* Vitamin A deficiency *
Definition:
Vitamin A (called retinol in mammals) is a fatsoluble vitamin. The recommended dietary
allowance (RDA) for vitamin A is 1.0 mg/day
for the adult man and 0.8 mg/day for the adult
woman. Since beta-carotene is converted to
vitamin A in the body, the body's requirement
for vitamin A can be supplied entirely by betacarotene.
Sources:
The best sources of vitamin A are eggs, milk,
butter, liver, and fish, such as herring, sardines,
and tuna. Beef is a poor source of vitamin A.
Plants do not contain vitamin A, but they do
contain beta-carotene and other carotenoids.
The best sources of beta-carotene are darkgreen, orange, and yellow vegetables; spinach,
carrots, oranges, and sweet potatoes are
excellent examples. Cereals are poor sources
of beta-carotene.
* Vitamin A is called Retinol, Anticancer,
Antixerophthalmic.
* It is fat soluble, heat stable, destroyed by
oxidation or drying.
* The target tissue is retina, skin, bone, liver,
adrenal.
Vitamin A is used in:
1- Used in the eye, it is a component of the eye's
light-sensitive parts, containing rods and
cones, that allow for night-vision or for seeing
in dim-light circumstances.
2-Vitamin A (retinol) occurs in the rods. Another
form of Vitamin A, retinoic acid, is used in the
body for regulating the development of various
tissues, such as the cells of the skin, and the
lining of the lungs and intestines.
3-Vitamin A is important during embryological
development, since, without vitamin A, the
fertilized egg cannot develop into a fetus.
4- Boosts body‘s natural immunity in mouth,
respiratory, urinary tract ,thus resistant to
infection by vitamin A.
Definition of vitamin A deficiency:
Vitamin A deficiency exists when the
chronic failure to eat sufficient amounts
of vitamin A or beta-carotene results in
levels of blood-serum vitamin A that are
below a defined range. Beta-carotene is a
form of pre-vitamin A, which is readily
converted to vitamin A in the body.
Causes:
inadequate intake of foods high in vitamin A
(liver, kidney, butter, milk, cream, cheese, and
fortified margarine) or carotene, a precursor of
vitamin A found in dark green leafy vegetables
and yellow or orange fruits and vegetables.
(Six mg of beta-carotene is equal to 1 mg of
vitamin A.) The recommended daily allowance
for vitamin A is 1 mg for adult males and 0.8
mg for adult females.
Less common causes include:
* Malabsorption due to celiac disease, sprue,
cirrhosis, obstructive jaundice, cystic fibrosis,
giardiasis, or habitual use of mineral oil as a
laxative
* Massive urinary excretion caused by cancer,
tuberculosis, pneumonia, nephritis, or urinary
tract infection
* Decreased storage and transport of vitamin A
due to hepatic disease.
Signs and symptoms :
1-The first symptom of vitamin A
deficiency is night blindness (nyctalopia)
degeneration of retina , which usually
becomes apparent when the patient enters
a dark place or is caught in the glare of
oncoming headlights while driving at
night.
2- xerophthalmia, or drying of the conjunctivas,
with development of gray plaques (Bitot’s
spots); if unchecked, perforation, scarring, and
blindness may result.
3- keratinization of epithelial tissue causes dry,
scaly skin; follicular hyperkeratosis; and
shrinking and hardening of the mucous
membranes, possibly leading to infections of
the eyes and the respiratory or genitourinary
tract.
4- An infant with severe vitamin A deficiency
shows signs of failure to thrive and apathy,
along with dry skin and corneal changes,
which can lead to ulceration and rapid
destruction of the cornea.
5-Retarded growth.
Diagnosis:
- Dietary history and typical ocular lesions suggest
vitamin A deficiency. Carotene levels less than 40
mcg/dl also suggest vitamin A deficiency, but they
vary with seasonal ingestion of fruits and vegetables.
- Confirming diagnosis A serum level of vitamin A that
falls below 10 mcg/dl confirms the diagnosis. Levels
between 10 and 19 mcg/dl are also considered low
but the patient isn’t likely to have developed
significant symptoms.
Treatment:
-Mild conjunctival changes or night blindness
requires vitamin A replacement in the form of
cod liver oil or halibut liver oil.
-Acute deficiency requires aqueous vitamin A
solution I.M., especially when corneal changes
have occurred. Therapy for underlying biliary
obstruction consists of administration of bile
salts; for pancreatic insufficiency, pancreatin.
* Dry skin responds well to cream-based or petroleumbased products.
* In patients with chronic malabsorption of fat-soluble
vitamins, and in those with low dietary intake,
prevention of vitamin A deficiency requires aqueous
I.V. supplements or an oral water-miscible
preparation.
*Vitamin A deficiency can be prevented or treated by
taking vitamin supplements or by getting injections of
the vitamin.
* The specific doses given are oral
retinyl palmitate (110 mg), retinyl
acetate (66 mg), or injected retinyl
palmitate (55 mg) administered on
each of two successive days, and
once a few weeks later if symptoms
are not relieved.
Supervised by:
Dr. Kdriyah EL-Deeb.
Prepared by:
* Maryam AL-Khawajah.
* Faheemah AL-Awami.