Mod 1- Vitamin D

Question 1

How is Vitamin D made in the body?

Answer 1

It is synthesised from sunlight using a precursor derived from cholesterol in the skin.

Question 2

Do you need to get Vitamin D from food if you get enough sun?

Answer 2

No, adequate sun exposure makes dietary Vitamin D unnecessary.

Question 3

What are the two main types of Vitamin D?

Answer 3

D2 (Ergocalciferol – plant-derived) and D3 (Cholecalciferol – animal-derived).

Question 4

What is the first step in Vitamin D production in the skin?

Answer 4

UV rays from the sun activate a precursor in the skin and convert it to previtamin D3.

Question 5

How is previtamin D3 turned into Vitamin D3?

Answer 5

Body heat helps convert previtamin D3 into Vitamin D3 (cholecalciferol).

Question 6

What two organs are involved in activating Vitamin D through hydroxylation?

Answer 6

The liver and kidneys.

Question 7

What does the liver do during Vitamin D activation?

Answer 7

It converts calciol to calcidiol.

Question 8

What does the kidney do during Vitamin D activation?

Answer 8

It converts calcidiol to calcitriol, the active form of Vitamin D.

Question 9

What is the active form of Vitamin D classified as?

Answer 9

A hormone that sends messages to target organs.

Question 10

How is Vitamin D transported to target organs?

Answer 10

By a Vitamin D-binding protein.

Question 11

What are the main target organs of Vitamin D for bone health?

Answer 11

Intestines, kidneys, and bones.

Question 12

How do these organs respond to Vitamin D?

Answer 12

They make minerals available for bone growth and maintenance.

Question 13

Which two minerals does Vitamin D help the body absorb?

Answer 13

Calcium and phosphorus.

Question 14

Besides bones, which other body systems does Vitamin D affect?

Answer 14

Brain, immune system, nervous system, pancreas, skin, muscles, cartilage, and reproductive organs.

Question 15

How does Vitamin D increase blood calcium levels?

Answer 15

By increasing intestinal absorption of calcium and phosphorus from the diet.

Question 16

How does Vitamin D affect the kidneys regarding calcium?

Answer 16

It increases the reabsorption of calcium in the kidneys.

Question 17

What role does Vitamin D play with osteoclasts?

Answer 17

It activates osteoclasts to release calcium from bones into the blood.

Question 18

Why is releasing calcium from bones important?

Answer 18

To maintain optimum blood calcium concentration.

Question 19

What percentage of Vitamin D in our body comes from sun exposure?

Answer 19

About 80%.

Question 20

Name some natural food sources of Vitamin D.

Answer 20

Eggs, liver, and fatty fish like mackerel, herring, and salmon.

Question 21

What food is fortified with Vitamin D by law in Australia?

Answer 21

Margarine.

Question 22

Which foods are voluntarily fortified with Vitamin D?

Answer 22

Low fat milk, powdered milk, soy milk, and yoghurt.

Question 23

How much sun exposure is needed in summer for sufficient Vitamin D synthesis?

Answer 23

5–10 minutes between 10am and 2pm on the face, hands, and arms.

Question 24

How much sun exposure is needed in winter in southern Australia for enough Vitamin D?

Answer 24

2–3 hours of sunlight on the face, hands, and arms.

Question 25

Name some factors that reduce Vitamin D synthesis in the skin.

Answer 25

Wearing sunscreen SPF 8 or higher, darker skin, smog, heavy clouds, smoke, pollution, and spending lots of time indoors.

Question 26

What environmental factors affect Vitamin D synthesis?

Answer 26

Latitude, season, and time of day.

Question 27

What is the Adequate Intake (AI) of Vitamin D for children and adults under 50 years?

Answer 27

5 mcg/day (200 IU), including pregnant and lactating women.

Question 28

What is the AI of Vitamin D for men and women aged 51 to 70 years?

Answer 28

10 mcg/day (400 IU).

Question 29

What is the AI of Vitamin D for men and women over 70 years?

Answer 29

15 mcg/day (600 IU).

Question 30

Who set the Vitamin D AI values, and when?

Answer 30

The NHMRC (National Health and Medical Research Council) in 2006.

Question 31

What assumption is made about sun exposure in the Vitamin D AI?

Answer 31

The AI assumes no, or minimal, exposure to sunlight.

Question 32

What is Vitamin D deficiency?

Answer 32

When the body doesn’t have enough Vitamin D to maintain healthy bones and support functions like calcium absorption and immune health.

Question 33

Name some factors that contribute to Vitamin D deficiency.

Answer 33

Breastfeeding mothers who are deficient, low sun exposure, darker skin, and poor diet lacking Vitamin D-rich foods.

Question 34

What childhood disease is caused by Vitamin D deficiency?

Answer 34

Rickets.

Question 35

What are symptoms of rickets?

Answer 35

Poor bone formation, soft and flexible bones, bowlegs, and beaded ribs.

Question 36

What adult condition is caused by Vitamin D deficiency?

Answer 36

Osteomalacia.

Question 37

What happens to bones in osteomalacia?

Answer 37

Bones don’t mineralise properly, become soft, brittle, flexible, and deformed.

Question 38

What is a common symptom of osteomalacia?

Answer 38

Bone pain.

Question 39

What usually causes Vitamin D toxicity?

Answer 39

Taking supplements, not from sun exposure or food.

Question 40

Is Vitamin D from sunlight and diet generally safe?

Answer 40

Yes, it stays within the limits set by Nutrient Reference Values (NRVs).

Question 41

What happens when there is too much Vitamin D in the body?

Answer 41

Blood calcium levels rise too high.

Question 42

What health problems can high blood calcium from excess Vitamin D cause?

Answer 42

Kidney stones and hardening of blood vessels (especially in the heart, lungs, and joints).

Question 43

What is the upper limit (UL) of Vitamin D intake for adults?

Answer 43

80 micrograms per day (or 3200 IU/day).