2. Introduction
Vitamin A is a fat soluble vitamin
Active forms of vitamin A are the oxidation
products of retinol, all-trans-retinal and all-
trans-retinoic acid.
Carotenoids are provitamin A substances
found in vegetables.
3. Absorption & Metabolism
• Absorbed as an ester, as part of chylomicrons.
• Absorption is affected by impaired chylomicron formation and
altered fat absorption.
• Retinol is absorbed as free alcohol by an active transport system
containing a cellular retinol binding protein (RBP) II.
• The yellow beta-carotene requires bile salts for absorption and is
converted to vitamin A in the intestines.
• Once absorbed, vitamin A is stored in the liver as retinyl
palmitate.
• The liver releases vitamin A to the circulation, bound to RBP and
transthyretin.
4. Sources
• Animal foods: Oils extracted from shark and cod liver, eggs,
butter, cheese etc
• Plant foods: Carrots, dark-green leafy vegetables, Squash,
oranges and tomatoes.
• Many processed foods and infant formulas are fortified with
preformed vitamin A.
Eg: Vanaspati
5. Recommended daily allowance
Infants 300- 400 µg;
Children 400-600 µg;
Adolescents 750 µg.
✓ 1 µg retinol = 3.3 international units (IU) of vit A; = 12 µg beta-
carotene.
• Hence, 30 mg retinol = 100,000 IU
6. Physiological functions
Maintenance of vision, especially night vision
Maintenance of epithelial tissues
Differentiation of various tissues, particularly during
reproduction & gestation by regulating gene
expression.
7.
8. Vitamin A deficiency
Signs of Vitamin A deficiency are predominantly ocular.
Defective dark adaptation is a characteristic early clinical feature,
resulting in night blindness.
• The syndrome of vitamin A deficiency in infants consists of Night
blindness, Conjuctival xerosis, Bitot spots, Corneal xerosis,
keratomalacia,
• Extra ocular manifestations- Hyperkeratosis, growth failure,
anorexia..
• The deficiency disease in humans was called xerophthalmia (dry
eyes) because of the prominence of the eye signs.
• Diets consisting of polished rice with little or no vegetables or fruits
11. Conjunctival xerosis
One or more patches of dry, lustreless, non-wettable
conjunctiva
Described as “emerging like sand banks at receding
tide” when child ceases to cry
14. Keratomalacia
Stroma defects occur due to necrosis & takes several
forms
Small ulcers occur peripherally [1-3 mm] ; circular with
steep margins
and sharply demarcated
Large ulcers- extend centrally or
involve entire cornea
15. Diagnosis
Clinical diagnosis : from symptoms and signs of xerophthalmia
Confirmation of diagnosis : serum retinol levels
Mild leukopenia and serum retinol level of 15 µg/dl or less
(normal 20 to 80 µg/dl).
Clouding of the cornea in a child with vitamin A deficiency is an
emergency and requires parenteral administration of 50,000 IU to
100,000 IU (15 to 30 mg retinol).
16. Treatment
Oral vitamin A at a dose of-
✓ 50,000 IU in children aged <6 months
✓ 1,00,000 IU in children aged 6-12 months
✓ 2,00,000 IU in children aged > 1 year
• The same dose is repeated next day and 4 weeks later.
• Alternatively, parenteral water-soluble preparation are administered in
children with persistent vomiting or severe malabsorption (parenteral
dose is half the oral dose for children above 6-12 months and 75% in <6
months old).
• Local treatment with antibiotic drops and ointment and padding of the
eyes enhances healing.
17. Prevention
National vitamin A prophylaxis
programme,Sponsored by Ministry of Health and
Family Welfare
Children between 1-5 years age were given oral
doses of 200,000 IU every six months.
Inadequate coverage
Currently, it is given only to children under 3 years
age, since they are at greater risk.
Administration of first two doses is linked with
routine immunisation to improve coverage.
18. A dose of 100,000 IU is given with measles vaccine at 9 months
200,000 IU with the DPT booster at 15-18 months.
Then one dose every 6 months upto the age of 5 years.
Route of administration is oral.
In endemic areas 3 more doses are administered at 24, 30 and 36
months.
Dietary improvement is necessary to prevent vitamin A
deficiency.
Children with measles and severe malnutrition should receive
vitamin A at 100,000 IU if <1-yr-old and 200,000 IU if older.
