Amino acids are among the basic substances of life. They are the building blocks of all proteins, which make up muscles, enzymes, hormones and other tissues. The way amino acids are arranged in proteins determines their properties and function. In addition, amino acids are also precursors to a number of important compounds – for example, creatine, neurotransmitters (dopamine, serotonin) or hormones .
What are amino acids?
Amino acids are compounds containing an amino group (–NH₂) and a carboxyl group (–COOH) . Thanks to this combination, they can react with other amino acids to form peptide bonds, i.e. proteins.
The body is constantly turning over proteins – old ones are broken down and new ones are formed from the released amino acids. This process maintains a pool of free amino acids , which serves as a reserve for the creation of new proteins, enzymes and substances important for energy metabolism.
Essential vs. non-essential amino acids
Approximately 20 amino acids play a role in the human body, some of which the body can produce itself, while others must be obtained from the diet.
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Essential amino acids (EAA) – the body cannot synthesize them, so they must be consumed in food.
These include: leucine, isoleucine, valine, lysine, methionine, phenylalanine, threonine, tryptophan and histidine. -
Non-essential amino acids – are formed from other amino acids or intermediate products of metabolism.
These include, for example, alanine, asparagine, aspartic acid, glutamine, serine or glycine.
A special group is the so-called BCAA (branched-chain amino acids) – leucine, isoleucine and valine . They represent approximately 20% of the amino acids in muscle protein and are the only ones that are oxidized directly in the muscles (not in the liver). They play an important role in energy metabolism during exercise.
What are amino acids used for?
Amino acids participate in a wide range of processes necessary for the proper functioning of the body:
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Muscle protein formation and repair (protein synthesis) – crucial after physical exertion and during regeneration.
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Formation of enzymes, hormones and neurotransmitters – e.g. tyrosine → dopamine, adrenaline; tryptophan → serotonin.
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Energy sources during long-term exercise – some amino acids can be oxidized in the TCA cycle (especially BCAA and alanine).
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Support for immune functions and metabolism – for example, glutamine serves as an energy source for immune system cells.
Sources of amino acids
The best source of all essential amino acids is complete proteins of animal origin – meat, eggs, milk and dairy products.
Among plant foods, quality sources include soy, quinoa, buckwheat, or a combination of legumes and cereals , which together provide the full spectrum of EAA.
BCAA vs. EAA – What the Science Says About Supplementation
BCAAs have long been popular among athletes, largely due to the idea that they promote muscle growth or speed up recovery. However, scientific evidence shows a different picture:
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Although leucine activates the mTOR signaling pathway, which triggers protein synthesis (MPS),
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but without the presence of all essential amino acids (EAAs), the synthesis of new proteins cannot fully occur.
So BCAAs "turn on" the anabolic signal, but the body lacks the rest of the building blocks.
Studies show that taking BCAAs alone after training will only increase MPS to about half the effect that can be achieved by consuming a complete protein or EAA blend.
Other claims – for example, that BCAAs reduce muscle soreness or protect muscles from damage – have conflicting results based on current knowledge and cannot be considered clearly proven.
Practical summary
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For most athletes, sufficient intake of quality protein from the diet (e.g. 1.4–2 g/kg of body weight per day) is completely sufficient.
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BCAA supplementation itself is not necessary, as the same amino acids are contained in regular proteins or, for example, whey proteins.
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If supplements are used, complex EAA blends or quality protein have a greater physiological effect than isolated BCAAs.
In other words, the best source of amino acids is a balanced diet , not an isolated dietary supplement.
Conclusion
Amino acids are essential for regeneration, muscle growth and many other functions in the body. The body cannot produce essential amino acids on its own, so it is necessary to ensure their sufficient intake from food.
BCAAs play an important role in energy metabolism, but their isolated supplementation does not have a significant benefit if the diet is rich in protein.
A simple rule applies to both regular and performance athletes:
What is most important is the overall intake of quality protein, not a specific form of amino acid supplement.
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