Week 7

Question 1

What are the fat soluble vitamins?

Answer 1

vitamins A, D, E and K

Question 2

Food sources of Vitamin D

Answer 2

fish and meat

Question 3

Forms of Vitamin in food sources, supplements and endogenous production?

Answer 3

Food sources: vitamin D3
Supplements: Vitamin D2
endogenous production: D3

Question 4

How is Vitamin D endogenous produced and activated?

Answer 4

• UVB rays from the sun reactive with 7-dehydrocholesterol in the skin to product Cholecalciferol (Vit D3)
• In the liver, Cholecalciferol is hydrolyzed to 25-hydroxycholecalciferol (hydroxyvitamin D3) by 25-hydroxylase
• In the kidney, this is hydrolyzed again to 1,25 hydroxycholecalciferol or calcitriol which is the active form of vitamin D

Question 5

How is Vitamin D absorbed?

Answer 5

Via Micelles and enterocytes: bile and pancreatic lipase dependent
Into chylomicrons through the lymphatic system and into the liver

Question 6

How is Vitamin D transported around the body?

Answer 6

Via lipoproteins

Question 7

Where is Vitamin D stored?

Answer 7

In adipose tissue, liver, and kidney

Question 8

How is Vitamin D excreted?

Answer 8

bile and feces

Little in urine

Question 9

Mechanism of action of Vitamin D in bone health

Answer 9

Vitamin D helps maintain blood calcium homeostasis:

• when blood calcium levels are low this causes the parathyroid hormone (PTH) and calcitriol to mobilize calcium from the bone
• Calcitriol stimulates intestinal calcium absorption
• Increases calcium reabsorption in the distal renal tubules

Question 10

Discuss deficiency symptoms of Vitamin D, how it is measured and when/why is it likely to occur

Answer 10

Symptoms: rickets in children and osteomalacia in adults

How it occurs: through less sun exposure and absorption of UVB light (season, location, dark skin, aging skin), liver and kidney disease, intestinal disease

How it is measured: measure serum 25-hydroxyvitamin D concentration as this reflects total body vitamin D reserves.

Question 11

How do you convert international units to the quantity of vitamin D in a supplement?

Answer 11

1UI = 0.025ug cholecalciferol or 0.005ug 25-hydrocholecalciferol (multiply Vit D3 by 40 to get international unit)

Question 12

What are the symptoms caused by excess consumption of vitamin D as a supplement?

Answer 12

• Over absorption of calcium leading to hypercalcemia, calcium deposit in kidney, joints, blood vessels, heart
• Can lead to bone demineralization via too much bone resorption and can be fatal in chronic excess

Question 13

Define Free radicals

Answer 13

a molecular that has one or more unpaired electrons and is therefore highly reactive.

Question 14

Define oxidative stress

Answer 14

An imbalance between pro and antioxidants in favour of prooxidants

Question 15

Define oxidative damage

Answer 15

Damage to lipids, proteins, and DNA produced by excess production of free radicals

Question 16

What is Redox Homeostasis

Answer 16

Balance between pro and antioxidants

Question 17

Define Antioxidants

Answer 17

a substance that donates an electron to free radicals inhibiting oxidation reactions

Question 18

What is the antioxidant capacity?

Answer 18

The antioxidant capacity defines the synergistic work between the endogenous and the exogenous, enzymatic and non-enzymatic antioxidant systems in keeping free radicals in equilibrium

Question 19

What is the free radical theory of aging?

Answer 19

The free radical theory of aging states that organisms age because cells accumulate free radical damage over time

Question 20

What are the endogenous sources of free radicals?

Answer 20

Endogenous: metabolic process requiring oxygen produce ROS; enzymatic oxidation, exercising, systemic oxidation, exercising, obesity.

Question 21

What are the exogenous sources of free radicals?

Answer 21

Exogenous: Radiation, dietary components prone to oxidation, smoking, cooking methods by-products, air and water pollution, exposure to pesticides, solvent, environmental toxins, and drugs.

Question 22

Describe the antioxidant defense system of the body

Answer 22

The antioxidant defense system is able to reduce the damage done by free radicals by either being electron donors and stabilizing the free radical or by deactivating free radicals activity by converting them into stable compounds.

Question 23

What is the role of the Enzymatic antioxidant system

Answer 23

deactivate free radicals by enzymatic activity/converting free radicals into stable products e.g. H2O, O2, H2 (neutralising or turning into stable products)

Question 24

What is the role of the non-Enzymatic antioxidant system

Answer 24

electron donors to stabilize free radicals to stop the chain reaction of free radicals

Question 25

What are the components of the Enzymatic antioxidant system and what are the dependant on

Answer 25

SOD1: Cu and Zn dependent 
SOD2: Mn dependent 
SOD3: Fe dependent 
Catalase: Fe 
GPx: Se

Question 26

What is the function of superoxide dismutase (SOD), catalase?

Answer 26

SOD: converts superoxide to hydrogen peroxide
Catalase: converts hydrogen peroxide to water and oxygen

Question 27

What are the components of the Non-Enzymatic antioxidant system and what are the dependant on

Answer 27

Phytochemicals: 
- exogenous: 
>activation of nrf2 
>Vitamins A, C, E: electron donors 
- Endogenous 
> Glutatione: electron donor 
> albumin 
> Bilrubin

Question 28

Outline the difference between water and fat soluble vitamins.

Answer 28

Fat soluble:

• absorbed into the lymphatic system first then blood
• transport via chylomicrons
• stored in cells associated with fat ( adipose tissue and liver)
• toxicity is likely
• periodic doses

Water soluble:

• absorbed straight into the blood
• transported freely in the CVS
• storage in water-filled parts of the body
• toxicity with supplements
• need frequent doses

Question 29

What is calcitriol?

Answer 29

The active form of Vitamin D