Vitamins are organic compounds that are required in small amount (µg or mg/day) for normal growth metabolism and proper functioning of the body.
Vitamins are also known as accessory food factors or food hormones. Animal can’t synthesize vitamins, and therefore depends upon plants and microbes for their supply.
Any deficiency of vitamins for a longer period or presence of anti-vitamins in the diet causes deficiency disease or avitaminosis.
However, treatment with antibiotics often results in deficiency of B-Complex vitamins because the intestinal bacteria that synthesize them get killed by such drugs.
For this reason, doctors recommend vitamin B-complex during antibiotic therapy. Excess intake of vitamins may cause some pathological conditions called hyper-vitaminosis. However, it is rare and occurs in case of fat soluble vitamins which can be stored in considerably high amounts.
Types of Vitamins:
On the basis of solubility, vitamins are of two types:
(a) Fat soluble vitamins: Vitamins A, D, E & K.
(b) Water soluble vitamins: Vitamins C and B-complex (B1, B2, B6 etc.)
These are the organic compounds having similar biological properties like vitamins but required in larger amounts.
They are of following types:
(a) Fat soluble vitaminoids:
Essential Fatty acids and ubiquinone’s.
(b) Water soluble vitaminoids:
Biotin (Vit-B), Choline (Vit-B4), Inositol (Vit-B8), bioflavonoids, N- Lipoic acid etc.
Lunin (1881) first discovered them and Funk (1912) coined the term ‘vitamins’. Later, Drummond (1920) proposed the term vitamin by dropping the final ‘e’
Pseudovitamin, Antivitamin and Provitamin:
Pseudovitamins (false vitamins) are certain organic compounds that are structurally similar to some vitamins but don’t show the physiological actions of the vitamin. For example, methylcobalmine is a pseudovitamin of cyanocobalamine (Vit – B12).
Antivitamin is a compound which resembles structurally to a vitamin but inhibits or antagonize the function of the vitamin. For example, pyrithiamine, galactoflavin and avidin are antivitamins of thiamine, riboflavin and biotin respectively. Provitamin is the precursor of a vitamin which when taken through diet is converted into the vitamin in the body, e.g. (3-carotene (provitamin (A), ergosterol (Provitamin D) etc.
Fat Soluble Vitamins:
Axerophthol, antixeropthalmic or antinyctalopic vitamin.
Chemically, vitamin A (C20H29OH) is an unsaturated alcohol called retinol. Vitamin A exists in two isomeric forms: vitamin A (retinol) is a trans-isomer and occurs naturally, whereas vitamin A2 (dehydroretinal or retional2) is a cisisomer and has 30 – 40% of vitamin A actively.
Plant sources like green vegetables, fruits, and cereals supply pro vitamin A (β-carotene) in diet. Animal sources of vitamin A are liver, milk, butter, egg yolk etc. Liver of fresh water fish contain A2.
(i) Retinol (vitamin A aldehyde) combines with lysine residues of opsin protein to form rhodopsin pigments of rod cells of retina, so it is essential for night vision,
(ii) Retinoic acid (vitamin A acid) has some anticancer effects,
(iii) Vitamin A maintains the integrity of epithelial cells; permeability of cell membranes as well as the membranes of organelles,
(iv) In young animals vitamin A causes growth, formation of bones and teeth.
(i) Vitamin A deficiency causes the defective night vision called night blindness (nyctalopia or Henerolopia).
(ii) In children deficiency of vitamin A2 causes xerophthalmia (drying of conjunctiva) and keratomalacia ulceration and softening of cornea) that may lead to complete blindness,
(iii) Toad’s skin is another detectable early symptom of vitamin A where the skin becomes dry and rough particularly in the lateral part of forearms and sides of thigh.
In acute cases of hypervitaminosis A headache, nausea, vomiting and drowsiness noticed. But in chronic cases (prolonged intake) the symptoms develop are anorexia (loss of appetite), alopecia (loss of hair), cracking of lips, dry itchy skin, pain in bones and joints.
Clinically, Vitamin D is called antirachitic vitamin because it possesses the property of curing or preventing ticket.
Chemically Vitamin D is a steroid which is related to calcium metabolism. Hence it is called calciferol. Vitamin D exists in 2 forms i.e. Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol). They are synthesized from the provitamins by the action of UV-rays of sunlight. Because of it, vitamin D is called sunshine vitamin. The provitamin D2 (ergosterol) occurs in plants and the provitamin D3 (7-dehydrocholesterol) occurs in animals. The term vitamin D1 is no longer used.
Vit. D3 obtained from fish liver oil, egg, milk, butter, ghee etc.
(i) Vitamin D3 is also considered as a prohormone which gives rise to a hormone colcitriol (1, 2, 5 Dihydroxy cholecalciferol) by various metabolic changes. Calcitriol has a role in calcium and phosphate metabolism,
(ii) Vitamin D activates the transcription of mRNA for calcium binding protein,
(iii) It helps in the growth and development of bone and teeth,
(iv) Increase the excretion of phosphate.
Vitamin D deficiency leads to rickets in children and osteomalacia in adult. Rickets is characterized by bowlegs, knock knees, bending of ribs leading to pigeon’s breast, enlargement of ankles, knees, wrists, elbow etc. In osteomalacia the bones become weak and fragile instead of being soft due to decalcification of bones.
Excess intake of vitamin D cause increase level of Ca and P. As a result, kidney, arteries, muscles, etc. become calcified. The early symptoms cause anorexia (loss of appetite), thrist, constipation and polyuria followed by nausea, vomiting and diarrhea.
It is called antisterility vitamin or fertility vitamin because of its requirement in proper functioning of reproductive system.
Tocopherol (tokes = child birth; phero = to bear, ol = alcohol)
Vegetable oil, leafy vegetables, milk, cheese, egg, meat etc.
(i) It acts as an antioxidant and prevents oxidation of vitamin A, K, essential fatty acids.
(ii) It keeps the skin glowing by reducing keratinization. Hence, it is also called as beauty vitamin,
(iii) It helps in the normal functioning of skeletal muscles, gonads and renal tubules.
(i) Causes sterility and miscarriage,
(ii) Causes muscular weakness and dystrophy (degeneration.)
It is called antihemorrhagic vitamin or vitamin for blood clotting or coagulation vitamin.
Chemically vitamin K is a naphthoquinone derivative. Naturally it occurs in two forms, i.e. vitamin K1 (phylloquinone) and vitamin K2 (menaquinone or farnoquinone). The vitamin K3 (mendione) is a synthetic product.
Green leafy vegetables, soybean, carrots, potatoes, milk, fish and meats etc.
140 – 200 mg.
(i) Act as co-enzyme Q and participate in oxidative phosphorylation in ETC.,
(ii) Acts as a co-factor of carboxylase,
(iii) Required for fat absorption.
(i) Delay in blood clotting,
(ii) Cause hemorrhagic disease of newborn,
(iii) Defective functioning of liver.
Water Soluble Vitamin
It is called antiscorbutic acid because it prevents scurvy. It is also known as anti- rabies or and cancer vitamin.
Chemically it exists in L-ascorbic acid and L-dehydroascorbic acid (ascorbone). The L-ascorbic acid is ay-lactone (with internal esterification) that is synthesized in plants and most animals except primates and guinea pigs.
Citrus fruits (lemons, oranges), grapes, apple, papaya, guava, vegetables etc.
40 – 50 mg.
(i) It is required for absorption of iron,
(ii) It keeps gums and capillary walls healthy.
(iii) It gives resistance against cold and viruses. Hence, it is often called as anti-viral vitamin,
(iv)It is necessary for wound healing,
(v) It acts as co-enzyme for hydroxylation and oxidation -reduction reactions. Thus, it helps in metabolism of amino acids, collagen synthesis etc.
Deficiency symptoms: It causes scurvy (Sailor’s disease) characterized by bleeding gums, loosening of teeth, fragile capillaries, failure in wound healing, anemia, general weakness etc.
It includes at least 10-11 different water soluble vitamins. They are grouped together as B-complex because all the members’ acts as coenzymes and their actions are closely related.