Vitamins are organic compounds required by the body in small amounts for metabolism, to protect health, and for proper growth and body functions. Vitamins also assist in the formation of hormones, blood cells, nervous-system chemicals, and genetic material. They generally act as catalysts, combining with proteins to create metabolically active enzymes that in turn produce hundreds of important chemical reactions throughout the body. Without vitamins, many of these reactions would slow down or cease.
Vitamins are organic compounds of different chemical nature. These are alcohols, aldehyde, organic acids, their derivatives or nucleotide derivatives.
Classifications of Vitamins
Vitamins are classified according to their ability to be absorbed in fat or water.
- Fat Soluble Vitamins: These are oily and hydrophobic compounds. These are stored in the liver and are not excreted out of the body. Bile salts and fats are required for their absorption. Vitamin A, D, E and K are fat soluble vitamins. Because these vitamins can be stored, their excessive intake may have toxic effect and can result in Hypervitaminosis.
- Water Soluble Vitamins: Vitamin B complex and vitamin C are water soluble. They are compounds of carbon, hydrogen, oxygen and nitrogen. They are not stored in the body therefore they are required daily in small amount.
Fat Soluble vitamins
Vitamin A
Vitamin A is a pale yellow primary alcohol derived from carotene. It includes Retinol (alcoholic form), Retinal (Aldehyde form) and Retinoic acid (acidic form).
Source
- In animal form, vitamin A is found in milk, butter, cheese, egg yolk, liver, and fish-liver oil.
- In plant source it is obtained from vegetables as carrots, spinach, sweet potatoes etc.
Physiological Significance:
- All three forms of vitamin A are necessary for proper growth, reproduction, vision, differentiation and maintenance of epithelial cells.
- Vitamin A accelerates normal formation of bones and teeth.
- Retinoic acid is needed for glycoprotein synthesis.
Deficiency of Vitamin A:
- An early deficiency symptom is night blindness (difficulty in adapting to darkness).
- Other symptoms are excessive skin dryness
- Lack of mucous membrane secretion, causing weakness to resist bacterial attack
- Dryness of the eyes due to a malfunctioning of the tear glands.
- improper growth, exophthalmia
Hypervitaminosis of Vitamin A
Excess vitamin A can interfere with growth, stop menstruation, damage red blood corpuscles, and cause skin rashes, headaches, nausea, and jaundice.
Stability
Vitamin A is sensitive to atmospheric oxygen, trace metal, UV light and acidic pH. It is stable in alkalis and can be stabilized by anti-oxidants e.g., α-tocopherol, hydroquinone.
Assay: Vitamin A can be assayed by UV–Spectrophotometer measurement.
Vitamin D
Vitamin D is found as a mixture of ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3)
Source:
- Vitamin D is obtained from egg yolk, cod liver oil and liver oil from other fishes.
- It is also manufactured in the body when sterols, which are commonly found in many foods, migrate to the skin and become irradiated.
Physiological Significance:
- This vitamin is necessary for normal bone formation and for retention of calcium and phosphorus in the body.
- It also protects the teeth and bones against the effects of low calcium intake by making more effective use of calcium and phosphorus.
- It decreases pH in the lower intestine.
Deficiency:
- Vitamin D deficiency produces rickets in children and Osteomalacia in adult.
- Rickets is characterized by abnormities of the rib cage and skull and by bowlegs, due to failure of the body to absorb calcium and phosphorus.
- Osteomalacia is characterized by softness of pelvic girdle, ribs and femoral bones.
Hyper-vitaminosis of Vitamin D:
- Because vitamin D is fat-soluble and stored in the body, excessive consumption can cause vitamin poisoning, kidney damage, lethargy, and loss of appetite.
Stability
It is sensitive to atmospheric oxygen, trace metals. It is stabilized by anti-oxidants and protective coatings. It should be stored in sealed glass containers and protected from light.
Assay
UV-Spectrophotometry, colorimetry and HPLC.
Vitamin E
The active form of vitamin E is alpha-tocopherol.
Source
- Vitamin E is found in vegetable oils, wheat germ, liver, and leafy green vegetables, fish meal, rice bran, barley grains
- They are also present in little amount in meat, milk and eggs.
Physiological Significance:
- Vitamin E acts as antioxidants. antioxidants used to prevent oxidation of lipids (mainly phospholipids, PUFA’s)
- They play some role in forming red blood cells and muscle and other tissues and in preventing the oxidation of vitamin A and fats.
- It is also associated with cell maturation and differentiation.
- It plays an important role in the management of habitual abortion
Deficiency:
- Deficiency of vitamin E causes sterility in both male and females.
- It causes muscular dystrophy.
- In children it causes haemolysis, creatinuria.
Stability
Vitamin E is sensitive to atmospheric oxygen and UV light.
Assay
Biological method using rat fertility indicator. is used in Vitamin E assay. It can be assayed chemically using Ceric sulphate titration as well as UV-Spectrophotometric method
Vitamin K
Vitamin K is a complex unsaturated hydrocarbon found in two forms Vitamin K1 (Phylloquinone) and Vitamin K2 (Menaquinone).
Source:
- The richest sources of vitamin K are alfalfa, fish livers, leafy green vegetables, egg yolks, soybean oil, and liver.
- It is also produced by bacteria in human intestine therefore no dietary supplement is needed.
Physiological Significance:
- This vitamin is necessary mainly for the coagulation of blood.
- It aids in forming prothrombin, an enzyme needed to produce fibrin for blood clotting.
- Acts as an inducer for the synthesis of RNA.
- It is also required for the absorption of fat.
Deficiency:
- Digestive disturbances may lead to defective absorption of vitamin K and hence to mild disorders in blood clotting.
Hyper-vitaminosis of Vitamin K:
- Administration of large doses of vitamin K produces haemolytic anemia and jaundice in infants because of breakdown of RBCs.
Stability:
Vitamin K is fairly stable to heat. It is decomposed by sunlight and alkali
Assay
Biological assay of vitamin K is by measuring the clotting time of blood from chicks on controlled diets and comparing with standard. Chemical assay of same is via Redox titration and UV spectrophotometer.
Water Soluble Vitamins
Water soluble vitamins are made up of mainly vitamin B complex, and vitamin C. These are fragile, water-soluble substances, several of which are particularly important to carbohydrate metabolism. They include VitaminB1 (Thiamine), Vitamin B2 (Riboflavin), Vitamin B3 (Niacin or Nicotinic Acid), Vitamin B5 (Pantothenic acid), Vitamin B6 (Pyridoxine), Vitamin B9 (Folic acid), Vitamin B12 (Cobalamin) etc.
Vitamib B1 (Thiamine)
Function: metabolism of carbohydrate.
sources: brewers yeast, wheat middlings, rice bran, rice polishings, wheat bran, soybean meal
deficiency: central nervous system failure
Requirement: 2.5 mg/kg (tilapia), 10-15 mg/kg (salmon) and 40-50 mg/kg (shrimp).
Vitamin B2 Riboflavin
Function: metabolic degradation of proteins, COH, lipids
Sources: plants, bacteria, yeast, fish
Deficiency: cataracts (fish), vision, crooked limbs
Requirements: 9 mg/kg (channel catfish), 5 mg/kg (tilapia)
50 mg/kg (shrimp).
Vitamin B3 (Niacin)
.Physiological Significance:
- Nicotinic acid is essential for the normal functioning of skin, intestinal tract and the nervous system.
- Vitamin B3 works as a coenzyme in the release of energy from nutrients.
Source:
- The best sources of niacin are liver, poultry, meat, canned tuna and salmon, whole grain and enriched cereals, dried beans and peas, and nuts.
- The body also makes niacin from the amino acid tryptophan
Deficiency:
- A deficiency of niacin causes pellagra, the first symptom of which is a sunburn like eruption that breaks out where the skin is exposed to sunlight.
- Later symptoms are a red and swollen tongue, diarrhea, mental confusion, irritability, and, when the central nervous system is affected, depression and mental disturbances.
Requirements: 14-28 mg/kg (carp, catfish), 400 mg/kg (shrimp).
Vitamin B3 (Pantothenic Acid)
Physiological Significance:
- Pantothenic acid is essential for growth of infants and children,
- It plays a major role in the metabolism of proteins, carbohydrates and fats.
Source:
- Its main sources are liver, milk, meat, eggs, wheat germ, wheat bran, potatoes, sweet potatoes, tomatoes, cabbage, cauliflower and broccoli. Fruit and other vegetables also have pantothenic acid.
Deficiency:
- Its deficiency causes nausea, vomiting, gastrointestinal disorders, improper growth and fatty liver.
Vitamin B6 (Pyridoxine)
Source:
- The best sources of pyridoxine are whole (but not enriched) grains, cereals, bread, liver, avocadoes, spinach, green beans, and bananas.
- It is also found in milk, eggs, fish, chicken, beaf, pork and liver.
Physiological Significance:
- Pyridoxine, or vitamin B6, is necessary for the absorption and metabolism of amino acids.
- It also plays roles in the use of fats in the body and in the formation of red blood cells.
Deficiency:
- Pyridoxine deficiency is characterized by skin disorders, cracks at the mouth corners, smooth tongue, convulsions, dizziness, nausea, anemia, and kidney stone
Vitamin B9 (Folic Acid)
Physiological Significance:
- Folic acid acts as a coenzyme and help in synthesis of purines and pyrimidines during DNA synthesis.
- It helps in formation and maturation of red blood cells.
Source:
- Folic acid is found in yeast, liver and kidney.
- Fish meat and green leafy vegetables, milk and fruits also provide folic acid.
Deficiency:
- Folic acid deficiency gives rise to megaloblastic anemia.
- The patient suffers from retarded growth, weakness, infertility, inadequate lactation in females and gastrointestinal disorders.
Requirements: 1-4 mg/kg (fish, shrimp)
Vitamin B12 (Cyanocobalmine)
- chemically complex, cobalt nucleus
Physiological Significance:
- It is necessary in minute amounts for the formation of nucleoproteins, proteins, and red blood cells.
- It is necessary for the functioning of the nervous system.
- It stimulates the appetite of the subject
Source:
- Cobalamin is obtained only from animal sources—liver, kidneys, meat, fish, eggs, and milk. Vegetarians are advised to take vitamin B12 supplements.
Deficiency: pernicious anemia, nerve disorders
Requirement: very low 0.015 mg/kg or not at all.
Vitamin C (Ascobic Acid)
Physiological Significance:
- Vitamin C also known as ascobic acid or antiscorbutic vitamin is important in the formation and maintenance of collagen, the protein that supports many body structures and plays a major role in the formation of bones and teeth.
- It also enhances the absorption of iron from foods of vegetable origin.
- The connective tissue fibrils and collagen are synthesized with the help of vitamin C.
- It plays important role in wound repair.
- It protects body against stress.
Source
- Sources of vitamin C include citrus fruits, fresh strawberries, cantaloupe, pineapple, and guava.
- Good vegetable sources are Broccoli, Brussels sprouts, Tomatoes, Spinach, Kale, Green Peppers, Cabbage, and Turnips.
Deficiency:
- This well-known Scurvy is the classic manifestation of severe ascorbic acid deficiency. Its symptoms are loss of the cementing action of collagen and include hemorrhages which lead to loosening of teeth and cellular changes in the long bones of children.
Requirement: 100 mg/kg varies w/age, metabolism.