Calcium and Vitamin D

Question 1

in 1920’s what was the cure that was found for rickets

Answer 1

UV light and cod liver oil

Question 2

what is the main source of vitamin D

Answer 2

the sun

Question 3

other sources of vitamin D

Answer 3

cod liver oil
sardines
smoked salmon
eel
fortified soy milk

Question 4

Is NZ dairy fortified with vitamin D

Answer 4

very rarely

Question 5

how does sunlight provide our bodies with vitamin D

Answer 5

UVB light comes through the skin goes through a non enzymatic reaction, causes 7-dehydrocholesterol to form vitamin D3

(action of the sun on the skin does this)

Question 6

what is shortest wave length of sunlight

Answer 6

UVC

Question 7

what sunlight wavelength has the largest affect on the top layer of the skin and what does it cause

Answer 7

UVB - causes burning / redness / skin cancer

Question 8

why is UBV both problematic and useful

Answer 8

has the most use to us but also causes burning / skin cancer

Question 9

what is the longest wavelength of sunlight

Answer 9

UVA = reaches deep into the layers of skin causing aging and wrinkling

Question 10

what are the behavioural factors that affect vitamin D status

Answer 10

clothing (blocks UVB)
sunscreen
time of the day
time spent outdoors
supplements
diet (smaller effect as few foods contain vitamin D)

Question 11

what are host related factors that affect vitamin D status

Answer 11

skin colour (melanin)
-gives the skin, eyes and hair dark colour is the natural protection against the harmful effects of UV light

age- as you get older, your skin is going to have less of the 7-dehydrocholesterol in it, that means lower ability to form vitamin D

sex-in high income countries, men tend to have higher levels than women

BMI- people who are overweight or obese have less circulation vitamin D as it is a fat soluble vitamin (it gets sequested into adipose tissue)

genetic differences in vitamin D binding protein and receptors

Question 12

what are the environmental factors that affect vitamin D status

Answer 12

season
latitude
altitude
clouds
atmospheric pollution

Question 13

what are the two major forms of vitamin D

Answer 13

D2 and D3

Question 14

where do you get vitamin D3

Answer 14

from animals

Question 15

what type of vitamin D does the skin make when exposed to UV light

Answer 15

D3

Question 16

what is the longer name for vitamin D3

Answer 16

cholecalciferol

Question 17

how is vitamin D3 formed

Answer 17

beta ring on 7-dehydrocholesterol is broken by UVB light, this forms pre vitamin D3, then heat converts that to vitamin D3

Question 18

what does vitamin D2 start out as and how is it converted to D2

Answer 18

starts out as ergosterol, B ring is broken down by UVB light, pre vitamin D2 is produced, then heat turns it to vitamin D2

Question 19

what is the longer name for vitamin D2

Answer 19

ergocalciferol

Question 20

what is the difference between vitamin D3 and D2 in terms of binding affinity and what does this mean

Answer 20

vitamin D2 has lower affinity for the vitamin D binding protein, so therefore cleared faster from the circulation

Question 21

which is more effective, D2 or D3

Answer 21

D3

Question 22

vitamin D is a fat soluble vitamin, so therefore what is needed for it to be absorbed

Answer 22

requires fat so it can be absorbed

Question 23

what are mixed micelles and why is this important

Answer 23

vitamin D is soluble in the hydrophobic core of micelle, phospholipids and bile acids surround it

Question 24

what do bile acids on the outside of a micelle do

Answer 24

make the micelle soluble in the hydrophilic gut lumen

Question 25

once absorbed in the upper small intestine, where is vitamin D transported to

Answer 25

transported from the small intestine to the liver by vitamin D binding globulin

Question 26

is the vitamin D from our food or skin biologically active, what does it require

Answer 26

no, it requires metabolic activation in the body

Question 27

how is vitamin D metabolic activated (what happens in the liver then where is this transported to and what happens here )

Answer 27

in the liver D3 or D2 will be converted to 25-hydroxyvitamin D (calcidiol) calcidiol is transported from the liver to the kidney in the kidney, calcidiol will be converted to 1,25 dihydroxyvitamin D

Question 27

calcitriol is used as a biomarker of what status

Answer 27

vitamin D levels

Question 27

what is the active form of vitamin D

Answer 27

calcitriol

Question 28

vitamin D floating around your body will be in what form, and if something needs to be done what form will it be in

Answer 28

calcidiol = floating round calcitriol = activated when needed

Question 29

what is the % of vitamin D deficiency in NZ

Answer 29

5%

Question 30

where is vitamin D deficiency lowest in NZ

Answer 30

Northern regions

Question 31

what is rickets

Answer 31

softening of the bones which can lead to fractures and deformity

Question 32

what is heliotherapy

Answer 32

sun therapy

Question 33

what is osteomalacia (younger + older adults)

Answer 33

softening of the bones younger adults = bowing of bones older adults = fractures

Question 34

what is the pain associated with osteomalacia

Answer 34

dull aching bone pain, not relieved by rest

Question 35

what is osteoid

Answer 35

the bone protein matrix (primarily collagen)

Question 36

in rickets or osteomalacia what happens to osteoid and why

Answer 36

insufficient mineral > the osteoid does not mineralise properly > unmineralized osteoid accumulates

Question 37

what is the non bone effect of vitamin D

Answer 37

1,25(OH)2D (calcitriol) is the ligand for the vitamin D receptor found in nearly every tissue, controlling hundreds of genes

Question 38

what could lead to vitamin D toxicity

Answer 38

supplement / fortification errors

Question 39

what are the non specific symptoms of vitamin D toxicity

Answer 39

anorexia, nausea, vomiting, weakness, changes in mental state

Question 40

what are the symptoms of vitamin D toxicity related to high blood calcium levels

Answer 40

high blood calcium levels > vascular and tissue calcification > damage to the heart and kidneys : may be fatal

Question 41

when does bioavailability of calcium decrease

Answer 41

decrease with age

Question 42

what is the bioavailability of calcium in dairy products

Answer 42

~30%

Question 43

what foods decrease the bioavailability of calcium

Answer 43

foods rich in oxalic acid or phytate

Question 44

what are the two mechanisms of calcium absorption

Answer 44

absorption by active active transport = requires vitamin D passive diffusion = increasingly important as Ca intakes increase

Question 45

for the body to function the serum calcium must be within the narrow range of …

Answer 45

2.12-2.62nmol/L

Question 46

what maintains the serum calcium levels

Answer 46

levels maintained through an endocrine system with strict controlling factors and feedback mechanisms (calcitriol and parathyroid hormone play key roles in this)

Question 47

drop in calcium levels in the blood stimulates what

Answer 47

parathyroid gland to release PTH

Question 48

in response to PTH release, what will happen

Answer 48

calcium released from the bones will increase and calcium uptake in the kidneys will decrease and stimulate calcitrol to be released from the kidneys

Question 49

what will release of calcitriol cause

Answer 49

the calcium in the intestines will have increased absorption

Question 50

how does negative feedback associated with calcium and PTH work

Answer 50

as calcium levels increase in the blood, your PTH levels begin to drop

Question 51

if calcium levels get too high what will be increased from the thyroid gland

Answer 51

calcitonin is released which will block the bone calcium absorption

Question 52

almost 98% of the total body calcium is found where and in what form

Answer 52

as calcium hydroxyapatite in bones and teeth

Question 53

the other 2% of total body calcium is critical for what

Answer 53

vascular contraction and vasodilation muscle function nerve transmission intracellular signalling hormone secretion

Question 54

what is reduced bone strength

Answer 54

osteoporosis

Question 55

calcium deficiency can be hypocalcaemia, what can this also be caused by

Answer 55

usually due to vitamin D or magnesium deficiency or hypoparathyroidism (underperforming parathyroid glands)

Question 56

what are the wide range of symptoms associated with hypocalcaemia

Answer 56

perioral numbness, tingling hands and feet, muscle spasms renal and brain calcification, depression, heart failure, seizures, coma

Question 57

how common is calcium toxicity

Answer 57

rare in healthy people

Question 58

calcium toxicity is usually a result of

Answer 58

cancer primary hyperparathyroidism

Question 59

what does calcium toxicity result in

Answer 59

poor muscle tone renal insufficiency constipation nausea weight loss fatigue higher risk CVD mortality

Question 60

actions of 1,25(OH)2D - calcitriol

Answer 60

promotes intestinal absorption of calcium and phosphate increases calcium reabsorption from kidney direct action of cartilage and bone to promote normal skeletal development and turnover inhibits PTH

Question 61

thinning of bone mass is due to imbalance in what

Answer 61

imbalance in bone resorption and formation