Why Are the Nine Essential Amino Acids Called Essential?

Steak contains protein, which can provide you with the amino acids you need for your body to function properly.

Steak contains protein, which can provide you with the amino acids you need for your body to function properly.

Your body produces a number of amino acids that perform numerous bodily functions, from growing and repairing body tissue to breaking down food. But your body can’t produce all the amino acids it needs to function properly. The ones it can produce are called nonessential amino acids. But your body needs nine other amino acids, all of which must come from your diet. That’s why they’re called essential amino acids.

Essential Amino Acids

Your body can’t store the amino acids it needs to function properly, so you must get them from your diet every day. If your body doesn’t get the essential amino acids every day, it won’t be able to function properly. Adults need these nine essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. In addition to those essential amino acids, children also need arginine.


Amino acids are the building blocks of protein. You need protein to build muscles, but you also need them to carry oxygen in your blood to every part of your body, to digest food and to fight bacteria and viruses. The amino acids you consume in your diet join together in different ways to form the different proteins your body needs. For instance, the hemoglobin protein handles the blood oxygen flow, while the alpha-keratin protein forms your hair and fingernails.


Amino acids offer a good energy source when they’re not being used in other functions. For instance, if a protein strand is damaged or no longer needed, it breaks down to the basics – those amino acids used to form it. Once that happens, the remainder of those molecules can be oxidized to form energy. Your body can also break down most amino acids into glucose, when it’s low on the substance, to use as energy. Glucose is typically formed by carbohydrates.


Your brain and nerve cells need a way to communicate, and amino acids often fill that role. Enzymes help to convert amino acids to neurotransmitters – that’s a chemical messenger to pass signals between nerve cells and other cells. For instance, your body can’t produce the mood regulator known as serotonin without tryptophan. Likewise, phenylalanine is a precursor to an important neurotransmitter with adrenergic properties – important for regulating the heart rate, metabolic shifts and the diameter of your blood vessels and air passages.

About the Author

Lucy D'Berry has been a writer for nearly 30 years, specializing in nutrition and health issues, as well as in education and government. She has written for daily newspapers and edits a national magazine. She has earned both a bachelor's degree and a master's degree in the communications field.

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