VITAMIN C
VITAMIN C
V
and those with malabsorption or severe
alcohol dependence. Riboflavin defi-
ciency may also occur as a result of
serious illness, surgery, or injury. Pro-
longed deficiency may cause soreness
of the tongue and the corners of the
mouth,
and eye disorders such as
amblyopia
and
photophobia.
Excessive
intake of riboflavin is not known to have
any harmful effects.
Niacin plays an essential role in the
activities of various enzymes involved in
the metabolism of carbohydrates and
fats, the functioning of the nervous and
digestive systems, the manufacture of
sex hormones, and the maintenance of
healthy skin. The main dietary sources
are liver, lean meat, fish, nuts, and dried
beans. Niacin can be made in the body
from tryptophan (an
amino acid
). Most
cases of deficiency are due to malab-
sorption disorders or to severe alcohol
dependence. Prolonged niacin deficiency
causes
pellagra
. Excessive intake is not
known to cause harmful effects.
Pantothenic acid is essential for the
activities of various enzymes involved in
the metabolism of carbohydrates and
fats, the manufacture of
corticosteroids
and
sex hormones,
the utilization of
other vitamins, the functioning of the
nervous system and
adrenal glands
, and
growth and development. It is present
in almost all vegetables, cereals, and
animal foods. Deficiency of pantothenic
acid usually occurs as a result of mal-
absorption or alcoholism, but may also
occur after severe illness, surgery, or
injury.
The
effects
include
fatigue,
headache,
nausea,
abdominal
pain,
numbness and tingling, muscle cramps,
and susceptibility to respiratory in-
fections. In severe cases, a
peptic ulcer
may develop. Excessive intake has no
known harmful effects.
Pyridoxine aids the activities of vari-
ous enzymes and hormones involved in
the utilization of carbohydrates, fats,
and proteins, in the manufacture of red
blood cells and antibodies, in the func-
tioning of the digestive and nervous
systems, and in the maintenance of
healthy skin. Dietary sources are liver,
chicken, pork, fish, whole grains, wheat-
germ, bananas, potatoes, and dried
beans. Pyridoxine is also manufactured
by intestinal bacteria. People who are
susceptible to pyridoxine
deficiency
include elderly people who have a poor
diet, those with malabsorption or severe
alcohol dependence, or those who are
taking certain drugs (including
penicil-
lamine
and
isoniazid).
Deficiency may
cause weakness, irritability, depression,
skin disorders, inflammation of the
mouth and tongue,
anaemia
, and, in
infants,
seizures
. In very large amounts,
pyridoxine may cause
neuritis
.
Biotin is essential for the activities of
various enzymes involved in the break-
down of fatty acids and carbohydrates
and for the excretion of the waste prod-
ucts of protein breakdown. It is present
in many foods, especially liver, peanuts,
dried beans,
egg yolk,
mushrooms,
bananas, grapefruit, and watermelon.
Biotin is also manufactured by bacteria
in the intestines. Deficiency may occur
during prolonged treatment with
antibi-
otics
or
sulphonamide drugs
. Symptoms
are weakness, tiredness, poor appetite,
hair loss, depression, inflammation of
the tongue,
and eczema.
Excessive
intake has no known harmful effects.
Folic acid is vital for various enzymes
involved in the manufacture of
nucleic
acids
and consequently for growth and
reproduction, the production of red
blood cells, and the functioning of the
nervous system. Sources include green
vegetables, mushrooms, liver, nuts, dried
beans, peas, egg yolk, and wholemeal
bread. Mild deficiency is common, but
can usually be corrected by increasing
dietary intake. More severe deficiency
may occur during pregnancy or breast-
feeding, in premature or low-birthweight
infants, in people undergoing
dialysis
,
in people with certain blood disorders,
psoriasis
, malabsorption, or alcohol de-
pendence, and in people taking certain
drugs. The main effects include anae-
mia, sores around the mouth, and, in
children, poor growth. Folic acid sup-
plements taken just before conception,
and for the first
12
weeks of pregnancy,
have been shown to reduce the risk of
a
neural tube defect.
vitamin C A water-soluble
vitamin
that
plays an essential role in the activities
588
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