Which Amino Acids Are Present in Our Body?

October 31, 2025 •

4 min read

Our body needs 20 different amino acids to grow and function properly, serving as the building blocks for all proteins. These vital organic compounds are categorized into essential, non-essential, and conditionally essential, determining whether we must obtain them from our diet or if our body can produce them.

Quick Summary

The human body requires 20 protein-forming amino acids, classified based on whether the body can synthesize them. Nine are essential and must come from food, 11 are non-essential and produced internally, and others become conditionally essential during periods of illness or stress.

Key Points

Essential Amino Acids: There are nine essential amino acids that must be obtained from the diet, as the human body cannot produce them.
Non-Essential Amino Acids: The body can synthesize the 11 non-essential amino acids, making dietary intake less critical but still beneficial.
Conditionally Essential: During times of illness or stress, some non-essential amino acids, like arginine and glutamine, become conditionally essential.
Protein Building Blocks: All 20 amino acids are the fundamental components used by the body to build and repair thousands of different proteins.
Dietary Sources: Complete proteins from sources like meat, eggs, and soy provide all nine essential amino acids, while incomplete plant proteins can be combined to achieve a complete profile.
Diverse Functions: Beyond building proteins, amino acids perform vital roles in metabolic processes, hormone production, and supporting immune function.
Balanced Intake: Ensuring a consistent and varied intake of protein sources is the best way to maintain a healthy supply of all amino acids.

Amino acids are the fundamental building blocks of proteins, which are essential for virtually every physiological function in the human body. From tissue repair and muscle growth to hormone production and immune system support, the body's entire operational structure depends on a sufficient supply of these organic compounds. All 20 amino acids can be found within the body, but how they are sourced and utilized varies dramatically based on their classification.

The Three Types of Amino Acids

Amino acids are divided into three primary categories: essential, non-essential, and conditionally essential. This classification is based on the body's ability to synthesize them, which directly impacts our dietary needs. Understanding these classifications is crucial for maintaining a balanced diet and supporting overall health.

Essential Amino Acids: The Dietary Nine

Essential amino acids are those the body cannot produce on its own and must be obtained through food. There are nine essential amino acids that are critical for various functions. A balanced diet rich in 'complete proteins' from sources like meat, eggs, and dairy ensures a proper intake of all nine. For vegetarians and vegans, combining different plant-based proteins can provide all essential amino acids throughout the day.

Non-Essential Amino Acids: The Body's Own Supply

Non-essential amino acids are still vital for bodily functions. The term simply means the body can produce them, so they are not essential to obtain from the diet. There are 11 non-essential amino acids.

Conditionally Essential Amino Acids: The 'Sometimes' Nine

Some non-essential amino acids become 'conditionally essential' during periods of stress, illness, or rapid growth. During these times, the body's demand outpaces its ability to produce them, requiring dietary intake.

Comparison of Amino Acid Types


Feature	Essential Amino Acids	Non-Essential Amino Acids	Conditionally Essential Amino Acids
Source	Must be obtained from diet	Synthesized by the body	Synthesized by the body, but diet is necessary during stress/illness
Number	9	11	Subset of non-essential (e.g., arginine, glutamine)
Dietary Requirement	Strictly required from food sources like meat, eggs, and complete plant proteins	Not strictly required from diet, but dietary sources are still beneficial	Required from diet during certain physiological states
Regulation	Intake directly impacts protein synthesis and overall health	Production is internally regulated based on body's needs	Demand is increased during specific health conditions
Example Function	Building muscle protein (Leucine)	Detoxifying the body (Alanine)	Supporting immune function during illness (Glutamine)

The Role of Amino Acids in Protein Synthesis

All 20 standard amino acids are crucial for the synthesis of the thousands of different proteins our bodies produce. Proteins are formed when amino acids are linked together in long chains, with the specific sequence determining the protein's unique structure and function. Think of amino acids as the letters of an alphabet, and proteins as the words formed by combining these letters in different ways.

The Impact of Diet on Amino Acid Availability

For most healthy adults, a balanced diet is sufficient to obtain all essential amino acids. Animal products like meat, poultry, fish, eggs, and dairy are considered 'complete' proteins because they contain all nine essential amino acids. Certain plant-based foods, such as soy, quinoa, and buckwheat, are also complete proteins. Other plant sources like nuts, seeds, beans, and grains are 'incomplete' but can be combined throughout the day to ensure a complete amino acid profile.

Conclusion: Fueling the Body's Building Blocks

In summary, the human body contains all 20 of the standard amino acids necessary for life. The key distinction lies in whether the body can produce them internally or if they must be consumed through our diet. The nine essential amino acids are non-negotiable dietary requirements. The 11 non-essential amino acids are produced by the body, though dietary intake is still beneficial. Additionally, certain non-essential amino acids become conditionally essential during periods of physiological stress. A balanced and varied diet, rich in diverse protein sources, is the most effective way to ensure your body has access to all the amino acids it needs to build, repair, and function optimally. A diet that provides an adequate supply of these vital compounds is foundational for robust health, energy, and overall well-being. For more information, consult resources from authoritative health institutions like {Link: MedlinePlus https://medlineplus.gov/ency/article/002222.htm}.

Lists of Amino Acids

List of Essential Amino Acids

The nine essential amino acids are Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine. {Link: StatPearls https://www.ncbi.nlm.nih.gov/books/NBK557845/}

List of Non-Essential Amino Acids

The 11 non-essential amino acids include Alanine, Arginine, Asparagine, Aspartic Acid (Aspartate), Cysteine, Glutamic Acid (Glutamate), Glutamine, Glycine, Proline, Serine, and Tyrosine. {Link: NCBI https://www.ncbi.nlm.nih.gov/books/NBK557845/}

Which Amino Acids are present in our body?

Amino Acids as Protein Building Blocks: Your body uses all 20 standard amino acids to synthesize the proteins necessary for growth, repair, and function.
Essential vs. Non-Essential: The primary distinction is the source; some must come from your diet (essential), while your body can produce others (non-essential).
Vital Functions: Amino acids are crucial for muscle repair, hormone production, and supporting the immune system.
Dietary Importance: A balanced diet is necessary to ensure adequate intake of essential amino acids, particularly for those on plant-based diets.
Conditional Needs: During stress or illness, some non-essential amino acids become conditionally essential, requiring increased dietary intake.

Frequently Asked Questions

The main difference is their source. Essential amino acids cannot be produced by the body and must come from food, while non-essential amino acids can be synthesized internally from other molecules.

The human body needs 20 standard amino acids to function correctly. This includes nine essential and 11 non-essential ones.

No, you don't need to consume complete proteins at every meal. Your body can store amino acids and combine them from various food sources throughout the day to meet its needs.

Excellent sources of essential amino acids include animal products like meat, poultry, fish, and eggs. Plant-based complete proteins include soy, quinoa, and buckwheat.

BCAAs are a group of three essential amino acids: leucine, isoleucine, and valine. They are particularly important for muscle metabolism and are often used by athletes for muscle growth and repair.

Non-essential amino acids become conditionally essential during periods of high stress, illness, or rapid growth. During these times, the body's demand for these amino acids exceeds its production capacity.

Amino acids are crucial for the proper functioning of immune cells and the production of antibodies. For example, glutamine supports immune cell proliferation, especially during illness or stress.

Yes, a deficiency in essential amino acids can lead to various health problems, as the body cannot produce the proteins it needs for essential functions like tissue repair and immune response.

For most healthy individuals with a balanced diet, supplements are not necessary. However, some people, including athletes or those with specific health conditions, may use them. It's always best to consult a healthcare provider before taking supplements.