Proteins are one of the macronutrient. These are building blocks of living organisms. The smallest part of proteins are called amino acids .In general, its recommended that 15 – 20% of your total daily calories be derived from protein. Every cell in human body is made up of protein. Proteins give structure for the cell. Proteins are required for maintenance in adults and for growth in infants and children. Proteins play different roles in the body as enzymes, antibodies, hormones, neurotransmitters. Protein helps in tissue repair. The muscles in our body are made up of proteins. The primary sources of proteins are not to provide energy for the body but for maintenance of tissues. But 1 gm of protein provides 4 kcals. The human body is about 45% of proteins. The daily recommended requirement of protein is 1gm per kg body weight per day. Children, pregnant and lactating women require more than this ratio of protein for growth and development and other physiological needs. Protein requirement goes up in conditions such as burns and trauma. When protein is consumed, the body breaks it down into amino acids. There are 20 amino acids. These amino acids can come of dietary sources or from body’s own pool amino acids. These are essential and non- essential amino acids. Essential amino acids come from dietary sources and are not synthesized in the body .Non – essential amino acids are amino acids which can be synthesized in the body.

Essential amino acids:

Arginine, Histidine, Methionine, Valine, Leucine, Iso leucine, Lysine, Tryptophan, Phenylalanine, Histidine. Threonine.

Non-Essential amino acids: Alanine, Proline, Glycine, Glutamine, Cysteine, Asparagine, Aspartate, Tyrosine, glutamate, Serine.

Proteins have many functions in the body. Proteins are known as complete or incomplete proteins. Proteins are called complete when it provides all of the essential amino acids. Protein sources from animals for example meat, milk, eggs, fish, Chicken and cheese are known to be complete protein sources. Incomplete proteins are those when one or more of the essential amino acids are low. In different proteins the limiting amino acid tends to be different. In Cereals the limiting amino acid is lysine and in pulses the limiting amino acid is methionine. So they both can compensate eachother.

Protein requirements:

• Infants  1.8 – 4gm/kg BW
• Children  1gm/kg BW
• Adults      0.8gm/kg BW
• Catabolic states  2gm/kg BW

Food sources of proteins
Animals: Meat, Eggs, Milk, Poultry, Dairy products.

Plants: Beans, Peas, Legumes and pulses .Soy beans are the only plant protein considered to be complete protein.