How many amino acids must be obtained in the diet because they cannot be made by the body brainly?

December 27, 2025 •

3 min read

The human body requires 20 amino acids to build and repair tissues, but can only synthesize 11 of them on its own. This leaves nine amino acids that must be obtained in the diet because they cannot be made by the body, which are officially called essential amino acids.

Quick Summary

There are nine essential amino acids that the human body cannot produce and must be obtained from food. A balanced diet with complete protein sources is necessary to ensure proper intake of these vital nutrients for bodily functions.

Key Points

Nine Essential Amino Acids: The human body requires 20 amino acids but cannot produce nine of them, necessitating dietary intake.
Dietary Sources: Essential amino acids are found in complete proteins like meat, eggs, and soy, or a combination of incomplete plant proteins.
Bodily Functions: These amino acids are vital for protein synthesis, hormone production, tissue repair, and immune system support.
Conditionally Essential: Some amino acids become essential during periods of illness, trauma, or rapid growth when the body's needs exceed its production capacity.
Deficiency Risks: Inadequate intake of essential amino acids can lead to malnutrition, impaired growth, and various health problems.

The Nine Essential Amino Acids

All 20 amino acids play a vital role in health, but nine are classified as "essential" because the body cannot synthesize them. These essential amino acids are crucial for various bodily functions, including protein synthesis, hormone production, and tissue repair. To obtain them, a balanced diet is necessary. The nine essential amino acids are:

Histidine: Involved in immune response and digestion.
Isoleucine: A branched-chain amino acid (BCAA) supporting muscle metabolism.
Leucine: Another BCAA critical for protein synthesis and muscle repair.
Lysine: Essential for protein synthesis and calcium absorption.
Methionine: Important for metabolism and detoxification.
Phenylalanine: Needed to produce key neurotransmitters.
Threonine: A component of structural proteins.
Tryptophan: Precursor for serotonin, regulating mood and sleep.
Valine: The third BCAA, involved in muscle growth and energy production.

Essential vs. Non-Essential Amino Acids

Amino acids are classified based on the body's ability to produce them.

Essential Amino Acids: These must be consumed through the diet as the body cannot make them. This includes the nine listed above.
Non-Essential Amino Acids: The body can synthesize these from other sources, so dietary intake is not always required. There are 11 non-essential amino acids, such as alanine, arginine, and glutamine.

What Are Conditionally Essential Amino Acids?

Conditionally essential amino acids are typically non-essential but become essential under specific conditions, like illness, stress, or growth. In these situations, the body's demand exceeds its production capacity. Examples include arginine during injury recovery or tyrosine for individuals with phenylketonuria (PKU).

Dietary Sources of Essential Amino Acids

Ensuring adequate intake of all essential amino acids is best achieved by eating a variety of protein-rich foods. Protein sources are often categorized as complete or incomplete.

Complete Protein Sources: These foods contain all nine essential amino acids in sufficient amounts. Examples include meat, fish, poultry, eggs, and dairy, as well as plant-based options like soy, quinoa, and buckwheat.
Incomplete Protein Sources: Most plant proteins, such as nuts, seeds, beans, and grains, lack one or more essential amino acids. However, combining different incomplete proteins throughout the day can provide all essential amino acids for those following vegetarian or vegan diets.

Comparison of Amino Acid Types


Feature	Essential Amino Acids	Non-Essential Amino Acids	Conditionally Essential Amino Acids
Source	Must come from dietary intake.	Can be synthesized by the body.	Typically synthesized by the body, but require dietary intake during illness or stress.
Number	9 (Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine).	11 (Alanine, Arginine, Asparagine, Aspartic acid, Cysteine, Glutamic acid, Glutamine, Glycine, Proline, Serine, Tyrosine*).	Several, including Arginine, Cysteine, Glutamine, Glycine, Proline, and Tyrosine.
Necessity	Always required in the diet for basic function.	Not required in the diet for basic function.	Required in the diet under specific conditions.
Function	Crucial for protein synthesis, enzyme production, and other vital bodily processes.	Perform a wide range of functions, similar to essential amino acids.	Same functions as their non-essential counterparts, but with increased demand during specific states.

Note: Several amino acids, such as Arginine, are sometimes listed as both non-essential and conditionally essential due to context.

The Importance of a Balanced Protein Intake

Sufficient intake of all amino acids is vital for health. A lack of any essential amino acid can limit the body's ability to create new proteins, impacting nitrogen balance and metabolic function. This is particularly important for growth and repair. Consuming a diet rich in high-quality protein from various sources ensures the body has the necessary building blocks.

Health Implications of Amino Acid Deficiency

A deficiency in essential amino acids can have significant health consequences, though it is uncommon with a balanced diet. Severe long-term deficiency can lead to malnutrition. Less severe deficiencies may cause fatigue, weakness, and impaired immune function. These issues arise when the body cannot meet its protein synthesis demands. Individuals with poor diets or certain medical conditions are at higher risk.

Conclusion

In summary, nine amino acids must be obtained through the diet because the body cannot produce them: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. A varied diet incorporating complete protein sources generally ensures adequate intake. Understanding the different categories of amino acids is crucial for maintaining overall health. For further information, the National Institutes of Health is a valuable resource.

Frequently Asked Questions

The primary difference is that essential amino acids cannot be produced by the human body and must be obtained through the diet, whereas non-essential amino acids can be synthesized internally.

The nine essential amino acids for humans are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Complete protein sources are foods that contain all nine essential amino acids. Examples include animal products like meat, eggs, and dairy, as well as plant-based options like soy, quinoa, and buckwheat.

Yes, vegans and vegetarians can obtain all essential amino acids by eating a variety of incomplete plant proteins throughout the day. Combining foods like rice and beans or consuming complete plant proteins like soy and quinoa is effective.

If you don't consume enough essential amino acids, your body's ability to produce proteins is hindered, which can lead to fatigue, weakness, poor immune function, and, in severe cases, malnutrition.

No, conditionally essential amino acids are only required from the diet under specific circumstances, such as illness, trauma, or during rapid growth, when the body's own production is insufficient.

Amino acids serve as the building blocks for proteins, which are essential for creating and repairing tissues, producing hormones and enzymes, and supporting numerous metabolic and immune functions.