Amino acids: Everything you need to know about the basic building blocks of protein

Amino acids are essential building blocks of life: They are therefore vital substances without which the human metabolism could not assemble proteins . In order to build up an endogenous protein, the human organism links a selection of the 20 proteinogenic amino acids into a chain. Depending on the chain length, we are talking about proteins or peptides. The chain length and the positions of the respective amino acids determine the function of the resulting protein.

According to the current state of knowledge, more than 20 proteinogenic amino acids are known as well as more than 250 amino acids that are referred to as non-proteinogenic: These are not detectable in proteins, but in the organism. The human body can produce most proteinogenic amino acids itself. Eight of them, however, not: They are called essential, i.e. vital amino acids. They must be supplied to the body through the daily diet.

Non-proteinogenic amino acids such as L-ornithine, L-citrulline, L-thyroxine (belongs to the thyroid hormones) or GABA (a neurotransmitter) are not involved in protein synthesis.

Numerous health complaints, which are now counted among the so-called civilization diseases, such as diabetes mellitus or obesity, can be traced back to a metabolic disorder and thus possibly to a lack of amino acids. However, doctors are now able to check exactly whether there is a deficiency symptom or not: A special amino acid analysis can be used to indicate the existing amino acid concentration in the body.

But not only an undersupply of amino acids can be harmful to health, but also an overdose. If the body is supplied with too high a concentration of amino acids over a longer period of time, organs such as the kidneys or liver, for example, can suffer.

Why are proteins actually so important for humans?

Proteins are the main components of most body cell structures and this is exactly why it is so important that everyone consumes enough protein in their daily meals. In certain phases of life - such as during pregnancy, during physical growth in children or even in the event of injuries and illnesses - the protein requirement is higher. The protein synthesis and thus also the amino acids are of vital importance for us humans, because they take over various bodily functions: For example, they contribute to the maintenance and increase of muscle mass, as well as to the maintenance of normal bones.

There are many different types of proteins in the organism, which also fulfill different tasks:

• So-called transport proteins ensure that important substances are passed on: For example, they transport oxygen through the organism.
• Structural proteins give shape to the most diverse body cells.
• Storage proteins ensure that we humans can store iron and other essential nutrients and that the organism can access these storage depots when needed.
• Protective proteins fulfill important functions in antibody formation and blood clotting.
• Enzymes are also proteins that enable or accelerate various biochemical body reactions.
• Hormones are also counted among the proteins. They control all processes in the body, including important metabolic processes.

In short: Without amino acids there would be no body proteins and these are indispensable for human health.

Essential and non-essential amino acids

On the one hand, amino acids can be ingested through daily nutrition or through dietary supplements. Every food with a protein content also contains amino acids. On the other hand, the body can synthesize some amino acids itself. This results in the classification between essential and non-essential amino acids.

Essential and semi-essential amino acids

The human body cannot produce the following amino acids itself, or it cannot produce them in sufficient quantities. Accordingly, they must be supplied from the outside. The organism cannot produce eight of these amino acids at all: They are therefore referred to as essential. Two amino acids can only be produced in very small quantities: they are therefore referred to as "conditionally essential" or "semi-essential". In other words: the human body can form these two amino acids itself, but the amount is not sufficient in certain situations, such as injuries or during the child's growth phase.

A complete protein contains all the essential amino acids in sufficient quantities. Complete proteins are found in fish, beef, poultry, milk, and chicken eggs, for example. Incomplete proteins do not contain all essential amino acids: Such proteins are found in green leafy vegetables, grains and legumes.

The essential amino acids at a glance

• isoleucine

This branched-chain essential amino acid is involved in the maintenance and regeneration of muscular tissue and acts as an important source of energy in strength and endurance sports. It belongs to the group of “Branched Chain Amino Acids” – BCAA for short. However, this amino acid is not only relevant for athletes, but also for people who are under severe stress, during operations and illnesses. In the organism, isoleucine is broken down again via the fatty acid metabolism, and small amounts are also excreted in the urine.

Isoleucine is mainly found in peanuts, legumes such as chickpeas, beef and veal, tuna and salmon. Wheat germ has the highest isoleucine content.

• leucine

The amino acid leucine is also very important for building and maintaining muscles. Adequate leucine intake is therefore required in order for a certain amount of muscle mass to be maintained in the body. In addition, this essential amino acid - which also belongs to the group of BCAAs - serves to provide energy in the muscles and also promotes various healing processes in the muscle. The leucine also stimulates the release of insulin in the pancreas: This regulates blood sugar in the body. Leucine also protects the liver from damage, for example from alcohol, and has a stimulating effect on fat burning.

The human body breaks down leucine through fat metabolism. Some of it is also excreted through sweat and urine.

This essential amino acid is found in cow's milk, salmon, tuna, eggs, beef, rice, whole wheat flour, olives, peas and walnuts.

• methionine

Alongside cysteine, this essential amino acid is the only proteinaceous amino acid containing sulfur. Methionine is primarily used as a supplier of methyl groups for important hormones such as adrenaline, creatine, choline and many more.

If the body is not sufficiently supplied with methionine, protein synthesis in the body comes to a standstill. The amino acid is particularly important for some structural proteins because it influences the structural strength of fascia, ligaments and tendons. Methionine is also important for hair and nail hardness.

In addition, the amino acid is able to cross the blood-brain barrier: it is therefore involved in the formation of the myelin sheaths of the nerves (also in the central nervous system).

Significant amounts of this essential amino acid are found in raw beef, raw salmon, dried soybeans, hard cheeses, Brazil nuts and sesame seeds.

• lysine

The essential amino acid is a main component of transport proteins of antibodies, hormones and in blood plasma. Lysine also stabilizes connective tissue and is an important component of L-carnitine production in the body. This amino acid is also important for proper energy metabolism and fat burning. Calcium absorption in teeth and bones is also influenced by the essential amino acid. In addition, lysine is also very important for a powerful immune system.

Lysine is mainly found in animal foods such as fish, eggs, parmesan, milk and milk products. However, lysine is also found in legumes such as beans, lentils and peas, but it is hardly found in vegetables. Small amounts can still be found in cereals and nuts.

• phenylalanine

This essential proteinogenic amino acid functions as an important building block of many peptides and proteins. The amino acid also plays an important role in nitrogen metabolism. In the liver, this essential amino acid can be converted into tyrosine. Tyrosine and phenylalanine play important roles in insulin, thyroxine, melanin, serotonin and dopamine synthesis.

This amino acid is found in many animal and plant-based foods: A balanced, varied diet is a good way to cover the requirement. Provided that there is a normal absorption capacity of the amino acid in the digestive tract, a phenylalanine deficiency is not to be feared.

Particularly high amounts of phenylalanine are found in dried soybeans and peas. The amino acid is also found in peanuts, pumpkin seeds, walnuts and various types of meat and fish.

• threonine

This essential amino acid fulfills several functions in metabolism and is an important protein component. A particularly high proportion of threonine is found in the connective tissue. In addition, this essential amino acid is an important component of antibodies and therefore particularly important for the immune system. Threonine is also very important for mucosal regeneration in the mouth and stomach. The amino acid is also an important part of ligaments, bones, tendons and teeth.

Threonine is found primarily in chicken eggs, chicken breast, salmon, beef, milk, whole wheat flour, brown rice, dried peas, and walnuts.

• tryptophan

The organism can synthesize various biogenic amines from this essential amino acid. These include tryptamine, serotonin and melatonin. The amino acid is also involved in many processes in the cardiovascular system, such as blood pressure. Tryptophan also accelerates blood clotting and wound healing. The intestinal movements are also influenced by this amino acid. Tryptophan is also considered a mood enhancer and is therefore of great importance for the emotional state.

Tryptophan is mainly found in chicken eggs, soybeans, cashews, walnuts, cow's milk, pork, salmon, unsweetened raw cocoa powder, oatmeal, unpeeled rice and cornmeal.

• valine

Together with the amino acids leucine and isoleucine, valine is a very important source of energy for muscle cells. With the help of pantothenic acid, valine also has a significant impact on nerve function. In addition, valine also stimulates the release of insulin and thus regulates both the protein structure and the blood sugar level in the body.

Significant amounts of valine are found in walnuts, tuna, salmon, veal and beef, peanuts, brown rice, whole wheat flour and dried peas.

Semi-essential amino acids

As mentioned, the human body can produce these amino acids itself, but the amount is not sufficient in certain phases of life. Especially in childhood, when the body is growing or during pregnancy, a sufficiently high intake is required. Even with underlying diseases such as high blood pressure, care must be taken to ensure adequate coverage of needs.

These semi-essential amino acids include:

• arginine

This amino acid reacts with oxygen and causes the human body to produce nitric oxide, which causes the blood vessels to dilate. Arginine thus minimizes the risk of cardiovascular disease. In addition, arginine stimulates cell growth and is therefore very important for a powerful immune system.

The amino acid is mainly found in pumpkin seeds, lamb and chicken, nuts, shrimp, tuna and legumes.

• histidine

Histidine is a basic amino acid, which indirectly also provides the body cells with energy and also has a detoxifying function. The pH of the blood is also regulated by the amino acid. Histidine can also accelerate wound healing and support growth processes. Tissue regeneration is also improved by histidine.

Children who are growing, but also people with renal insufficiency have such a high histidine requirement that this amino acid can definitely be classified as essential for them.

The amino acid is found primarily in lentils, soybeans, peas, pumpkin seeds, parsley, milk, eggs, walnuts and husked rice.

Non-Essential Amino Acids

The body can produce non-essential amino acids itself. If all non-essential and essential amino acids are present in sufficient quantities in a body cell, the cell can produce proteins very quickly. The blueprint for protein production is stored in the cell's genetic material (DNA).

The following amino acids are non-essential:

• alanine
• aspartic acid and aspargine
• glutamine and glutamic acid
• cysteine
• glycine
• proline
• serine
• tyrosine

Disorders of amino acid metabolism

Various disorders of amino acid metabolism can be hereditary.

In some sufferers, for example, certain amino acids are no longer broken down properly and they accumulate in the body. In other disorders, certain amino acids cannot be properly absorbed in the intestine or excreted from the body via the kidneys: the transport systems required for this do not work.

Doctors are now aware of more than 70 such inherited, i.e. congenital, disorders. The most common amino acid breakdown disorder is phenylketonuria, or PKU for short. Homocysteinuria or maple syrup disease are also disorders of the amino acid metabolism. If such a disorder is suspected, the important amino acid values ​​can be determined by means of a urine or blood serum analysis.

Amino Acid Deficiencies

Essential amino acids must be supplied to the organism from the outside - either through daily meals or through suitable dietary supplements. A balanced diet, one-sided radical diets, excessive stress, demanding competitive sports or chronic diseases can lead to deficiency symptoms in the amino acid balance. Amino acid requirements can also be higher than usual for newborn infants, during pregnancy or after serious injuries.

Non-essential amino acids are also important for the body. Compared to the essential ones, however, the organism is able to produce these amino acids itself without our intervention. How many non-essential amino acids are required or formed depends on various factors, such as age, individual performance requirements and whether or not you are pregnant.

With the help of a so-called aminogram - an amino acid profile of the body - a specialist laboratory can use a blood sample to precisely assess whether there is a deficiency or not.

The following signs can indicate an amino acid deficiency:

• listlessness
• immune system weakness
• Inner unrest
• indigestion
• Depressive moods
• concentration problems
• muscle building deficits
• drop in performance
• joint problems
• sleep problems

A healthy and balanced diet can basically cover the amino acid requirement well. Under certain circumstances, additional supplementation may be necessary, for example in special life circumstances such as pregnancy or in certain groups of people such as competitive and extreme athletes. The treatment of diseases such as hardening of the arteries (arteriosclerosis), high blood pressure or diabetes can also be supported with high-quality nutritional supplements. If you have any questions, always talk to your doctor.

DoctorBox's Amino Acid Test measures 16 essential, semi-essential and non-essential amino acids in your blood.

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