Essential Amino Acids — An Introduction
Dr. Jeethan Bendoor
M.B.B.S.
Private Practitioner, Metabolic and Anti-ageing Enthusiast, Mumbai
Correspondence: E-mail: drbendoor@gmail.com
Let's start by defining "amino acids". Amino acids are the fundamental building blocks, crucial for the synthesis of protein and other important nitrogen-containing compounds, such as creatine, hormones, and some neurotransmitters.
So, in simple terms, proteins are made up of amino acids. Although nature has over 500 amino acids, we need 21 of those to keep our biology ticking.
To keep this blog basic, lets go by a general classification where amino acids are broadly classified into essential amino acids (EAAs) and non-essential amino acids (NEAAs).
EAAs cannot be synthesized by human cells. Therefore, these amino acids have to be supplied from an exogenous source/diet.
EAAs include 9 amino acids:
· Histidine
· Isoleucine
· Leucine
· Lysine
· Methionine
· Phenylalanine
· Threonine
· Tryptophan
· Valine
The human body can synthesize NEAAs, and are not as important as EAAs to be included in a food-plan (well, this is true in most circumstances, unless a demand like pregnancy pops up).
NEAAs include 12 amino acids:
· Arginine
· Alanine
· Cysteine
· Aspartic acid
· Glutamine
· Asparagine
· Glycine
· Glutamic acid
· Proline
· Serine
· Tyrosine
· Selenocysteine
Generally, EAAs perform the following roles:
· Phenylalanine: Required for neurotransmitters tyrosine, dopamine, epinephrine, and norepinephrine; also plays an integral role in the structure and function of proteins and enzymes and the production of other amino acids.
· Valine: One of three branched-chain amino acids (BCAAs). Valine helps stimulate muscle growth and regeneration and is involved in energy production.
· Leucine: Like valine, leucine is a BCAA that is critical for protein synthesis and muscle repair. It also helps regulate blood sugar levels, stimulates wound healing, and produces growth hormones.
· Isoleucine: The last of the three BCAAs, this amino acid is involved in muscle metabolism and is heavily concentrated in muscle tissue. Also important for immune function, haemoglobin production, and energy regulation.
· Threonine: Important for structural proteins such as collagen and elastin, which are important components of skin and connective tissue. It also plays a role in fat metabolism and immune function.
· Tryptophan: A precursor to serotonin, a neurotransmitter that regulates your appetite, sleep, and mood.
· Methionine: Plays an important role in metabolism and detoxification. It’s also necessary for tissue growth and the absorption of zinc and selenium, minerals.
· Lysine: Lysine plays major roles in protein synthesis, calcium absorption, and the production of hormones and enzymes; also important for energy production, immune function, and collagen and elastin production.
· Histidine: Used in producing histamine, a neurotransmitter that is vital to immune response, digestion, sexual function, and sleep-wake cycles. It’s critical for maintaining the myelin sheath, a protective barrier that surrounds your nerve cells.
Clinical symptoms of inadequate intake of EAAs:
· Depression
· Anxiety
· Insomnia
· Fatigue
· Weakness
· Growth stunting in the young.
These symptoms are mostly caused by a lack of protein synthesis in the body because of the lack of EAAs.
So, why supplement with EAAs and not have a whole protein instead?
Firstly, we do not consume adequate whole proteins.
Secondly, the proteins that we generally consume may be of poor quality, with inadequate quantity of EAAs.
Thirdly, even if adequate whole proteins are consumed, digestion of those proteins (that will release EAAs) is a real challenge.
Therefore, it makes perfect sense to supplement with EAAs to ensure adequate availability.
References:
1) Francesco S. Dioguardi. Clinical use of amino acids as dietary supplement: pros and cons. J Cachexia Sarcopenia Muscle (2011) 2:75–80. DOI 10.1007/s13539-011-0032-8.
2) Protein and Amino Acids. Recommended Dietary Allowances: 10th Edition. https://www.ncbi.nlm.nih.gov/books/NBK234922/#:~:text=Nine%20amino%20acids—histidine%2C%20isoleucine,called%20the%20essential%20amino%20acids. Last accessed 25 February 2025.
3) Michael J. Lopez ; Shamim S. Mohiuddin. Biochemistry, Essential Amino Acids. NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health. https://www.ncbi.nlm.nih.gov/books/NBK557845/#:~:text=Among%20these%2020%20amino%20acids,histidine%2C%20leucine%2C%20and%20lysine. Last accessed 25 February 2025.
