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What Are the Essential Amino Acids?

What Are the Essential Amino Acids?

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This is an explanation of what essential amino acids are and a list of the essential amino acids for humans.

What Is an Essential Amino Acid?

An essential amino acid may also be called an indispensable amino acid. This is an amino acid that the body cannot synthesize on its own, so it must be obtained from the diet. Because each has its own physiology, the list of essential amino acids is different for humans than it is for other organisms.

Essential Versus Conditionally Essential Amino Acids

The essential amino acids for all people are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Several other amino acids are conditionally essential amino acids, meaning they are required at some stages or growth or by some people who cannot synthesize them, either because of genetics or a medical condition.

In addition to the essential amino acids, babies and growing children also need arginine, cysteine and tyrosine. Individuals with phenylketonuria (PKU) need tyrosine and also must limit their intake of phenylalanine. Certain populations need arginine, cystein, glycine, glutamine, histidine, proline, serine and tyrosine because they either cannot synthesize them at all or else are unable to make enough to meet the needs of their metabolism.

Learn More About Amino Acids

Amino Acid Facts
Amino Acid Structures
Amino Acid Chirality
Tryptophan Facts
Video - Intro to Amino Acids

List of Essential Amino Acids

Essential Amino Acids Non-Essential Amino Acids
histidine alanine
isoleucine arginine*
leucine aspartic acid
lysine cysteine*
methionine glutamic acid
phenylalanine glutamine*
threonine glycine*
tryptophan proline*
valine serine*
  tyrosine*
  asparagine*
  selenocysteine
  *conditionally essential

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