Amino acids are organic compounds that combine to form proteins. When proteins are digested, amino acids are left. The human body requires a number of amino acids to grow and breakdown food.

Amino acids are classified into two groups:

• Essential amino acids cannot be made by the body and must be supplied by food. These include cysteine, lysine, and tryptophan. Sources of essential amino acids include milk, cheese, eggs, certain meats, vegetables, nuts, and grains.
• Nonessential amino acids are made by the body from the essential amino acids or normal breakdown of proteins. They include aspartic acid, glutamic acid, and glycine.