Essential Amino Acids Vs Non-essential Amino Acids

There are two main types of amino acids: Essential Amino Acids and Non-Essential Amino Acids. These are also known as Indispensable Amino Acids and Dispensable Amino Acids.

Non-Essential Amino Acids, or Dispensable Amino Acids, are amino acids the human body can make (synthesize) on its own, and so do not require from outside protein sources in your diet.

Essential Amino Acids (EAAs), or Indispensable Amino Acids, are amino acids the body can not produce on its own, so we must acquire them from an outside protein source.

But the trick here is that the non-essential amino acids are made by using the essential amino acids.

You need the essential amino acids to make all the non-essential amino acids that you need. 

But even more, you need all of the essential amino acids to make any protein that your body needs.

Your body cannot make proteins without all of the essential amino acids. 

If it’s missing even one, it cannot make new protein.

This missing amino acid is known as the “limiting” amino acid as, when it’s missing, or to the degree that it’s missing, it limits the amounts of the other essential amino acids that can be used to synthesize new protein.

“…the biological value of the dietary proteins depends on its constituent amino acids and shows that if the eight essential amino acids are not available simultaneously at the time of the protein synthesis, the intracellular deficit, even though of only one amino acid, would limit the protein synthesis of the body.” (11)

This is why BCAAs, three of the essential amino acids known as Branched-Chain Amino Acids and touted as building new protein, do not build new protein. (10)

It’s physically impossible for them to do so.

Your body requires each one of the essential amino acids to build new proteins. And if it’s missing even one, no new proteins can be built. (7)

Also, it doesn’t need extra non-essential amino acids for this. It makes non-essential amino acids as it needs to for the proteins it needs to make.

But it goes even deeper than this. 

It doesn’t just need each of the essential amino acids. It needs each in an exact ratio one to another. 

This ratio is something scientists have been investigating for decades.

“Normal growth and maintenance of health in humans require all amino acids (IDAA [Indispensable Amino Acids], conditionally IDAA and dispensable amino acids) to be provided in appropriate quantity and form that is biologically utilizable (Pencharz and Young 2006). This aspect commonly referred to as availability or bioavailability, is very important to know because food proteins vary greatly in both the concentration and bioavailability of the IDAA and conditionally IDAA.”

It’s not one of each. It’s two of this one, three of that, one of this, and ten of that one, etc.

If your body receives all of the essential amino acids but is low on certain of them, then it won’t be able to use each of the others fully. 

This is known as the limiting amino acid. If all but one essential amino acid is present and in the correct ratio to make ten grams of new protein, but the quantity of one of them is only enough to make three grams of new protein along with the others, then no matter how many of the other EAAs you have, you can only make three grams of protein.

For example, if you were building a table from Ikea, you need one table top and four legs to build one table. 

If you had two table tops and 7 legs, you could still only build one table, as you’re missing a leg.

While there are more than two EAAs, it’s the same principle. Your body can only build as much new protein as it has each of the essential amino acids in proper ratio to one another. If you want ten times the protein synthesis, then you need to 10x each EAA according to its ratio number.

If you only increase one or two of them, then the amount increased is an excess, and cannot be used by the body to make new protein. 

And this is where different types of proteins come in. 

Because while whey, pea, soy, meats, eggs, etc. may contain all of the EAAs, the essential amino acid ratios each contain is different. 

How much new protein your body can synthesize from the EAAs in a specific protein source comes down to how much of each essential amino acid exists in the correct ratio within that protein source.

“The nutritional quality of a food protein depends on the absolute content of essential amino acids, the relative proportions of essential amino acids, and their ratios to nonessential amino acids."

If a protein source, such as whey, consists of only 18% EAAs in the correct ratio to make new protein, with the other 82% being individual EAAs in excess of the correct ratio, or of other non-essential amino acids, then only 18% of the whey you are consuming can be used inside the body to make new protein. 

The other 82% of the protein (essential and non-essential amino acids) is excess, and therefore cannot be used to make new protein on its own.

And this is where calories come in. 

Because this excess isn’t stored or saved for later, and your body has to do something with it.