Amino Acids: Nutrients & Supplements part I

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This is the first article of two, about some individual amino acids and their medical effects. Some of them can be taken as a dietary supplement.


Amino acids are the parts from which proteins are built. But that is not their only function. They also serve the body's biochemistry in other ways. Some work as catalysts, others take part in biochemical reactions; some have vitamin-like or outright medical properties. In short, they have a number of functions apart from being building blocks for various proteins. That's why some of them are sold as supplements. That, however, is primarily aimed at athletes, who are trying to influence their strength and the result of their exercise with amino acids. Yet every health-conscious individual should have at least a basic understanding of them. Unreflectedly ingesting a single amino acid is hardly worthwhile and might even be harmful. Except in very special cases, they should be taken in combinations or a complex to give full effect.

The amino acids that are precursors to proteins are called proteinogenic amino acids. These are the ones which, among other functions, serve as building blocks. Other amino acids, and there are many of them in nature, are called non-proteinogenic.

There are only 21 proteinogenic amino acids in the genetic code of eukaryotes (which includes all animals, plants, algae and fungi). That is the 20 from the standard genetic code and selenocysteine. For humans, 9 amino acids are essential, which means that they have to be ingested, while the other 11 of the standard genetic code can be synthesised from other molecules.

The essential amino acids (EAA) are Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine.

The other 11 of the standard genetic code are Arginine, Alanine, Asparagine, Aspartic acid, Cysteine, Glutamic acid, Glutamine, Glycine, Proline, Serine, and Tyrosine.

Of the essential amino acids, three are Branch-Chained Amino Acids (BCAA): Leucine, Isoleucine and Valine. Contrary to other EAAs which are metabolised in the liver, BCAAs are metabolised in the muscles.

Of the 12 non-essential amino acids, 6 (Arginine, Cysteine, Glycine, Glutamine, Proline, and Tyrosine) are conditionally essential. That means they are not generally essential but can be so under special circumstances.

Below, we will look at effects and functions of some individual amino acids. I divide this in two main sections. Proteinogenic and Non-proteinogenic amino acids.

I will not discuss all amino acids individually, this is just a selection of facts about the most interesting ones.

Proteinogenic Amino Acids



Histidine is a precursor to histamine, which protects against oxidation. It is also involved in the synthesis of carosene, which helps reduce the build-up of harmful lactic acid during muscle strain.


See BCAA below.


Leucine stimulates protein synthesis (no other amino acid can do that). Used for lean muscle growth and recovery after heavy exercise or other strain.

See also BCAA below.


Lysine stimulates the release of growth hormone, which facilitates all forms of healing. As an isolated supplement, it is especially useful for healing the gums. It also has an history of curing certain virus infections, most notably herpes. However, there is some dispute about whether or not this works.

Further, it promotes calcium absorption, and also plays a role in recovery after muscular strain.

Lysine has a reputation of curing oral herpes and certain other virus infections. The results of studies are non-conclusive, however, and anecdotal evidence gives the impression that it works in some cases but by far not in all.


Methionine is required for the synthesis of carnitine, cysteine, lecithin, phosphatidylcholine and other phospholipids, and for taurine.

Methionine chelates heavy metals and removes them from the body. It is sometimes given to dogs as a supplement to prevent “stones”.


Marketed as a pain-killer and anti-depressant. It is a precursor in the synthesis of the pigment melanin, dopamine, adrenaline and noradrenaline (Americans call them epinephrine and norepinephrine). It is sometimes used for its antidepressant effect. For athletes, it reduces exhaustion during strain.


Important for mental balance and the immune system. Otherwise insufficiently studied.


Tryptophan is a precursor to serotonin. It is a neurotransmitter that has the ability too suppress pain and stimulate sound sleep. It is also a precursor to melatonin, a substance that regulates sleep. Athletes sometimes take tryptophan to better stand the tolerance to pain in connection with hard strain, but its effect is unproved.


Valine helps to protect the muscle cells from damage during strain.

See also BCAA below.


Leucine, Isoleucine and Valine are Branched-Chain Amino Acids. They increase red blood cell count and haemoglobin, which increase the blood's ability to transport oxygen. They also increase serum albumin and lower glucose. Moreover, they are anti-inflammatory and stimulate the formation of blood cells.

Further, BCAAs can be used against liver disease, kidney failure, stress, and much more. In order to be efficient and not harmful, they should only be taken together with all the other essential amino acids, never separately.

The whole series about amino acids:

1. Amino Acids: Nutrients & Supplements part I

2. Amino Acids: Nutrients & Supplements part II

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(Lead Image by geralt/Pixabay, CC0/Public Domain.)

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2 years ago


This is very educative and informative article. It gives additional inputs to the students about chemistry for sure.

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2 years ago

One of the topics in Biochemistry, I enjoyed it at that time

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