Amino Acids and Their Functions
May 13, 2022

The body needs 20 Amino Acids to maintain good health and normal functioning. Eight of these Amino Acids, the so-called essential Amino Acids, must be ingested through food. Good food Sources are meat, eggs, tofu, soybeans, buckwheat, quinoa, and dairy products.


Amino Acids are the building blocks of proteins. When a person eats foods that contain protein, the digestive system breaks down the protein into Amino Acids. The body then combines Amino Acids in different ways to perform physical Functions. A healthy body can make the other 12 Amino Acids on its own, so it usually does not enter the body through food. Amino Acids help the body create muscle, initiate chemical processes, transport nutrients, and prevent disease, among other things. Amino Acid Deficiency can lead to weakened immunity, digestive problems, depression, childbirth problems, decreased mental alertness, slowed growth in children, and many other health problems. Each essential Amino Acid has a unique function in the organism, and depletion symptoms vary appropriately.

The essential amino acids are phenylalanine, tryptophan, lysine, methionine, threonine, isoleucine, leucine, and valine.

The non-essential amino acids are glycine, alanine, serine, cysteine, aspartic acid, glutamic acid, asparagine, glutamine, arginine, tyrosine, proline, and histidine.

Read about all 20 amino acids below!


Phenylalanine is an amino acid that exists in three forms: L-phenylalanine (naturally synthesized), D-phenylalanine (synthetic), and DL-phenylalanine (a mixture of the two). Phenylalanine is required for the formation of chemicals (neurotransmitters and hormones) used by the brain, such as dopamine, norepinephrine, and epinephrine. Likewise, phenylalanine is involved in the formation of thyroid hormones. Among other things, phenylalanine deficiency can cause depression, loss of appetite, cognitive problems (confusion, memory loss), loss of energy, and decreased alertness.


Some foods rich in this amino acid are beef, pork and fish, eggs, yogurt, cheese, soy products, and some nuts. 


Tryptophan helps in the formation of serotonin and melatonin, substances that regulate the sleep cycle. For this reason, this amino acid is used in antidepressant, sedative, and sleeping pills. It also affects pain tolerance, which is why it is used by athletes who are exposed to intense physical activity. The deficiency of this amino acid leads to insomnia, depression, and weight loss.


Tryptophan-rich foods include turkey, chicken, beef, fish, soybeans, rice, some nuts, and cheese.



Lysine is involved in the formation of L-carnitine, a compound that provides oxygen circulation in muscle tissues. Lysine is involved in the metabolism of lipids, due to which they are used as an energy source.


It also aids in the development of the immune system (due to the production of antibodies) and is involved in the formation of hormones, enzymes, and collagen (the protein that produces bone, cartilage, and connective tissue). Foods rich in lysine are fish, eggs, cheese, soy, potatoes, yeast, and dairy products. 


Methionine is involved in metabolism, promoting fat burning and the formation of other amino acids such as cysteine ​​and glutamine.


It is used to fight certain pathogenic bacteria and in the treatment of kidney stones. Other functions of this amino acid are the reduction of fat in the liver and muscle degeneration and maintaining healthy skin and nails. Methionine deficiency can lead to the accumulation of fat in the liver.


Some sources of methionine are lentils, red meat, fish, garlic, onions, eggs, yogurt, soybeans, and some seeds. 


Threonine is involved in the formation of vitamin B12. On the other hand, it promotes digestion and prevents liver disease (because it helps lower cholesterol levels in this organ and the blood). It interferes with the regeneration of collagen proteins and helps the body recover from muscle injuries. Foods that are a source of threonine are meats, cereals, dairy products, mushrooms and truffles, and vegetables.



Along with leucine and valine, isoleucine is important for protein development and energy storage. Helps the body recover from intense physical activity. In addition, isoleucine is necessary for the synthesis of hemoglobin and is one of the main elements of red blood cells. Isoleucine deficiency causes symptoms similar to those of hypoglycemia.


Sources of isoleucine include seeds, nuts, red meat (lamb, pork, and beef), fish (especially tuna), lentils, soybeans, pecorino, parmesan cheese), and eggs. 


Leucine plays an important role in the formation of muscle tissue, it helps to maintain this tissue after it is formed, and is necessary to maintain nitrogen balance in the body. In addition, leucine contributes to the restoration of muscle tissue, skin, and bones. Leucine-rich foods are cereals (soy, lentils, and chickpeas), nuts (peanuts, walnuts, and almonds), red meat (especially pork and beef), seafood, salmon, shellfish, and shrimp), eggs, and dairy products.



Valine is an amino acid that promotes tissue repair. It is involved in the accumulation of energy, regulates blood sugar levels, and contributes to the process of growth and development of the human body. Due to its regenerative and energy-saving properties, valine is one of the most important amino acids for athletes, so they consume it as a supplement (in smoothies, in tablets, etc.).


It can be pointed out that an excess of valine in the body causes hallucinations. Foods with the highest levels of valine are meat, dairy, soy, peanuts, and mushrooms. 


Glycine is the second most abundant amino acid in the human body.


It is part of the structure of hemoglobin and is one of the main inhibitory neurotransmitters in the human body. On the other hand, it is associated with the production of glycogen and is involved in suppressing the desire to consume sugar, and is part of the enzymes responsible for energy production. Finally, glycine turns toxic substances in the body into harmless ones.


People with hypoglycemia, anemia, chronic fatigue syndrome, and viral infections are deficient in this amino acid. 


Alanine is the main energy source for muscles and one of the most important amino acids involved in glucose metabolism. Helps produce antibodies that strengthen the immune system and are part of the body's connective tissue. Alanine deficiency is seen in people with low blood sugar, fatigue, viral infections, and elevated insulin levels.



Serine helps maintain blood sugar levels. It interferes with the creation of antibodies, so it helps to strengthen the immune system, promotes the growth of muscle tissue, and helps maintain it. Other functions include fat metabolism and brain protein formation. 


Cysteine ​​is an antioxidant.  It protects the human body from ultraviolet rays, radiation, and pollution. In addition, this amino acid plays an important role in the metabolism of certain enzymes.


On the other hand, it is about restoring skin tissue and maintaining its health. It is one of the main components of hair. 

Aspartic Acid

The main function of aspartic acid is to form resistance. This amino acid is involved in the metabolism of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Other functions include protecting the liver (by removing excess ammonia) and boosting the immune system (by creating antibodies).


The deficiency of aspartic acid in the human body leads to a decrease in the level of calcium and magnesium. 

Glutamic Acid

Glutamic acid is one of the most important non-essential amino acids. It is responsible for transporting glutamine and other amino acids through the blood. The presence of this molecule reduces the need to consume sugar and alcoholic beverages. It also increases the energy level in the human body.


Other functions include accelerating the healing process of wounds and ulcers and aiding in DNA synthesis.


An excess of this amino acid in brain tissue can cause cell damage. It is believed that during cardiovascular disease, the brain releases large amounts of this acid, damaging neurons. 


Asparagine helps remove ammonia from the body, increases resistance, reduces fatigue, removes harmful chemicals from the body, and is involved in DNA synthesis. It is found in high concentrations in the hippocampus and hypothalamus.


It is essential for maintaining homeostatic balance in the nervous system and plays an important role in short-term memory. 


Glutamine is important as it maintains blood sugar levels. It maintains the strength of the muscles and makes them able to withstand intense physical exertion. On the other hand, glutamine is important for the functioning of the digestive system.


The small intestine uses glutamine as its primary energy source and is the only organ in the body that does so. This amino acid is also involved in DNA synthesis. Glutamine deficiency can occur in people with chronic fatigue syndrome, alcoholism, and anxiety.



Arginine is essential for the proper functioning of the immune system. It is also involved in wound healing, and liver regeneration and increases insulin release. This amino acid is essential for the production and release of growth hormones. The deficiency of this amino acid causes muscle weakness, hair loss, skin irritation, and slow wound healing. 


Tyrosine reduces appetite, therefore, helps to reduce adipose tissue.


It increases energy levels and interferes with mental processes, improving concentration and reasoning skills. This amino acid is the precursor of the neurotransmitters dopamine, epinephrine, norepinephrine, and melanin. It is used as an antidepressant.


Tyrosine deficiency can lead to depression, chronic fatigue syndrome, and hypothyroidism. Parkinson's disease and drug addiction are also linked to a deficiency of this amino acid. 


Proline affects human nutrition and participates in cartilage formation.


This amino acid is thought to be a source of nitrogen. Therefore, it is very important to keep your joints, tendons, and ligaments healthy. Another function of this amino acid is to maintain the strength and health of the heart. It also works with vitamin C to protect the skin. This amino acid is essential at certain stages of human development, eg during childhood.


That's why it's called semi-mandatory because it's only required in certain circumstances. 


Histidine is involved in the formation of hemoglobin and is therefore used in the treatment of anemia. It is also used to treat rheumatoid arthritis and certain allergies.


It also helps maintain blood pH. A histidine deficiency can cause skin disease, and cognitive and language problems in children. On its own, excess of this amino acid reduces zinc levels.