Vitamins And Their Classifications, Sources And Functions

Vitamins

Vitamins are essential nutrients required by the body in very small amounts. Vitamins do not supply energy but they enable the body to use other nutrients. Since the body cannot synthesis vitamins, they must be provided by food.

Classification of vitamins

  1. Fat soluble vitamins: Vitamins A, D, E and K.
  2. Water soluble vitamins: Vitamins B complex and vitamin C.

Fat Soluble Vitamins

Vitamin A

It is an unsaturated alcohol. Carotene is the precursor of vitamin A. Carotenes exist in three forms viz. alpha, beta and gamma.

Functions

  1. It is necessary for the production of retinal pigments. These pigments are required for vision in dim light.
  2. It is essential for maintaining the integrity of epithelial cells.
  3. It supports growth, especially skeletal growth.
  4. It is anti-infective.
  5. It protects against cancers like lung cancer.

Sources

Vitamin A is present in carrot, spinach, green vegetables, papaya and mangoes. It is also prevent in diary products like milk, butter and cheese.

Deficiency

Deficiency of vitamin A leads to:

  1. Night blindness, xeropthalmia, and keratomalacia.
  2. Bitot’s spots: These are triangular silvery white spots in the bulbar conjuctiva. Their presence in children is characteristic of vitamin A deficiency.
  3. Abnormally thickened skin.
  4. Retarded growth.
  5. Lowered resistance to infection.
  6. Atrophy of epithelial cells lining mucous membranes and secretory glands.

Requirement

5000 I.U. daily.

Vitamin D

It occurs in two forms:

  1. Calciferol (Vitamin D2). It is obtained by irradiation of ergosterol.
  2. Cholecalciferol (D3). It is found in animal fats and fish liver oils. It is also produced on exposure of cholesterol of skin to UV rays of sunlight.

Functions

  1. In the intestine it promotes absorption of calcium and phosphorus.
  2. It is necessary for bone and teeth formation.
  3. In the kidney it increases the reabsorption of phosphate.
  4. It is also necessary for normal growth.

Deficiency

Deficiency of Vitamin D produces rickets in children and osteomalacia in adults. These tow diseases are characterized by deformities of bones.

Requirement

1000 I.U. daily.

Vitamin E

It belongs to a group of compounds called tocopherols. Alpha, beta, gamma and delta tocopherols are known. Of these, alpha tocopherol is the most active form.

Functions

  1. It is necessary for reproduction and its deficiency leads to sterility.
  2. It is necessary for muscle metabolism. It is required for the preservation or storage of creatine in muscles.
  3. By an antioxidant effect, it protects vitamin A from destruction.
  4. It prevents hemolysis by protecting unsaturated fatty acids of erythrocyte membrane.
  5. Of all these actions the antifertility effect is very important.

Source

Soya bean oil, wheat germ oil and rice germ oil.

Deficiency

deficiency of vitamin E produces abortion and sterility in animals. No symptom has been established in humans.

Requirement

The daily requirement of vitamin E is 15 to 30 mg.

Vitamin K

The major forms of vitamin K are vitamin K1 and vitamin K2

Functions

Vitamin K is necessary for the synthesis of clotting factors especially prothrombin. Its deficiency decrease prothrombin content of blood.

Sources

Vitamin K1 is present in liver, spinach, green leafy by intestinal bacteria.

Deficiency

Increase bleeding due to defective clotting mechanism.

Requirement

0.03 mg per kg daily.

Water soluble vitamins

The water soluble vitamins which belong to the group of vitamin B complex are thiamine, riboflavin, nicotinic acid, pyridoxine, pantothenic acid, inositol, biotin, methionine, folic acid and cyanocobalamin.

Thiamine (Vitamin B1, Aneurine)

Sources

Peas, beans, oatmeal, pea nuts, vegetables, and fruits.

Deficiency

Deficiency of thiamine produces

  1. Beriberi a symptom complex with characteristic neuropathy.
  2. Wernicke’s encephalopathy characterised by confusion, ophthalmoplegia, nystagmus, tremors, and mental retardation.

Beriberi can be prevented by eating a well balanced mixed diet rich in thiamine e.g. parboiled and undermilled rice.

Requirement

2mg daily; increases with intake of more carbohydrates.

Riboflavin (Vitamin B2)

sources

Milk, eggs, liver, kidney, green leafy vegetables, meat and fish.

Deficiency

Deficiency of riboflavin produces angular stomatitis. It is prevalent in malnourished children and it is used as an index for malnutrition. Other deficiency symptoms are:

  1. Delayed wound healing.
  2. increased susceptibility to cataract.
  3. impaired neuromotor function.

Requirement

2 to 3 mg daily.

NIACIN (Nicotinic Acid, Vitamin B3)

Sources

Liver, kidney, meat, poultry, fish, lengumes and ground nut.

Deficiency

Deficiency of niacin produces pellagra. This disease is characterised by three D’s diarrhea, dermatitis and dementia. In addition, glossitis and stomatitis may also occur.

Pellagra occurs in malnourished individuals who live on a diet containing maize or sorghum. Pellagra can be prevented by avoiding maize and sorghum and by taking a mixed diet containing milk and or meat.

Requirement

The daily requirement of niacin is 50 mg.

Pyridoxine (Vitamin B6)

Sources

Milk, liver, meat, egg yolk, fish, whole grain cereals, legumes and vegetables.

Deficiency

Irritability, abdominal distension, loss of body weight and anemia in children. In adults, the deficiency produces lesions of skin and mouth, peripheral neuritis and mental changes. Of these diseases peripheral neuritis is the most important deficiency diseases.

Requirement

2mg per day for adults. during pregnancy and lactation, the requirement is 2.5 mg per day.

Folic Acid

Sources

Rich in vegetarian foods like cabbage, spinach and all green leafy vegetables. Non-vegetarian foods contain less folic acid.

Deficiency

The deficiency of folic acid leads to defective maturation of red blood cells. This leads to megaloblastic anemia. This type of anemia is characterised by the release of abnormally large sized red blood cells. But these RBC’s have sufficient hemoglobin.

Requirement

100 to 300 micrograms daily.

Cyanocobalamin (Vitamin B12)

Sources

Non-vegetarian foods like meat, beaf, liver kidney, oysters, eggs and milk. Very little is present in vegetarian food like leguminous plants.

Deficiency

Deficiency of cyanocobalamin leads to megaloblastic anemia very similar to the deficiency of folic acid. Both cyanocobalamin and folic acid are required for the development of red blood cells.

Requirement

The daily requirement is 1 to 1.5 micrograms per day.

Ascorbic Acid (Vitamin C )

Sources

Citrous fruits, tomatoes and green vegetables. Amla and guava fruits are very rich sources of vitamin C.

Deficiency

Deficiency of vitamin C produces scurvy. The symptoms of scurvy are weakness, fatigue, pain in the joints and muscles. Also, there is bleeding of gums and loosening of teeth.

Requirement

40 to 50 mg daily.

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