Nutrition Lecture 7: Calcium

Question 1

What are rich sources of dairy?

Answer 1

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

Question 2

What happens to the bioavailability of calcium over a lifetime?

Answer 2

Decreases with age

Question 3

What is the bioavailability of calcium from dairy products?

Answer 3

30%

Question 4

What is the bioavailability of calcium from fortified soy milk?

Answer 4

20-30%

Question 5

What is the bioavailability of calcium from kale?

Answer 5

40%

Question 6

When does bioavailability of calcium decrease?

Answer 6

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

Question 7

What foods are rich in oxalic acid?

Answer 7

spinach, rhubarb

Question 8

What foods are rich in phytate?

Answer 8

Seeds, nuts, wholegrains

Question 9

What is the absorption of calcium from supplements?

Answer 9

30%

Question 10

At higher does what happens to calcium absorption?

Answer 10

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

Question 11

What is VDR?

Answer 11

Vitamin D receptor

Question 12

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

Answer 12

• Absorbed by active transport (transcellular)
• Passive diffusion (paracellular)

Question 13

What does active transport of calcium require?

Answer 13

Vitamin D

Question 14

When does the passive diffusion of calcium become increasingly important?

Answer 14

as Ca intakes increase

Question 15

How tightly is calcium homeostasis controlled?

Answer 15

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

Question 16

What is the serum calcium physiological range?

Answer 16

2.12-2.62

Question 17

How are serum calcium levels maintained?

Answer 17

Through an endocrine system with strict controlling factors and feedback mechanisms

Question 18

What molecules play key roles in maintaining Ca homeostasis?

Answer 18

Vitamin D (calcitriol) and parathyroid hormone (PTH)

Question 19

PTH is used as a marker of what?

Answer 19

Vitamin D sufficiency

Question 20

What does calcitonin do?

Answer 20

Blocks bone Ca resorption when serum levels drop

Question 21

When there is a drop in serum calcium what happens?

Answer 21

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

Question 22

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

Answer 22

• Ca release from bones increases
• Ca uptake in kidneys decreases
• Ca uptake in intestines increases

Question 23

What is the main function of calcium?

Answer 23

Formation and metabolism of bone

Question 24

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

Answer 24

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

Question 25

What is Calcium hydroxyapatite?

Answer 25

A crystalline structure that is what makes bones and teeth strong

Question 26

What are other functions of calcium?

Answer 26

- Vascular contraction and vasodilation - Muscle function - Nerve transmission - Intracellular signalling - Hormone secretion

Question 27

What can calcium deficiency cause?

Answer 27

Osteoporosis or rickets/osteomalacia

Question 28

What is osteoporosis?

Answer 28

Reduced bone strength

Question 29

What are rickets/osteomalacia more commonly due to?

Answer 29

Vitamin D deficiency, but sometimes cases caused by Ca deficiency

Question 30

What is Hypocalcaemia?

Answer 30

Low levels of calcium in the blood

Question 31

What is hypocalcaemia usually due to?

Answer 31

Vitamin D or magnesium deficiency or hypoparathyroidism

Question 32

What are the symptoms of hypocalcaemia?

Answer 32

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

Question 33

How common is calcium toxicity?

Answer 33

Rare in healthy people

Question 34

What is calcium toxicity usually a result of?

Answer 34

Cancer or primary hyperparathyroidism

Question 35

What does calcium toxicity result in?

Answer 35

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

Question 36

What do high supplement intakes cause?

Answer 36

Constipation

Question 37

What is calcitriol?

Answer 37

Active form of Vitamin D

Question 38

What does calcitriol inhibit?

Answer 38

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

Question 39

What does calcitriol promote/increase the absorption of?

Answer 39

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

Question 40

What does calcitriol have a direct action on?

Answer 40

Cartilage and bone, to promote normal skeletal development and turnover

Question 41

Are there non-bone affects of vitamin D deficiency?

Answer 41

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

Question 42

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

Answer 42

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

Question 43

What is the AI for Vitamin D?

Answer 43

5ug/day - increases with age

Question 44

What is the upper level of intake for vitamin D?

Answer 44

80ug/day

Question 45

What is the EAR for Calcium?

Answer 45

840mg/day

Question 46

What is the RDI for calcium?

Answer 46

1000mg/day

Question 47

What is the upper level of intake for Calcium?

Answer 47

2500mg/day