1. 1

3. 3
VITAMIN A
VITAMIN A :- Is widely distributed in
animal and plant foods
animals –pre-formed – Retinol.
plants – pro-formed - carotene

4. VITAMIN A
 Exits in 3 forms:
all trans-retinol
long chain fatty acyl ester of retinol (main
storage form)
retinal (the active form in the retina)
 retinoic acid is also considered to be
physiologically active
 provitamin A or carotene can be converted to
retinol in vivo

5. CH3
CH3
H3C
CH3
H3C CH3
H3C
CH3CH3
CH3
β-carotene
CH3
CH3
H3C
CH3
CH3
OH
CH3
CH3
H3C
CH3
CH3
O
H
liver
O2
retinal (active form in vision)
CH3
CH3
H3C
CH3
CH3
O
COOH
CH3
CH3
H3C
CH3
CH3
retinoic acid ("hormonally-active
form")R
O
vitamin A acetate (R = CH3)
vitamin A palmitate (R = C16H33
retinol (from diet)

6. Vitamin A
6
Lots of double bonds, good anti-oxidant

7. SOURCES

8. VITAMIN A & CAROTENOIDS
Sources
Retinoids - liver, dairy, fish
Carotenoids - brightly colored
fruits & vegetables
β-carotene - greatest provitamin A
activity
2009 Cengage-Wadsworth

9. 9
pre-formed vitamin
A:: meat, liver &
dairy products
PRO-FORM VITAMIN A :
Yellow, red and green
vegetables and fruits
Dietary Sources of Vitamin A

10. CH3
CH3H3C
CH3
CH2OH
CH3
VITAMIN A (RETINOL)
Vitamin A contains 5 conjugated double bonds
which are
key to some biological actions
Isolated in impure form by McCollum in 1915
RDA: 0.7 mg

11. VITAMIN A (RETINOL)
Retinol and beta–carotene preformed
vitamin A.
Beta carotene can be converted to
retinol in the body; 6mg of beta carotene
is equivalent to 1mg of retinol.

12. VITAMIN A & CAROTENOIDS
Carotenoids
Antioxidant functions
Carotenoids & eye health
Carotenoids & heart disease
Cell proliferation, growth, &
differentiation
Carotenoids & cancer
Carotenoids & health claims
2009 Cengage-Wadsworth

13. VITAMIN A & CAROTENOIDS
Digestion & absorption
Vitamin A requires digestion
Retinol bound to fatty acid esters
Retinyl esters & carotenes often
complexed with protein
2009 Cengage-Wadsworth

14. Emulsification of fat globules
Retinol absorbed via protein
carrier
Carotenoids absorbed via
transporters & passive diffusion

15. VITAMIN A & CAROTENOIDS
Carotenoids & retinoids metabolized
in enterocytes to some extent
Retinol esterified & incorporated into
chylomicrons for transport
Cellular retinol-binding protein
(CRBP) II
2009 Cengage-Wadsworth

16. Transport, metabolism, &
storage
Chylomicrons carry to liver
Additional metabolism in liver

17. Carotenoids transported as part
of lipoproteins
Carotenoids stored in liver &
adipose

18. VITAMIN A & CAROTENOIDS
Retinol that is esterified may be
stored in the liver
 Stellate cells & parenchymal cells
Transported in blood via 2
proteins
 Retinol-binding protein (RBP)
 Tranthyretin (TTR)
2009 Cengage-Wadsworth

19. 19
 Approximately 80% is absorbed.
 It is passed along with fat through the
lymphatic system into blood stream.
 absorption is poor in case of diarrhea,
jaundice and abdominal disorder.

20. absorption increases if taken with
fat.
 vitamin A which is not absorbed is
excreted within 1 or 2 days in feces .

21. 21
ABSORPTION & STORAGE
 The liver has enoromous capacity to
store – in the form of retinol
palmitate.
 under normal conditions a well-fed
person has sufficient Vitamin A
reserves to meet his need for 6 to 9
months or more.
 Free retinol is highly active but
toxic & therefore transported in
blood stream in combination with
retinol binding protein (liver)

23. VITAMIN A & CAROTENOIDS
Functions & mechanisms of action
Vitamin A
 Vision - rhodopsin
 Cellular differentiation
 Gene expression
 Growth
 Other functions - reproduction, bone
metabolism
2009 Cengage-Wadsworth

24. ADDITIONAL ROLE OF RETINOL
retinol also functions in the synthesis of
certain glycoproteins and
mucopolysaccharides necessary for
mucous production and normal growth
regulation
this is accomplished by phosphorylation
of retinol to retinyl phosphate which
then functions similarly to dolichol
phosphate

25. BIOLOGICAL ROLE OF VITAMIN-A
1. Retinol and retinoic acid have role
in normal reproduction
2. Retinal has a role in visual cycle
3. Retinoic acid has a role in
glycoprotein synthesis
4. Roll in MPS synthesis

26. 5. Vitamin-A is needed for
mitochondrial membrane function
6. Anti cancer role: β-carotene is an
antioxidant and trap peroxy free radicals
in tissues at low partial pressure of O2
7. Bone and teeth formation

27. 27
DAILY REQUIRMENT
 Men and women – 600 mcg.
 Pregnancy and lactation – 950 mcg.
 Infants – 350mcg.
 Children – 600mcg.
(RECOMMENDE BY ICMR – 1989)

28. (VISUAL CYCLE)
 Rhodopsin
 darkness light

Opsin Opsin
 + retinal +
 11cis retinal isomerase trans retinal


29. Walds Visual cycle
Rhodopsin
Photorhodopsin
Bathorhodopsin
Lumirhodopsin
Metarhodopsin I
Metarhodopsin II
Metarhodopsin III

30. PHYSIOLOGICAL FUNCTIONS OF
VITAMIN A
Vision
Epithelial cell
"integrity’
Reproduction
Resistance to
infectious disease
Bone remodeling
Growth

31. 31
VISION
 Retinal is a necessary
structural component of
rhodopsin or visual purple,
the light sensitive pigment
within rod and cone cells of
the retina. If inadequate
quantities of vitamin A are
present, vision is impaired.

32. 32
EPITHELIAL CELL "INTEGRITY
 Many epithelial cells appear to require vitamin
A for proper differentiation and maintenance.
 Lack of vitamin A leads to dysfunction of many
epithelia - the skin becomes keratinized and
scaly, and mucus secretion is suppressed. It
seems likely that many of these effects are due
to impaired transcriptional regulation due to
deficits in retinoic acid signalling.

33. Fig. 11-4, p. 372
Vitamin A maintains
healthy cells in the
mucous membranes.
Without vitamin A, the
normal structure and
function of the cells in
the mucous membranes
are impaired.
Mucus Goblet cells
Stepped Art

34. 34
Reproduction:
 Normal levels of vitamin A is required for sperm
production,
 Normal reproductive cycles in females require adequate
availability of vitamin A.
Bone remodeling:
 Normal functioning of osteoblasts and osteoclasts is
dependent upon vitamin A.

35. 35
DEFICIENCY
SYMPTOMS

36. Deficiency symptoms
 Xeropthalmia
 Follicular conjunctivitis
 Keratomalacia
 Nyctalopia (night blindness)
 Follicular hyperkeratosis and keratizing metaplasia
 Urolithiasis

37. SYMPTOMS
 Alteration of skin and mucous
membrane
 Hepatic dysfunction
 Headache
 Drowsiness
 Peeling of skin about the mouth and
elsewhere

38. Follicular Hyperkeratosis

40. 40
RESISTANCE TO INFECTIOUS DISEASE
 In almost every infectious disease studied,
vitamin A deficiency has been shown to
increase the frequency and severity of
disease.

41.  Several large trials with malnourished
children have demonstrated dramatic
reductions in mortality from diseases such as
measles by the simple and inexpensive
procedure of providing vitamin A
supplementation.

42. 42
THE SIGNS OF VITAMIN A DEFICIENCY
Ocular
 Night blindness.
 Conjunctival xerosis
 bitot’s spot
 Corneal xerosis
 keratomalacia
Extra ocular
 Retarded growth
 Skin disorders
 Effect on
reproductive organs.
 Effect on bone

43. 43
NIGHT BLINDNESS
 Lack of vitamin A causes night
blindness or inability to see in
dim light.
 night blindness occurs as a result
of inadequate pigment in the
retina.
 It also called tunnel vision.
 Night blindness is also found in
pregnant women in some
instances, especially during the
last trimester of pregnancy when
the vitamin A needs are
increased.

45. RETINOPATHY

47. 47
BITOT'S SPOTS
These are foamy and
whitish cheese-like
tissue spots that
develop around the
eye ball, causing
severe dryness in the
eyes. These spots do
not affect eye sight in
the day light.

48. 48
CONJUNCTIVAL XEROSIS
 Conjunctiva becomes dry
and non wettable.
 Instead of looking smooth
shiny it appears muddy &
wrinkled.

49. KERATOMALACIA

50. 50
KERATOMALACIA
 One of the major cause
for blindness in India.
 cornea becomes soft and
may burst open .
 The process is rapid
 If the eye collapses
vision is lost.

51. 51
INCREASED RISK OF MORTALITY
FROM INFECTIOUS DISEASE
It has been best studied in malnourished children,
but also is seen in animals. In such cases,
supplementation with vitamin A has been
shown to substantially reduce mortality from
diseases such as measles and gastrointestinal
infections.

52. HYPERVITAMINOSIS A
Excess of vitamin A induce series of toxic
effects known as hypervitaminosis A
syndrome. Seen usually among
Eskimos who consume livers of polar
bear and arctic foxes.

53. 53
HYPRRVITAMINOSIS A
If the daily dose > 30,000mcg
toxic symptoms:-
 painful joint
 thickening of long bones.

54.  anorexia
 low grade fever
 rashes
 irregular menstruation
 fatigue.
 loss of hair

55. 55
CAROTENEMIA
 A condition in which conversion
of carotene to vitamin A is
impaired by inborn metabolic error
or hepatic diseases
 generalized yellowish skin and
mucosa.
 excessive deposition of carotene
which is result of high intake of
foods containing carotene.

56. SUMMARY

57. SUMMARY VITAMIN A

58. VITAMIN A
SOURCES
Animal sources
•Liver oil
•Butter
•Milk
•Cheese
•Egg yolk
Plant sources
•Tomatoes
•Carrot
•Green-yellow vegetables
•Spinach
•Mangoes
•Papaya
•Corn
•Sweet potato
RDA: Adults 3000-5000 IU/day
Children, pregnant and lactating women

59. sources:
Retinol is found in liver, whole
milk, cheese and butter.
Carotenes are found in milk,
carrots, dark green leafy
vegetables and orange coloured
fruits, e.g. mango and apricots.

60. 60
TREATMENT
 vitamin deficiency should be treated urgently .
 depending upon deficiency symptoms it is given in
the dose of 7,500 to 15,000 mcg per day for one
month
 nearly all of the early stages of xerophthalmia can be
reversed by administration of a massive dose –
2,00000 IU or 110mg orally on two successive days
(30).
 If Hypervitaminosis restriction of diet