Essential Amino Acids – Definition, Function and Types

Amino acids are the basic structure of proteins . Its function is dependent on each type.

Some amino acids can be synthesized naturally, these are the essential ones. The rest are defined as nonessential and conditional.

Read on to find out what the definition of amino acids is, what types there are, and how many are needed per day to reap its benefits.

What are essential amino acids? – Definition

Amino acids are organic compounds that are part of proteins, in total there are 20. They can be classified into different types according to their function or chemical structure.

By definition, essential amino acids are those that cannot be synthesized by the human body; so they must be included through food or dietary supplements.

The essential amino acids are 9: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. The benefits of covering the recommended amount of these compounds range from improving muscle recovery processes, achieving hormonal balance, to fighting sleep disorders.

Types of amino acids

Amino acids can be classified into 3 types:

1. Essential amino acids

Essential amino acids are those that the body is not able to synthesize by itself, so they must necessarily be ingested from an external source through the diet. The essential amino acids are:

  • isoleucina
  • leucine
  • lysine
  • methionine
  • phenylalanine
  • threonine
  • tryptophan
  • histidine
  • valina

2. Nonessential amino acids

Nonessential amino acids are those that can be synthesized by the body even if foods or supplements that contain them are not included. The body has the necessary tools to manufacture them. The non-essential amino acids are:

  • to the girl
  • arginine
  • asparagina
  • aspartic acid
  • cysteine
  • glutamic acid
  • wisteria
  • proline
  • serine
  • tyrosine

3. Conditional amino acids

This is one of the types of amino acids that refers to those that can change category depending on the health status of a person. Under stress or illness they can go from nonessential to essential. The conditional amino acids are:

  • arginine
  • cysteine
  • glutamine
  • tyrosine
  • wisteria
  • ornitina
  • proline
  • serine

And the branched chain amino acids?

Branched amino acids are those that are accompanied by a chain of extra atoms in the form of a branch on one side of their structure.

These types of amino acids are also known under the acronym BCAA, which stands for  B ranched- C hain  A mino  A cids  (branched or branched chain amino acids in English).

The main characteristic is its particular molecular geometry: a branch shape that comes out from its main structure. The branched amino acids are 3: valine, leucine and isoleucine.

When doing physical exercise at high intensities, these are the first to be extracted from the muscle fibers. That is why one of the benefits of taking branched- chain amino acids is to reduce the processes of muscle destruction.

Essential Amino Acids – Function and Structure

Here is a description of the function and structure of all essential amino acids:

1. Histidine

Histidine fulfills the function of regulating sleep processes, it is necessary for the synthesis of melatonin . A lack of this amino acid is associated with a higher chance of sleep disorders .

2. Lysine

This is one of the essential amino acids that plays a fundamental role in the absorption of calcium in the body. It also plays an important role in the regeneration of muscle tissue.

3. Valina

One of the 3 branched chain amino acids. Its main function is the regeneration of muscle mass, as well as it is of great importance to achieve a proper functioning of the liver. (2)

3. Isoleucina

The main function of isoleucine is the regulation of the immune system and the production of hemoglobin.

4. Isoleucina

Isoleucine is critical in the physiological functions of the entire body, such as growth, immunity, protein metabolism, fatty acid metabolism, and glucose transport. Isoleucine can enhance the immune system , including immune organs, cells, and reactive substances.

5. Methionine

Methionine has an antioxidant action and participates in the absorption of some microminerals such as zinc. Correctly absorbing zinc is essential for normal testosterone levels . (3)

6. Phenylalanine

The importance of phenylalanine is as a precursor of neurotransmitters: norepinephrine and dopamine. Its main function is the production of proteins and enzymes related to the nervous system. (1)

8. Tryptophan

The body needs tryptophan to make serotonin . When there is a lack of tryptophan in the body, brain function can be affected.

9. Threonine

Threonine is an essential amino acid for healthy skin. Its main function is to participate in the synthesis of collagen in the body. Thus it fulfills a fundamental function in the metabolism of fats. (4)

How many essential amino acids are needed per day?

The recommended amount of essential amino acids according to the World Health Organization is (4):

  • Histidina: 14 mg
  • Isoleucina: 19 mg
  • Leucina: 42 mg
  • Lysine: 38 mg
  • Metionina: 19 mg
  • Fenilalanina: 33 mg
  • Treonina: 20 mg
  • Tryptophan 5 mg
  • Valina: 24 mg

The easiest way to reach these amounts is to eat proteins of high biological value , such as albumin .

Foods with essential amino acids

The recommended amount of these compounds can be covered with both plant and animal foods. Foods rich in essential amino acids are:

  • meats
  • Eggs
  • Dairy products
  • Cereals
  • Pseudocereales
  • Fruits of the sea

For a vegetarian, covering the dose of essential amino acids is usually more difficult. Including foods like quinoa , buckwheat, and amaranth is critical when adhering to this type of diet.

Cereals such as wheat, rice, and oats provide similar amounts to milk. The amount of essential amino acids in cereals can be seen in the following table:

Amount of essential amino acids in 100 g of food:

Lysine Cysteine Isoleucina Leucine
Amaranth 5.0 4.0 3.0 4.7
Buckwheat 6.2 1.6 3.7 6.2
Wheat 2.8 2.2 3.3 6.7
Avena 3.8 1.4 3.8 3.2
Milk 5.8 2.1 5.0 7.3

Benefits of essential amino acids

All amino acids can be provided correctly through food. The benefits of taking supplements with essential amino acids apply only when there is a lack in the diet. The benefits of taking essential amino acid supplements are:

1. Hormonal balance

One of the benefits of taking essential amino acids is the balance of sex hormones. Studies claim an improvement in GH and testosterone levels in men. (2)

2. Increased muscle strength and endurance

Taking essential amino acids (particularly branched ones) can improve muscle strength and endurance. The rationale: Taking supplements has seen significant drops in levels of the  stress hormone cortisol . (5)

3. Less muscle fatigue in older adults

Leucine is a branched essential amino acid that helps reduce muscle fatigue. Studies recommend taking a dose of leucine supplements can prevent muscle fatigue in older adults. (6)

4. Fight sleep disorders

Supplements that contain essential amino acids such as tryptophan and histidine are key to the synthesis of the sleep hormone. Including them when there is a lack can help combat sleep disorders such as: insomnia , shallow sleep and nightmares. (7)

5. Eliminate body fat

Although there is still more research to confirm what are the effects of supplements with essential amino acids in eliminating body fat . Some studies (8) suggest a positive link in burning fat without losing muscle mass.

Consequences of a lack of essential amino acids

Chronic lack of essential amino acids leads to a negative nitrogen balance and the development of vitamin absorption deficiencies. (1). The symptoms depend on what is missing in the diet, methionine being one of the most common. (9) The most frequent symptoms of a lack of essential amino acids are:

  • Weakened immune system
  • Loss of muscle mass
  • Hormonal dysregulation
  • Fatty liver
  • Growth retardation in children and adolescents
  • Dry skin and brittle nails
  • Hair loss
  • Loss of appetite
  • Sleep disorders
  • Anxiety and depression

ABSTRACT

By definition, essential amino acids are the components of proteins that cannot be synthesized by the human body; in total there are 9.

The recommended daily amount can be covered both with food and through supplements. Chronic lack of essential amino acids can cause all kinds of disorders in human metabolism.

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