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A complete protein (or whole protein) is a source of protein that contains an adequate proportion of all of the essential amino acids for the dietary needs of humans or other animals. ^[1] This does not refer to the protein source only containing all the essential amino acids, but also containing them in complete proportion for use by the human body. A source may contain all essential amino acids, but contain one in lower proportion to the others, making it an incomplete protein.

The following table lists the optimal profile of the essential amino acids, which comprises a complete protein ^[2]:

Complete proteins contain adequate amounts and proportions of these essential amino acids.

Nearly all whole foods contain protein, and nearly all forms of protein contain all twenty protein-forming amino acids in some quantity. However, proportions vary, and some forms of protein are partly lacking in one or more of the essential amino acids. Meals prepared with a mix of protein foods can provide a better balance of the essential amino acids and therefore a more complete protein source. Apart from soybeans, vegetable sources of protein are more often lacking in one or more essential amino acids than animal sources,^[3] typically being deficient in lysine and methionine.^{[citation needed]}

A variety of proteins in the diet is one way of assuring that the body's amino acid needs are met. All the essential amino acids can be obtained on their own from various everyday plant sources, which, contrary to popular belief, do not need to be combined in the same meal (see Protein combining).^[4]

Sources of complete protein

• Complete proteins, also known as high quality proteins, "contain all the essential amino acids in amounts adequate for human use; it may or may not contain all the others. Generally proteins derived from animal foods (meats, fish, poultry, cheese, eggs, yogurt, and milk) are complete, though gelatin is an exception. Proteins derived from plant foods (legumes, grains, and vegetables) tend to be limited in essential amino acids. Some are notably low, such as corn protein.

• Some foods contain all the essential amino acids on their own in a sufficient amount to qualify as a "complete protein". Complete protein foods that also obtain the highest possible PDCAAS score of 1.0 are certain dairy products, egg whites, and soy protein isolate. Other foods, such as amaranth, Aphanizomenon flos-aquae, buckwheat, hempseed, meat, poultry, soybeans, quinoa, seafood, and spirulina also are complete protein foods, but may not obtain a PDCAAS score of 1.0.^[1][5]

Notes