Proteins are the macro nutrients essential for building up the human body. They are called macro nutrients because they form the bulk of the food. Proteins play an important role in human diet.

The essential amino acids are methionine, threonine, tryptophan, valine, isoleucine, lysine, phenylalanine, histicline, leucine.

The rich sources of proteins are both animal and plant sources. The animal sources are egg, milk, meat, cheese, fish etc. The plant sources are cereals, pulses, beans etc.

Proteins constitute about 25% of the body weight of adults. Proteins are the building blocks of the body. They are the prime nutrients involved in bodybuilding. They also supplied energy. 1 gm of protein yields 4 kilocalories of energy. They are also essential for maintenance of structure and function of human body. They are essential for the synthesis of hemoglobin, enzymes, plasma proteins, antibodies, coagulation factors and soon.