Vitamins are organic molecules needed in small amounts that the human body cannot synthesize. Vitamins include fat soluble vitamins A, D, E, K and water soluble B vitamins and vitamin C. Deficiencies can cause diseases like night blindness or scurvy, while too much can also be toxic. Vitamins are absorbed and transported differently depending on whether they are fat or water soluble. They have many important functions and recommended daily intakes help prevent deficiencies.

1. VITAMINS

2.  Vitamins are heterogenous group of organic molecules that
are needed in small quantities for normal growth,
reproduction, and homeostasis but that the human body is
unable to synthesise in adequate amounts

3. Provitamins are precursors of vitamins that upon
metabolism in the body are converted to vitamins
Provitamin Vitamin
Carotene Vitamin A
7 dehydrocholesterol Vitamin D
 Anti- vitamins are antagonists of vitamins which act by
decreasing the absorption of the vitamin or competitively
inhibiting the vitamin or degrading the vitamin
Vitamin Antivitamin
Vitamin K Dicoumarol
Biotin Avidin
Thiamine Thiaminase

4.  Hypovitaminosis- Caused due to deficiency of a
vitamin.
Vitamin Hypovitaminosis
Vitamin A Night blindness
Vitamin D Rickets
Thiamine Beri-beri
Vitamin C Scurvy
 Hypervitaminosis-caused due to overdosage of the
vitamin usually fat soluble vitamins.
 Hypovitaminosis is more common than hypervitaminosis

5. 1. MINIMUM DAILY REQUIREMENT (MDR):
Smallest amount of the vitamin needed by a person to
prevent deficiency syndrome. It is considered to represent
the body’s basic physiological requirement of the vitamin
2. RECOMMENDED DAILY ALLOWANCE (RDA)
Amount of the vitamin needed daily to maintain good
nutrition in most healthy people. RDA values are intended
to serve as nutritional goals.
RDA values have also been established for minerals,
energy, protein, electrolytes, and water by food and
Nutrition Board of the National Academy of Sciences of
the USA

6. CLASSIFICATION OF VITAMINS
1. Fat soluble vitamins – A,D,E & K
2. Water soluble vitamins
*B complex vitamins – Thiamine, Niacin, Riboflavin,
Pyridoxine, Folic acid,
Pantothenic acid, Biotin & B12
* Vitamin C
3. Vitamin like substances – Choline, inositol, lipoic acid,
para aminobenzoic acid &
vitamin P

7. COMMON PROPERTIES OF FAT SOLUBLE VITAMINS
 Synthesised from isoprenoid units
 Absorbed into intestinal lymphatics along with
dietary lipids
 Lipid malabsorption accompanied by steatorrhoea
results in poor uptake of all fat soluble vitamins (FSV)
 Stored in the liver and adipose tissue and therefore
deficiency is difficult to produce in adults

8. OBJECTIVES
 Sources
 Absorption, transport & storage
 Functions
 Recommended daily allowance
 Deficiency manifestations (Hypovitaminosis)
 Over dosage (Hypervitaminosis)

9. VITAMIN A (ANTI-XEROPHTHALMIC FACTOR)

10. CHEMISTRY OF VITAMIN A
 Contains β ionone ring and poly-isoprenoid side chain
 There are 2 types of vitamin A-A1 and A2. A1 is the
most commonly occuring type & biologically active type
Vitamin A1 exists in three oxidation states
1. Retinol
2. Retinal
3. Retinoic acid
 Vitamin A1 exists in various isomeric forms-
1. All trans retinol(al)
2. 11 cis retinol(al)

11. CHEMISTRY OF VITAMIN A ----CONT
 Vitamin A is heat stable and upon oxidation it loses
its biological activity
 Vitamin A reacts with antimony trichloride to give
blue colour ( Carr and Price reaction)

12. SOURCES OF VITAMIN A
 Preformed vitamin A (retinyl esters, free vitamin A):
Egg yolk, butter, milk, cod liver oil and liver
 Provitamin A (β carotene) – Carrot, papaya, mangoes,
tomatoes, pumpkin ,spinach and broccoli

13. ABSORPTION OF VITAMIN A
INTESTINAL LUMEN
Dietary RetinolDietary Retinylesters
Retinol
INTESTINAL MUCOSA
Retinol
Long chain fatty acidAcyl CoA:retinol
Acyl transferase
Retinylesters + Carotenoids
CHYLOMICRONS
Retinyl ester hydrolase

14. LYMPH AND BLOOD
CHYLOMICRONS
Chylomicron remnant (Retinyl ester) LIVER
Retinol
Retinyl ester hydrolase
Fatty acid
Retinol Binding Protein
Retinol : Retinol Binding Protein
Retinol – RBP – Prealbumin (1:1:1) BLOOD
GonadsRetina Skin Epithelia

15. FUNCTIONS OF VITAMIN A
1. Role in vision (Wald’s visual cycle)
Rhodopsin Lumi Rhodopsin
Light
Meta Rhodopsin
All trans retinal + OpsinOpsin + 11 cis retinal
Isomerase
dark
Retinal
reductase
NADH + H+
NAD+
Retinal
reductase
NADH + H+
NAD+
11 – cis retinol All trans retinol
Isomerase

16. 2. Vitamin A is essential for the differentiation
and maintenance of epithelial cells
3. Role in glycoprotein synthesis
4. Bone remodeling
5. Essential for normal growth
6. Essential for normal reproduction
7. May act as an antioxidant

17. INTERCONVERSION OF RETINOIDS AND THEIR FUNCTIONS
Retinol Retinal Retinoic acid
Retinol Retinal
Dehydrogenase Dehydrogenase
• Differentiation of Vision Cellular differentiation
Epithelial cells Growth
• Growth Steroid hormone
• Mucous production
• Bone remodeling
• Glycoprotein synthesis
• Reproduction

18. RECOMMENDED DAILY ALLOWANCE FOR VITAMIN A
Infants - 400 Retinol Equivalent (RE)
Children - 400 – 700 RE
Adults - Males - 1000 RE
- Females - 800 RE
- Pregnancy- 1000 RE
- Lactation - 1200 RE
1 Retinol Equivalent = 1 micro gram of retinol (or)
6 micro gram of β carotene

19. VITAMIN A DEFICIENCY (HYPOVITAMINOSIS A)
Causes - malnutrition, malabsorption & intake
Symptoms - 1.Lesions of eye
- Nyctalopia (Night blindness)
- Conjunctival xerosis
- Bitots spot
- Corneal xerosis
- Xerophthalmia
- Keratomalacia
- Blindness

20. Symptoms (cont…)
2. Follicular hyperkeratosis
3. Keratinisation of mucosal cells lining respiratory,
gastrointestinal & genitourinary tracts resulting in
frequent infections
DIAGNOSIS OF VITAMIN A DEFICIENCY
Abnormalities of the dark adaptation test
 Serum vitamin A level <30 microgram / dL
 Retinol binding protein in serum is decreased

21. TREATMENT OF VITAMIN A DEFICIENCY
Early deficiency - 6000 RE /day for 1 week
Advanced deficiency - 4000 RE / kg bw for 5 days
VITAMIN A TOXICITY(HYPERVITAMINOSIS A
 Occurs after ingestion of daily dose of > 5,000RE/day
for more than 3 months, Eskimos who eat liver of
polar bear
 Symptoms – Dry scaly skin, hair loss, mouth sores,
anorexia, vomiting, headache, irritability
and hepatomegaly