The protein you consume in your diet is made up of compounds called amino acids. The human body relies on amino acids, along with other compounds, for survival. These amino acids play a pivotal role in DNA replication, muscle building, tissue repair and much more. Registered dietitian Gordon Wardlaw states that there are 20 amino acids used in DNA replication and protein synthesis.
Essential Amino Acids
Of the 20 amino acids, nine of them are considered essential, meaning that they cannot be produced in the body in sufficient amounts or cannot be produced whatsoever. This is why they must be included in the diet. These nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. The best sources for essential amino acids include beef, chicken, fish, dairy, whey protein and soy.
Nonessential Amino Acids
The other 11 amino acids are considered unessential. This means that these amino acids can be produced by the human body sufficiently or can be made from some of the essential amino acids. These 11 nonessential amino acids are alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.
Conditionally Essential Amino Acids
Within the group of nonessential amino acids, there is a subgroup considered to be conditionally essential amino acids. In a healthy individual they would be produced sufficiently; however, under some conditions -- disease states or particular groups of individuals, such as infants -- the body cannot produce them sufficiently. These five conditionally essential amino acids are arginine, cysteine, glutamine, proline and tyrosine. The amounts needed of these acids are also dependent upon age, according to a report in the November 2005 issue of "Journal of Pediatric Gastroenterology and Nutrition." These amino acids should be added into your diet through foods such as meats, dairy, soy and protein supplements. If you supplement each amino acid individually, amino acid imbalances can occur. Food sources have the amino acids in a ratio that is best utilized by the body.