Vitamin C

Question 1

Function

Answer 1

Antioxidant (reducing agent).

Reduces mineral cofactors: norepinephrine synthesis, collagen synthesis, etc.

Reverses oxidation. Electron donator.

Question 2

CVD

Answer 2

Inhibits LDL oxidation which diminishes plaque formation.

Question 3

Interaction with iron

Answer 3

Enhances absorption of non heme iron.

Keeps iron reduced in collagen and carnitine synthesis.

Question 4

Excretion

Answer 4

Urine as ascorbic or dehydroascorbic acid.

Oxidation to dehydroascorbic acid occurs in liver.

Question 5

RDA

Answer 5

90 mg men

75 mg women

Question 6

Deficiency

Answer 6

Scurvy.

Question 7

Toxicity

Answer 7

2g
Abdominal pain and osmotic diarrhea due to unabsorbed vitamin C in the GI.

Risk of kidney stones in renal PT and iron toxicity in individuals with iron metabolism problems.

Question 8

Assessment

Answer 8

Leukocytes reflect body stores.

Serum.

Question 9

Sources

Answer 9

Red peppers and papaya. OJ.

100% absorption at intake

Question 10

Transporters

Answer 10

Transported through blood in free form.

Ascorbic acid: sodium dependent transporter (SVCT1 and SVCT2)

Dehydroascorbic acid: oxidized in GI then transported via glucose transporters (GLUT1 and GLUT3). Competes with glucose.

Question 11

Glutathione (GSH)

Answer 11

Reduces DHA back to ascorbic acid.
Spares vitamin C.

Recycles.
Uses niacin.

Question 12

Gulonolactone oxidase

Answer 12

Last enzyme in vitamin C synthetic pathway. Polymorphism.