2. Vitamins are an organic compounds occurring in small
quantities in different natural foods either as such or as
utilizable precursors, which are required in minute amounts
for normal growth, maintenance and reproduction, i.e. for
normal nutrition and health.
3. 1. Vitamins differ from other organic food stuffs in that:
• They do not enter into tissue structures, unlike proteins.
• Do not undergo degradation for providing energy unlike
carbohydrates and lipids.
• Several B complex vitamins play an important role as
coenzymes in several energy transformation reactions in the
body.
2. Vitamins differ from hormones: In not being produced
within the organs, and most of them have to be provided in the
diet.
4. Classification
All vitamins are divided into two groups according to
solubility.
1. Fat-soluble Vitamins
• Vitamin A
• Vitamin D
• Vitamin E
• Vitamin K.
7. The major differences between these two groups of vitamins are given in
Table In general, deficiency of vitamins may occur due to:
8. deficiency of vitamins may occur due to:
a. Reduced intake
b. Impaired absorption
c. Impaired metabolism
d. Additional requirements
e. Increased losses
13. These forms are sometimes referred to as retinoids. Vitamin A is a
derivative of certain carotenoids which are hydrocarbon (polyene)
pigments (yellow, red).
14. Dietary Sources
• Animal sources: Liver oil, butter, milk, cheese, egg yolk.
• Plant sources: In the form of provitamin carotene, tomatoes,
carrots, green-yellow vegetables and fruits such as mangoes,
papayas, corn, sweet potatoes.
Daily requirement: Adult male and female require about
3000 IU per day
It is higher in growing children, pregnant women and
lactating mothers and in hepatic disease.
.
15. Absorption, Storage and Transport
• Vitamin A and its carotene precursors are absorbed in the small
intestine
Free retinol is absorbed and undergoes re esterification in the intestinal
epithelial cells.
It is stored in the liver as retinyl ester, normally as retinyl palmitate.
• Conversion of carotenes to retinol occurs in intestinal epithelial cells in
few animals
In man liver is the only organ where carotenes are converted to vitamin
A.
• Retinol is transported in the blood in association with a specific retinol
binding protein (RBP).
16. FUNCTIONS OF VITAMIN A
1. Role in Vision
continual supply of retinol is essential for normal visual function.
2. Role in Reproduction
3. Role in Bone and Teeth Formation
4. Growth
Metabolism
It may be involved in protein synthesis and may play a role in
metabolism of DNA.
17. - β-carotene as an Antioxidant and Anticancer.
-Retinoic Acid: Functions and Therapeutic Uses
- Collagen Break down: Retinoic acid inhibits the enzyme
“collagenase” and thus prevents breakdown of collagen.
- Role in keratinisation: Retinoic acid prevents keratinisation
of epithelial cells.
-Thus it keeps the mucous membranes healthy and moist
19. Keratomalacia Keratinization
Daily Requirement of Vitamin A
The recommended daily allowance (RDA) for
i. Children = 400–600 mg/day
ii. Men = 750–1000 mg/day
iii. Women = 750 mg/day
iv. Pregnancy =1000 mg/day
20. Hyper vitaminosis A or Toxicity
Symptoms of toxicity include:
* anorexia
* irritability
* headache
* peeling of skin
* drowsiness and vomiting.
* Sometimes swelling over long bones (bony exocytosis) may occur
with painful bones.
* Enlargement of liver is also seen in children.
22. Formation of Vitamin D
Vitamin D is derived either from 7-dehydrocholesterol or ergosterol by
the action of ultraviolet radiations.
7-dehydrocholesterol, an intermediate pathway of cholesterol synthesis
Synthesis of cholecalciferol or vitamin D3
23. Vitamin D3 or cholecalciferol occurs in fish liver and also produced in
human skin by ultraviolet light.
The inactive natural precursors of the vitamin D are the ‘provitamins’.
Only two of these have been found in nature.
• Ergosterol: Provitamin D2 found in plants.
• 7-dehydrocholesterol: Provitamin D3 found in the skin.
24. Dietary Sources
Fish liver oil is the richest source of vitamin D. Egg-yolk, margarine,
also contain considerable quantity of vitamin D. Some quantity is also
present in butter, cheese, etc
Daily Requirement
IU = 0.025 μg of vitamin D3. About 100 IU or 2.5 μg of vitamin D3 is
the daily requirement in adult man.
Pregnant and lactating mother as well as infants and children require
about 220 IU per day.
Vitamin is easily supplied by synthesis in sunlight in tropical countries.
25. Absorption and Transport
Like most other fat-soluble vitamins, bile salts help in absorption of
vitamin D from duodenum and jejunum.
After absorption, it is carried in chylomicron droplets of the lymph in
combination with serum globulin in blood plasma.
26. Biomedical role
Vitamin D is considered as a “Prohormone” and calcitriol (1,25-di-OH-
D3) as a hormone.
• Vitamin D3 (cholecalciferol) is synthesised in human skin by Uv
irradiation from its precursor Provitamin D 3 (7-dehydrocholesterol).
• Vitamin D3 as such is inactive and is only the storage form.
It is converted in liver to 25-OH-D3 (calcidiol) and biological active 1,25
{(OH)2-D 3 (calcitriol)} in kidney.
Calcitriol maintains calcium homeostasis,
28. Vitamin D and Absorption of Calcium
Calcitriol promotes the absorption of calcium and phosphorus
from the intestine.
Effect of Vitamin D on Bone
Mineralization of the bone is increased by increasing the activity of
osteoblasts . Calcitriol coordinates and increases bone mineral density
Effect of Vitamin D on Renal Tubules
Calcitriol increases the reabsorption of calcium and phosphorus by renal
tubules
29. Causes for Vitamin D Deficiency
* occur in people who are not exposed to sunlight properly
* Nutritional deficiency of calcium or phosphate
*Malabsorption of vitamin.
*Deficient renal absorption of phosphates.
Deficiency of Vitamin D
The deficiency diseases are rickets in children and osteomalacia in
adults. .
32. Dietary Sources
Cottonseed oil, corn oil, sunflower oil, wheat germ oil and margarine are
the richest sources of vitamin E. Fish liver oils It is also found in dry
soya beans, c, yeast, apple seeds, peanuts
Normal blood level = 1.2 mg/dl.
Recommended Allowance
• Children: 10–15 IU/day
• Adults: 20–25 IU/day
Dietary intake of unsaturated fatty acids in which case the daily
requirement is increased. Requirement is also more in pregnancy and
lactation.
33. Biochemical Role of Vitamin E
* Vitamin E is the most powerful natural antioxidant
*Removal of free radicals:
The free radicals would attack bio-membranes. Vitamin E protects RBC
from hemolysis
*aging
* Reproduction
34. Deficiency of Vitamin E
• Muscular dystrophy:
Hemolytic anemia
Atherosclerosis
Atherosclerotic plaque in a blood vessel is shown in left
side. It may be prevented by vegetables containing vitamin E
36. VITAMIN K
Chemistry: Vitamin K compounds are naphthoquinone derivatives.
Daily Requirement of Vitamin K
Recommended daily allowance is 50–100 mg/day. This is
usually available in a normal diet
37. *They are absorbed in intestine along with chylomicrons.
*They are also synthesized by intestinal .
*Storage is in the liver and transported in plasma is along with
beta lipoproteins.
*Vitamin K is involved in blood coagulation.
*Vitamin K is required for post-translational modification of coagulation
factors.
38. Signs and Symptoms of Vitamin K Deficiency:
Hemorrhage deficiency is rare in adult
39. Biochemical Role of Vitamin
FUNCTIONS OF VITAMIN K
1. Blood Coagulation
The main function of vitamin K is the promotion of blood coagulation by
helping in the modifications of blood factors such as prothrombin, and
factors II, VII, IX, X.
2. Calcium Binding Proteins
3. Role in Oxidative Phosphorylation
Vitamin K is a necessary cofactor in oxidative phosphorylation being
associated with mitochondrial lipids.
