium chloride magnesium (in decreasing order)

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9
Q

define vitamin

A

essential organic nutrients required in small amounts

different forms of a vitamin can have different functions and precursors

function as coenzymes

susceptible to degradation in food

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10
Q

what are fat soluble vitamins

A

D,E,A,K

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11
Q

what are water soluble vitamins

A

Vit Bs, C

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12
Q

5 B vitamins?

A

thiamin, niacin, riboflavin, pantothenic acid, pyridoxine

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13
Q

role of B vits?

A 
Thiamin: pyruvate decarboxylation
niacin: NAD NADP
Riboflavin: FAD FMN
Pantothenic acid: CO! in acetyl coa
pyridoxine: transamination rxns
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14
Q

2 coenzyme functions?

A

hormonal (A and D) and antioxidant (C and E)

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15
Q

function of vit A as reinoic acid (hormonal function)

A

as retinoic acid: cell differentiation

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16
Q

hormonal function of vit D as calcitriol

A

calcium availability

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17
Q

2 types of bone tissues

A

cortical (outside bone)

trabecular (inside bone. more metabolically active)

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18
Q

bone composition?

A

65%mineral crystals: strength and structural support

35% collagen: flexibility

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19
Q

role of mineral crystals:

A

strength and structural support

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20
Q

role of collagen in bone?

A

flexibility

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21
Q

bone mineral density corresponds to….

A

bone strength

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22
Q

describe cortical bone

A

compact bone

very dense

part of outer walls of larger bones and main tissue of small bones

80% of mineral structure

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23
Q

describe trabecular bone

A

lacy architecture

end of long bones

vertebrae

responds readily to hormones

20% of mineral structure

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24
Q

3 steps in bone turnover are:

A
  1. bone growth
  2. bone modeling
  3. bone remodeling
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25
Q

describe bone growth in bone turnover

A

determines bone size
begins in the womb
continues until early adulthood

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26
Q

describe bone modelling in bone turnover

A

determines bone shape
begins in womb
continues until early adulthood

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27
Q

describe bone remodelling in bone turnover

A

maintains integrity of bone

replaces old bone with new bone to maintain mineral balance

involves bone resorption and formation

occurs predominantly during adulthood

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28
Q

what is bone resorption

A

when surface of bones is broken down

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29
Q

bone resorption when young vs old?

A

young: high formation. low resorption
old: less osteoclasts which takes away more bone than putting in. (high resorption low formation)

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30
Q

define osteoclasts ( in bone resorption)

A

cells that erode the surface of bones

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31
Q

what is bone formation

A

new bone in resorption pit

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32
Q

osteoblasts?

A

cells that produce the collagen-containing component of bone

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33
Q

describe process of osteoporosis

A

trabecular thins until completely lost

less matrix = less bone strength and mass

results in compressed vertebrae (pain and less mobility)

bones become susceptible to fractures

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34
Q

prevalence of osteoporosis

A

1 in 4 women

1 in 8 men

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35
Q

describe type 1 osteoporosis

A

“postmenopausal osteoporosis”

50-70 years old

loss of trabecular bone

fracture sites: wrist and spine (falling forward or on bum)

gender incidence 6 women to 1 man

primary cause: rapid loss of estrogen in women after menopause. loss of testosterone in men from old age

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36
Q

describe type 2 osteoporosis

A

“senile osteoporosis”

70 years and older

loss of trabecular and cortical bone

fracture sites: hip (falling sideways or straight back)

gender incidence: 2 women to 1 man

causes: reduced calcium absorption, increased bone mineral loss, increased risk of falling

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37
Q

describe difference between primary causes of type 1 and type 2 osteoporosis

A

type 1: rapid loss of estrogen (W) and testosterone (M)

type 2: reduced Ca absorption. increased bone mineral loss. increased risk of falling

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38
Q

what type of disease is osteoporosis

A

pediatric disease

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39
Q

lifetime risk of sustaining a hip fracture in W and M?

A

15% W

5% M

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40
Q

prevention of osteoporosis

A

focus on maximizing peak bone mass (get strongest bones possible when developing in children and teens)

insure maximal skeletal density which prolongs the time it takes for bone density to fall below the fracture threshold

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41
Q

what age is peak bone mass reached

how can you have the strongest bones possible?

A

30 years

have high vit D and calcium to maximize bone growth when growing (before reaching peak bone mass)

42
Q

why can men reach higher peak bone mass

A

testosterone

43
Q

what period does steep bone mass decline occur in women?

A

menopause

44
Q

describe loss in bone mass graph in women

A

peak bone mass at age 30

gradually lose bone mass until menopause

during menopause: steep loss of bone mass

after menopause: gradual decrease

45
Q

most important factor in bone density?

A

physical activity: working muscles pull on bone which causes more trabecular bone grow denser

must combine cardio and resistance

want to offset bone loss in older people and stimulate growth in children

46
Q

risk factors for osteoporosis

A

old age

low bmi (= low bone density because higher bmi means more work for bones = high bone density)

excess alcohol consumption

sedentary lifestyle

female

inadequate calcium and vit D

47
Q

how does BMI affect bone density

A

high bmi = high bone density because need higher mass to carry more weight

48
Q

how does excess alcohol consumption affect bone density

A

high alcohol = high urinary Ca excretion

may be toxic to osteoblasts

49
Q

how doe ssmoking affect bone density

A

earlier menopause. lower postmenopausal estrogen levels, decreased blood flow to bone

50
Q

osteoporosis prevention/treatment:

A

nutrition
physical activity
no smoking, less alcohol

51
Q

osteoporosis vs osteopenia

A

osteopenia: bone mineral density 1-2.5 SD below the mean established for a young normal population
T score: 1-2.5
(precursor to osteoporosis. bone mineral density is lower than normal)

osteoporosis: bone mineral density less than 2.5 SD
T score: less than 2.5

52
Q

What is the T score?

A

compares to healthy population

53
Q

what are the 2 methods of bone assessment?

A

Dual energy x-ray absorptiometry (DXA): measures bone density with a full body scan and low level xray. Recommended for postmenopausal women

Quantitative ultrasound: uses sound waves. measures bone denstiy at heel, wrist, kneecap. recommended for screening

54
Q

what are calcium functions in acute health?

A

muscle contractions, nerve function, blood clotting, immune function

Ca as an ion in solution

55
Q

calcium functions in chronic health?

A

mineral of bones and teeth (99%), maintain bone turnover

Ca as a mineral in bone

56
Q

what is the most abundant mineral in the body?

A

calcium

57
Q

what happens when the extracellular fluid contains too little calcium?

A

parathyroid glands release parathyroid hormone

kidneys reabsorb Ca

Ca levels increase

58
Q

Describe acute calcium regulation

A

increase/decrease of blood Ca is caused by regulation problems (Not diet problems)

blood Ca must be maintained (can cause tetany/rigor - uncontrolled muscle contraction). low blood calcium does not reflect lack of calcium, but is caused by a lack of vit D or abnormal secretion of regulatory hormones

59
Q

describe chronic calcium regulation

A

caused by low Ca intake from diet

causes stunting in children and osteoporosis

60
Q

how does blood calcium change with diet?

adequate vs inadequate?

A

with adequate Ca intake, blood calcium remains normal and bones deposit Ca. Result is strong, dense bones

with Ca deficiency, blood Ca remains normal but bones give up Ca to the blood (because Ca bank is in the bones). Result is weak, osteoporotic/osteopenic bones (or lack of growth in children)

someone can be Ca deficient for years, but not notice because blood Ca remains the same. But they will notice later on when older because they are susceptible to fractures

61
Q

What does calcitonin do?

A

inhibits activation of vit D when levels are high

62
Q

function of parathyroid hormone?

A

stimulates activation of vit D when levels are too low

63
Q

describe what happens when blood calcium rises

A
  1. rising blood signals thyroid gland to secrete calcitonin
  2. calcitonin prevents calcium reabsorption in kidneys
  3. calcium absorption in intestines is limited
  4. inhibits osteoclast cells from breaking down bone. Release of calcium into blood is prevented
  5. calcitonin is inhibited once blood Ca levels are low enough
64
Q

describe when blood Ca falls

A
  1. parathyroid glands secrete parathyroid hormone
  2. PTH stimulates activation of vit D
  3. vit D and PTH stimulates Ca reabsorption in kidneys
  4. vit D enhances Ca absorption in intestine
  5. vit D and PTH stimulates osteoclast cells to break down more bone = more Ca is released into the blood
  6. blood Ca rises = inhibits PTH secretion
65
Q

current DRI-RDA for Ca in adults (19-70)?

A

1000mg/d

66
Q

why are recommendations of Ca so variable?

A

need more Ca in teens and children for growth.

Need more Ca in 70 and older to maintain bone

67
Q

RDA of 9-13 and 14-18 years?

A

1300mg/d

68
Q

RDA of 70 or older?

A

1200mg/d

69
Q

RDA in pregnancy/lactation mothers?

A

no increase (1000mg)

70
Q

why don’t pregnant women need more Ca?

A

they have increased absorption and decreased excretion (body regulated)

small amounts are taken by bones if not enough Ca in diet

71
Q

What is the UL of Ca?

A

2500mg/d (except for infants and babies 0-12months. Not determinable.)

72
Q

what are serving sizes based on?

A

amount of Ca from milk

73
Q

how much Ca absorption in adults, children, pregnant mothers?

A

30% adults

50%children and pregnant

74
Q

what increases Ca absorption?

A 
anabolic hormones
gastric acid (meal)
vit D
low phospahte intake
lactose (in infants only)
75
Q

what decreases Ca absorption

A 
ageing
lack of stomach acid
vit D deficiency
high phosphate intake
high insoluble fibre diet
phytates, oxalates
high protein intake
76
Q

What are some foods that have Ca more than 50% absorbed?

less than 5% absorbed?

A

50: cauliflower, kale, broccoli, bok choy, brussels sprouts
5: spinach, swiss chard, rhubarb

77
Q

Define bioavailability

A

degree to which the particular nutrient from a food source can be utilized

78
Q

What influences urinary Ca excretion?

A 
Ca intake
Age
caffeine
dietary Na
Dietary protein (excretion of sulphate from sulphur amino acids)
79
Q

describe use of Ca supplements

A

should never be used to displace Ca from diet

useful for people who are lactose intolerant, milk allergy, vegan. (at risk for inadequate Ca intake)

80
Q

what is the Ca UL?

A

2500mg

81
Q

what happens past the Ca UL?

A

compromised Fe status (Ca inhibits absorption)

kidney stones

vit D toxicity

82
Q

What is another name for vit D?

A

cholecalciferol

83
Q

sources of vit D?

A

fatty fish, egg yolk, liver, fortified milk

84
Q

describe synthesis of vit d

A

from cholesterol
10-15 mins of summer sunlight
decreases with age, dark skin, latitude, winter
—-
steps:
1. 7-dehydrocholesterol in the skin (precursor made from cholesterol) becomes previt D3 from UV rays
2. becomes vit D3 (inactive)
3. foods also become inactive vit D3
4. in the liver: inactive vit D3 is hydroxylated into 25-hydroxy vit D3
5. in the kidneys: becomes 1,25-dihydroxy vit D3 (active form)

85
Q

functions of vit d

A

required for Ca absorption (calbindin)

regulates blood Ca levels
stimulates osteoclasts

necessary for bone calcification

immunity and cell differentiation

86
Q

actions of vit D in intestine, kidney, bone?

A

intestine: increase Ca absorption from diet
kidney: decrease Ca excretion in urine
bone: increase Ca release from bone

87
Q

how does vit D act as a hormone?

A

travels in blood

activated in and acts on liver and kidneys

increases Ca availability

88
Q

how does vit D act as a vitamin?

A
  1. it’s essential in the diet (has a specific function and absence causes deficiency)
  2. we can’t synthesize as much as we need
  3. activated to a hormone
89
Q

what is the RDA of vit D?

A

15 ug/d (600 IU)
assumes adequate sun exposure

increases with age (20ug/d for over 70 years)

90
Q

what is the RDA for over 70 years?

A

20ug/d

91
Q

sources of vit D?

A

most foods have little vit D

fatty fish are best sources

vit D is best obtained from fortified foods

92
Q

what happens with too much vit D consumption?

A

results in hypercalcemia and calcification of soft tissues

can’t be caused by too much sun exposure. but can occur from excess supplements/fishoils

93
Q

vit D UL?

A

100micrograms/d (4000 IU)

94
Q

vit D deficiency?

osteomalacia and rickets

A
  1. osteomalacia occurs with less than 2.5 ug/day.
    decreased Ca absorption
    bone matrix is lost = bone pain = hip fracture risk
  2. Rickets.
    vit D deficiency in children = bones don’t grow properly.
    results in stunting, softening of bone, bowed legs, teeth problems.

prevalence decreased due to milk fortification

95
Q

what are the roles of phosphorous in the body?

importance in the body?

A

found in all body cells as a major buffer system (phosphoric acid and salts).

Part of DNA and RNA. Thus necessary for all growth

roles:

  • assists in energy metabolism.
  • many enzymes and b vits are active only when phosphate is attached
  • ATP uses phosphate groups
  • lipids use phosphorus as part of their structures (ie. phospholipids which are important components in cell membranes)
  • proteins (ie. casein in milk. has phophoproteins)
96
Q

what does phosphorous for with Ca?

what happens with high intake of P?

A

P + Ca forms hydroxyapatite mineral of bone

high intake decreases Ca absorption

97
Q

role of magnesium in the body?

A
  • bone structure and regulation of mineralization
  • vit D metabolism
  • blood clotting
  • muscle contraction (Ca promotes, Mg inhibits)
  • acts on soft tissue cells (part of protein making machinery)
  • necessary for energy metabolism (ATP synthesis) and enzyme systems
98
Q

what is the role of Ca and Mg in muscle contractions and blood clotting?

A

Ca promotes
Mg inhibits
interaction of Ca and Mg regulates blood pressure and lung function

99
Q

Vit K role?

A

co-enzyme synthsize bone protein

100
Q

deficiency of vit K

A

cannot bind to minerals

101
Q

role of vit A

A

bone remodelling, osteoclast activity

102
Q

role of vit C

A

cofactor for collagen synthesis

NUTR207 (Nutrition and Health) (9 decks)

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