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The Nine Essential Amino Acids: An Overview

Amino acids are the building blocks of protein. This article discusses the nine essential amino acids and their functions in your body. Find out what these are, where to find them, and how they help your body function correctly

Emilia Moore
The Nine Essential Amino Acids: An Overview
Table Of Contents

You would be aware of the importance of consuming protein for building muscles. Your body needs protein to build muscle, fight germs, and recover from illness. These protein molecules are made up of different types of amino acids

Our body needs 20 different amino acids to function correctly. Out of these 20, nine are essential amino acids that are not produced by our bodies. Essential amino acids should be consumed by the food we eat. You can find essential amino acids in many foods, including beef, eggs, and dairy.

To study the essential amino acids in our body, let us first see what amino acids are.

What are Amino Acids? 

When we consume proteins, it is broken down into different amino acids. There are thousands of protein types in your body, each with an essential feature. Long chains make these proteins of amino acids that allow them to take on different forms and perform different functions in your body.

Amino acids can be thought of as the letters of the alphabet. Combining letters in different ways can result in different words. The same goes for amino acids - when they are combined in different ways, you get different proteins.

Amino acid is an organic chemical that has a carbon-hydrogen bond. Each type of amino acid has the same basic structure. Each molecule comprises a central carbon atom linked together with a carboxylic acid or side-chain group, a hydrogen group, and a basic ammonium atom. 

The R-group is the key to distinguishing amino acids. The chemical nature of each amino acid is determined by its R-group. The chemical nature of amino acids determines their interaction with other amino compounds and the environment.

Proteins are formed when amino acids and peptide bonds are joined. The forces from other amino acids and the effects of their R-groups transform the protein into specific three-dimensional forms. 

Your body uses amino acids for the production of proteins. Each protein's function is determined by the amino acids used and combined. Amino acids play distinct roles in the body. Amino acids help: 

  • Breakdown food.
  • Restore and grow body tissue.
  • Make hormones and brain chemicals (neurotransmitters)
  • Provide energy sources
  • Help keep your hair and nails healthy.
  • Develop muscle.
  • Boost your immune system.
  • Sustain a normal digestive system.

The human body does not make nine amino acids produced in our body from thousands of amino acids. These are called essential amino acids. Let us further look into the details of these nine essential amino acids. 

The Nine Essential Amino Acids 

Your body does not make these nine essential amino acids, so you should consume them from the food you eat. These nine essential amino acids, their function, and food sources are as follows. 

1. Histidine

Histidine helps produce a brain chemical known as the neurotransmitter histamine, which works as a mediator of autoimmune conditions and allergic reactions. It also helps ensure the proper functioning of the immune system. Histamine can also play a role in sexual arousal. This is why antihistamines may decrease sexual desire.

Histidine is not only responsible for creating histamine. It also plays a role in tissue repair, maintenance of pH, and the synthesis of hemoglobin, a protein found in red blood cells that transports oxygen. 

Studies have also shown that people with rheumatoid arthritis have lower serum levels of histidine. This could indicate the role of histidine in treating this condition.

Histidine also helps maintain the myelin sheaths, protecting nerve cells in the central nervous system. It protects tissues against radiation and heavy metals.

Histamine plays a vital role in your body's immune system, digestion, and sexual function.

Food sources of histidine include:

  • Meat
  • Poultry
  • Fish
  • Eggs
  • Whole grains
  • Dairy products
  • Nuts
  • Seeds
  • Beans

2. Isoleucine

Isoleucine is one of three branched-chain amino acids (or BCAAs). This group of amino acids is composed of branched side chains: the shorter chains attached to the main or backbone of the molecule.

Isoleucine, like histidine, is an essential component of hemoglobin. Isoleucine is also helpful in wound healing and blood clotting. Like the other BCAAs, isoleucine can also be found in high concentrations in muscle tissue. 

This regulates energy and blood sugar, aids muscle repair and metabolism, improves immune function, and helps the body recover from exercise.

Food sources for isoleucine include:

  • Meat
  • Poultry
  • Fish
  • Eggs
  • Tofu
  • Dairy products
  • Spirulina
  • Legumes

3. Leucine

Leucine is the most abundant essential amino acid in the muscles. It promotes muscle growth by aiding in protein synthesis. Leucine is similar to isoleucine in that it contributes to both muscle recovery and energy production.

It is found in muscle tissue and increases the number of muscle mitochondria, which are the energy centers of the cells. Leucine also promotes bone growth and repair, stimulates growth hormone secretion and insulin secretion, and speeds wound healing. 

Food sources of leucine:

  • Meat
  • Poultry
  • Fish
  • Eggs
  • Tofu
  • Dairy products
  • Legumes
  • Pumpkin seeds

4. Lysine

Lysine is an essential component of producing and using hormones, energy, and other chemicals. Like all essential amino acids, lysine is necessary for protein synthesis. 

However, it's also required to ensure proper intestinal absorption. Lysine is also an essential amino acid that aids the immune system in producing antibodies and protects the body from viruses.

Lysine is required for tissue repair and the building of collagen. This structural protein is essential for creating and maintaining many types of connective tissue, including skin and joint cartilage. 

Lysine is essential for the prevention and treatment of atherosclerosis. Lysine can also treat stress-related anxiety, diarrhea, and other symptoms. It may also protect your gut by having an anti-inflammatory effect on the intestinal lining.

Although lysine is a common amino acid in animal proteins, it is often the limiting amino acid in plant protein, particularly those made from cereal grains. Vegetarians and vegans must be careful when selecting dietary protein sources. They can opt for supplements to fulfil their lysine needs. 

Food sources for lysine:

  • Meat
  • Poultry
  • Sardines
  • Parmesan cheese
  • Tofu
  • Fenugreek
  • Buckwheat
  • Quinoa 
  • Legumes

5. Methionine

Methionine aids in tissue growth, metabolism, and detoxification. Methionine is also helpful in absorbing essential minerals like zinc, sulphur, and selenium. Methionine can be used as a medication. Without it, protein synthesis will never get started. 

Methionine, like lysine, also aids in the formation of cartilage by encouraging cells to create more cartilage tissue.

Additionally, methionine strengthens joints by creating sulphurous chains that connect. Its anti-inflammatory and antioxidant properties, as well as its analgesic properties, can help alleviate arthritis symptoms.

Methionine is essential for the bioavailability and absorption of minerals like zinc and selenium. It aids in the detoxification and elimination of chemicals like lead and mercury. It also helps the liver to metabolize fats.

Food sources for methionine:

  • Meat
  • Poultry
  • Fish
  • Eggs
  • Dairy products
  • Brazil nuts
  • Sesame seeds
  • Broccoli
  • Onions

6. Phenylalanine

Although phenylalanine plays a critical role in the structure and function of many enzymes and proteins, its primary role is that of a precursor to the amino acid tyrosine. This is then transformed into thyroid hormones and various other brain chemicals.

These chemicals can affect mood, focus, and other aspects of cognitive function. Dopamine, epinephrine, and norepinephrine are just a few crucial chemicals. Phenylalanine is also found in three different forms: D-phenylalanine, L-phenylalanine, and DL-phenylalanine (DLPA). 

The L form is used by the body to produce protein. The D-form, which is a synthetic mirror image for the L-form, has been proven in at least some experiments (results were conflicting) to be used as a painkiller. As you can see, the DL form combines both the L and D forms.

In some studies, phenylalanine has been suggested to play a beneficial role in depression and skin conditions like vitiligo due to its association with neurotransmitter production. It also helps with multiple sclerosis (MS), Parkinson's disease, attention deficit-hyperactivity disorder (ADHD), and rheumatoid arthritis. 

Food sources of phenylalanine

  • Meat
  • Poultry
  • Fish
  • Eggs
  • Parmesan cheese
  • Soybeans roasted
  • Legumes
  •  Kamut
  • Pumpkin seeds

7. Threonine

Threonine supports the cardiovascular, immune, and central nervous systems. It is also a precursor to serine and glutamine, which create muscle tissue, collagen, and elastin. This protein is found in elastic connective tissues such as skin, blood vessels, and tendons.

Threonine is also crucial for tooth enamel and strong bones, fat metabolism and preventing fat from building up in the liver. It is also necessary to maintain the integrity of the gastrointestinal mucosa. This is an essential factor in leaky stomach syndrome. Studies have also shown that threonine can treat multiple sclerosis and depression.

Threonine is an essential component of collagen and elastin. These proteins give structure to your skin and connective tissue. They are also responsible for forming blood clots that prevent bleeding. Threonine is also essential in fat metabolism and immune function.

Food sources of threonine:

  • Meat
  • Poultry
  • Salmon
  • Shellfish
  • Cheese
  • Watercress
  • Pumpkin seeds

8. Tryptophan

Tryptophan is essential for average infant growth and maintaining a healthy balance between protein synthesis in adults and children. Tryptophan is used as a foundation for niacin and the inhibitory neurotransmitter serotonin.

Because of its ability to regulate mood and promote self-esteem, serotonin is sometimes called the "happy chemical". The majority of serotonin, or about 90%, is produced in your digestive tract. 

Low levels have been associated with Irritable Bowel Syndrome (IBS). Serotonin is also involved in osteoporosis and cardiovascular disease. It also plays a critical role in many physiological and cognitive functions such as memory, learning, vasoconstriction, and vasodilation. 

Low serotonin levels may also be responsible for fibromyalgia and eating disorders.

 Food sources of tryptophan:

  • Meat
  • Poultry
  • Tuna
  • Eggs
  • Legumes
  • Mozzarella
  • Oatmeal

9. Valine

The final BCAA requires Valine for tissue repair, muscle metabolism, and blood sugar control. It is also crucial for normal cognitive function and supports the immune and central nervous systems. Valine is also important in regulating the body's nitrogen balance, indicating overall health.

Food sources of valine:

  • Meat
  • Poultry
  • Fish
  • Soybeans
  • Legumes
  • Mushrooms
  • Whole grains

The body makes the remaining 11 amino acids that you require. These are known as nonessential amino acids. These nonessential amino acids are alanine and arginine, asparagine; aspartic acid; cysteine; glutamic acid, glutamines, glycines, proline, serine, and tyrosine. 

How Many Amino Acids do Your Body Needs

While you don't have to consume amino acids in every meal, it is essential to maintain a healthy balance. For each essential amino acid, the daily recommended allowance is 2.2 lbs.

  • Histidine: 14 milligrams
  • Isoleucine: 19 milligrams
  • Leucine: 42 milligrams
  • Lysine: 38 milligrams
  • Methionine: 19 milligrams
  • Phenylalanine: 33 milligrams
  • Threonine: 20 milligrams
  • Tryptophan: 5 milligrams
  • Valine: 24 milligrams

Why Do You Need Amino Acid Supplements?

A balanced, healthy diet can often provide all of the essential amino acids that your body requires. However, amino acid supplements can help improve your sleep quality, mood, and athletic performance. 

If you are not getting the required amount of essential amino acids from your diet, the DMoose amino acid supplements will help ensure that you get the required amount of amino acids for your body and brain. 

This supplement targets essential amino acids supplements to meet your amino acid requirements. Essential amino acids can benefit those who exercise regularly or do strength-building exercises. EAA's aid in creating more muscle mass, preserving muscle tissue, increasing strength during exercise, and improving workout performance.


Protein molecules are made up of different amino acids, out of which nine are essential amino acid molecules. Our bodies do not produce these essential amino acids. Therefore, we should consume them through food or supplements to fulfil our daily amino acid requirements. 

These nine essential amino acids are crucial for our cognitive and complete body functioning, such as hormone production, digestion, sexual health, muscle building, and cardiovascular health. Make sure to consume enough amino acids to maintain a healthy balance.  

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Article Sources

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Emilia Moore

Emilia Moore earned her master’s degree in community health education from a well known University. She’s a freelance writer based in America whose work has appeared in various online publications, including not only DMoose, but other known blogging websites. Today, it's easy to find health

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