Vitamin C

Question 1

Food sources

Answer 1

Oranges, pineapple, lemons, pepper, onions, mangoes, potato, grapefruit, tomato

Question 2

RDA:

Answer 2

60 mg/day for females and 90 mg/day for males

Question 3

Absorption

Answer 3

By both active transport and simple diffusion.

Question 4

Functions

Answer 4

• Required for formation of collagen from procollagen form
• Sructural component of blood vessels, tendons, ligaments, and bones.
• Synthesis of norepinephrine, carnitine
• Cholesterol metabolism to bile acids
• Antioxidant action

Question 5

Importance of carnitine

Answer 5

Transport of fatty acid from the cytoplasm into the mitochondria of cardiac and skeletal muscle, where the fat is converted to energy by beta oxidation.

Question 6

Describe the antioxidant action of Vitamin C

Answer 6

Readily donating electrons to break the chain reaction in lipid peroxidation process.

Question 7

Vitamin C’s antioxidant action is enhanced by…

Answer 7

…its ability to regenerate other antioxidants such as tocopherol and glutathione from oxidized form

Question 8

How does Vitamin C deficiency cause scurvy?

Answer 8

It is a cofactor in up to 8 enzymatic reactions, including several collagen synthesis reactions, that when dysfunctional, causes the most severe symptoms of scurvy.

Question 9

Scurvy symptoms include

Answer 9

• bleeding and bruising easily
• hair and tooth loss
• joint pain and swelling

Question 10

Scurvy symptoms appear to be related to

Answer 10

the weakening of blood vessels, connective tissue, and bones

Question 11

Name one early symptom of scurvy

Answer 11

Fatigue

Question 12

Early symptoms of scurvy like fatigue may result from

Answer 12

diminished levels of carnitine, which is needed to derive energy from fat, or from decreased synthesis of norepinephrine

Question 13

Therapeutic uses of vitamin C

Answer 13

Prevention and management of vitamin C deficiency

Question 14

Toxicity of Vitamin C

Answer 14

• Gastrointestinal disturbances (e.g. diarrhoea)

* May increase risk of kidney stones due to vit C metabolite, oxalate buildup.

Question 15

Vitamin C and warfarin

Answer 15

Reduces effect

Question 16

Oestrogen containing contraceptives and Vitamin C

Answer 16

Lower plasma and leukocytes vitamin C levels

Question 17

Aspirin and Vitamin C

Answer 17

Aspirin can lower vitamin C levels if taken frequently; primarily by increasing urinary excretion of vitamin C.

Question 18

High doses of vitamin C interferes with interpretation of which laboratory tests

Answer 18

Serum bilirubin and creatinine, and the guaiac assay for occult blood