Vitamins are chemical organic compounds that are present in the bodies of animals. They are present in minute quantities, but they are of paramount importance to the metabolism of the animals. The primary source of vitamins is the food that the animals eat, but many vitamins are also produced in the bodies of the animals. Today, there are several vitamins available in synthetic forms too. Vitamins are vital for the proper functioning of the human body – they help in growth and development. The deficiency of vitamins will impair this growth and development and also lead to some serious diseases.

Vitamins are broadly classified into two groups, based on their physical solubilities. The vitamins A, D, E and K are not soluble in water, but they are soluble in fats. They are therefore called as the fat soluble vitamins. On the other hand, the vitamins of the B complex and vitamin C are not soluble in fats, but they are soluble in water. So, they are called water soluble vitamins.

Vitamin A, chemically known as retinol, is extremely important in the proper maintenance of human eyesight. It helps us to adjust our vision in dim light conditions. Apart from vision, vitamin A is also important for the maintenance of hair, mucus membranes and even the skin. It also governs, to some extent, bone and tooth development, proper reproduction and the proper maintenance of the epithelial cells. A deficiency of vitamin C causes a condition known as nyctalopia (night blindness) and xeroderma (excessive drying of the skin).

The main dietary sources of vitamin A are carrots, spinach, sweet potatoes, butter, broccoli and all yellow and orange vegetables and fruits. Among the main animal sources are included eggs, milk, fish oil and liver.

Vitamin B is not a single vitamin, but it is a whole family of closely related vitamins. The individual members here are thiamin (vitamin B1), riboflavin (vitamin B2), niacin (vitamin B3), along with folic acid, biotic, pantothenic acid and cobalamin. This group of vitamins is responsible for the proper functioning and regeneration of the red blood cells and the proper metabolic functioning of the body. They provide energy to the body and help in the synthesis of proteins. They come primarily through green vegetables and citrus foods. Whole grain foods, peas and beans are also good sources. Animal sources are eggs, poultry products, meats and seafood. There is a long list of deficiencies of vitamin B complex, which include beriberi, pellagra, chapped lips, problems with red blood cells and nervous system, underdevelopment of muscles, etc.

Vitamin C is ascorbic acid. The most important significance of this vitamin is that it is an antioxidant. It produces a protein known as collagen which is important in blood clotting, but is also essential for the growth and development of bones and muscles, cartilage and blood vessels. It prevents the oxidation of vitamins A and C. The most important sources of vitamin C are fresh fruits and vegetables. Deficiency can lead to scurvy, a disease characterized by poor healing of wounds, pains in the joints, muscle wasting, bleeding of gums and subcutaneous hemorrhage.

Vitamin D or calciferol is important for the growth and development of bones by adjusting the level of calcium in it. It is also vital for dental health. Vitamin D is found in egg yolk, milk and fish liver oils. Deficiency causes rickets, a disease that is characterized by weak bones and bow legs. Excessive intake of vitamin D can cause weight loss, loss of appetite, headache, nausea and depression.

Vitamin E is tocoferol. This vitamin is needed to slow down the oxidation of the blood tissues and for the formation of blood cells. The vitamin also prevents lungs from damage due to pollution. Chief sources of this vitamin are whole grains, green leafy vegetables, wheat germ, nuts, bread, cereals and seeds and animal sources such as eggs and sardines. Deficiency of vitamin E can cause some very serious diseases such as diabetes, cardiac diseases, Alzheimer’s Disease and even some cancers.