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1) Nutrition & Health > Calcium, Vitamin D and Bone Health > Flashcards

Calcium, Vitamin D and Bone Health Flashcards

1
Q

What are bones made of? What are the different parts role?

A
  • 65% mineral crystals (strength and structural support)

- 35% collagen (flexibility)

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2
Q

What does bone mineral density correspond to?

A

Bone strength

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3
Q

Name the 2 types of bone tissues.

A

1) Cortical bone (compact bone, 80% of mineral structure)

2) Trabecular bone (lacy bone, 20%)

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4
Q

Describe the cortical bone.

A

Very dense; part of outer walls of larger bones and main

tissue of small bones

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5
Q

Describe the trabecular bone.

A

Lacy architecture; ends of long bones, vertebrae, responses readily to hormones

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6
Q

Describe the 3 steps in bone turnover.

A

1) Bone growth
2) Bone modeling
3) Bone remodeling

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7
Q

Which step in bone turnover determines bone size?

A

Bone growth

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8
Q

Which step in bone turnover determines bone shape?

A

Bone modeling

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9
Q

Which step of bone turnover occurs primarily in adulthood and replaces old bone with new bone?

A

Bone remodeling

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10
Q

Define resorption. What is it associated with?

A

surface of bones is broken down

- Osteoclasts

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11
Q

Define osteoclasts.

A

cells that erode the surface of bones

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12
Q

Define formation. What is it associated with?

A

formation of new bone in resorption pit

- Osteoblasts

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13
Q

Define osteoblasts.

A

cells that produce the collagen- containing component of bone

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14
Q

What does osteoporosis cause?

A
  • Compressed vertabrae (pain, less mobility)

- Bones susceptible to fractures

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15
Q

What is the prevalence of osteoporosis in Canada?

A
  • 1 in 4 women

- 1 in 8 men

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16
Q

What is the acute care cost for osteoporosis?

A

20 billion annually

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17
Q

What is another name for type 1 osteoporosis? Type 2?

A

Type 1: Postmenopausal

Type 2: senile

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18
Q

What is the age of onset of type 1 osteoporosis? Type 2?

A

Type 1: 50-70 years old

Type 2: 70 years and older

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19
Q

Where are the fracture sites for type 1 osteoporosis? Type 2?

A

Type 1: wrist and spine

Type 2: hip

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20
Q

Compare the gender incidence of type 1 and type 2 osteoporosis.

A

Type 1: 6 women to 1 man

Type 2: 2 women to 1 man

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21
Q

What are the primary causes of type 1 osteoporosis?

A

Rapid loss of estrogen in women following menopause; loss of testosterone in men with advancing age

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22
Q

What are the primary causes of type 2 osteoporosis?

A

Reduced calcium absorption, increased bone mineral loss, increased propensity to fall

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23
Q

What is the lifetime risk of sustaining a hip fracture in women? Men?

A

Women: 15%
Men: 5%

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24
Q

What happens to most patients after a hip fracture?

A

Most are unable to walk unassisted

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25
Q

How should we prevent osteoporosis?

A

Focus should be placed on maximizing peak bone mass.

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26
Q

Why is insuring maximal skeletal density healthful?

A

will prolong the time it takes for bone density to fall below the fracture threshold in response to age-related bone losses

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27
Q

Why is physical activity good for bone density? Who does it affect the most?

A
  • Working muscles pull on bone, causing more trabeculae
    and bones grow denser
  • Bones of active people are denser and stronger than sedentary people (weight training)
  • Older women and children
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28
Q

Name some risk factors for osteoporosis.

A
  • Older age
  • Low BMI
  • Heritage
  • Cigarette smoking and alcohol
  • Sedentary lifestyle
  • Female gender
  • Maternal history of osteoporosis
  • Estrogen deficiency (women), testosterone deficiency (men)
  • Lifetime diet inadequate in calcium and vitamin D
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29
Q

Name some protective factors for osteoporosis.

A
  • Younger age
  • High BMI
  • African American heritage
  • Regular weight-bearing exercise
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30
Q

Why does smoking affect osteoporosis?

A
  • Associated with leanness
  • Earlier menopause
  • Lower postmenopausal
    estrogen levels
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31
Q

Why does alcohol affect osteoporosis?

A
  • Can increase urinary calcium excretion
  • Associated with lower dairy food intakes
  • May be toxic to osteoblasts
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32
Q

What is the treatment for osteoporosis?

A
  • Anti-resorptive agents inhibit osteoclasts (hormone replacements, calcitonin, biphosphonates)
  • Anabolic agents to stimulate osteoblasts (PTH)
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33
Q

Define osteopenia.

A
  • Bone mineral density 1–2.5 SD below the mean established for a young normal population
  • (T Score: – 1 to – 2.5)
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34
Q

Define osteoporosis.

A
  • Bone mineral density > 2.5 SD below the mean established for a young normal population
  • (T Score: >- 2.5)
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35
Q

Name 2 ways to carry-out a bone assessment.

A
  • DEXA (dual energy X-ray absorptiometry)

- Quantitive ultrasound

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36
Q

Who are the players in the bone growth team?

A
  • Protein - collagen

- minerals - Ca, P, Mg, F

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37
Q

Who are the coaches in the bone growth team?

A
  • Vitamin D, parathyroid hormone

- Calcitonin

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38
Q

Who are the assistants/scouts in the bone growth team?

A

Vitamins A, C, K

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39
Q

Name the 2 types of calcium functions.

A
  • Acute Health

- Chronic Health

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40
Q

Name the functions of calcium in acute health.

A

Ca as an ion in solution

  • muscle contraction
  • nervefunction
  • bloodclotting
  • immunefunction
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41
Q

Name the functions of calcium in chronic health.

A

Ca as a mineral in bone

  • Mineral of bones and teeth - 99% of calcium
  • Maintain bone turnover
42
Q

How is acute calcium regulated?

A
  • Blood Ca MUST be maintained

- excess/lack of blood Ca is a problem of regulation NOT DIET!!!

43
Q

How is chronic calcium regulated?

A

low dietary Ca - robs the “bone RRSP” i.e. decreases bone mineralization

44
Q

What happens when bone mineralization decreases?

A
  • Stunting in children

- Osteoporosis

45
Q

What is the RDA for calcium for 9-18 year olds, 19 to 70 year olds and 70 or older?

A

9-18: 1300 mg/day
18-70: 1000 mg/day
70+: 1200 mg/day

46
Q

Do pregnant women need more calcium?

A

No increase

47
Q

What is the tolerable upper intake level for calcium? Why life cycle does it not apply to? Why?

A

2500 mg/day EXCEPT infants (0-12 months) for whom this value was not determinable

48
Q

Compare calcium absorption in adults vs childhood, pregnancy and lactation.

A

Adults: 30%

Childhood, pregnancy, lactation: 50%

49
Q

Name factors that increase calcium absorption.

A
  • anabolic hormones
  • gastric acid (meal)
  • vitamin D
  • low phosphate intake
  • Lactose (in infants only)
50
Q

Name factors that decrease calcium absorption.

A
  • ageing
  • lack of stomach acid
  • vitamin D deficiency
  • high phosphate intake
  • high insoluble fibre diet
  • phytates, oxalates
  • high protein intake
51
Q

Name sources of calcium that are well absorbed.

A

Cauliflower, watercress, brussels sprouts, rutabaga, kale, mustard greens, bok choy, broccoli, turnip greens

52
Q

Define bioavailibility.

A

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

53
Q

Does the presence of calcium within a food insure that the food is a good source of calcium?

A

No

54
Q

Name 3 types of substances that bind to Ca and reduce absorption.

A
  • Insoluble fiber: binds cations
  • Phytates: legumes, nuts, and cereals
  • Oxalates: spinach, beets, celery, eggplant, okra, berries, nuts, tea, cocoa
55
Q

What is urinary calcium excretion influenced by?

A
  • Calcium
  • Age
  • Caffeine
  • Dietary sodium
  • Dietary protein
56
Q

What should individuals with hypercalciuria be advised?

A

To restrict sodium intakes to minimize urinary calcium

57
Q

Why does dietary protein influence calcium excretion?

A

Excretion of sulphate from sulphur amino acids

58
Q

Calcium supplements are useful for who?

A

Lactose intolerance, milk allergy, vegans

59
Q

Which calcium supplement is well absorbed? How much?

A
  • Calcium citrate, gluconate, malate, carbonate etc

- 30%

60
Q

Why are multivitamins not a great calcium supplement?

A

Mineral interactions decrease absorption

61
Q

What is the UL for calcium?

A

2500 mg

62
Q

Name 2 consequences of calcium toxicity.

A
  • Compromised Iron Status (and other minerals) Ca inhibits absorption
  • Kidney stones
63
Q

How can supplements increase the exposure to contaminants?

A

If supplements are from bone meal or dolomite

64
Q

Name sources of vitamin D from the diet.

A

 Fatty fish
 egg yolks
 liver
 milk - fortified

65
Q

What is vitamin D synthesized from?

A

From cholesterol

66
Q

How do you get vitamin D?

A

10-15 minutes of summer sunlight (UVB rays)

67
Q

Vitamin D synthesis decreases as a consequence of what?

A

with age, dark skin, latitude, winter

68
Q

D3 cholecalciferol is in what kind of foods?

A

Animal foods

69
Q

D2 ergocalciferol is in what kind of foods?

A

Plant foods

70
Q

Vitamin D synthesis occurs in 3 organs, name them in order.

A
  • Skin
  • Liver
  • Kidneys
71
Q

Name 5 functions of vitamin D.

A
  • Required for calcium absorption (calbindin)
  • Regulates blood calcium levels
  • Stimulates osteoclasts
  • Necessary for bone calcification
  • New functions: immunity and cell differentiation
72
Q

How does vitamin D affect calcium in the intestine?

A

Increase Ca absorption from diet

73
Q

How does vitamin D affect calcium in the kidneys?

A

Decrease Ca excretion in the urine

74
Q

How does vitamin D affect calcium in the bones?

A

increase Ca release from bone

75
Q

Rising blood calcium signals the thyroid gland to release what?

A

Calcitonin

76
Q

Falling blood calcium signals the parathyroid gland to secrete what?

A

Parathyroid hormone

77
Q

What role does calcitonin play in infants and young children?

A

against the dangers of rising blood calcium that can occur when regular feedings of milk deliver large quantities of calcium to a small body.

78
Q

Is vitamin D a hormone or a vitamin?

A

Both

79
Q

How does vitamin D act as a hormone?

A
  • Travels in the blood
  • Activated in the liver and kidneys
  • Acts on intestine, kidney, bones
  • To increase Ca availability for bone mineralization and remodelling
80
Q

How does vitamin D act as a vitamin?

A
  • Essential for the diet (specific function and absence results in deficiency)
  • We can’t synthesize as much as we need
  • Vitamin is activated to a hormone
81
Q

What does the RDA of vitamin D assume in Canada?

A

assume that a person’s sun exposure is inadequate

82
Q

What latitudes receive inadequate sun in the winter?

A

> 40° N or > 40 °S

83
Q

What is the RDA for vitamin D in ug/d and in IU?

A

15 ug/d and 600 IU

84
Q

How does the RDA for vitamin D change with age?

A

Increases with age (20 ug/d for >70 years old)

85
Q

What are the best sources of vitamin D? How is most obtained?

A
  • Fatty fish (salmon, sardines) best sources

- obtained from fortified foods such as milk and margarine

86
Q

How do vegetarians receive vitamin D?

A

from the sun, fortified plant-based milks or supplements

87
Q

Can you consume too much vitamin D from skin synthesis?

A 
Skin synthesis (sun exposure) cannot cause
excess vitamin D formation
88
Q

How can vitamin D toxicity occur? What happens?

A
  • excess supplements or fish oils

- hypercalcemia and calcification of soft tissues, potentially fatal

89
Q

What is the UL for vitamin D in ug/d? In IU?

A

100 μg/d and 4000 IU

90
Q

Does sunscreen affect vitamin D intake?

A

Yes

91
Q

Define osteomalacia.

A
  • Vitamin D deficiency in adults
  • Decreased CA absorption
  • Bone matrix is decreased (defective mineralization)
  • Softening of bone (bone pain, hip fracture)
92
Q

Define rickets.

A
  • Vitamin D deficiency in children

- Growing bones don’t mineralize properly (softening of bone, bowed legs, stunting, teeth probs)

93
Q

When does osteomalacia occur?

A

when vitamin D intake is less than 2.5 ug/day

94
Q

What forms the hydroxyapatite mineral of bone?

A

Phosphorus and calcium

95
Q

How does phosphorus affect Ca absorption?

A

High intake decreases Ca absorption

96
Q

What are the functions of magnesium?

A
  • Bone structure and regulation of mineralization, vitamin
    D metabolism
  • ATP synthesis
  • Blood clotting, muscle contraction (Ca promotes, Mg inhibits)
97
Q

Which vitamin is a coenzyme to synthesize bone protein?

A

Vitamin K

98
Q

What happens during vitamin K deficiency?

A

Cannot bind minerals

99
Q

How is vitamin A related to bones?

A

Bone remodelling, osteoclast activity

100
Q

How is vitamin C related to bones?

A

Cofactor for collagen synthesis (organic matrix)

1) Nutrition & Health (21 decks)

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