A Complete Guide to Amino Acids


Calcium.  Vitamin D.  Melatonin.  Turmeric.  Fish Oil.  Garlic.

Sound familiar?  We thought so!

Now how about Glutathione, Gamma-Aminobutyric Acid, Tyrosine, N-Acetyl Cysteine, and 5-Hydroxytryptophan.

Not so much, right?

The names of our amino acid supplements may not be easy to remember, spell, or pronounce, but don’t let this prevent you from reaping their many benefits.  Here’s an overview.

What Are Amino Acids?

Amino acids perform a variety of functions related to cellular metabolism, but most importantly, they form the crucial building blocks of the protein necessary for normal growth and development in the human body.  Since protein helps to construct and maintain all of the critical structures in the body, amino acids are necessary for survival.

Amino acids are distinguished by their structure, their specific function in metabolic processes, and by the human body’s ability to produce them.  Here we’ll examine the 22 amino acids, including those used as supplements, plus a handful of amino ‘cousins’ that also boast nutritional benefits.

Essential Amino Acids

Essential amino acids cannot be made by the body and must be obtained from food or consumed as nutritional supplements.

The 9 essential aminos are Tryptophan, Valine, Leucine, Isoleucine, Lysine, Phenylalanine, Methionine, Threonine, and Histidine.[1]

Most people won’t recognize Tryptophan as a stand-alone nutritional supplement, but Puritan’s Pride customers may know the supplement 5-HTP, which serves as an intermediary in the conversion of tryptophan to the neurotransmitter serotonin.  5-HTP supplements help promote a calm and relaxed mood, as well as feelings of well-being.*

Valine, Leucine, and Isoleucine form the group of branched-chain amino acids (BCAA’s) commonly used by athletes and bodybuilders.  BCAA’s comprise a large percentage of the amino acid composition in muscle tissue, and they help support muscle nitrogen and protein metabolism within muscle tissue.*  BCAAs are biochemically unique since they are the only known amino acids metabolized directly in the muscle cell as opposed to the liver, providing a source of nitrogen.*

Lysine is used by the body in the production of collagen and in the maintenance of tissues.*  As a nutritional supplement, Lysine is most often used to promote the health and integrity of skin and lips, though it also plays an important role in supporting immune system function and may help the body absorb calcium.*  High-protein foods like eggs, meat, beans, and soy are generally good sources of dietary Lysine.[2]

Phenylalanine can be readily converted into the non-essential amino acid Tyrosine (discussed below), and it also serves as a precursor for certain neurotransmitters. [3]

Occasionally produced as a nutritional supplement, Methionine supports the production of the cellular antioxidant Glutathione.* In the body, Methionine can also be converted into SAM-e (S-Adenosyl Methionine) – a compounds that supports emotional well-being, joint mobility, and liver health.*

Threonine and Histidine are not commonly produced as nutritional supplements on their own, but are often included as an ingredient in multi-amino products, like this one.   Not surprisingly, Histidine is a precursor of Histamine – a key compound produced by the body’s immune system.

Conditionally Essential Amino Acids

The aminos that are considered ‘conditionally essential’ can be synthesized by the body under normal circumstances.  However, certain conditions may disrupt or limit the body’s natural ability to produce them.

The 6 conditionally essential amino acids are Arginine, Glutamine, Cysteine, Glycine, Proline, and Tyrosine.[4]

Hitting the gym today?  If so, you may recognize the first two aminos on our list.  Both Arginine and Glutamine play a multitude of roles that are of relevance to those who partake in intense athletic training programs.

Arginine, though available on its own as a nutritional supplement, is commonly included as an ingredient in pre-workout supplements because of the role it plays in stimulating nitric oxide (NOS) production.*  During and after workouts, NOS can help support circulation and the delivery of critical aminos and carbohydrates to active cells, especially when combined with your pre- and post-workout shakes.* Arginine also plays a role in the formation of creatine – a bioactive compound involved in the energy transfer between active cells.*

Glutamine, also popular among bodybuilders and fitness enthusiasts, is the most highly concentrated amino acid in skeletal muscle.  The body uses Glutamine as cellular fuel, releasing it from muscle cells during exercise and allowing it to act as an energy precursor.* Additionally, Glutamine may promote the replenishment of the body’s glycogen stores after exercise when combined with carbohydrates, and it also supports the proper functioning of the GI tract by serving as a primary source of fuel for intestinal cells.*

Cysteine is one of the body’s chief sources of sulfur – an essential compound of all living cells and one of the most abundance elements in the healthy human body.  N-Acetyl Cysteine, known as NAC, is the most common form used in supplementation.

Glycine is an amino acid found primarily in muscle tissue, connective tissue, and the skin, and it also plays a role in nervous system function.*

Proline is essential to the synthesis of collagen – the most abundant protein in mammals.

Tyrosine, an amino naturally present with in the blood and nervous system tissues, performs a number of roles that are vital to cellular growth and maintenance.

Dispensable Amino Acids

The 5 dispensable amino acids, Serine, Alanine, Glutamic Acid, Aspartic Acid, and Asparagine, can be synthesized by the body, though some are still used in nutritional supplementation.

Serine is not used on its own in supplementation, but you may be familiar with its cousin Phosphatydylserine, or ‘PS’ for short.  PS a natural, fat-like substance that’s an important component of over 1 trillion brain cell membranes.  PS is especially active in neurons – the complex series of central nervous system pathways responsible for exchanging sensory information.*  Neuro-PS® plays a role in these crucial neurotransmissions, supporting brain function and a healthy mind.*

Beta Alanine combines with Histidine to synthesize Carnosine—a compound that functions as a buffer for acid produced during strenuous exercise, thus helping to maintain optimum muscular PH levels.[5]

Glutamic Acid, also known as Glutamate and not to be confused with Glutamine, is naturally involved in nervous system function as a neurotransmitter, and serves as a nitrogen acceptor during the catabolism of various amino acids.

Aspartic Acid and Asparagine are not normally produced as nutritional supplements.

Amino Cousins

For a handful of reasons, some compounds that are frequently categorized as amino acids do not technically qualify as essential, conditionally essential, or non-essential.

Carnitine, though frequently classified as an amino acid, is actually a conditionally essential nitrogen-containing compound found in the mitochondria of cells.  About 95% of the body’s Carnitine is located in skeletal and cardiac muscle.  L-Carnitine supplements assist in fat metabolism by making fatty acids available for muscle tissue.*

Theanine, is structurally similar to the amino acids Glutamic Acid and Glutamine, is a compound found naturally in green tea leaves that supports mood centers in the brain.* Unlike other amino acids, theanine is not incorporated into the structure of proteins. Theanine influences alpha brain wave activity and interacts with the neurotransmitter GABA, which is believed to provide the beneficial effect of supporting a clam, relaxed mood.*

Ornithine is another non-proteinogenic amino that plays a role in the urea cycle – the process by which an organism converts ammonia to urea for excretion.[6]

Citrulline, also involved in the urea cycle, is a compound found naturally in watermelon that plays an important role in liver function and supports heart health.*   In its malate form, studies providing 8 grams showed Citrulline to help male weightlifters increase reps and reduce muscle soreness.*

Gamma-Aminobutyric acid, better known as GABA and often mistaken for an amino acid, is a neurotransmitter produced naturally in the body that’s important in nervous system functioning.*[7]

Glutathione is an antioxidant compound made up of the amino acids Glutamic Acid, Cysteine, and Glycine.

Taurine, one of the most abundant compounds in the brain and heart, is involved in metabolic processes and bile salt synthesis.  Taurine supplements also supports muscle recovery from weightlifting.*

Confused?  No worries – you can always reap the benefits of multiple aminos in one with an amino acid complex.


[1] https://medlineplus.gov/ency/article/002222.htm

[2] http://www.umm.edu/health/medical/altmed/supplement/lysine

[3] https://medlineplus.gov/ency/article/001166.htm

[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4788713/

[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257613/

[6] https://pubchem.ncbi.nlm.nih.gov/compound/L-ornithine#section=Top

[7] https://pubchem.ncbi.nlm.nih.gov/compound/119#section=Top

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