Human Nutrition 3(3+0)

Lesson 31 : Vitamin C

Physiological and biochemical functions

Ascorbic acid is essential for:

 

1. Formation of collagen and intercellular cementing substance
   Ascorbic acid is essential for the hydroxylation of proline into hydroxyproline for synthesis of collagen. Ascorbic acid is also concerned in the formation of intercellular cement substance in the capillaries, teeth, bone etc. In ascorbic acid deficiency, these are not formed fully.


2. Metabolism of tyrosine
   When tyrosine is fed to scorbutic guinea pigs in quantities of 0.5gm, the animals excrete homogentisic acid, p-hydroxy phenyl pyruvic acid and P-hydroxy phenyl lactic acid. When ascorbic acid is administered the excretion of the above metabolites ceases. This indicates that ascorbic acids is involved in the metabolism of tyrosine.


3. Absorption of iron and incorporation of plasma iron in ferritin:
   Ascorbic acid acts as a reducing agent and helps in conversion of ferric iron to ferrous state in the intestines and thus helps in the absorption of iron. For the incorporation of plasma iron in the tissues as ferritin, ascorbic acid and ATP are required.


4. Hydroxylation of aromatic nuclei:
   Ascorbic acid plays an important role in:
• hydroxylation of deoxycorticosterone
• hydroxylation of tryptophan to 5-hydroxytryptophan
• Conversion of phenylalanine to tyrosine.


5. Bone formation:
   Vitamin C is necessary for formation of normal gel like for proper bone ossification.


6. Adrenal cortex function
   Ascorbic acid is involved in the synthesis of cortical hormones. In scorbutic guinea pigs, hypertrophy of adrenal cortex glands occurs.


7. Electron transport:
   Ascorbic acid is involved in the electron transport.


8. Healthy immune system:
   Vitamin C promotes a healthy immune system and helps in wound healing of wounds.