Understanding if All 20 Amino Acids Are Needed to Make Proteins and Which Can Be Synthesized in Your Body and Are Thus Non-Essential

December 29, 2025 •

3 min read

Over 500 naturally occurring types of amino acids exist, though the human body primarily uses 20 to function correctly and create proteins. A key aspect of human biology is determining if all 20 amino acids are needed to make proteins and if some can be synthesized in your body and are thus non essential.

Quick Summary

All 20 standard amino acids are required for the body's complete protein synthesis capabilities, but only nine must be consumed through diet. The body can produce the remaining 11, classifying them as 'non-essential', a term related to dietary intake, not biological importance.

Key Points

All 20 are Needed: All 20 standard amino acids are required to build the full range of proteins the body needs to function correctly.
Essential vs. Non-Essential: The distinction between essential (9) and non-essential (11) amino acids is based on whether the body can synthesize them, not on their importance.
Dietary Dependence: Essential amino acids must be obtained from food, while the body can produce non-essential ones internally.
Conditionally Essential: Some non-essential amino acids become 'conditionally essential' during illness, stress, or growth when the body's need exceeds its production capacity.
Balanced Intake is Key: For protein synthesis to proceed without interruption, all necessary amino acids must be available to the body, emphasizing the importance of a balanced diet.
Source Matters: A varied diet can ensure all essential amino acids are consumed, especially for those following plant-based diets.

The Building Blocks of Life: Amino Acids

Amino acids are fundamental organic compounds that serve as the building blocks for proteins. Proteins, in turn, are involved in virtually every function within the human body, from building and repairing tissues to creating enzymes and hormones. The human body requires a total of 20 different amino acids to synthesize the thousands of unique proteins it needs. These 20 amino acids are combined in various sequences and lengths to create diverse protein structures. The complexity and sheer number of possible combinations allow for an incredible variety of proteins with specialized functions.

The Essential vs. Non-Essential Distinction

The categorization of amino acids into 'essential' and 'non-essential' is based on whether the human body can synthesize them internally. This classification can be misleading, as all 20 amino acids are necessary for building proteins; the label simply refers to their source.

Essential Amino Acids (EAAs)

There are nine amino acids that the human body cannot produce on its own or cannot produce in sufficient quantities under normal conditions. These are deemed 'essential' because they must be acquired from dietary sources. A deficiency in any of these can negatively affect growth and overall health. The nine essential amino acids are Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine. They play diverse roles in the body, including immune function, muscle metabolism, protein synthesis, and neurotransmitter production.

Non-Essential Amino Acids (NEAAs)

Non-essential amino acids are those that the body can synthesize using metabolic pathways. Although the name suggests they are less important, they are just as vital for protein formation as the essential ones. The 11 non-essential amino acids are Alanine, Arginine, Asparagine, Aspartic Acid, Cysteine, Glutamic Acid, Glutamine, Glycine, Proline, Serine, and Tyrosine.

Conditionally Essential Amino Acids

Some amino acids are typically non-essential but become required from the diet under specific conditions of stress, illness, or rapid growth. These are termed conditionally essential amino acids. For example, individuals with liver disease may not synthesize enough cysteine and tyrosine, making dietary intake crucial. Examples of conditionally essential amino acids include Arginine, Cysteine, Glutamine, Tyrosine, Glycine, Proline, and Serine.

The Protein Assembly Line

Protein synthesis is a complex process starting with DNA, transcribed into mRNA, and then translated by ribosomes into an amino acid chain. All 20 amino acids must be available for assembly according to the genetic code. A lack of even one essential amino acid can halt protein synthesis or result in incomplete proteins. However, not all proteins contain all 20 amino acids; smaller proteins may omit certain types. The availability of the full 20-amino acid pool is necessary for the body's complete protein repertoire. For more information, refer to the National Institutes of Health's resource on Biochemistry, Essential Amino Acids [https://www.ncbi.nlm.nih.gov/books/NBK557845/].

Comparison of Amino Acid Types


Type	Description	Dietary Source	Examples
Essential	Cannot be synthesized by the body and must be obtained from diet	Required from food, found in complete proteins like meat, eggs, and dairy	Leucine, Lysine, Tryptophan, Valine
Non-Essential	Can be produced by the body under normal circumstances	Not required from diet but still important for biological functions	Alanine, Aspartic Acid, Serine, Glycine
Conditionally Essential	Normally synthesized by the body but required from diet during illness, stress, or growth	Required from food during specific physiological periods or conditions	Arginine, Cysteine, Glutamine, Tyrosine

Conclusion

Yes, all 20 standard amino acids are needed to make proteins, which is fundamental for bodily functions. While 11 are non-essential as the body can synthesize them, the remaining nine are essential and must come from the diet. The distinction is about the source, not their biological importance. A balanced diet with complete or varied plant-based protein sources ensures the body has all the necessary building blocks for optimal health and cellular repair.

Frequently Asked Questions

Yes, this is true. While the body needs all 20 amino acids to synthesize its full range of proteins, individual proteins often do not contain all 20 types, especially smaller ones.

The primary difference is their source. Essential amino acids (9) must be obtained from your diet because the body cannot synthesize them, whereas non-essential amino acids (11) can be produced by the body itself.

Yes, some can become 'conditionally essential' under specific circumstances like stress, illness, or rapid growth. In these situations, the body's demand for the amino acid can exceed its ability to produce it.

Examples of conditionally essential amino acids include arginine, cysteine, glutamine, glycine, proline, serine, and tyrosine.

When you eat protein-rich foods, your body breaks the proteins down into individual amino acids during digestion. The body then reassembles these amino acids into the specific proteins it needs.

Complete proteins are foods that contain all nine essential amino acids in adequate amounts. Excellent sources include animal products like meat, eggs, and dairy, as well as plant-based options like soy and quinoa.

Yes, the term can be misleading. While it correctly refers to the amino acids the body can produce, it can be misinterpreted as meaning they are unimportant. All 20 amino acids are equally vital for the body's overall function.