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HUNT241 > Nutrition Lecture 7: Calcium > Flashcards

Nutrition Lecture 7: Calcium Flashcards

1
Q

What are rich sources of dairy?

A

Dairy products, fortified alternatives, tofu, leafy greens (kale), almonds

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2
Q

What happens to the bioavailability of calcium over a lifetime?

A

Decreases with age

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3
Q

What is the bioavailability of calcium from dairy products?

A

30%

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4
Q

What is the bioavailability of calcium from fortified soy milk?

A

20-30%

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5
Q

What is the bioavailability of calcium from kale?

A

40%

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6
Q

When does bioavailability of calcium decrease?

A

may be poorly absorbed from foods rich in oxalic acid or phytate

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7
Q

What foods are rich in oxalic acid?

A

spinach, rhubarb

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8
Q

What foods are rich in phytate?

A

Seeds, nuts, wholegrains

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9
Q

What is the absorption of calcium from supplements?

A

30%

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10
Q

At higher does what happens to calcium absorption?

A

absorption reduces at higher doses (>500mg) increases when consumed with a meal

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11
Q

What is VDR?

A

Vitamin D receptor

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12
Q

What are the two mechanisms for calcium to cross the intestinal mucosa?

A
  • Absorbed by active transport (transcellular)
  • Passive diffusion (paracellular)
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13
Q

What does active transport of calcium require?

A

Vitamin D

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14
Q

When does the passive diffusion of calcium become increasingly important?

A

as Ca intakes increase

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15
Q

How tightly is calcium homeostasis controlled?

A

Levels of circulating Ca must be within a narrow physiological range for body to function normally

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16
Q

What is the serum calcium physiological range?

A

2.12-2.62

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17
Q

How are serum calcium levels maintained?

A

Through an endocrine system with strict controlling factors and feedback mechanisms

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18
Q

What molecules play key roles in maintaining Ca homeostasis?

A

Vitamin D (calcitriol) and parathyroid hormone (PTH)

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19
Q

PTH is used as a marker of what?

A

Vitamin D sufficiency

20
Q

What does calcitonin do?

A

Blocks bone Ca resorption when serum levels drop

21
Q

When there is a drop in serum calcium what happens?

A

The stimulus acts on the parathyroid glands and tells them to release PTH

22
Q

What happens to bones, kidneys and intestines when serum calcium drops?

A
  • Ca release from bones increases
  • Ca uptake in kidneys decreases
  • Ca uptake in intestines increases
23
Q

What is the main function of calcium?

A

Formation and metabolism of bone

24
Q

Almost 98% of total body calcium is found as what?

A

Calcium hydroxyapatite (Ca10[PO4]6[OH]2)

25
Q

What is Calcium hydroxyapatite?

A

A crystalline structure that is what makes bones and teeth strong

26
Q

What are other functions of calcium?

A
  • Vascular contraction and vasodilation
  • Muscle function
  • Nerve transmission
  • Intracellular signalling
  • Hormone secretion
27
Q

What can calcium deficiency cause?

A

Osteoporosis or rickets/osteomalacia

28
Q

What is osteoporosis?

A

Reduced bone strength

29
Q

What are rickets/osteomalacia more commonly due to?

A

Vitamin D deficiency, but sometimes cases caused by Ca deficiency

30
Q

What is Hypocalcaemia?

A

Low levels of calcium in the blood

31
Q

What is hypocalcaemia usually due to?

A

Vitamin D or magnesium deficiency or hypoparathyroidism

32
Q

What are the symptoms of hypocalcaemia?

A

Tingling hands and feet, muscle spasms, depression, heart failure, seizures

33
Q

How common is calcium toxicity?

A

Rare in healthy people

34
Q

What is calcium toxicity usually a result of?

A

Cancer or primary hyperparathyroidism

35
Q

What does calcium toxicity result in?

A

Poor muscle tone, renal insufficiency, constipation, nausea, weight loss, fatigue

36
Q

What do high supplement intakes cause?

A

Constipation

37
Q

What is calcitriol?

A

Active form of Vitamin D

38
Q

What does calcitriol inhibit?

A

Inhibits PTH - if we have a higher vitamin D status this is associated with a reduced PTH and vice versa

39
Q

What does calcitriol promote/increase the absorption of?

A

intestinal absorption of Ca and phosphate, and increases Ca re-absorption from kidney

40
Q

What does calcitriol have a direct action on?

A

Cartilage and bone, to promote normal skeletal development and turnover

41
Q

Are there non-bone affects of vitamin D deficiency?

A

Lots of studies on cancer, CVD, diabetes and results are either negative or uncertain

42
Q

What does the MOH and cancer society recommend for vitamin D?

A

Need to balance risk of skin cancer vs risk of vitamin D deficiency

43
Q

What is the AI for Vitamin D?

A

5ug/day - increases with age

44
Q

What is the upper level of intake for vitamin D?

45
Q

What is the EAR for Calcium?

46
Q

What is the RDI for calcium?

A

1000mg/day

47
Q

What is the upper level of intake for Calcium?

A

2500mg/day

HUNT241 (22 decks)

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