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Essential Amino Acids

Essential Amino Acids
Table Of Contents
  1. Nine Essential Amino Acids
  2. Functions of Essential Amino Acids
  3. Stimulating Muscle Protein Synthesis with Essential Amino Acids
  4. BCAAs are essential amino acids
  5. Daily Requirements
  6. Essential Amino Acids in Vegans

Proteins are composed of amino acids, which are the building blocks of the human body. Amino acids consist of an amino group (-NH2), a carboxyl group (-COOH), and a side chain that is specific to each amino acid.

In the body, amino acids are assembled into peptides and proteins. They are needed as constructive and reparative components. Amino acids are essential components of enzymes, hormones, neurotransmitters, transport proteins, as well as body tissues such as muscles and skin. Furthermore, they play an important role in the immune system.

Amino acids are divided into non-essential, semi-essential, and essential amino acids. Essential amino acids cannot be synthesized by the body and therefore must be obtained through diet. They are also referred to as vital amino acids.

Under certain conditions such as illnesses and excessive stress, non-essential amino acids can become essential for the body.

Nine Essential Amino Acids

There are a total of nine different essential amino acids 1:

  1. Histidine
  2. Isoleucine
  3. Leucine
  4. Lysine
  5. Methionine
  6. Phenylalanine
  7. Threonine
  8. Tryptophan
  9. Valine

Functions of Essential Amino Acids

The following lists provide an overview of the functions of essential amino acids and briefly explain their significance for the body:


  • essential for children
  • involved in the formation of red and white blood cells
  • required for growth and tissue repair
  • protects nerve cells
  • histidine is metabolized into the neurotransmitter histamine, which is part of the immune system, involved in the release of stomach acid, and contributes to sexual arousal 2
  • Histidine Foods


  • involved in the formation of hemoglobin, regulation of blood sugar levels, and thus the body's energy metabolism
  • supports wound healing
  • detoxifies nitrogenous waste
  • stimulates immune function
  • promotes the release of several hormones 3
  • Isoleucine Foods


  • important for the formation and repair of muscle and bone tissue
  • supports wound healing and synthesis of growth hormones
  • prevents breakdown of muscle proteins after trauma or intense exercise 4
  • Leucine Foods


  • helps with the absorption of calcium 5
  • required for growth and tissue repair
  • aids in the formation of collagen (connective tissue), carnitine (important for energy metabolism), and elastin (provides elasticity to connective tissue), among others
  • supports the production of antibodies, hormones, and enzymes 6
  • Lysine Foods


  • plays a role in protein synthesis, acts as a methyl donor in DNA methylation and polyamine synthesis 7
  • needed for growth and tissue repair
  • helps maintain a healthy skin color and skin suppleness
  • strengthens hair and nails
  • prevents excessive fat buildup in the liver 8
  • Methionine Foods


  • important for the structure and function of many proteins and enzymes
  • plays a key role in the formation of other amino acids such as tyrosine, which is used for the synthesis of neurotransmitters and hormones like dopamine and noradrenaline, which positively influence brain processes and contribute to mood enhancement 9
  • Phenylalanine Foods


  • Component of many proteins such as tooth enamel, collagen, and elastin
  • Plays an important role in fat metabolism
  • Prevents fat accumulation in the liver 10
  • Threonine Foods


  • Required as a precursor for the formation of serotonin and melatonin
  • Serotonin (the happiness hormone) is a tissue hormone and neurotransmitter in the central nervous system; it is involved in the regulation of sleep, depression, anxiety, aggression, appetite, temperature, sexual behavior, and pain 11
  • Melatonin is known as the sleep hormone
  • Tryptophan can also be converted to vitamin B3 (niacin) in the body 12
  • Tryptophan Foods


  • promotes muscle growth and tissue regeneration
  • improves energy (Valine is also used as an energy source)
  • enhances endurance 13
  • Valine Foods

Stimulating Muscle Protein Synthesis with Essential Amino Acids

Essential amino acids stimulate muscle protein synthesis 14 15 16 17. Also, the intake of smaller amounts of essential amino acids or intact proteins (unprocessed and complete with all amino acids) increases post-exercise protein synthesis rates and net protein balance 18. Therefore, they enhance anabolic responses after exercise. Muscle proteins are synthesized within the muscle cells, allowing for muscle building to occur.

With an ample supply of essential amino acids within 1-3 hours before or after exercise, muscle protein synthesis could be further supported 19. Results suggest that consuming a protein shake containing approximately 0.1 g per kg body weight of essential amino acids positively increases muscle protein synthesis within the initial hours of recovery after heavy training 20.

Essential amino acids support muscle preservation during illness, prevent muscle wasting, and have benefits on body composition. 21 22 23 24 25.

BCAAs are essential amino acids

The essential amino acids isoleucine, leucine, and valine are also grouped together as branched-chain amino acids (BCAA). These three amino acids make up about one-third of the mass of human skeletal muscle. BCAAs are called branched-chain amino acids because, unlike other amino acids, they have a branch in their chemical structure.

Daily Requirements

The following recommended amounts of amino acids have been issued as guidelines (IOM = Institute of Medicine, 2005) 26:

Amino Acidmg per kg of body weight
Histidine 14
Isoleucine 19
Leucine 42
Lysine 38
Methionine and Cysteine 19
Phenylalanine and Tyrosine 33
Threonine 20
Tryptophan 5
Valine 24

Essential amino acid requirements according to FAO/WHO/UNU (2007) 27:

Amino Acidmg per kg of body weight
Histidine 10
Isoleucine 20
Leucine 39
Lysine 30
Methionine and Cysteine 15
Phenylalanine and Tyrosine 25
Threonine 15
Tryptophan 4
Valine 26

This article shows how high the overall daily protein requirement is..

Essential Amino Acids in Vegans

In 2015, scientists published the results on the daily intake levels of amino acids and their occurrence in blood levels 28. There were a total of four groups (vegans, ovo-lacto-vegetarians, pesco-vegetarians, and meat-eaters) with 98 male subjects each aged 30 to 49 years. Vegans had approximately 47% lower amino acid intake levels compared to meat-eaters. The levels of essential amino acids were also low in vegans. The concentrations of lysine, methionine, and tryptophan were the lowest among vegans 29. Other study results confirm that vegans have lower amounts of lysine and methionine intake 30. This is mainly because lysine and methionine are the limiting amino acids in plant-based proteins 31. Nevertheless, the vegan men achieved all recommended levels of essential amino acids. The following amounts of essential amino acids were obtained through a vegan diet 32:

Amino Acidg per Day
Histidine 1.52
Isoleucine 2.47
Leucine 4.33
Lysine 2.82
Methionine 0.88
Phenylalanine 2.93
Threonine 2.19
Tryptophan 0.77
Valine 2.95

The plasma levels of all amino acids vary less significantly. Compared to the meat-eating group, the amino acid concentrations range from -13% to +16% 33.

Protein-Rich Foods can be found here. Particularly high-quality plant protein sources can be viewed here. Vegan protein powder could be an option for those who find it difficult to meet their protein needs through plant-based foods.