Vitamin A is a fat-soluble vitamin that exists in multiple forms including retinol, retinal, and retinoic acid. It plays important roles in vision, cell growth, reproduction, and immune function. Vitamin A is found naturally in animal sources like liver and dairy, and plant sources like carrots and leafy greens provide carotenoids like beta carotene which can be converted to vitamin A. While deficiencies can cause night blindness and other issues, toxicity from overconsumption can lead to skeletal malformations and liver damage.

1. Rabia Aurangzeb
1st Year BDS

2. What Is Vitamin?
• Vitamins are
• non-caloric essential nutrients
• necessary in very small amounts
• for specific metabolic control and disease prevention.
• It cannot be synthesized in sufficient quantities by an organism,
and must be obtained from the diet.

3. CLASSIFICATION

5. • Fat soluble vitamins usually accumulate in
tissues and are not leached out quickly
• Unlike water soluble vitamins, and excess of a
fat soluble vitamin can be just as harmful as a
deficiency

6. TYPES OF FAT SOLUBLE
VITAMINS

8. • Vitamin A is a fat-soluble vitamin and
essential nutrient for humans.
• It is a group of organic compounds that
include :
• Retinol
• Retinal
• Retinoic acid
• Several carotenoids

9. VITAMIN A (RETINOL)
• Foods from animal source provide various
retinoid that are easily converted to retinol in the
body
• Foods from plants source provide carotenoids
• Over 500 carotenoids found in nature
• Less than 10% with pro vitamin A activity
• Beta carotene highest activity
• Must be acted upon in the gut or by the liver to
form retinol

10. SOURCES
Animal sources
• Liver
• Milk
• Egg yolk
Plant sources
• Carrots
• Green leafy vegetables
• Orange coloured fruits e.g mango and apricots

11. RETINOIDS
• Three forms of Vitamin A are important for
health
1. Retinol (key player can be converted to other
forms)
2. Retinal
3. Retinoic Acid
• Beta Carotene
Potent Pro Vitamin A

12. METABOLIC FUNCTIONS OF
VITAMIN A
• Each form of retinoid plays a specific role in
the body. Retinal (the aldenhyde form)
participates in vision.
• The hormone like action of retinoic acid is
essential for growth and development of cells
including bone development
• The retinol (alcohol form) supports
reproduction and healthy immune system
• In addition Vitamin A may help prevent cancer

14. FUNCTIONS
Vitamin A is needed for;
 Vision
 Prevents night
blindness
 Healthy skin hair
growth
 Keeps mucus
membrane healthy
 Promotes bone
development
 Boost Immunity
(retinoic acid and
carotenoids)
 Cell growth
 Reproduction
 Fetal development

15. RHODOPSIN CYCLE OR WALDS VISIUAL
CYCLE
• Rhodopsin: Combination of a protein part
(opsin) and 11- cis retinal (only cis form can bind
with opsin)
• When light energy is absorbed by rhodopsin, the
rhodopsin decompose, converts 11-cis retinal into all-
trans retinal
• In order to maintain the ability to detect light, the rods
must reconvert the all-trans into 11-cis retinol
• The process only occurs under the dark environment
• DARK ADAPTATION TIME

17. VITAMIN A DEFICIENCY
• More obvious deficeincy symptoms than
other vitamins
• Night blindness (leading cause of
blindness in third world countries
• Cell keratinization
• Dry skin
• Xerophthalmia (dryness of the cornea and
conjuctiva)
• Reproductive failure
• Abnormal skeletal
development/maintenance
• Immune dysfunction

19. VITAMIN A TOXICITY
• Not readily excreted
• Hypervitaminosis A in humans
• Self medication and overprescription
• SYMPTOMS
 Skeletal malformations , spontaneous
fractures
 Birth defects and miscarriage
 Decalcification, joint pain fragility
 Dry itchy skin
 Hair loss
 Liver damage
• Overconsumption of the beta carotene
from food sources may cause skin to
turn yellow but is not harmful

20. BENEFICIAL EFFCETS OF B-
CAROTENE
• Antioxidant role of B-carotene
• Increased consumption of B-carotene is
associated with decreased incidence of heart
attacks, skin and lung cancer
• High doses of carotene for long periods are
not toxic