An amino acid is an organic compound used to create proteins in the body. Amino acids are the building blocks of proteins, and proteins are the building blocks of life. When your body digests proteins, it breaks them down into amino acids, which are then used to make more proteins. It may sound confusing, but let's look at the difference among the three types of amino acids. We have nonessential amino acids that can be made by the body, even if we don't consume food that help us make them. Conditional amino acids are usually only essential during times of stress and illness. Essential amino acids are not made by the body, so we HAVE to get them through our food. There are nine essential amino acids required for adults, and they are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Children have an extra essential amino acid called arginine, but once a person reaches adulthood, this amino acid is no longer essential.