Essential Amino Acids (EAAs) – Why Take Them?

Essential Amino Acids (EAAs) – Why Take Them?

Essential amino acids (EAAs) are a key element in building muscle mass.

Furthermore, we must consume them to avoid suffering a deficiency disease associated with their deficiency. We know that amino acids are something similar to protein, but we have also talked about branched-chain amino acids, isolated amino acids, such as leucine, which we said was the metabolic key that initiates the process of muscle anabolism..

You might be a little confused right now, aren’t you? Don’t worry, in this article I’m going to give you the information you need to distinguish essential amino acids from other protein sources, learn how to consume them and how to benefit from their effects.

What is an amino acid?

Amino acids are the minimum structural and functional unit of protein, and are the compounds that are absorbed in the intestine for circulation in the blood.

  • So protein is made up of amino acids? That’s right!
  • And amino acids are actually the molecules we use from the protein we consume, right? Yes! You get the picture.
Protein that we consume is hydrolysed, i.e. broken down, by enzymes that live in our stomach and intestine called proteases, which release the amino acids so that they can cross the epithelial barrier of the enterocytes, which is responsible for regulating the passage of substances into the blood.

what is an amino acid

Figura I. Molecular structure of an amino acid, a peptide and a protein; sequenced structures from least to most complex. Retrieved from:


There is an intermediate step: we can consume or degrade proteins in such a way that peptides are generated.

A peptide is nothing more than a (short) chain of amino acids that can be absorbed at the intestinal barrier we talked about earlier, by a different route than amino acids. However… by the time they reach the blood, the peptides have already been dissolved and arrive in the form of free amino acids.
amino acid peptides

Figura II. Distribution of oligopeptides and free amino acids in an intestinal epithelial cell (enterocyte) and their transport into the blood. Amino acids enter the cell via sodium-dependent transporters, and oligopeptides are transported via hydrogen-dependent transporters (pepT1) and degraded by peptidases inside the cell, to obtain amino acids that can pass into the blood. Retrieved from:

With this section I want to make it clear to you that, broadly speaking, protein, peptides and amino acids are nitrogenous substances that are related to each other, in fact they are “the same” and only differ in the presence or absence of bonds between their amino acids

How are they distributed in the body?

In the body we have a total of 20 amino acids that make up the different proteins that are present in our body

Our body always prefers to handle small molecules from any source, as it is easier for it. Hence, as mentioned above, only free amino acids circulate in the blood, not amino acid chains; this reaction is called “catabolism” or oxidative reaction.

Anabolism and Catabolism

Figura III. Schematic graphic description of the processes of catabolism and anabolism. Retrieved from:

However, the body then wants to use these amino acids. Some are used for metabolic functions and “disappear”, are degraded and their waste products are mainly eliminated through urine and sweat.

Others, however, are used for the repair and construction of structures, for which the body expends energy to bind these amino acids that it has previously broken down, and to form new proteins on demand;

This reaction is called “anabolism” or the reductive reaction: we are talking about the muscle protein synthesis

What does “essential” mean?

So far we have talked about amino acids, but what are essential amino acids?

An essential nutrient is an organic or inorganic compound that we must consume through our dietary intake, because if we do not, our body does not have the tools to create it by itself, and its deficit in the long term would make us sick. Of the 20 amino acids we have previously mentioned, 9 are essential, these are:

Leucine, Isoleucine, Valine, Lysine, Methionine, Threonine, Tryptophan, Histidine and Phenylalanine

In turn, the first 3 mentioned above are the well-known branched-chain amino acids or BCAAs (Branched-Chain Amino Acids).

Essential amino acids are found in practically all foods containing protein.

However, not all proteins are equal; currently the proposed model for determining the quality of a protein is based on the quantification of a number of quality criteria including biological value (Hoffman & Falvo, 2004).

Biological value is a numerical value that classifies the quality of a protein according to its presence or absence of certain essential amino acids.

Amino acidsChickenEvoeaasSoy

Tabla I. Comparison of amino acid profile between chicken breast, soya beans and EvoEaas (expressed /100g. of product) (Bernard, Mahungu & Eric, 2018; Srinivas et al. 2015)

As we can see, 100g of EvoEAAs provide significantly more essential amino acids than the main source of animal (chicken) and vegetable (soy) protein.

Therefore, to receive the amount of essential amino acids equivalent to 100g of these products, it would be sufficient to consume approximately 10g of EvoEAAs, which is close to the recommended mass per serving (13.5g)

How are essential amino acids obtained?

Well, we already know what amino acids are, their similarities and differences with respect to other protein forms, but where do we get essential amino acids from?

In most cases, supplement brands obtain both essential and branched-chain amino acids from a process that uses the hair or feathers of certain animals for their extraction.

This can pose ethical dilemmas for the consumer, which is why at HSN we obtain our amino acids through a vegetable fermentation process mediated by enterobacteria.

So our product is suitable for consumption by vegans (as it does not contain any animal sources) and is suitable for coeliacs.

Why should I consume essential amino acids?

Amino acids have the same functions in the organism as protein, since in fact, as we have explained above, they are derived from protein

Amino acids are substances that are used as building blocks::

  • Structural
  • Contractile
  • Co-catalysts of metabolic reactions (support metabolism)
  • Transporters and reservoir (e.g. fatty acids)
  • Cellular recognition and defence (protein antibodies)
  • Genetics
  • Energetic (in extreme cases)
These functions are shared with protein, since protein is nothing more than a set of amino acids linked together by peptide bonds. Do you want to know in which cases essential amino acids in free form are more interesting than protein? Then read on!

Protein requires a process of degradation by its gastrointestinal passage through the action of a series of proteolytic enzymes.

Process of protein degradation into amino acids

Figura IV. Process of degradation of proteins into amino acids. Organs are shown in red, hormones in blue and enzymes in green. Retrieved from:

As you can see, there is a long process from the time you ingest a protein source, until its amino acids reach your bloodstream to be metabolised in the liver and used for the wide variety of functions mentioned above.

This process of degradation and absorption of its amino acids is necessary, but it involves an investment of time, which depending on the protein source used will be greater or lesser; it should be borne in mind that the co-ingestion of other macronutrients together with the protein (carbohydrates or fats) may affect its digestion process or not, but in no case does it affect the anabolic potential of the protein ingested (Gorissen et al., 2014; Gorissen et al., 2017).

But there may be a time when you want to get an almost immediate supply of amino acids into your bloodstream, right? To make them quickly available for their functions.

This is where essential amino acids in free form and their consumption through supplementation come into play, as the response they generate in the body is (logically) a much higher concentration of amino acids in the blood much faster.

Plasma Amino Acid Concentration

Figura V. Changes in amino acid concentration in blood plasma after consumption of essential amino acids in free form (dashed line) or the same amount of essential amino acids from a complete protein (solid line). (Gropper & Acosta, 1991 citado en MacDonald et al., 2019)

Essential Amino Acid Supplementation

It is an ideal supplement for:

  • To break the fasting state and provide a quick supply of amino acids, especially if you train in the morning.
  • As a pre-workout to ensure a rapid release of amino acids into the blood.
  • As an intra-workout to provide amino acids while exercising, which is a time when splanchnic blood flow is reduced by up to 80% (Qamar, 1987 cited in De Oliveira, Burini & Jeukendrup, 2014), causing our digestive capacity to be drastically reduced during this period.
  • In people with irritable bowel syndrome (IBS), intestinal bacterial overgrowth syndrome (IBOS), or other pathologies characterised by intestinal permeability; as the consumption of free amino acids eliminates the enzymatic activity necessary for protein degradation.
  • In people who are using fasting protocols to improve digestive symptoms usually derived from a high caloric intake volume.

When do I have to take essential amino acids?

Essential amino acids can be consumed at any time of the day, as they are absorbed very quickly and for practical purposes act just like protein.

The optimal time for its intake is when we take advantage of its free profile compared to the consumption of a milk protein, for example, which has the complete food matrix.

Therefore, around training (pre-/intra-/post-), on an empty stomach or even between meals.

Bibliographic Sources

  1. de Oliveira, E. P., Burini, R. C., & Jeukendrup, A. (2014). Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations. Sports Medicine (Auckland, N.Z.), 44 Suppl 1(Suppl 1), S79-85.
  2. Gorissen, S. H. M., Burd, N. A., Hamer, H. M., Gijsen, A. P., Groen, B. B., & van Loon, L. J. C. (2014). Carbohydrate coingestion delays dietary protein digestion and absorption but does not modulate postprandial muscle protein accretion. The Journal of Clinical Endocrinology and Metabolism, 99(6), 2250–2258.
  3. Gorissen, S. H. M., Burd, N. A., Kramer, I. F., van Kranenburg, J., Gijsen, A. P., Rooyackers, O., & van Loon, L. J. C. (2017). Co-ingesting milk fat with micellar casein does not affect postprandial protein handling in healthy older men. Clinical Nutrition (Edinburgh, Scotland), 36(2), 429–437.
  4. Hoffman, J. R., & Falvo, M. J. (2004). Protein – Which is Best? Journal of Sports Science & Medicine, 3(3), 118–130.
  5. MacDonald, A., Singh, R. H., Rocha, J. C., & van Spronsen, F. J. (2019). Optimising amino acid absorption: essential to improve nitrogen balance and metabolic control in phenylketonuria. Nutrition Research Reviews, 32(1), 70–78.
  6. Oloo, B., S., M., Kahi, A., & Amonsou, E. (2018). Quantity and Functionality of Protein Fractions Isolated from 3 Ecotypes of Indigenous Chicken in Kenya. Food Science and Nutrition Studies, 2, 70.
  7. Rayaprolu, S., Hettiarachchy, N., Horax, R., Satchithanandam, E., Chen, P., & Mauromoustakos, A. (2015). Amino Acid Profiles of 44 Soybean Lines and ACE-I Inhibitory Activities of Peptide Fractions from Selected Lines. Journal of the American Oil Chemists’ Society, 92(7), 1023–1033.

Related Entries

  • If you want to know more about when to take amino acids, click here
  • Have you ever wondered whether it is better to take Amino Acids in powder or tablet form? Go click below to find out the answer.
  • Do you think it is better to take amino acids or protein? Here here is our opinion.
  • For further information on the amino acid leucine, read the following post
  • More information about Branched Amino Acids or Branched-Chain Amino Acids
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About Alfredo Valdés
Alfredo Valdés
He is a specialist in metabolic physiopathology training and in the biomolecular effects of food and physical exercise.
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