vitamin a def and hypervitaminosis A

1. BY
MOHAMED ABED
EGH

2.  The word "vitamin" comes from the Latin word
vita, means "life".
 Vitamins are chemicals found in very small
amounts in foods.
 “Vitamins have been defined as organic
compounds which are required in tiny
amounts to maintain normal health of
organisms’.
 cannot be synthesized in sufficient quantities by
an organism, and must be obtained from the diet

3. FAT SOLUBLE
 A
 D
 E
 K
Water soluble
 B1- Thiamine
 B2- Riboflavin
 B3– Niacin
 B5 – Pantothenic acid
 B6 –Pyridoxine
 B8 – Biotin
 B 9 -Folic acid
 B12 -CyanoCobalamin
 C (Ascorbic acid)

4. Water soluble vitamins Fat soluble vitamins
Solubility Water soluble Fat soluble
Absorption Simple Along with lipids
Storage *No storage Stored in liver
Excretion Excreted Not excreted
Excess intake Nontoxic Toxic
Deficiency Manifests rapidly Manifests slowly
Treatment Regular dietary supply Single large dose
Difference b/w water soluble & fat soluble
vitaminsVITAMINS

5. Vitamins have diverse biochemical functions.
 Some have hormone-like functions as regulators of
mineral metabolism (e.g. vitamin D)
 Regulators of cell and tissue growth and
differentiation (e.g. some forms of vitamin A)
 Others function as antioxidants e.g .vitamin E and
sometimes vitamin C
 The largest number of vitamins (e.g .B complex
vitamins) function as precursors for enzyme
cofactors ,that help enzymes in their work as
catalysts in metabolism .

6.  Vitamin A is an essential nutrient needed in
small amounts for the normal functioning of
the visual system, and maintenance of cell
function for growth, epithelial integrity, red
blood cell production, immunity and
reproduction.
 Needed in lysosomal membrane stability
 Plays a role in keratinization, cornification,

7.  Vitamin A occurs in two forms in food
Retinoids
Retinol
Retinal
Retinoic acid
Carotenes
α- carotene
β- carotene
γ- carotene

8. Retinol (vitamin A alcohol) :
N retinol plasma values:
15-30 mcg/dl in infants
30-90 mcg/dl in adults

9.  This is an aldehyde form obtained by the
oxidation of retinol.
 Retinal and retinol are inter convertible.

10.  produced by the oxidation of retinal.
 However, retinoic acid cannot give rise to the
formation of retinal or retinol.
 Beta-Carotene (provitamin A) :
 Found in plant foods.
 lt is cleaved in the intestine to produce two
moles of retinal

11.  Retinoids
 Retinyl esters broken down to free retinol in
small intestine - requires bile, digestive
enzymes, integration into micelles
 Once absorbed, retinyl esters reformed in
intestinal cells
 90% of retinoids can be absorbed
 Carotenoids
 absorption rate much lower
 Intestinal cells can convert carotenoids to
retinoids

12.  Liver stores 90% of vitamin A in the body in
form of Retinyl palmitate
 Reserve is adequate for several months
 Transported via chylomicrons from intestinal
cells to the liver
 Transported from the liver to target tissue as
retinol
 Free retinol is highly active but toxic &
therefore transported in blood stream in
combination with retinol binding protein

13.  Some lost in urine
 Kidney disease and aging increase risk of
toxicity because excretion is impaired

14.  Vision (night, day, colour)
 Epithelial cell integrity against infections
 Immune response
 Haematopoiesis
 Skeletal growth
 Fertility (male and female)
 Embryogenesis

15.  Roles in the Body
 Vitamin A in Vision
 Helps to maintain the cornea
 Conversion of light energy into nerve
impulses at the retina
 Rhodopsin is a light-sensitive pigment
of the retina that contains a protein
called opsin.

17. • Retinoic acid is necessary for cellular
differentiation
• Important for embryo development, gene
expression
• Retinoic acid influences production,
structure, and function of epithelial cells
that line the outside (skin) and external
passages (mucus forming cells) within the
body

19.  Roles in the Body
 Vitamin A in Reproduction and Growth
 Sperm development in men
 Normal fetal development in women
 Growth in children
 Remodeling of the bone involves
osteclasts, osteoblasts, and lysosomes.

20.  Vitamin A deficiency also diminishes the ability to
fight infections. In countries where children are not
immunized ,infectious disease like measles have
higher fatality rates.
 Even mild, subclinical deficiency can also be a
problem, as it may
 Increase children's risk of developing respiratory and
diarrheal infections
 Decrease growth rate
 Slow bone development
 Decrease probability of survival from serious illness.

21.  Roles in the Body
 Beta-Carotene as an Antioxidant
 Beta-carotene helps protect the body
from diseases, including cancer.(Lung,
oral, and prostate cancers)
 Prevention of cardiovascular disease

23. Causes Inadequate intake
Impaired absorption
Impaired storage and transport
Increased excretion [RBP]
Alcoholism

24. Men and women – 750-1000 μg.
Pregnancy and lactation – 1000 μg.
Infants – 350 μg.
Children – 400-600 μg.

25.  Vitamin A in Foods
 Retinol is found in fortified milk, cheese, cream, butter,
fortified margarine, and eggs.
 Beta-carotene
 Spinach and other dark green leafy vegetables
(chlorophyll pigment masks the color)
 Deep orange fruits
 Deep orange vegetables like squash, carrots, sweet
potatoes
 White foods are typically low in beta-carotene.
 Vitamin A is poor in fast foods and foods with the
xanthophyll pigments (beets, corn).
 Liver is rich in vitamin A.

27.  Vitamin A deficiency is a lack of vitamin A in humans.
Because vitamin A is stored in the body, it would take
a year or more to develop a deficiency in the
presence of inadequate intake.
 Night blindness is one of the first signs of vitamin A
deficiency .
 Night blindness is the difficulty for the eyes to adjust
to dim light. Affected individuals are unable to
distinguish images in low levels of illumination.
People with night blindness have poor vision in the
darkness, but see normally when adequate light is
present.

28. Ocular
 Night blindness.
 xerophthalmia
 bitot’s spot
 keratomalacia
Extra ocular
 Retarded growth
 Skin disorders
 Effect on
reproductive
organs.
 Effect on bone

29.  Conjunctiva become dry, thick and wrinkled

30.  Conjunctive keratinizes and develops
plaques- BITITS SPOT
 Grayish white triangular spots in
conjunctiva

31.  Infection leads to corneal ulceration and
total blidness

34.  SKIN CHANGES- Scaly, toad like
(phrynoderma)
 Squamous metaplasia of respiratory
mucosa more prone to RESPIRATORY
INFECTIONS
 Alteration in mucosa of renal pelvis and
UB formation of RENAL AND VESICAL
CALCULI
 Atrophy of germinal epithelium

35. © 2008 Thomson - Wadsworth

36.  Assessment of dietary vit.A
 Eye examination
 SERUM RETINOL level(normal level is 28 to
86 μg/dl (1 to 3 µmol/L) not an acurrate
indicator unless the deficiency is severe
and liver stores depleted
 Night vision threshold test

37.  For VAD syndromes, treatment includes daily oral
supplements, as follows: Children aged 3 years
or younger - 600 mcg (2000 IU)
 Children aged 4-8 years - 900 mcg (3000 IU)
 Children aged 9-13 years - 1700 mcg (5665 IU)
 Children aged 14-18 years - 2800 mcg (9335 IU)
 All adults - 3000 mcg (10,000 IU)
 Therapeutic doses for severe disease include
60,000 mcg (200,000 IU), which has been shown
to reduce child mortality rates by 35-70%

38. PARENTERAL WATER SOLUBLE VIT. A
DOSE- 3/4th DOSE <6 months
½ DOSE 6-12 months
INDICATION-
1. Impaired oral intake
2. Persistent vomiting
3. Severe malabsorption

39. 6 -12 months > 1 yr
 Immediately 100,000 IU 200,000 IU
 Next day 100,000 IU 200,000 lU
 2–4 weeks later 100,000 IU 200,000 IU
 Severe Protein-Energy Malnutrition (PEM) Monthly
until PEM resolves
100,000 IU 200,000 IU

40.  LOCAL TREATMENT
CORNEAL ULCER-
ANTIBIOTICS DROPS/OINT. THRICE DAILY
(to prev. sec. infection)
PADDING OF EYE (to prevent dehydration and furthur
corneal exposure)
MYDRIATIC- ATROPINE DROP 1% OR OINT. ONCE
DAILY

41. mothers of breast-fed infants living in regions
where vitamin A deficiency is common.
2 doses of 200,000 IU (60 mg) of vitamin A are
given to the mother immediately after
delivery,
and the infant is given 3 doses of 25,000 IU
(7.5 mg) of vitamin A at 1-3 mo of age

42.  CONSUMPTION OF FOODS RICH IN VIT A
 LONG TERM PREVENTION STRATEGIES
1. Nutrition education and dietary diversification
2. HORTICULTURAL INTERVENTION incl. Home
gardening
3. Nutritional supplementation
4. Selective fortification for high risk and special
groups

43. All Infants with birth weight of ≤1 kg should receive
5000IU of Vitamin A i.m 3 times a week for first 4
weeks- slightly reduce the incidence of chronic lung
disease
Manual of neonatal care – john p cloharty, 6th ed

44.  Hypervitaminosis A refers to the effects of excessive
vitamin A )specifically retinoid) intake
 Hypervitaminosis A occurs when the maximum limit for
liver stores of retinoids is exceeded.
 The excess vitamin A enters the circulation causing
systemic toxicity.
 Betacarotene (is an organic compound which is a
strongly-coloured red-orange pigment abundant in plants
and fruits. β-Carotene is also the substance in carrots
that colours them orange) a precursor of vitamin A, is
selectively converted into retinoids, so it does not cause
toxicity.

45. © 2008 Thomson - Wadsworth

46. Acute Intoxication:
 Infants: drowsiness or irritability w/signs
of increased ICP
 Adults: drowsiness, irritability, headache &
vomiting
 Serum vitamin A values = 200-1000 IU/dl
(N: 50-100 IU/dl)

47.  Acute – symptoms disappear when
intake stops
 GI effects
 Headaches
 Blurred vision
 Poor muscle coordination

48.  Results when >50,000 IU/day ingested for several
wks or more
 Signs & symptoms in infants:
 Early are anorexia, pruritus, irritability,
tender swollen bones w/motion limitation
 Alopecia, seborrhea, cheilosis & peeling of
palms & soles
 Hepatomegaly & hypercalcemia observed
 Craniotabes & hyperostosis of long bones
 Elevated serum vit A levels confirms diagnosis
 Reversible manifestations when vitamin A
discontinued

49. One ounce
of polar
bear liver
contains
enough
vitamin A
(retinol) to
kill a
person!