Proteins (and amino acids) are one of the most popular macronutrients today , largely because foods rich in these molecules are part of many diets designed to lose weight (high-calorie diets).

But leaving aside their benefits in weight loss and improving body aesthetics, proteins are one of the bases of every vital process, since they are absolutely necessary for our organism and their functions are several: they allow the cells to defend themselves from external agents, they control and regulate functions within our body, they repair damage…

Amino acids important to humans

The units with which proteins are built are the amino acids (AA) , and although there are hundreds of amino acids that play an important role in nature, there are only 20 that are part of proteins (protein or canonical amino acids).

However, there are also other AA, known as non-proteins, which play a determining role for the human being and which have their own function, for example GABA.

  • You can find out more about this neurotransmitter in our article: “GABA (neurotransmitter): what it is and what role it plays in the brain”

What are non-essential amino acids

Canonical amino acids are the raw material of proteins , but they can be classified in two ways: essential and non-essential. The main difference between these types of amino acids is that some of them are synthesized by the human body and others are not, so it is necessary to get them through the diet.

The first are the non-essential amino acids, while the second are the essential amino acids. Non-essential amino acids are just as important as the essential ones. They participate in building strong muscles, as well as in maintaining a healthy and productive brain.

Amino Acid Table

In the following lines you can find the 20 amino acids (essential and non-essential) that are part of the proteins, and we explain what their functions and characteristics are.

Types of essential amino acids

The protein amino acids that are not synthesized by the body and therefore must be ingested through the diet are as follows.

1. Phenylalanine

These amino acids are associated with the feeling of well-being, as they are regulators of endorphins . Among their most important functions are the reduction of excess appetite and the reduction of pain.

Phenylalanine is also involved in the synthesis of the catecholamines adrenaline, dopamine and noradrenaline, thus promoting alertness, improving memory and learning and increasing vitality. Supplements containing this amino acid can be used to improve the symptoms of Parkinson’s, vitiligo, chronic pain or for the comprehensive treatment of depression.

2. Isoleucine

The deficit of this amino acid seems to be involved in some mental and physical disorders : depression, behavioural disorders, decrease in muscle mass, etc. This AA is essential for the formation of haemoglobin and muscle tissue, and stabilises and regulates blood sugar and energy levels. It also helps in the healing of wounds, skin and bones.

3. Leucine

It is one of the 3 branched chain amino acids (BCAA) along with isoleucine and valine , which are involved in protein synthesis. It is a powerful insulin stimulator, necessary for wound healing and bone healing. It modulates the release of encephalines, which are natural analgesics.

4. Lysine

Inhibits the development of viruses within the body and, as a result, is used in the treatment of Herpes , as well as viruses associated with chronic fatigue syndrome. Lysine participates in the synthesis of L-carnitine along with vitamin C.

It also helps form collagen, the connective tissue present in bones, ligaments, tendons and joints. It promotes calcium and is therefore essential for children, as it is essential for bone formation. It also participates in the production of hormones and decreases serum triglyceride levels.

5. Threonine

Threonine is necessary for the formation of collagen and helps in the production of antibodies . It is also necessary for the normal functioning of the gastrointestinal tract and can be converted into glycine, a central nervous system neurotransmitter.

6. Tryptophan

One of the amino acids best known to psychologists, since it is involved in the synthesis of serotonin and melanin . Therefore, it actively participates in the improvement of mood and helps to improve the quality of sleep.

  • You can learn more about this amino acid in our article: “Tryptophan: characteristics and functions of this amino acid”

7. Valina

This amino acid competes with tyrosine and tryptophan when crossing the blood-brain barrier . The higher the valine level, the lower the levels of the other two AA’s in the brain. Valine is actively absorbed and used directly by the muscle as an energy source, so it is not processed by the liver before entering the bloodstream.

Valine deficiency causes the other amino acids (and proteins) to be absorbed in smaller amounts by the gastrointestinal tract.

8. Arginine

Arginine is essential for the normal activity of the immune system and for wound healing . It also participates in the release of growth hormone and increases the release of insulin and glucagon. It is a precursor to GABA, decreases the size of tumors, and is necessary for spermatogenesis.

9. Histidine

Useful in the treatment of anemia due to its relationship with hemoglobin . It is a precursor of histamine and therefore has been used to treat allergy. It helps maintain the proper pH of the blood and has also been used to treat rheumatoid arthritis.

10. Methionine

It actively participates in the decomposition of fats and helps reduce cholesterol in the blood . It helps to prevent disorders of the hair, skin and nails. It is an antioxidant and participates in the synthesis of RNA and DNA.

Non-essential amino acids

The essential amino acids, i.e. those synthesized by the human body, are as follows.

11. Aspartic acid

Aspartic acid increases endurance and physical performance and is good for chronic fatigue . It is one of the two main excitatory amino acids, the other being glutamic acid). It helps protect the liver, participates in DNA and RNA metabolism and enhances the immune system.

12. Glutamic acid

Another of the excitatory amino acids, along with the previous one, so they share many of the functions . It improves physical performance and reduces fatigue. It is essential for the synthesis of DNA and RNA and helps protect the body and enhances the immune system.

13. Alanina

Alanine is important for muscle growth and is a great source of energy for the muscle . It intervenes in the metabolism of sugar, increases the immune system through the production of antibodies and is essential for the connective tissue.

14. Asparagine

Asparagine is the binding of aspartic acid with ATP (adenosine triphosphate) . It is involved in the process of short-term memory, helps remove ammonia from the body, decreases fatigue and participates in DNA synthesis.

15. Cysteine

Cysteine is an antioxidant and protects against radiation , pollution, ultraviolet light and other phenomena that cause the production of free radicals. It acts as a natural “detox”, and is essential for the growth, maintenance and repair of skin and hair. It is a precursor of the amino acid taurine and chondroitin sulfate. The latter is the main component of cartilage.

16. Glycine

It is part of the structure of hemoglobin, and is one of the two main inhibitory neurotransmitters of the nervous system (the other is GABA). It is also part of the cytochromes, which are enzymes involved in the production of energy. It participates in the production of glucagon, which aids in the metabolism of glycogen.

17. Glutamine

Glutamine is a precursor of two of the most important neurotransmitters in the CNS : glutamate and GABA. It allows maintaining normal and constant levels of sugar in the blood and is involved in muscle strength and endurance. It is essential for gastrointestinal function.

18. Proline

Essential component of cartilage, and therefore key to the health of joints, tendons and ligaments . It helps to keep the heart strong. The main precursor of proline is glutamate. One of its most important functions is to maintain healthy skin and joints.

19. Serina

It participates in the improvement of the immune system by assisting in the production of antibodies and immunoglobulins and participates in the development of myelin sheath. Serine is necessary for the growth and maintenance of muscle.

20. Tyrosine

Tyrosine is an amino acid precursor of the hormone thyroxine , which is involved in metabolic processes. It is also a precursor of growth hormone and the neurotransmitters dopamine, norepinephrine, epinephrine (adrenaline), and serotonin, thus improving mood, sleep, clarity of thought, concentration, and memory.