The word ‘protein’ is derived from the Greek word protos meaning ‘first’. Protein is the basic chemical unit of liv-ing organisms and is essential for nutri-tion, building of new tissues (growth) and maintaining and repairing of those already built. Casein from milk, albu-min in egg and gluten in wheat, are examples of proteins occurring in foods.
Classification: The proteins are classi-fied as:
Complete proteins e.g. Egg proteins
Partially complete proteins e.g. wheat proteins
Incomplete proteins e.g. Gelatin or zein
Functions: Proteins perform the fol-lowing functions;
· Necessary for growth
· Wear and tear of human body is repaired
· For regular supply of raw materials for the formation of digestive juices, hormones, plasma proteins, hemo-globin, vitamins and enzymes.
· Each gram of protein supplies 4 Kcal of energy
Food Sources: Animal foods like Meat, Fish, Eggs and Milk are excel-lent sources of Proteins. Plant Sources like Pulses, Oil seeds and nuts are also good sources of Protein
Deficiency: Deficiency of protein causes protein energy malnutrition which covers a wide spectrum of clini-cal stages ranging from the severe forms like kwashiorkor and marasmus to the milder forms like growth retardation. Protein energy malnutrition is due to “food gap” between the intake and requirement. The average energy deficit in Indian children is 300kcal/day. Defi-ciency of protein is discussed in detail in the section Protein energy malnutrition