Scurvy results from a deficiency of Ascorbic Acid (Vitamin C).
Biochemical functions promoted:
The main biological role of vitamin C
appears to be as a reducing agent in
a number of important hydroxylation
reactions in the body.
Ascorbic acid is required for the
hydroxylation of proline and lysine
on the polypeptide chains of protocollagen.
Without the hydroxylation of these amino acids,
the protocollagen is unable to properly
cross-link into normal collagen fibrils.
Collagen is the major connective tissue
in the body. It is also a component of
the organic matrix for bone tissue as
well as a component of the ground substance
surrounding capillary walls.
Vitamin C is required for the hydroxylation
reactions in the synthesis of steroids,
and epinephrine. The concentration of
ascorbic acid is high in the adrenal gland
especially during periods of stress.
Ascorbic acid acts as a reducing agent
in non-enzymatic reactions:
e.g., it aids in absorption of iron
by reducing it to ferrous state in the stomach,
it spares vitamin A, vitamin E
and some B vitamins by protecting them
from oxidation, and it enhances the
utilization of folic acid by aiding
the conversion of folate to tetrahydrofolate.
Deficiency:
Most of the symptoms of vitamin C deficiency
can be directly related to its metabolic roles.
Symptoms of mild vitamin C deficiency include
ecchymoses (large areas of bleeding into the skin),
corkscrew hairs, and the formation of petechiae
(small pinpoint hemorrhages in the skin)
due to increased capillary fragility.
These symptoms can be explained by
weaken collagen fibrils.
Severe deficiency results in scurvy.
Scurvy itself is associated with decreased
wound healing, osteoporosis, hemorrhaging,
bleeding into the skin (petichiae and ecchymoses),
anemia, and friable bleeding gums with
loosened teeth (gingivitis).
A child with scurvy may prefer to lie
on its back with legs and arms layed out
in the so called ``frog position''
because of pain in joints.
The osteoporosis results from the inability
to maintain organic matrix of the bone
followed by demineralization.
The anemia results from the extensive
hemorrhaging coupled with defects in
iron absorption and folate activation.
Sources and requirement:
Fruits, especially citrus fruits,
tomatoes and green vegetables are
rich sources of vitamin C.
An intake of 30 mg per day is sufficient
to replenish the quantity of ascorbic acid
metabolized daily.
An intake of 45 mg per day maintains
an adequate body pool.
There is some uncertainty over the need
for vitamin C in periods of stress and
trauma. Smoking has been shown to cause
lower serum vitamin C.
Aspirin appears to block uptake
of vitamin C by platelets.
Oral contraceptives and corticosteriods
also lower serum levels of vitamin C.
The possibility of marginal C deficiencies
should be considered with any patient
under these circumstances.
Large doses of vitamin C (0.5 to 5 gm per day)
have been claimed to reduce the discomfort
caused by the common cold.
This claim is partly substantiated in a few
double-blind studies.
The number of colds experienced by
vitamin C supplemented groups appears to be
the same as the control groups,
but the severity and the duration
of the colds were significantly decreased.
Megadoses of vitamin C have not been shown
to be harmful except for the potential
of formation of oxalate kidney stones in
predisposed individuals.
Oxalate is a major metabolite of ascorbic acid.
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