The Relationship Between Proteins & Essential Amino Acids

Amino acids are organic compounds that attach to one another to form proteins. Although the exact number of amino acids in existence is still in dispute, the consensus is that the total number of amino acids is 20. These 20 amino acids are classified into three groups based on whether you can obtain them from the foods you eat.

Classification of Amino Acids

Amino acids are classified as nonessential and essential. Nonessential amino acids are those that your body can produce in adequate amounts to meet your needs. Because your body can produce these amino acids, you do not have to include them in your diet. Your body produces a total of 11 nonessential amino acids. Essential amino acids are those that the body cannot produce in adequate amounts, and therefore, you must include them in your diet. The essential amino acids number nine total.
Under certain circumstances, some nonessential amino acids become essential. This change may occur during an illness or extreme stress that prevents your body from producing the amino acids. These amino acids are called conditional amino acids. The exact number of conditional amino acids remains in dispute.

Essential Amino Acids and Protein

The sequence in which amino acids come together determines what type of protein the amino acids make. The type and amount of amino acids that a protein contains is called its amino acid profile. Proteins that contain all of the essential amino acids are referred to as complete proteins. Proteins that are missing one or more of the essential amino acids, or contain a low amount of a specific essential amino acid, are considered incomplete proteins. Animal proteins, like meat, fish, poultry, eggs and milk, are usually complete proteins, whereas vegetable proteins, like nuts, beans and rice, are generally incomplete proteins.

Protein Quality

The amino acid profile of a protein also determines its quality. Protein quality describes the amino acid profile as well as how easily the protein is digested; it is measured on a scale called the protein digestibility corrected amino acid score, or PDCAAS. Proteins that contain all of the essential amino acids are considered higher quality than those that are missing one or more. The higher the quality of the proteins, the higher the score on the PDCAAS scale. Milk, which contains all nine essential amino acids and is easily digested, rates 100 percent, whereas wheat, which is missing some essential amino acids and is more difficult to digest, scores only 44 percent.

Complementary Proteins

Just because a protein is missing one or more essential amino acids does not mean that it cannot be part of a healthy diet. The key is to combine incomplete proteins to create a complete protein. This is called complementing the protein. If you do not eat animal protein, consider combining complementary vegetable proteins to ensure that you are consuming all of the essential amino acids you need. Try rice and beans or hummus on pita bread.