Relating To Vitamins

Question 1

Vitamin D

Answer 1

Comes from sunlight

Responsible for the maturation and regulation of immune cells

Question 2

Vitamin B12

Answer 2

Lack of impairs cell division, particularly in the rapidly dividing blood cells of the bone marrow and intestinal mucosa leading to megaloblastic anaemia

Question 3

Which vitamin is principally important in the conversion of tryptophan to serotonin?

Answer 3

B6

Question 4

Symptoms of lack of B2

Answer 4

Lesions of the margins of the lips and mouth corners; painful desquamation (shedding of outermost layer - geographical tongue) of the tongue, scaly dermatitis especially around the mouth and nose

Question 5

What substances/food adversely impact calcium absorption?

Answer 5

Oxalic acid - forms insoluable calcium oxalate in the digestive track and decreases ca absorption

Phytic acid or phytate, a phosphorous compound found in outer husk of grains combines with ca forming calcium phytate which cannot be absorbed

Dietary fibre may decrease absorption but only in higher amounts

Fat malabsorption - ca forms fatty acids-ca soaps, which decreases absorption of ca

Low Vit D intake or and inadequate sunlight exposure reduces ca absorption

Question 6

Importance of zinc levels in relation to Vit A?

Answer 6

Zinc is required to make retinol binding protein.
RBP moves Vit A from liver storage to tissues for utilisation
People displaying Vit A deficiency may sufficient levels of Vit A but inadequate zinc levels to move the Vit A to where it is required.

Question 7

Why are alcoholics prone to B1 (Thiamine) deficiency?

Answer 7

Thiamine is absorbed in the small intestine by active transport that is inhibited by alcohol.

Question 8

What is the full digestive process for proper Vit B12 absorption?

Answer 8

Vit B12 requires adequate stomach acid.

It is attached to a protein that must be removed in the stomach by gastric acid and an enzyme called pepsin.

Once in the small intestine, a substance called intrinsic factor (produced in the stomach) takes B12 from the binding protein and allows it to be absorbed into the blood.

Question 9

What are vitamins?

Answer 9

Vitamins are organic compounds required by the body in small amounts for normal metabolic functioning; they are essential i.e. body cannot manufacture them.

Question 10

Vitamins - what can and cannot they do?

Answer 10

cannot be converted into energy but some are essential cofactors in energy production (B5 = coA synthesis; Vit B6 for NAD+ or B2 into FAD)

Question 11

What is transamination?

Answer 11

the transfer of an amino group from one molecule to another, especially from an amino acid to a keto acid.

Question 12

What are the stages of vitamin insufficiency?

Answer 12

1. subclinical insufficiency
   - preliminary reduction of nutrient stores - no symptom
   - reduction in enzyme activity through lack of vitamin co-enzymes
   - physiological impairment that manifests as adverse behavioural effects
2. End-stage manifestations of nutrient inadequacy
   - classical deficiency syndrome
   - terminal tissue pathology.

Question 13

What is Xerophthalmia?

Answer 13

abnormal dryness of the conjunctiva and cornea of the eye, with inflammation and ridge formation, typically associated with vitamin A deficiency.

Question 14

How do carotenoids get converted to retinal?

Answer 14

by the enzyme beta-carotene-15,15’dioxygenase found in the intestinal epithelium and in the liver; activity and efficiency of this enzyme is subject genetic variation (in a 2009 study 42% of caucasian women have reduced ability to convert by 57%).

Question 15

Where are retinols and carotenoids absorbed?

Answer 15

they are absorbed from the small intestine dissolved in fat

Question 16

what is the difference in absorption rates between retinols and carotenoids??

Answer 16

70 - 90% of retinol is absorbed (hence danger of toxicity); absorption of carotenoids varies between 5% and 60%.

Question 17

What is the importance of Zinc in relation to Vitamin A?

Answer 17

Zinc is needed to make retinol binding protein which moves vitamin A from liver storage to tissues for utilisation.

Question 18

What vitamin modulates iron metabolism?

Answer 18

Vitamin A; inadequate amounts lead to defective red blood cell formation and issues with iron storage and release (more research need to elucidate the mechanism required); anaemia improves when both iron and vitamin a levels are address together.

Question 19

Why is Vitamin A important for bone health?

Answer 19

Retinoids are vital for the synthesis of certain glycoproteins that support normal bone development. Retinoic acid is essential for the normal responses to Vitamin D and calcium. too much Vit A has been linked to increased risk of osteoporosis (Sweden).

Question 20

What are the different compounds of Vitamin A?

Answer 20

pre-formed (retinol oxidised to retinal oxidised to retinoic acid; provitamin A = variety of carotenes

Question 21

what is cryptoxanthin?

Answer 21

an important vitamin A source

Question 22

different retinoids impact on what body parts?

Answer 22

retinol (alcohol) - health of retine
retinal (aldehyde) - vision - rod and cones and reproduction
retinoic acid - growth and differentiation of epithelial cells

Question 23

How does Vitamin A support vision?

Answer 23

the light sensitive pigment in the retina is retinal bound to the protein opsin. when a photon of light hits this complex, the retinal initiates a chain of events that result in the transmission of an impulse up the optic nerve.

Question 24

What group of people should not be given beta carotene supplements?

Answer 24

smokers and asbestos workers as high levels of vit A accelerate the progress of lung cancer.

Question 25

what are the different forms of Vitamin D?

Answer 25

D2 ergocalciferol (plants)
D3 cholecalciferol (meat)
in liver becomes calcidiol (inactive)
kidney turns in into calcitriol (active)

Question 26

how does the body turn UV light into Vit D?

Answer 26

plants contain ergosterol. exposure of ergosterol to UV results into ergocalciferol (D2).
animals convert cholesterol to 7-dehydrocholesterol. exposure of this to UV light results in the conversion in the skin to cholecalciferol (D3)
both inactive.

Question 27

What does Vitamin D increase intestinal absorption of?

Answer 27

calcium and phosphorus

Question 28

how is vitamin D metabolism regulated?

Answer 28

Calcitriol (through negative feedback mechanism) acts to reduce it’s own synthesis and PTH that gets secreted if there is a fall in blood calcium. acts to increase Vit D synthesis and causes the release of calcium from the bone.

Question 29

How do the potential anti-cancer effects of Vit D work?

Answer 29

by controlling of cell proliferation: inhibiting of cell proliferation and stimulating cell differentiation and the inhibition of angiogenesis.

Question 30

How does Vit D enhance the immune system?

Answer 30

inhibit the development of autoimmunity; decreases the inflammatory response to viral infections without jeopardising viral clearance;

Question 31

what is the difference between rickets and osteomalacia?

Answer 31

Rickets is poor mineralisation of bones in children and teenagers whereas osteomalacia results from demineralisation of bone (several pregnancies without sun exposure or elderly)

Question 32

What nutrients rejuvenate oxidised Vit E?

Answer 32

Vitamin C and Selenium as part of the enzyme gluatathione peroxidase.

Question 33

How do tocotrienols lower cholesterol?

Answer 33

they act to reduce the activity of HMG CoA reductase, the enzyme essential for cholesterol synthesis. this is mimicked by statins.