How do I know what is considered a high quality source of protein?

Proteins are made up of amino acids. Of the known amino acids, only nine have been identified as being absolutely essential for the human body. These are histidine, isoleucine, leucine, lysine, methionine, phyenylalanine, threonine, tryptophan and valine. They are called essential because the body cannot synthesize them in high enough rates to meet body needs. They must come from the diet.

Protein found in foods is of varied quality. If a protein has all the essential amino acids in the right balance, it is a high quality protein. A poor quality protein may be low in one or more of the essential amino acids. Proteins from plant sources are generally of lower quality than the proteins from animal and dairy sources.