Vitamin C

VITAMIN-C- ASCORBIC ACID
  • Not synthesized in humans, the guinea pig, bats, passeriform birds, and most fishes, due to deficiency of gulonolactone oxidase.
  • In animals: synthesized from the uronic acid pathway.
  • Vitamin C is excreted in urine.
  • Active form: ascorbic acid.
  • Good dietary sources: Amla, citrus fruits, green vegetables (especially broccoli), tomatoes, and potatoes.
  1. Amla(Indian gooseberry) has the highest amount of vitamin C .
  2. Milk is a poor source of Vitamin C.
  3. Vitamin C would most likely become deficient in a person who develops a completely carnivorous lifestyle.
  • RDA: 90 mg/d for males and 75 mg/d for females.
  • Exhaustive treatise on scurvy was published by James Lind.
  1. James lind is known for prevention of scurvy by fruits.
BIOCHEMICAL FUNCTIONS OF VITAMIN C
  • Collagen formation : Vitamin C plays the role of a coenzyme in hydroxylation of proline and lysine while protocollagen is converted to collagen (i.e. post-translational modification).
  1. The hydroxylation reaction is catalysed by lysyl hydroxylase (for lysine) and prolyl hydroxylase (for proline). This reaction is dependent on vitamin C, molecular oxygen and a-ketoglutarate
  • Bone formation : Bone tissues possess organic matrix, collagen and the inorganic calcium, phosphate etc. Vitamin C is required for bone formation.
  • lron and hemoglobin metabolism :
  1. Ascorbic acid enhances iron absorption by keeping it in the ferrous form. This is due to the reducing property of vitamin C. lt helps in the formation of ferritin (storage form of iron) and
  2. mobilization of iron from ferritin.Vitamin C is useful in the reconversion of methemoglobin to hemoglobin.The degradation of hemoglobin to bile pigments requires ascorbic acid.
  • Tryptophan metabolism
  • Tyrosine metabolism,
  • Conversion of dopamine to norepinephrine 
  • Folic acid metabolism
  • Peptide hormone synthesis
  • Synthesis of corticosteroid hormones :
  • lt is believed that vitamin C is necessary for the hydroxylation reactions in the synthesis of corticosteroid hormones.
  • lmmunological function : Vitamin C enhances the synthesis of immunoglobulins (antibodies) and increases the phagocytic action of leucocytes.
  • Preventive action on chronic diseases:As an antioxidant, vitamin C reduces the risk of cancer, cataract, and coronary heart diseases.
  • Proline hydroxylase is required in formation of osteocalcin and the C1q component of complement.
  • Vitamin K-dependent protease that hydrolyzes activated factor V in the blood-clotting cascade.
  • Reducing agent in several different reactions.
DEFICIENCY OF VITAMIN C- SCURVY
• Scurvy: first disease identified due to dietary deficiency.
• Primary metabolic bone disorder in scurvy is decreased osteoid matrix formation.
Clinical features

  • Swollen gums which bleed easily
  • Perifollicular and petechial hemorrhages 
  • Ecchymoses, Hemarthrosis 
  • GI bleeding 
  • Anemia 
  • Poor wound healing 
  • Coiled hairs
  • Bowing of legs
  • Pseudoparalysis.
  • Hyperkeratosis
Radiological features
  • Most commonly around knee
  • Pencil thin cortex Trummer field zone(metaphyseal lucency)
  • Frenkel white line
  • Pelkan spur(lateral extension of white line)
  • Wimberger sign(ringed epiphysis): Definitive sign.
  • Zone of rarefaction below white line
  • Cortical spur
  • Epiphyseal separation
  • Metaphyseal porosis
  • Metaphyseal infarction
  • Metaphyseal calcification
Exam Question of:
  • Pelkan spur’ is a radiological feature of Scurvy.
  • Bowing of legs is seen in Scurvy.
  • Radiological signs of scurvy are Winberger sign,Trimmerfeld zone,Frenkel's line ,Pelican spur, Bony thickening,Metaphyseal porosis, Metapyseal infarction, Metaphyseal calcification ,Epiphyseal separation,Cortical spur
  • Vitamin C is excreted in urine.
  • Vitamin C is required in proper synthesis of collagen.
  • Amla(Indian gooseberry) has the highest amount of vitamin C .
  • Primary metabolic bone disorder in scurvy is decreased osteoid matrix formation.
  • Vitamin C would most likely become deficient in a person who develops a completely carnivorous lifestyle.
  • Exhaustive treatise on scurvy was published by James Lind.
  • Vitamin C is required for hydroxyproline to proline conversion.
  • In vitamin C deficiency, post translational modification of Lysine is defective.
  • Vitamin C increases absorption of oral iron.
  • A six month old infant fed totally on cow's milk has been brought with bleeding spots, anaemia, fever and generalised tenderness. On examination, there were swelling in both the lower extremities and the blood count was normal. The most likely diagnosis is Scurvy.
  • Pseudoparalysis in an infant is suggestive of vitamin C deficiency.
  • Boy who refuses to eat fruit comes with knee swelling and hematoma, deficiency of vitamin C is suspected .
  • Definitive sign of scurvy in X-ray is Ringed epiphysis (Wimburger sign).
  • James lind is known for prevention of scurvy by fruits.
  • Milk is a poor source of Vitamin C.
  • The daily requirement of Vitamin C is 70 mg.
  • Vitamin C deficiency causes Scurvy.
  • A 78 year old man who lives alone and prepares his own food is found to have ecchymotic patches over posterior aspect of his lower extremities. He has haemorrhagic areas around hair follicles, hair are fragmented and splinter haemorrhages are present in nail beds and several hematomas are present in the muscles of arms and legs. PT and CT are normal. This clinical syndrome is most
  • likely due to Vitamin C deficiency .
  • Subperiosteal hematomas with tenderness,Gingival bleeding,Ecchymosis of lower limbs, hyperkeratosis are the manifestations of Scurvy.
  • Biochemical reactions where vitamin C is required are Posttranslational modification , Synthesis of epinephrine ,Tyrosine metabolism.
  • Most important vitamin, which promotes wound healing is Vitamin C.
  • Vitamin C acts as a reducing agent.

Don't Forget to Solve all the previous Year Question asked on Vitamin C