List of the 22 Known Amino Acids

Protein-rich foods provide a wide spectrum of amino acids.

Protein-rich foods provide a wide spectrum of amino acids.

About a fifth of your body is made of protein, according to the Department of Food Science at Technology at Ohio State University. Any time you eat something that contains protein, it breaks down into amino acids, which help your body produce energy and work efficiently. Get enough amino acids by consuming protein from a variety of sources.

Essential amino Acids

Your body can't make nine of the amino acids on its own, so you have to get them from your diet. These essential amino acids include phenylalanine, valine, threonine, tryptophan, isoleucine, methionine, leucine, lysine and histidine. It's easy to get all of them from food if you regularly eat animal products, such as meat, poultry or fish. Some food combinations, such as rice with beans or a peanut butter sandwich on whole-wheat bread, can also supply you with all of the essential amino acids.

Nonessential Amino Acids

Alanine, aspartic acid and glycine are nonessential amino acids because your body makes them on its own. Conditional amino acids, including arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline and serine, are nonessential for most people whose bodies are healthy enough to manufacture them. However, people with some health problems or illnesses may not be able to make conditional amino acids on their own, so they have to get these, along with the essential amino acids, from food.

Nonstandard Amino Acids

Many nutritional guides talk about the 20 amino acids, but 22 actually exist. Scientists discovered selenocysteine in 1986 and pyrrolysine in 2002, according to a "Science Daily" article published in 2011. Pyrrolysine and selenocysteine are called nonstandard amino acids because they're not found in the human body. A team of University of Nebraska researchers, who published a study in "Nucleic Acids Research" in 2007, found these amino acids in a gutless marine worm, the organism that has the largest known concentration of pyrrolysine and selenocysteine. Clearly, you don't need to worry about getting these amino acids.

Dosage Recommendations

The Institute of Medicine recommends that each gram of protein you eat includes 18 milligrams of histidine, 25 of isoleucine, methionine and cysteine, 55 of leucine, 51 of lysine, 47 of phenylalanine and tyrosine, 27 of threonine, 7 of tryptophan and 32 of valine. Because food manufacturers rarely list amino acid amounts on their labels, the best way to ensure that you get enough of each is to eat protein from a variety of sources. Meat, fish and poultry are rich in all the essential amino acids. Grains are low in lysine, according to University of Cincinnati biology professor Janet L. Stein Carter, but beans are rich in lysine. Conversely, grains have more cysteine and methionine than beans do, so eating grains and beans together is the healthiest way to get all the amino acids you need.

 

About the Author

Maia Appleby is a NASM-certified personal trainer with more than 15 years of experience in the fitness industry. Her articles have been published in a wide variety of print magazines and online publications, including the Gale Encyclopedia of Nursing and Allied Health, New Moon Network and Bodybuilding.com.

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