A healthy diet contains protein, which your body breaks down into its constituent parts, or amino acids. The amino acids play various roles in the regular operation of your body, including assisting in breaking down food and the creation and repair of body tissue. A typical balanced diet contains the types of protein you need to obtain all the amino acids your body requires.
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Essential Amino Acids
Your body must obtain nine types of amino acid from food because it cannot produce them. These nine amino acids -- called the essential amino acids -- are leucine, histidine, isoleucine, valine, methionine, tryptophan, phenylalanine and threonine.
Nonessential Amino Acids
Your body uses other amino acids as well, but you don’t need to obtain these from your diet because your body produces them naturally. These nonessential amino acids include asparagine, alanine, aspartic acid and glutamic acid. The descriptors "essential" and "nonessential" refer only to whether you need to obtain those amino acids in your diet, not to whether they are necessary for normal body processes, which all 13 are.
Conditional Amino Acids
The remaining category of amino acids is called "conditional" because they are not always necessary. But if you have certain illnesses or high stress, your body might require them. Conditional amino acids include arginine, tyrosine, cysteine, glutamine, ornithine, glycine, serine and praline.
All animal and plant food sources contain some protein, but not all of them provide the same types of amino acids. If you follow a typical balanced diet, you should have enough variety in your diet to supply the various amino acids. However, if you follow a diet that restricts certain protein sources, you might need to find alternate protein sources that replace the particular amino acids your diet lacks. For example, animal proteins, or meats, contain all the essential amino acids your body needs. But this presents a problem for vegetarians and vegans, who must find plant sources that supply whichever essential amino acids their diets lack. Soybeans and quinoa are two commonly consumed plant-based foods that contain complete proteins.
If you have an atypical diet, consult a doctor or nutritionist to help you design an eating plan that will provide all the nutrients your body needs, including essential amino acids. Otherwise, incorporate into your diet a variety of high-protein sources, such as fish, poultry, lean beef, low-fat dairy products, seeds, legumes and nuts. The recommended intake for protein is 46 grams per day for women and 56 grams per day for men.