There are 13 vitamins A, C, D, E, K, B12, and 7 grouped under the vitamin B complex.

Human body can synthesize vitamin B(niacin) and vitamin D on their own.

Vitamins are categorized into two groups;
1. Fat soluble Vitamins - A, D, E and K. Lipids such as triglycerides contain these vitamins, which are absorbed from the intestine into the bloodstream and then stored in fatty tissue such as liver.
2. Water soluble Vitamins - Vitamin C, B complex and B 12. only small amounts of Vitamin C and B complex are stored by the body and hence, regular intake of these vitamins is necessary.

Functions: normal growth, formation of bones and teeth, maintenance of night vision, and protecting the linings of the respiratory, digestive, and urinary tracts against infection.

Vitamin A is absorbed by the body in the form of retinol.  Carotene, the precursor of retinol, is found in various vegetables(carrots) and fruits.

Dietary sources: liver, fish-liver oils, egg yolk and dairy products.

Deficiency diseases: Night blindness, Xerophthalmia, Keratomalacia, and complete blindness.

Excessive intake leads to loss of appetite, reduced resistance to infection, skin peeling, stunted growth, hair loss and irregular menstruation. Excessive intake during pregnancy may cause birth defects. In infants, excessive intake may cause skull deformities, which disappear if the diet is corrected.

Vitamin B12

(cyanocobalamin)

Functions: production of the genetic material, production of red blood cells in bone marrow, utilization of folic acid and carbohydrates in the diet, and functioning of the nervous system.

Dietary sources: liver, kidney, chicken, pork, fish, eggs, and dairy products.

Deficiency diseases: Megaloblastic anaemia, sore mouth and tongue, numbness and tingling in the limbs, depression and memory loss. High intake of vitamin B12 has no known harmful effects.

1. Thiamine(vitamin B1)(Aneurin)

Functions: Essential for various enzymes involved in the utilization of carbohydrates, functioning of nerves, muscles, and the heart.

Dietary sources: whole-grain cereals, wholemeal breads, brown rice, pasta, liver, kidney, pork, fish, beans, nuts, and eggs.

Mild deficiency results in tiredness, irritability, and loss of appetite.

Severe deficiency causes abdominal pain, constipation, depression, memory impairment, and beriberi.

In alcoholics, it causes Wernicke–Korsakoff syndrome, which leads to loss of memory for recent events although long term memory is intact.

Vitamin B1 is lost in polished rice.

2. Riboflavin(vitamin B2)

Functions: necessary for enzymes involved in the breakdown and utilization of carbohydrates, fats, and proteins; the production of energy in cells; the utilization of other B vitamins; and hormone production by the adrenal glands.

Dietary sources: Liver, whole grains, milk, eggs, and brewer’s yeast.
Deficiency disorders: soreness in and around tongue and mouth, eye disorders such as amblyopia and photophobia.

3. Niacin(Nicotinic acid)

Functions: needed by enzymes involved in the metabolism of carbohydrates and fats, the functioning of the nervous and

digestive systems, the manufacture of sex hormones, and the maintenance of healthy skin.

Dietary sources: liver, lean meat, fish, nuts, and dried beans.
Deficiency disorders: Pellagra - causes gastrointestinal disturbances and erythema, dermatitis, diarrhoea, and nervous or mental disorders. Pellagra is often linked to over-dependence on maize as a staple food.

4. Pantothenic acid

Functions: essential for the enzymes involved in metabolism of carbohydrates and fats, manufacture of corticosteroids

and sex hormones, utilization of other vitamins, functioning of the nervous system and adrenal glands, and growth and development.

Dietary sources: vegetables, cereals, and animal foods.

Deficiency leads to fatigue, headache, nausea, abdominal pain, numbness and tingling, muscle cramps, and susceptibility to respiratory infections. Prolonged deficiency leads to peptic ulcer.

5. Pyridoxine(vitamin B6)

Functions: needed by enzymes and hormones involved in the utilization of carbohydrates, fats, and proteins, manufacture of red blood cells and antibodies, functioning of the digestive and nervous systems, and maintenance of healthy skin.

Dietary sources: liver, chicken, pork, fish, whole grains, wheat germ, bananas, potatoes, and dried beans.

Pyridoxine is also synthesised by intestinal bacteria.

Deficiency may cause weakness, irritability, depression, skin disorders, inflammation of the mouth and tongue, anaemia, and, in infants, seizures. In very large amounts, pyridoxine may cause neuritis.

6. Biotin(vitamin H)

Functions: essential for enzymes involved in the breakdown of fatty acids and carbohydrates and for the excretion of the waste products of protein breakdown.

Dietary sources: liver, peanuts, dried beans, egg yolk, mushrooms, bananas, grapefruit, and watermelon.

Biotin is also synthesised by intestinal bacteria.

Deficiency causes weakness, tiredness, poor appetite, hair loss, depression, inflammation of the tongue, enteritis and eczema.

7. Folic acid

Functions: necessary for enzymes involved in the manufacture of nucleic acids and consequently for growth and

reproduction, production of red blood cells, and functioning of the nervous system.

Dietary sources: green vegetables, mushrooms, liver, nuts, dried beans, peas, egg yolk, and wholemeal bread.
Deficiency disorders: anaemia, sores around the mouth, and, in children, poor growth.

Severe deficiency may occur during pregnancy or breastfeeding.

Vitamin C

Ascorbic acid

Functions: growth and maintenance of healthy bones, teeth, gums, ligaments, and blood vessels; production of certain neurotransmitters and adrenal gland hormones; immunity against infection and wound healing and absorption of iron.

Dietary sources: citrus fruits and vegetables.

Mild deficiency leads to weakness, general aches, swollen gums, and nosebleeds.

Serious deficiency leads toscurvy and anaemia.

Excessive consumption forms kidney stones(calculi).
Vitamin C is lost when foods are processed, cooked, or kept warm.

Vitamin D2 - Calciferol

Vitamin D3 - Cholecalciferol

Function: regulates the balance of phosphate and calcium in the body, aids calcium absorption in the intestine, and promote strong bones and teeth.

Dietary sources: oily fish, liver, and egg yolk.

Vitamin D is synthesized by the action of ultraviolet light on a particular chemical in the skin.

Deficiency leads to: rickets in children; long-term deficiency in adults leads to osteomalacia.

Excessive intake of vitamin D may lead to hypercalcaemia and abnormal calcium deposits in the soft tissues, kidneys, and blood vessel walls. In children, it may cause growth retardation.

Vitamin E

Tocopherol

Functions:  essential for normal reproduction, maintaining the activities of certain enzymes and formation of red blood cells.

Vitamin E also protects the lungs and other tissues from damage by pollutants and slows aging of cells by neutralizing free radicals.

Dietary sources include vegetable oils, nuts, meat, green vegetables, cereals, and egg yolk.

Deficiency leads to anaemia.

Functions: aids in formation of substances that promote blood clotting.

Dietary sources:  green vegetables, vegetable oils, egg yolk, cheese, pork, and liver.

Vitamin K is also synthesised by intestinal bacteria.

Deficiency leads to nosebleeds and bleeding from the gums, intestine, and urinary tract. Severe cases lead to brain haemorrhage.

Bioflavonoid(citrin)

Regulates the permeability of the capillary walls, found in citrus fruit, blackcurrants and rosehips.

Vitamin was first discovered by F.G. Hopkins but the term 'vitamin' was coined by Casimir Funk.

Vitamin F is obsolete.

Vitamin G is another name for Vitamin B2.

Vitamin B complex was formerly regarded as single vitamin.

Vitamin D - used to treat osteomalacia.

Vitamin A - used to treat severe acne.

Golden rice - variety of rice (Oryza sativa) produced through genetic engineering to biosynthesize beta-carotene, a precursor of vitamin A, in the edible parts of rice.

In 2005, a new variety called Golden Rice 2, which produces up to 23 times more beta-carotene than the original golden rice, was announced.

Although golden rice was developed as a humanitarian tool, it has met with significant opposition from environmental and anti-globalization activists.