A quick review about vitamin A - presentation by Dr.Dhivya

1. -T.DHIVYA
VITAMIN-A

2. CONTENTS
• Introduction
• Vitamin A –chemistry
• Sources
• Requirement
• Absorption
• Physiological actions
• Deficiency manifestations
• Risk group
• Acute poisoning
• Treatment
• Immunization
• summary

3. What are vitamins?
• Vitamins are non energy yielding organic
substances that are essential for several
enzymatic functions in human metabolism.
• Nutrients that our body doesn’t make on its
own.Thus we must obtain them from the foods
we eat,or via vitamin supplements.

4. History
• Discovery –casimir funk
• Vital+amine.
• Earlier identified ones had amino groups,
• It was later realized that only a few of them are
amines.
• The term vitamin continued without the final letter
“e”.

5. Classification

6. VITAMIN A

7. Introduction
• A fat soluble vitamin.
• Present only in foods of animal origin.
• Its provitamins carotenes are found in plants.
• Retinol,retinal,retinoic acid are called vitamers
(anologs) of vitamin A.
• Retinol –one of the most active and usable
forms.

8. Chemistry
1. Retinol (vitamin A1)
- It is an alcohol containing beta-ionone ring.
- The side chain has 2 isoprenoid units,4 double
bonds and 1 hydroxyl groups.
- Retinyl esters with long chain fatty acids-in
animal tissues.

9. Contd….
2.Retinoic acid
-This is produced by the oxidation of retinal.
- Retinoic acid cannot give rise to retinol or
retinal.
- Retinol Retinal Retinoic acid.

11. Where does it come from?
ANIMAL
SOURCES
PLANT SOURCES
-Egg yolk
-Meat
-Butter
-Milk
-Liver
-Kidney
-Cod liver oil
-Halibut fish oil
-Carrots
-Sweet Potatoes
-Mango
-Turnip
-Apricots
-Broccoli
-Spinach
-Pumpkin

12. What do these plants have in
common?
carotenoids
• Pigments found in green plants.
• Precursor of vitamin A.
• Orange or yellow in colour.
• Beta-carotenoid –inactive.
• 2 molecules of retinol.

13. How much is enough?
LIFE STAGE Microgram/day
Infants 400-500
Children 300-600
Adolescents 900M-700F
Adults 900M-700F
Pregnant woman 750-800
Lactating women 122-1300

14. Vitamin A Units
1 microgram of retinol = 3.3 IU of vitamin A
activity.
1 Retinol Equivalent =6 microgram of dietary
carotene.
100 mg carrots contain 10 mg of b-carotene.

15. Absorption and Fate

16. PHYSIOLOGICAL ROLE AND
ACTIONS

17. 1.Visual cycle

20. 2.Epithelial tissue
• Differentiation
• Mucus secretion
• Inhibits keratinization
• Resistance to infection
• Reduces risk of malignancies
• Bone growth

21. 3.Reproduction
• Spermatogenesis
• Organogenesis-fetal development
• Cell growth& differentiation

22. 4.Immunity
• For antibody response
• Lymphocyte proliferation
• Killer cell function
• Deficiency-infection

23. Deficiency manifestations
xerosis

24. Bitot’s spots

25. keratomalacia

26. Corneal opacities

27. Nyctalopia

28. Phrynoderma

29. Other manifestations…….
• Hyperkeratinization
• Atrophy of sweat glands
• Diarrhoea
• Formation of urinary stones
• Sterility
• Growth retardation
• Impairment of special senses

30. Follicular hyperkeratosis in
vitaminA deficiency

31. Who is at risk for deficiency?
• Young children.
• Children with inadequate health care.
• Adults in countries with high incidences of
vitamin A deficiency or measles.
• Adults or children with diseases of the pancreas,
liver, intestines, or inadequate fat
digestion/absorption.

32. Therapeutic uses
• Prophylaxis - 3000 to 5000 IU/day
• Treatment - 50,000 to 100,000 IU
- i.m. or orally for1-3 days
• Skin diseases - Retinoic acid
-2nd &3rd generation retinoids.
• Acute promyelocytic leukemia
• Cancer prevention

33. Interactions
• Vitamin E
• Liquid paraffin
• Neomycin

34. Too much can be toxic!!
Hypervitaminosis A
• >100,000 IU daily for months.
• Toxicity symptoms
-nausea, vomitting, itching, erythema,dermatitis,
exfoliation,hair loss ,bone &joint
pains,irritability,bleeding,raised ICT,CLD.
• Don’t exceed 20,000 IU.

35. “Polar bear liver can kill a person!!”

36. Acute poisoning
• Polar bear liver - 30,000 IU/g vitamin A.
• Single ingestion (>1 million IU) causes…..
-headache, drowsiness, irritability, liver
enlargement, shedding of skin.
• d/t saturation of RBP – excess retinol esters
• Surfactant property.

37. Treatment
• Stop ingestion
• Supportive measures
• Vitamin E

38. Retinoic acid
• Active in epithelial tissues-growth
• Inactive in eye& reproductive organs
• All trans RA- topically
• 13 cis RA-orally for acne
• Not stored but rapidly metabolised
• CRABP- in skin and other tissues not in retina
• Not involved in visual cycle.

39. Retinoid receptors
• Acts like steroid hormone receptors
• Two types of receptors
• RAR (Retinoic acid receptors) - all trans
retinoic acid.
• RXR (Retinoid X receptors)-9 cis retinoic
acid.
• Forms dimers with vit.D receptors-responsible
for impaiment of biochemical effects of vit.D
in vitamin A deficiency.

40. Immunization
VACCINE WHEN TO GIVE DOSE ROUTE
Vitamin A (1st dose) 9 months along with
measles
100,000 IU Oral
Vitamin A(2nd to 9th
dose)
16 months. Then one dose
every 6 months upto 5 years
200,000 IU Oral