Vitamins are complex organic compounds, whose presence in trace amount in the food is essential for growth and other physiological activities. Vitamins do not have any energy value. However they are essential for controlling energy yielding processes. The identified vitamins are classified asA,B,C,D,E and K. Of these, vitamin B and C are water soluble in nature. Vegetables and fruits containing these vitamins if washed in water as cut pieces would loose them easily. Vitamin A,D,E and K, if consumed beyond required level may cause defects, commonly referred to as vitaminosis.
Of the various vitamins, vitamin D or calciferol on exposure to sunlight can be synthesised by our body through the lipid compound called ergosterol, found below our skin. Hence it is known as 'sunshine vitamin'.
The most important functions of vitamins include.
1. Physiological processes : Vitamin A plays a very important role in visual perception. Vitamin E might ensure fertility in animals. The clotting of blood is aided by vitamin K. Vitamin C provides immunity against infections and it may also support processes of growth.
2. Maintenance of body tissues : The epithelial tissues of the body are maintained by vitamin A and B2. The growth of bones is ensured by vitamin D. Vitamin E plays a role in the rejuvenation of tissues. Nourishment to nerve cells is provided by vitamin B1. The process of maturation of erythrocytes is due to vitamin B12.
3. Metabolic processes : The process of calcium and phosphorus metabolism happens due to the presence of vitamin D. Vitamin E remains an antioxidant. Vitamin B1 remains as a co-enzyme in tissue metabolism and it is found useful in the process of oxidation of glucose in CNS. Vitamin B2 is essential for carbohydrate metabolism. Niacin (vitamin B) plays a role as a co-enzyme and is essential for oxidation-reduction reactions. Normal metabolism of amino acids and fat are due to vitamin B6. Biotin (vitamin B) serves as a co-enzyme and co-factor in oxidative metabolism. Vitamin C activates certain intra-cellular enzymes.
1. Atrophy of lacrymal glands of the eye and reduction in tear secretion
2. Corneal epithilium becomes red and dry (xerosis). It may also become wrinkled and Keratinised (xeropthalmia). Appearance of Bitot's spot in the cornea might happen.
3. Cornea may get necrosed and get infected (keratomalacia).
4. May cause night blindness (nyctalopia).
Vitamin D :- Defective calcification of bone, deficiency of vitamin-D, causes rickets in growing children and osteomalacia in adults.
Vitamin E :- Rare in human, sterility in experimental animals.
Vitamin K :-
1. Lack of vitamin K leads to defect in blood coagulation.
2. In humans, vitamins K deficiency leads to haemorrhagic manifestations.
Gross deficiency of vitamins B1, leads to a condition known as beri beri. Beriberi affects nervous and cardiovascular systems.In children andinfants the onset is acute.
Vitamin B2 :
Loss of appetite and other gastro-intestinal symptoms, soreness and burning of lips, mouth and tongue. Fissures appear at edges of the mouth.
Vitamin Niacin :
Its deficiency leads to pellagra. The principal symptoms of pellagra include mental changes, (dementia) dermatitis and stomatitis. The tongue becomes smooth, red and painful.
Vitamin B6: (Pyridoxine)
In human pyridoxine deficiency causes dermatitis around eyes, nose and behind the ears. Fissures appear above the lips and angles of the mouth.
Vitamin B12 :- Its deficiency causes pernicious anaemia, typical sore tongue and several neurological problems related to the spinal cord.
Vitamin C :- Its deficiency in the body leads to scurvy, a diseses charaterised by bleeding gums, loosening and falling out of teeth and intra muscular haemorrages. In the absence of this vitamin the collagen and connective tissue proteins are not synthesised properly.