Protein transports nutrients in and out of cells and is responsible for their growth, maintenance and regeneration. Protein is also needed for the formation of hormones and enzymes. It is important to the immune system, as it is used to make antibodies and white blood cells.

All protein is made up of amino acids, which join together in a variety of ways to form the various different kinds of proteins.

There are around 22 amino acids. Some of which can be made in the body, and therefore termed nonessential, and eight that the body cannot produce, the essential amino acids. Children have ten essential amino acids

Foods which have all eight essential aminos in roughly equal proportions, are said to be complete proteins. Foods that lack or are extremely low in one or more essential aminos are called incomplete proteins.

Most vegetables, grains and fruits are incomplete protein foods. By combining two or more incomplete protein foods to obtain a balance of aminos a complete protein meal can be made.

The eight essential acids are lysine, methionine, leucine, threonine, valine, tryptophan, isoleucine and phenylalanine. In addition, histidine and arginine are considered essential for children to support growth.