Essential Amino Acids: Definition, Benefits and SideEffects

Essential Amino Acids The importance of the essential amino acids is often overlooked, as people tend to think of protein as an essential nutrient. However, protein is not a “complete” protein, and a diet should provide all the essential amino acids in adequate amounts. The main functions of these amino acids are to “encode” proteins that build and repair tissues, regulate metabolism, and support the immune system.   Amino acids contain essential amino acids, nonessential amino acids, and conditionally essential amino acids as a whole. These are compound structures, also known as the building blocks of protein present in our muscles; they play vital roles in our human body. They have more significant roles in protein-building processes, synthesizing hormones and other neurotransmitters efficient for our various body processes.  

Professional athletes and fitness lovers also go for essential amino acid supplements for improving their performance naturally. These supplements are a great mood booster and come with many delicious flavor variants.

This article comprises all information about essential amino acids(EAAs), their function. These foods can be derived, the benefits of taking critical amino acids, their side effects, and the best essential amino acid supplements available in the market.

What are Essential Amino Acids?

Our body requires 20 different amino acids to carry out the body’s processes with proper functioning and grow properly.

All these 20 amino acids are vital for our body and are needed to stay healthy, but only nine amino acids are essential.

Essential amino acids are the building blocks of protein. The body requires them for various bodily functions, such as the maintenance of our muscles, tissues, immune system, nervous system, and the production of hormones like insulin. The nine essential amino acids are isoleucine (I), leucine (L), lysine (K), methionine (M), phenylalanine (P), threonine (T), tryptophan (W), valine (V), and arginine (R). The “essential amino acids” must be present in sufficient amounts to complete the “building blocks” of protein in the body. The other essential nutrients are the required vitamins and minerals.  

Different Types of Essential Amino Acids

Essential Amino Acids List


 Tryptophan is found in many foods, most notably protein-rich foods. It is utilized by the body to produce a brain chemical called serotonin. Serotonin is a hormone important for sleep, mood, and appetite control. Tryptophan is also utilized to produce the body’s sleep hormone melatonin. It plays a crucial role in the production of a hormone called growth hormone. Growth hormone is a peptide hormone that promotes growth and development in children and adolescents and adult athletes.

Tryptophan, also known as 5-hydroxytryptamine, is an essential amino acid used by the body to produce certain neurotransmitters. It is found in various foods and is particularly high in turkey, avocado, cheese, sesame seeds, and other nuts and seeds. The scientific name for tryptophan is L-tryptophan. There are several types of tryptophan, depending on where it is used in the body.  


Leucine is an essential EA that is a constituent of protein. However, leucine is not synthesized in the human body, and it is transported in the blood by a carrier protein called high-affinity protein transfer protein (HPT).   Leucine is a branched-chain amino acid (BCAA) that is used in creating energy and repairing muscles. Leucine is one of the three branched-chain amino acids (BCAAs). These three are Isoleucine, Valine, and maybe the most important of all, leucine. Leucine is the most abundant amino acid in meat and other foods. It is used primarily to preserve muscle mass and has other functions such as improving protein synthesis and controlling blood sugar. In addition, leucine stimulates the release of other BCAAs, threonine, valine, and lysine. It also is involved in the production of other substances, including certain growth factors. Leucine is available in many foods but is not present in significant amounts in most foods.  

Leucine is a kind of amino acid that has a very short half-life, and that is why it is important to include regular amounts of protein in our diet to provide the body with sufficient leucine. The liver or the kidneys usually oxidize the leucine found in protein into its essential form, which is then transported and used by the body as a source of fuel. Research has demonstrated that leucine is an excellent anabolic hormone, thanks to which the effectiveness of post-workout protein ingestion is increased.


IsoLeucine is a branched-chain amino acid that plays a key role in our bodies. It is considered essential because it must be obtained from the diet. However, IsoLeucine is not present in many high-quality protein sources, which is why supplementation is recommended. Since IsoLeucine is a branched-chain amino acid, it has the ability to be turned into other compounds; and those compounds are used for different purposes and in different areas of the body. Isoleucine not only helps in the formation of protein. It also helps controlling the levels of enzymes(e.g., glutathione) in the body that help in the formation of essential proteins.  


Valine is also a branched-chain amino acid (BCAA) synthesized in the liver from leucine. It is an essential amino acid crucial for the structure of proteins that form muscle. It is not present in plant sources of protein but is found in most animal-derived foods. Valine is also found in egg whites and is a component of the glycoprotein that makes up a hen’s egg shell. Valine is also found in the feathers of birds. You can also find this amino acid in hair, skin, nails, and teeth.

It is an essential amino acid that is primarily synthesized from isoleucine, methionine, and phenylalanine. Valine is a semi-essential amino acid in the human diet, meaning that it can be synthesized from other amino acids. In fact, most of the essential amino acids in the human diet are synthesized from other essential amino acids.


Lysine is one of the essential amino acids that our bodies cannot make independently; it is the essential amino acid that got the most press when it was discovered in the early 1900s. Since then, it has been named as the “mother” of all amino acids. This amino acid is essential to our body as it is essential for producing other amino acids. Lysine is also important for the production of collagen proteins. Collagen is a protein present in the human body and plays a vital role in maintaining the body’s structure. Collagen helps the body to maintain a strong immune system and protects the body from various diseases and illnesses. Lysine is an essential amino acid that belongs to the group of aspartic acid and glutamic acid. L-lysine is obtained by eating food that contains lysine or by taking supplements. Lysine is one of the most abundant amino acids in the human body. In the United States, its content in the humanized diet is about 3.3 g/day. This amino acid is used in the synthesis of structural proteins and the synthesis of some hormones, enzymes, and neurotransmitters. Lysine is also necessary for the growth and maintenance of the skin, hair, and nails.


Phenylalanine is an essential amino acid. The function of phenylalanine is to serve as an intermediate in the metabolism of tyrosine to tyramine, 3- hydroxyphenylglycol, and phenylethylamine.
Phenylalanine, or more specifically, hippuric acid, is found in many food sources, including meat, eggs, and dairy products. It is a precursor to tyrosine, an amino acid that is essential for producing various hormones, such as epinephrine and norepinephrine. However, there have been some concerns over the human body’s ability to convert hippuric acid into tyrosine efficiently. This could result from the fact that the body can only produce small amounts of tyrosine from hippuric acid and that the conversion rate is shallow. Phenylalanine or Phe is an essential amino acid that is responsible for protein synthesis. The amount of Phe in the body is not sufficient for the synthesis of proteins. Deficiency of Phe results in the buildup of phenylalanine that is then converted to tyrosine.


Threonine (Thr) is an essential amino acid with an important function in the body, but it can be difficult to obtain in adequate quantities. The standard American diet consists mostly of animal-based proteins, which raises the threonine requirement. In fact, in the past few years, threonine shortage has become a concern for physicians and dieticians alike.
Threonine is an essential amino acid found in protein-containing foods such as egg white, meat, milk, soy, wheat, and dairy products. However, most plants are not found, so vegetarians and vegans can’t get enough threonine through diet alone. Threonine has an important role in the synthesis of glucose, cholesterol, and fatty acids. The human body cannot produce threonine, but if threonine is not consumed, the body will break it down and eventually discard it.
Threonine is a component of proteins. It is also known as methionine. This protein component is critical for the function of a variety of cells. Other than that, it is also important for the recovery of muscle cells. This amino acid helps in forming new proteins in the body. The body needs threonine to produce the new proteins. Also, this amino acid helps in the growth of the new cells.


The histidine (HIS) family of amino acids contains several derivatives, including histidine itself and histidyl, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. It also contains important enantiomers such as L-leucine and D-histidine and several non-canonical histidine derivatives. Histidine is an essential amino acid with a molecular weight of 22.43g/mol that is synthesized primarily by the liver and kidneys from other amino acids. Its natural abundance in foods has been rising due to a lack of biological research on its effects on human health. This lack of research has resulted in a lack of knowledge about the biochemical functions of histidine, making it difficult for scientists to understand its role in human biology fully.

It is a compound that is usually found in foods such as meats, dairy products, eggs, and some nuts. It plays a critical role in the metabolic processes along with helping in protein deposition.
Histidine is an essential amino acid, meaning it is not synthesized within the body. It is used in the prevention and treatment of histamine-mediated allergic responses. It is used to produce many enzymes, hormones, neurotransmitters, and substances necessary for the body to function properly. Without histidine, there would be no amino acids produced, and therefore no proteins or enzymes made.


Methionine is another essential amino acid that is not produced by the body and is, therefore, an essential dietary supplement. It is necessary for life and functions in the human body. It is a common amino acid in both plant and animal proteins. However, it is present as a trans-sulfur compound in only animal proteins. Methionine is synthesized in all body tissue, from muscle to skin, and from the body’s food intake. It is one of the 3 building blocks that make up proteins and aids in building muscle. It is also a vital component of most of the human metabolic pathways. The human body can convert the amino acids leucine, isoleucine, and valine into methionine. It is found in foods such as meat, eggs, fish, nuts, and dairy products. Methionine is also the most abundant amino acid in the human body. It is also a precursor to the amino acid cysteine. Cysteine is required for the formation of cystine, which is the building block for collagen. Methionine is also an essential precursor to vitamin B6.

Methionine is an essential amino acid that needs to be consumed during our diet to maintain healthy nutrition. It is a water-soluble amino acid that is one of the building blocks of protein and assists with forming sulfur-containing compounds. The metabolism of methionine is also critical to the synthesis of cysteine, whereas its deficiency may lead to various metabolic disorders.

These nine amino acids constitute the list of essential amino acids(EAAs). These are termed EAAs as these can’t be produced by our bodies, unlike nonessential amino acids. So we have to obtain these through our daily routine natural diet or supplements.

The best essential amino acid foods are obtained from animals. These foods include meat, poultry, beef, and eggs.

When we consume protein either through protein-rich foods or whey protein supplements, the protein gets crippled into different amino acids. Our body uses these amino acids to help with essential human body processes such as building our muscles and improving immune function.

Conditionally Essential Amino Acids

An essential amino acid is an amino acid that the human body cannot synthesize by itself; in other words, it must be provided by the diet. There are 20 essential amino acids and are gamma-aminobutyric acid (GABA), serine, glycine, alanine, threonine, valine, isoleucine, leucine, phenylalanine, methionine, glutamic acid, aspartic acid, asparagine, cysteine, cystine, lysine, arginine, histidine, proline, lysine, and tyrosine.

Conditionally Essential Amino Acids are the amino acids generally placed under the category of nonessential amino acids. Still, they are considered essential under some particular circumstances, like in certain illnesses or stress.

For instance, our body needs arginine when fighting challenging diseases like cancer, but it is considered nonessential otherwise when not in need.

So in those specific situations, arginine is needed to be supplemented through natural foods or some arginine supplements to meet our body’s arginine requirements.

Benefits of Essential Amino Acids

In advancing age, it is important to know about the benefits that essential amino acids can provide. They play key roles in the body and help with a wide range of issues, from immune function, tissue growth, muscle repair, energy levels, mental focus, and sleep quality. Certain diets will also claim to provide essential amino acids, but in reality, they are not as effective as those in real food.

Now, you might be wondering about the benefits of Essential Amino Acids, So there you go.

There are many foods from which we can obtain our EAAs or take various supplements rich in EAAs with varying doses. 

Taking the amino acids in supplement form does trigger many health benefits.

1. Helps Prevent Muscle Loss

Muscle loss is a prevalent thing experienced by people due to long-term ailments and excessive bed rest, more frequently in people above the age of 30 years.

According to various researches, EAAs are proven to maintain lean body mass and slow down or prevent muscle protein breakdown due to the inability to carry out regular workouts.

There was a 10-day study conducted on 22 adults who were on bed rest. The study showed that the group of adults who consumed 15 grams of mixed EAAs suffered almost no changes in their muscle protein synthesis compared to those who didn’t. The ones who were not taking EAAs did go through a 30 % decrease in their protein synthesis processes.

As already said, essential amino acid supplements play a vital role in maintaining lean body mass in older adults or professional athletes. 

2. Encourages Weight Loss

There have been studies that suggest that the use of branched-chain EAAs is effective in stimulating fat loss.

And adding some more facts to your knowledge, an eight-week study was conducted on 36 professional gym athletes, which demonstrated that adding 14 grams of branched-chain amino acids in their daily routine induced fat burning processes. This led to a noticeable loss in body fat percentage, which was not the case when consuming whey protein or other supplements drinks.

The same results were noticed even in the rats’ experiment. The rats given a diet supplemented with 4% leucine experienced faster fat loss and a much more significant decrease in body weight.

But, doctors are still finding the direct link between the use of branched-chain amino acids and weight loss.

Theory demands more evidence to concrete these facts that amino acids promote weight loss.

3. Helps Improve Workout Performance

Leucine, Isoleucine, and Valine: the three branched-chain EAAs help cut down fatigue, improve workout performance, and increase muscle recovery after heavy workouts.

In a study conducted with 16 strength-trained professionals, it was demonstrated that branched-chain amino acid supplements help enhance their workout performance with increased muscle recovery and lowered muscle soreness compared to those who were not taking these supplements.

Moreover, many unprofessional people who occasionally don’t work out frequently were given 4 grams of leucine consistently for 12 weeks every day. They also experienced increased strength which depicts that EAAs also benefit non-athletes reasonably enough.

Research suggests that including branched-chain amino acid supplements in our daily diet is believed to promote protein synthesis, improving our muscle recovery, and decrease the extent of muscle soreness after intense workouts.

4. Improves Mood and Sleep Quality

A neurotransmitter in our body, Serotonin is a chemical that Tryptophan produces for serotonin’s production.

Serotonin plays a vital role in enhancing your mood, sleep quality, and behaviors.

Low serotonin levels lead to a depressed mood along with sleep disturbances. Studies also show that supplementing our diet with tryptophan also helps in reducing depression symptoms. It also boosts our mood and improves the quality of sleep.

A study conducted for 19 days on 60 different women, each of age above 40 years, showed that 1 gram of tryptophan per day in their diet gave an increased energy boost and enhanced happiness compared to the average population.


From the above data, we learned about various essential amino acid benefits in our daily day-to-day workout routine.

How to get Essential amino acids

Essential Amino Acids are not only important for the body but also for the mind. As we age, we develop a decreased ability to utilize amino acids consumed in the diet. This often causes a decline in mental clarity, concentration, and physical performance. The ability of our bodies to utilize amino acids is called the “Kwashiorkor” response. It is a rapid and efficient way to speed up our body’s metabolism and get more out of the food we eat.Top view of fresh delicate Brompton stock flowers with pink petals placed on white table with various jars of bath salts  

Essential Amino Acids and the Human Body

Amino acids are a vital part of every cell of the human body, and an imbalance in these can cause diseases or health problems. There are many different amino acids, but the most important are the 9 different essential amino acids and how they can affect your body. The 9 essential amino acids have a close connection with each other and are all essential to the human body.   The human body is a machine. When you eat, your body breaks down your food into individual components, including protein, carbohydrate, fat, and water. Each of these components provides different nutrients and helps to fuel your body. One of the most important of these components is amino acids. Amino acids are the building blocks of protein, a nutrient that occurs naturally in foods and is an essential part of a healthy diet. Have you ever wondered what would happen if you took away some of the essential amino acids from your daily diet? Well, if you have, I have good news for you. Our body needs these essential amino acids to perform various important functions, such as protein metabolism and muscle growth. So, the question is, do you really know what these essential amino acids are and which ones you should be getting the most of each day?  

Daily Recommended Intake

The human body is made up of over two-thirds of the protein, and we need this to stay healthy and function properly. It’s worth remembering that since protein is an essential food, it must be consumed to stay healthy. Now, the body needs to be able to utilize this protein to be of any use to us, so we need to consume adequate amounts in our diet. The most important are the essential amino acids that perform the job role of breaking down proteins in the body.

Our body can produce 50mg of each amino acid per day. In contrast, the recommended intake for the amino acids is the Daily Value (DV) for all the essential amino acids together.

Essential Amino Acids (EAAs) are absolutely vital for the body and can be found in many foods varying from meat, fish, eggs, dairy, legumes, nuts and seeds, and vegetables. To our benefit, we should be happy that there are a good number of foods that have a high concentration of essential amino acids, or in simple words, these are the foods high/rich in essential amino acids that make it way easier for us to fulfill our daily need of EAAs. As the name suggests, numerous food sources contain essential amino acids. However, with all the different essential amino acids, it can be a nightmare trying to find the right foods to eat.

So, these are the suggested daily intake amounts for the nine essential amino acids, respectively:

  • Isoleucine: 19 mg
  • Lysine: 38 mg
  • Leucine: 42 mg
  • Methionine (+ non-essential amino acid cysteine): 19 mg
  • Phenylalanine (+non-essential amino acid tyrosine): 33 mg
  • Hsitidine:14 mg
  • Valine: 24 mg
  • Tryptophan: 5 mg
  • Threonine: 20 mg

Foods Rich in Essential Amino Acids

Although it is possible and effortless to be deficient in essential amino acids, most people can get enough of them by following a diet containing protein. The foods on the following list are the most common sources of essential amino acids:

  • Lysine can be easily found in meat, eggs, soy, black beans, quinoa, and pumpkin seeds.
  • Meat, fish, poultry, nuts, seeds, and whole grains contain high amounts of histidine.
  • Cottage cheese and wheat germ contain high amounts of threonine.
  • Methionine is found in eggs, grains, nuts, and seeds.
  • Valine is found in soy, cheese, peanuts, mushrooms, whole grains, and vegetables.
  • Isoleucine is abundant in meat, fish, poultry, eggs, cheese, lentils, nuts, and seeds.
  • Dairy, soy, beans, and legumes are good sources of leucine.
  • Phenylalanine is found in milk, meat, poultry, soy, fish, beans, and nuts.
  • Tryptophan is found in most protein-rich foods, including wheat germ, cottage cheese, chicken, and turkey.

These are just a few examples of foods rich in essential amino acids. All kinds of protein, whether plant or animal, will contain at least some of the essential amino acids.

Free stock photo of asian, asian cuisine, asian food

Complete Proteins

How many of you know what complete proteins are? I would say a majority of people don’t know. Let me explain what they are when in a simple way. Complete Proteins are proteins that are made up of all the essential amino acids. It is tough to get all of the essential amino acids from one food source, so it is important to make sure you are getting enough variety. What are the major benefits of eating a complete protein? The major benefits of eating a complete protein are that it will help you maintain a healthy weight, it will help promote muscle recovery, and it will help you feel fuller for longer.   The things that you need in your diet to stay healthy can be tricky to find at times. One of those key things is complete proteins. Many people are under the impression that it’s only animal sources such as meat, eggs, and dairy that offer complete proteins. Many people have allergies or don’t eat meat, eggs, or dairy due to religious beliefs. Plant-based complete proteins offer those people alternatives.

Foods with complete protein content in them:

  • Poultry
  • Dairy Products
  • Seafood
  • Meat
  • Eggs

The other veg plant-based foods with complete protein sources in them are soy, buckwheat, and quinoa.

Sometimes people mistakenly include beans and nuts also in the category of plant-based sources of protein. But these foods fall short of including all the EAAs and hence, are not the complete proteins.

If you are really serious and abiding by your plant-based diet dedicatedly, you can get complete nourishment and consume all the EAAs. For complete nutrition, you can always go for varieties of plant protein foods or supplements.

You can exclude all the animal products by replacing animal products with various plant-based veg foods with EAAs. You can also add other vegetables to fulfill your requirements.

Essential Amino Acids Side effects

In a word, I will clear the confusion; there are no potential side effects of these.

Just think that till now, we have discussed various benefits of EAAs, different types of amino acids, and why these amino acids are important for us, right?

But you might be wondering about the side effects of essential amino acids.

A lot of people are not aware of the potential side effects when taking amino acids. A form of amino acid is also a popular dietary supplement. The side effects that can occur to someone who takes amino acids can vary from mild to severe.

A person who takes an amino acid supplement might experience things such as heart palpitations, fast heart rate, upset stomach, diarrhea, nausea, and excitability. A person who has a severe reaction might experience things such as confusion, difficulty breathing, and loss of consciousness. If a person suddenly develops any of these symptoms, they should stop taking the amino acid supplement immediately.

Final Takeaway

Essential Amino Acids improve our health to a greater extent. There are all the right reasons we should give our body proper nutrition, complete its daily dietary protein intake and amino acid requirement. EAAs supplements also help to have the right protein levels in our diet, which keeps problems like protein deficiency away. There are many sources of protein available naturally and also in the form of whey protein supplements. Amino Acid Supplementation has some side effects also, but they are scarce. You can take your regular plant and dairy foods without a second thought.

Leave a Comment