Proteins are organic nitrogenous substances essential for human body. The building blocks of protein are amino acids. About 20 amino acids are needed by the human body for growth. Of these 9 amino acids cannot be synthesized by the human body and should by the human body and should be supplied through 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.