2. Vitamins are organic compounds occuring
in natural food either as such or as
utilizable Precursors which are required
by the body in trace ammounts to perform
specific cellular functions like growth and
reproduction.

3. Vitamins are different from other food
stuffs,
 Donot enter into tissue structure like
proteins.
 Donot undergo degradation to provide
energy like carbohydrates and lipids.

4. Vitamins are categorized based on their solubility:
3. Water soluble vitamins
5. Lipid (Fat) soluble vitamins

6. Water soluble Fat soluble vitamins
•Polar and •Apolar and
hydrophilic hydrophobic
•Isoprene derivatives
•Hetrogenous except vit.D which is
sterol derivative.
•Fat soluble,absorbed
•Water soluble, along with fats.
absorbed along with
water. •TPT along with
•Donot require lipoproteins or
specific binding specific binding
proteins for transport. proteins.

7. •Excreted in the •Not readily excreted
urine. in the urine but via
bile.
•Stored in liver and
•Not stored in the adipose tissue.
body therefore
required daily. •Excess can be toxic
•Non toxic •Vit.K act as
•Act as coenzymes coenzyme,D and A
are more like a
hormone in
function.E is

9. Vitamin A (retinoids) is essential for growth,
reproduction,vision and maintenance of
epithelial tissues.

10.  Preformed vitamin A
 Retinoids (retinal, retinol, retinoic acid)
 Found in animal products
 Provitamin A
 Carotenoids
 Must be converted to retinoid form
 Intestinal cells can split carotene in two
(molecules of retinoids)
 Found in plant products

12. Vitamin A in Foods
 Preformed(Retinoids)
 Liver, fish oils, fortified milk,
eggs, other fortified foods
 Provitamin A (carotenoids)
 Dark leafy green, yellow-orange
vegetables/fruits

13. RECOMMENDED DIETARY ALLOWANCE
(RDA)
 1000 Retinol equavelents for males and 800
RE for females.
1 Retinol equavalent = I μg of retinol,6 μ g of ß
carotene or 12 μ g of other carotenoids.

14. Absorption of vitamin A

15. FUNCTIONS OF Vit.A
VISUAL CYCLE
 Rhodopsin,the visual pigment of the rod
cells in the retina,consists of 11-Cis retinal
specifically bound to protein opsin.

17. Growth and Differentiation of Cells
• 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. GROWTH AND REPRODUCTION
 Retinol and Retinal are essential for
normal reproduction,supporting
spermatogenesis in male and preventing
fetal resorption in females.

20. ACNE AND PSORIASIS
 Retinoic acid and its derivatives are used
to treat acne.
 Mild acne is topically treated with
Tretinoin.
 Severe acne is treated with Isotretinoin
,administered orally.

21. Prevention of chronic diseases
 β Carotene decreases the incidence of lung
and skin cancer.
 β Carotene functions as an antioxidant.

23. Deficiency of Vitamin A
 Most susceptible populations:
 Urban poor
 Alcoholism
 Liver disease (limits storage)
 Fat malabsorption

24.  Consequences:
 Night blindness
 Decreased mucus production
 Decreased immunity
 Bacterial invasion of the eye
 Conjunctival xerosis
 Bitot’s spots
 Xerophthalmia
 Irreversible blindness
 Follicular hyperkeratosis
 Poor growth

25. Toxicity of Vitamin A
 Acute – short-term megadose (amounts
exceeding 7.5mg/day); symptoms
disappear when intake stops
 GI effects
 Headaches
 Blurred vision

26.  Teratogenic (may occur with as little as 3 x
RDA of preformed vitamin A)
 Tends to produce physical defect on
developing fetus as a result of excess
vitamin A intake
 Spontaneous abortion
 Birth defects