Fat-soluble Vitamins

Question 1

How was Vitamin A discovered?

Answer 1

Ancient Egyptians recognized that night blindness could be treated by consumption of liver. In the late 1920s, through the efforts of a Swiss scientist, the fat-soluble compound in liver was isolated and termed vitamin A

Question 2

Vitamin A is a subclass of a family of lipid-soluble compounds called ______________

Answer 2

Retinoic acids

Question 3

What are the 2 main forms of vitamin A?

Answer 3

Provitamin A carotenoids (e.g. beta-carotene, alpha-carotene, beta-cryptoxanthin)

Preformed vitamin A (Retinols, retinoic acid, retinyl esters)

Question 4

What are the common food sources of PREFORMED vitamin A?

Answer 4

Liver, kidney, egg yolk, butter

Question 5

What are the common food sources of Provitamin A?

Answer 5

Green leafy vegetables, sweet potatoes, carrots

Question 6

Which type of vitamin A tends to cause toxicity?

Answer 6

Preformed vitamin A.
They come from animal sources or supplements.

Question 7

What is the role of vitamin A?

Answer 7

Vision: Prevent xerophthalmia (Corneal and conjunctival abnormalities)

Cellular differentiation and integrity in the eye: All the cells in the conjunctiva and the retina have retinol-binding proteins (RBPs), suggesting the dependence of these tissues on retinoic acid.

Question 8

What are the sources of vitamin D?

Answer 8

Fatty fish, eggs, milk, breakfast cereal, UV exposure

Question 9

What causes vitamin D deficiency and resistance?

Answer 9

Unusually low sun exposure and malabsorption of food

Question 10

How does Vitamin D intoxication arise?

Answer 10

Due to hypercalcemia (confusion, polyuria, polydipsia, anorexia, vomiting, muscle weakness)

Question 11

Vitamin D
- Name
- Major form of vitamin D in circulation
- MOA

Answer 11

Calciferol (4-ringed cholesterol backbone)

25 hydroxyvitamin D (25[OH]D)

Promote enterocyte differentiation and intestinal absorption of calcium

Suppression of PTH release from parathyroid to regulate osteoblast function

Question 12

Vitamin E
- Name
- Sources

Answer 12

Tocopherol (Alpha)

Almonds, vegetables, oils, cereals

Question 13

What are the forms of vitamin E?

Answer 13

Primary Bioactive form: Alpha-tocopherol

Other naturally occurring vitamin E
- Beta, Gamma, Delta Tocopherol
- Alpha, Beta, Gamma, Delta Tocotrienol

Question 14

Vitamin E MOA

Answer 14

Free radical scavenger (Antioxidant)

Protects polyunsaturated fatty acids found in the structural component of the cell membrane from peroxidation

Question 15

Why does gamma tocopherol have important adverse effects?

Answer 15

Gamma tocopherol is associated with alterations in the level of inflammation and airway hyperresponsiveness although it may also oppose neutrophil-mediated inflammation

Question 16

What are the potential benefits of vitamin E supplementation?

Answer 16

Non-alcoholic fatty liver disease: Improved aminotransferase abnormalities

Age-related macular degeneration: Delayed progression of the disease when supplemented together with zinc

Question 17

Why have theoretical concerns been raised with regards to vitamin E supplementation in operative bleeding?

Answer 17

Vitamin E inhibits platelet aggregation and adhesion in vitro