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Essay on Vitamins
Essay Contents:
- Essay on the Introduction to Vitamins
- Essay on the Characteristics of the Vitamins
- Essay on the Vitamins Acting on Different Body Systems
- Essay on the Types of Vitamins
- Essay on the Vitamins and Endocrines
- Essay on the Role of Vitamins on Metabolism
Essay # 1. Introduction to Vitamins:
The disease Scurvy is said to have afflicted the Crusaders. During 1400’s and 1500’s it was one of the prevalent diseases in Europe. Scurvy was reported by Vasco de Gama during his sea voyages, and Jacques Cartier in 1535 reports loss of 25% of his sailing crew due to scurvy.
As early as 1601 ships of the East India Company carried oranges and lemons to prevent scurvy on the recommendation of the English privateer, Sir James Lancaster. In 1720 Kramer, an Austrian Army Physician, had written about the disease scurvy and its cure after the intake of oranges or green vegetables.
In 1753 Captain Lind of the British Navy proved that Scurvy could be cured by oranges and lemons. In 1882 Admiral Takaki, Director-General of the Medical Service in Japan, observed that Beriberi could be cured by increasing fresh vegetables meat, fish and other proteins in the diet. In 1890 Eijkman in Dutch East Indies found out that birds fed with polished rice developed Polyneuritis along with other signs similar to that of Beriberi.
Dr. Casimir Funk of the Lister Institute of London isolated in the antiberiberi substance in pure form and as it was though to be an amine, and at the suggestion of Dr. Max Nierenstein the term vitamine was used. In 1888 Lunin and Professor Bunge of Basle observed that life was not sustained by diet containing purified proteins, carbohydrates, fats and minerals, but when such food was supplemented by milk the normal growth and longivity are maintained.
So they concluded that there must be some substances, besides carbohydrate, protein, fat and minerals, which are essential for nutrition. In 1915 McCollum and Davis established the presence of essential factors for growth in milk and egg-yolk, (a) ‘Fat-soluble A’ found in eggs and butter, (b) ‘Water-soluble B’ in milk, etc. In 1920 Professor J.C. Drummond suggested the term for the essential factor (vital) as vitamin after dropping the word.
So the vitamins may be defined as potent organic compounds which is found in foods in variable and minute quantity, and must be supplied to the animal organisms from external sources, so that specific physiological functions, vital to life, may go on normally.
They are neither oxidized to supply energy nor used to build tissue structures. However, it is difficult to give a proper definition which would be concise and complete due to the diverse and incomplete knowledge regarding these substances.
Essay # 2. Characteristics of the Vitamins:
i. Distribution:
The vitamins are widely distributed in nature-both in the animal and vegetable kingdoms. All vitamins are manufactured in plants. The animals can manufacture a few only but can store all to some extent. Almost all common articles of food contain more than one vitamin.
ii. Daily Requirement:
Vitamins can perform their work in very low concentration. Hence, the total daily requirement is usually very small. The daily need of any vitamin for any individual is not a fixed quantity. It varies according to the rate of metabolism. In people undergoing heavy muscular work, in hyperthyroidism, pregnancy, lactation, growing children, i.e., in all cases where metabolism is very high, the vitamin requirement is proportionally more. Generally, a man doing ordinary work can obtain enough vitamins from his balanced mixed diet.
iii. Store:
Vitamins can be stored in the body to some extent, for example, the fat-soluble vitamins are stored in the liver and the subcutaneous tissue, vitamin C in adrenal cortex, etc.
iv. Fate:
Vitamins are partly destroyed and are partly excreted.
v. Synthesis in the Body:
Some vitamins are synthesized in the body, viz., and vitamin A from pro-vitamin carotene and vitamin D from ultra-violet irradiation of vitamin D-precursors, e.g., ergosterol. Some members of the vitamin B complex are synthesized by micro-organisms in the intestinal tract. Vitamin C is also synthesized in some animals e.g., rat.
vi. Vitamins are not Destroyed in the Digestive Process:
Vitamins are not destroyed in the digestive process and are, therefore, absorbed as such. Hence, all vitamins are effective when administered orally.
vii. Mode of Action:
Not exactly known in all cases. Several of them have been proved to act as a coenzyme of other metabolic enzymes. Since the enzyme system of a tissue is specific in nature, it is quite probable that, a particular vitamin acts selectively upon one tissue (i.e., acts as a coenzyme of the specific enzymes of these tissues). This conception will help one to explain why the deficiency of a particular vitamin specially affects some tissues and systems and leaves others more or less untouched.
viii. Essential Constituent of Diet:
Although they are essential for life, yet all vitamins are not required for all the species of animals. One which is required for rats may not be so for man. The physiological requirement is met with the synthesis of a particular vitamin in the organism.
ix. Non-Antigenic:
Vitamins are not antigenic.
x. Solubility:
Some of them are soluble in water and others in fats and fat-solvents.
xi. Artificial Synthesis:
Most of the vitamins have been artificially synthesized.
Essay # 3. Vitamins Acting on Different Body Systems:
The following is a brief summary of the various vitamins acting on different tissues and systems, it must be remembered that, like the endocrines, vitamins also act in close co-operation with one another. The functions of a particular vitamin are not independent, but depend upon the proper activity of other vitamins.
i. Vitamins Acting on Nervous System:
(1) Vitamin A (2) Vitamin B – (a) Thiamine, (b) Nicotinic acid (Niacin), (c) Pantothenic acid, (d) Pyridoxine, (e) Choline, (3) Vitamin D – Indirectly through its action on bones.
ii. Vitamins Acting on Alimentary System:
(1) Vitamin A – On the epithelium, glands and secretions.
(2) Vitamin B – Thiamine (tone, appetite and secretion), Riboflavin (ulcer mouth), Nicotinic acid (Niacin) (gastro-intestinal) disorders in pellagra).
(3) Vitamin C (malformations of teeth, haemorrhages from the gums, intestine, and increased susceptibility to infections of the gastro-intestinal tract, etc.)
iii. Vitamins Acting on Circulatory System and Blood:
(1) Vitamin B – (a) Thiamine (cardiac damage of beriberi, increased blood lactate), (b) Folic acid, (c) Cyanocobalamin (vitamin B12), (d) Pyridoxine. (2) Vitamin C (3) Vitamin D (on blood calcium) (4) Vitamin K (5) Vitamin P.
iv. Vitamins Acting on Bone Formation:
(1) Vitamin A.
(2) Vitamin C.
(3) Vitamin D.
v. Vitamins Acting on Epithelium, Skin and Hair:
(1) Vitamin A (2) Vitamin B (a) Riboflavin (b) Nicotinic acid (Niacin), (c) Biotin, (d) Pyridoxine, (e) Inositol, (f) Para-amino benzoic acid (PABA) (3) Vitamin C.
vi. Vitamins Acting on Reproductive System:
(1) Vitamin A. (2) Vitamin B – (a) Pyridoxine, (b) Folic acid, (c) Pantothenic acid, (d) Vitamin B12, (3) Vitamin C (4) Vitamin E.
vii. Vitamins Acting on Growth:
(1) Vitamin A (2) Vitamin B12 (3) Vitamin B, complex (including B12) (4) Vitamin C (5) Vitamin D.
Essay # 4. Types of Vitamins:
1. Vitamin A (Retinol):
Vitamin A is a fat soluble oily liquid which is concerned with the maintenance of healthy epithelium. Its deficiency leads to keratinisation of the epithelium of the respiratory tract, changes in the conjunctiva and in the cornea, which may lead to night blindness (xerophthalmia) and increased susceptibility to infections. Vitamin A in doses of 50,000 IU is given in deficiency states causing night blindness or epithelial changes.
Massive overdoses can cause rough skin, dry hair, liver damage, headache and vomiting. Excessive doses may be teratogenic and are best avoided in pregnancy and breast-feeding.
2. Vitamin B Group:
These are water-soluble vitamins.
3. Vitamin B1 (Thiamine):
Thiamine is essential for certain stages in carbohydrate metabolism. Its deficiency leads to a nervous system disorder known as beriberi, which is characterized, by heart failure and polyneuritis. Thiamine deficiency may result not only from inadequate intake, but also from disturbances of metabolism such as seen in chronic alcoholism.
Thiamine in high doses (50-100 mg daily) is used in polyneuritis, Wernicke’s encephalopathy and Korsakov’s psychosis caused by chronic alcoholism. Anaphylactic shock may occasionally occur after parenteral administration.
4. Vitamin B2 (Riboflavin):
Riboflavin is concerned with the intracellular metabolism and is necessary for antibody production, red blood cell formation, cell respiration and growth. Deficiency of riboflavin causes several symptoms, including angular stomatitis, glossitis, skin lesions, anemia, and neuropathy. The syndrome is called ariboflavinosis. Its deficiency may also result in increased incidence of cataract formation and vascularisation of cornea. Riboflavin is recommended in arteriosclerosis, hypertension, and diabetes, obesity, with oral contraceptives and during periods of strenuous exercise.
5. Vitamin B3 (Niacin):
Niacin (nicotinic acid) is converted 10 coenzyme, nicotinamide adenine dinucleotide (NAD), which is vital for the proper functioning of a large number of enzymes in the body. It has important roles in the normal secretions of gastric and bile fluids, in the synthesis of sex hormones, in proper functioning of the nervous and circulatory systems. It can lower triglycerides, raise HDL, and lower LDL.
Niacin deficiency leads to a disorder known as pellagra, which may occur in alcoholism and renal failure. Pellagra is characterized by the “3Ds”, namely diarrhea, dermatitis and dementia. Chronic alcoholism, renal failure and deficient diets are the usual cause for its deficiency.
Niacin is particularly useful in combined hyperlipidemia and in patients with low levels of HDL, treatment of pellagra. Niacin cream is used topically in the treatment of acne vulgaris.
Niacin is a potent vasodilator and requires extensive patient education in hyperlipidemia, where it causes flushing and tingling of the face, because of the use of large doses (maximum dose up to 2000 mg/day). For the treatment of niacin deficiency, it is available as 50 mg tablets. Niacin should be used with caution in pregnancy, diabetes, liver disease, gout, glaucoma and peptic ulcer.
6. Vitamin B6 (Pyridoxine):
Pyridoxine is involved in many metabolic processes. It is required for normal functioning of the nervous system, including the brain. It is involved in red blood cell formation and for that of DNA and RNA. It is important in immune function and is the body’s mechanisms to prevent atherosclerosis. It blocks the formation of homocysteine, which promotes the deposition of cholesterol around heart muscle.
Deficiency of pyridoxine causes dry and flaking skin, nausea and vomiting, stomatitis, peripheral neuritis, seizures, mental confusion, anemia, seborrhea like lesions, growth retardation and impaired wound healing. Drugs such as antidepressants, oral contraceptives, isoniazid, and estrogens may lead to deficiency of pyridoxine.
Pyridoxine is commonly used to prevent and treat vomiting of pregnancy or following irradiation, premenstrual syndrome, convulsions in infants and children, polyneuritis associated with drugs like isoniazid, hydralazine, penicillamine and cycloserine and for the wound healing. High doses can damage peripheral nerves and should only be used when indicated for a specific clinical condition.
7. Vitamin B12 (Cyanocobalamin):
Cyanocobalamin is the extrinsic factor required for the maturation of RBC. Its deficiency causes megaloblastic anemia, glossitis, and degenerative changes in the nervous system. The syndrome produced by cyanocobalamin deficiency is known as pernicious or Addison’s anemia. It is available as hydroxocobalamin and is given by injection in doses of 1 mg thrice weekly in pernicious anemia. Vitamin B complex also includes other substances such as aminobenzoic acid, biotin, choline, inositol and pentothinic acid but there is no evidence of their therapeutic value.
8. Vitamin C (Ascorbic Acid):
Ascorbic acid is water soluble and is necessary for the formation and maintenance of a cement-like substance between cells. Its deficiency causes a condition known as scurvy, which is characterized by bleeding tendencies due to increased capillary fragility.
Bleeding occurs into skin and mucous membranes involving the gums, periosteum of bones and joints producing pain and tenderness. Patient becomes anemic. Scurvy is treated by giving vitamin C in doses of 500 mg daily. Vitamin C has also been used for promoting wound healing or amelioration of cold though the efficacy of this medication is not proven.
9. Vitamin D (Calciferol):
Calciferol, a fat soluble vitamin, is essentially concerned with calcium metabolism and bone formation. Its deficiency leads to inadequate calcification of bones, resulting in their becoming soft and easily deformed. Calciferol deficiency causes rickets in children and osteomalacia in adults.
Calciferol requires hydroxylation by the kidney to its active form calcitriol, which is responsible for active calcium absorption in the gut. Calcitriol is effective in promoting calcium absorption and raising the plasma calcium concentrations in patients whose endogenous calcitriol production is impaired. This is the case in renal failure and in hypoparathyroidism (parathyroid hormone is required for renal production of calcitriol from calciferol).
Calcitriol and its analogue alfacalcidol are effective in microgram doses compared with the milligram doses needed with calciferol.
Calcitriol and alfacalcidol are indicated in patients with severe renal impairment, in hypoparathyroidism and postmenopausal osteoporosis in doses of 0.25-1 microgram daily.
Calciferol (vitamin D) either by mouth or by a single depot injection of 7.5 or 15 mg is the drug of choice for the treatment of nutritional osteomalacia or rickets.
Overdose with calciferol is dangerous and leads to deposition of calcium in the kidneys and other organs. Symptoms of over dosage include anorexia, lassitude, GIT disorders, weight loss, polyuria, sweating and headache.
10. Vitamin E (Tocopherol):
Deficiency of this fat soluble vitamin rarely occurs in adults and produces no clear clinical syndrome. In children, with congenital cholestasis, vitamin E deficiency is associated with neuromuscular abnormalities, which respond only to parenteral vitamin E. Vitamin E is an antioxidant and is believed to reduce the incidence of cancer, vascular, neurological and metabolic disorders and increase the life span, but there is little scientific evidence of its value.
11. Vitamin K (Phytomenadione):
Vitamin K is necessary for the production of blood clotting factors (pro-thrombin and factors VII, IX and X) and proteins necessary for the normal calcification of bone. It is fat soluble and requires bile salts for proper absorption. Vitamin K is also synthesized by the intestinal bacterial flora.
Deficiency of vitamin K may occur in biliary obstruction or hepatic disease. Infants are relatively deficient in vitamin K, because it is not synthesized by the gut bacteria which may lead to hemorrhagic disease of the new born.
Vitamin K is given prophylactically in all new born babies to prevent bleeding. It is used as an antidote to coumarin anticoagulants. Menadiol sodium phosphate is a synthetic analogue of vitamin K and is water soluble. It is given orally in malabsorption syndromes or states in which bile (necessary for absorption of fat soluble vitamin) is deficient.
Menadiol causes hemolytic anaemia in moderate doses especially in G6PD deficiency and vitamin E deficiency. It is contraindicated in neonates and infants and late pregnancy, as neonatal hemolytic anemia may lead to hyperbilirubinemia and kernicterus.
12. Ginseng:
Ginseng is a herbal preparation which is a constituent of many multivitamin tablets. It contains saponins, glycosides and sterols, and is claimed to have a wide variety of actions, including improvement in adrenal, muscular and cerebral functions. Ginseng has been used for its anti-fatigue and anti-stress action. Its use is not advisable in healthy individuals for long periods as it has estrogen like effects and is liable to cause hypertension.
Essay # 5. Vitamins and Endocrines:
Evidence is fast accumulating, indicating that some of vitamins and hormones act in close co-ordination in exerting their action on different physiological aspects.
Major examples are indicated below:
1. Vitamin A:
a. Adrenal Cortex:
A fall in the synthesis of adrenal cortical steroids has been observed in Vitamin A deficiency which results depressed neoglucogenesis. It is possible that Vitamin A or some loosely related molecule acts as a coenzyme for the enzyme, concerned in some steps in the synthesis of one or more cortical hormones controlling a triose → glucose reaction. It can be corrected after administration of this vitamin
b. Gonads:
Testicular atrophy develops in vitamin A deficiency which can be corrected by administration of this vitamin. There is also disturbance in oestrous cycle during deficiency of this vitamin. Administration of vitamin A has been observed to improve fertility in catties.
c. Thyroid:
Thyroid hormone is required for the conversion of carotene to vitamin A. Hypertrophy of the thyroid gland results in Vitamin A deficiency and atrophy in hypervitaminosis. Rate of formation of thyroxine decreases in vitamin A deficiency. As vitamin A is directly related to growth, naturally seems that it may be concerned with thyroid activity.
2. Vitamin D:
Parathyroid – Vitamin D and parathyroid act synergistically on calcium metabolism. So both cause resorption of bone and increased transport of calcium through intestinal and renal epithelium.
3. Vitamin E:
Sex glands – Although vitamin E itself does not affect the normal process of ovulation, fertilization or implantation in female rats, guinea-pigs or mice but it causes defective development of placenta and thereby death of foetus and its resorption takes place. In male animals degeneration of seminiferous tubules in testes has been noted in vitamin E deficiency.
4. Pantothenic Acid:
a. Adrenal Cortex:
It appears that there is a close functional relationship between pantothenic acid and adrenal cortex. In deficiency of pantothenic acid, adrenal necrosis has been noted. This vitamin has been found to protect rats from the harmful effects of excessive stress and to maintain adrenalectomised rats in good condition along with NaCl.
b. Gonads:
Impaired reproduction has been noted in deficiency of this vitamin.
5. Pyridoxine:
Gonads – The foetus has a high requirement of vitamin B6 and for this reason this vitamin should be supplied in larger amounts during pregnancy.
6. Vitamin B12:
a. Thyroid:
Vitamin B12 can correct the growth retardation of adult or young rats placed on diet supplemented with the thyroid hormone.
b. Gonads:
This vitamin is also important for normal reproduction in some classes of laboratory animals
7. Folic Acid:
Sex glands – Folic acid is required for the maintenance of normal pregnancy.
8. Ascorbic Acid:
a. Insulin:
The synthesis of insulin in the beta cells of islets of Langerhans is impaired during vitamin C deficiency, resulting in hyperglycaemia and disturbance in carbohydrate metabolism.
b. Adrenal Cortex:
Hypertrophy of the adrenal cortex has been noted in scurvy which might be due to its increased activity.
9. Thiamine:
This vitamin is concerned with the synthesis of cortical hormones which regulates the level of blood cholesterol.
Essay # 6. Role of Vitamins on Metabolism:
Following vitamins are related to metabolism:
I. Vitamin B Complex:
1. Thiamine (Vitamin B1):
a. Relation with Carbohydrate Metabolism:
Thiamine acts as a coenzyme of the carboxylase which helps in the oxidative decarboxylation of alpha-keto acids, viz., pyruvic acid and alpha-ketuglutaric acid. It also acts as a coenzyme in the reaction of transketolation. It is an essential step in the oxidation of sugar in the tissues including brain.
In the absence of this vitamin, pyruvic and lactic acids fail to be degraded and hence, they are accumulated in blood and tissues. The polyneuritis with tenderness of the muscles of the feet and legs, ataxia and muscular weakness which occur in beriberi, are all due to diminished utilization of carbohydrate. Pyruvic acid accumulates in the brain stem and cerebrospinal fluid. Hearts also become weak and enlarged due to accumulation of pyruvic acid.
b. Relation with Fat and Protein Metabolism:
Thiamine also helps the enzyme system which is responsible for the synthesis of fats from carbohydrates and proteins.
2. Lipoic Acid (Thiotic Acid):
It takes part in the oxidative decarboxylation of pyruvic acid and alpha-ketoglutaric acid along with other member of B vitamin to acetyl CoA and succinyl CoA respectively.
3. Riboflavin (Vitamin B2):
Relation with tissue oxidation and protein, carbohydrate and fat metabolism: Riboflavin containing coenzyme, flavin mono nucleotide (FMN) and flavin adenine dinucleotide (FAD) takes part in a number of enzymatic reactions. This vitamin is also related with the metabolism of protein. It helps in the general metabolic processes mainly relates to dehydrogenation.
4. Nicotinic Acid (Niacin):
Relation without tissue oxidation, carbohydrate and fat metabolism:
Nicotinic acid remains as a part of at least two enzymes systems:
(a) Nicotinamide adenine dinucleotide (NAD), and
(b) Nicotinamide adenine dinucleotide phosphate (NADP).
The reduced form of NAD and NADP are NADH and NADPH respectively, they all take part in various oxidation-reduction reactions of the body. Niacin helps in the general metabolic processes relating to the dehydrogenase system.
5. Pantothenic Acid (Vitamin B3):
Relation with carbohydrate and fat metabolism: Pantothenic acid as coenzyme A (CoA) is transformed into acetyl CoA or active acetate, a pivot on which transfer or acetyl mechanism depends. For various metabolism functions involving acetyl CoA vide p, 646. Active succinate and acyl-carrier protein (ACP), other derivatives of pantothenic acid take part in fatty acid and metabolism.
6. Pyridoxine (Vitamin B6):
Relation with protein, fat and carbohydrate metabolism: Pyridoxine is essential for lower mammals. This vitamin takes part in the normal tryptophan metabolism being a coenzyme of the enzyme kynurenase, in reaction of kynurenine to anthranilic acid.
It also acts as a coenzyme for the following enzymes:
(a) Transminase,
(b) Decarboxylase, enzymes which decarboxylase tyrosine, arginine, glutamic acid, 3-4 dihydroxyphenylanine (DOPA), etc.
(c) Deaminase, and
(d) Desulphydrases.
It is related to the metabolism of long-chain polyunsaturated fatty acids. It helps in the synthesis of fats from proteins and carbohydrates, all these show that pyridoxine definitely takes part in protein metabolism and possibly also in fat and carbohydrates metabolism.
7. Folic Acid:
Relation with Nucleoprotein Metabolism:
Folinic acid, derived from folic acid, acts as a coenzyme in the transfer of formyl and hydroxymethyl group in the biosynthesis of purines etc.
8. Cyanocobalamin (Vitamin B12):
a. Relation with Nucleoprotein Metabolism:
Vitamin B12 plays an essential role in the synthesis of nucleic acid. Deficiency causes a disturbance of the deoxyribose nucleic acid (DNA) metabolism.
b. Relation with Protein Metabolism:
This vitamin influences protein metabolism as it helps in the biosynthesis of methyl group, in the process of transmethylation and also in isomerisation as that of glutamic acid.
c. Relation with Carbohydrate and Fat Metabolism:
When a diet, high in carbohydrate but low in fat, fed to weanling rat, there is an increased requirement of vitamin B12. Dietary depriviations of vitamin B12 results decrease in reduced glutathione content, enzymatic degradation of glucose to ribose in the red blood cells and in the hepatic NADH + H+ as well as in the increase of CoA. After administration of Vitamin B12 or glutathione (GSH), hyperglycaemia can be corrected. These results show that vitamin B12 plays an important role in the conversion of carbohydrate to fat.
9. Biotin (Vitamin H):
Relation with protein metabolism: It acts as a coenzyme and helps in carboxylation reaction taking place in urea cycle in the process of biosynthesis of pyrimidines, fatty acids etc. It also helps in the deamination of threonine, serine and aspartic acid.
II. Vitamin C (Ascorbic Acid):
Relation with carbohydrate, protein and fat metabolism: Ascorbic acid is related to carbohydrate metabolism. After injection of dehydroascorbic acid in animals diabetic condition is produced. Vitamin C takes part in the tissue oxidation probably by acting as hydrogen – carrier. It helps in the oxidation of p-hydroxyphenyl pyruvic acid to homogentistic acid which is the intermediate metabolic product of tyrosine metabolism. It also helps in the development of protein matrix and deposition of calcium and phosphate in the bones.
III. Vitamin D:
Relation with Calcium and Phosphorous Metabolism:
Vitamin D helps in the bone formation by an indirect action or bone cells and in the development of the normal teeth. It attacks the tissue of phospholipids and liberates their phosphoric acids. The phosphoric acids combine with calcium and are deposited as calcium phosphate in bones. This vitamin also activates the enzyme phosphatase in bone and soft tissues.
IV. Vitamin A:
It plays some part in protein synthesis. It is directly concerned in the formation of mucopolysaccharides and has specific function on glucose synthesis by stimulating enzymes concerned.
V. Vitamin E:
It acts as a cofactor in the electron transport system operating between cytochromes b and c.