What are EAAs (essential amino acids)?

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EAAs (essential amino acids) are the building pieces of protein that the body cannot make on its own, so they must come from food.

What are EAAs (essential amino acids)?
Three letters you often see on supplement tubs
At the gym, you sometimes see people mixing EAA powder into water during a workout. Supplement shops also put EAA tubs next to protein powder. To understand EAAs, you first need to know what protein and amino acids are, so we go through them one at a time.
In short
The 9 pieces the body cannot make and must eat
EAA stands for Essential Amino Acids. Amino acids are the small pieces that make up protein. The 9 of them that the body cannot make on its own, and so must get from food, are called the essential amino acids.
First, what is protein?
The material that builds the body and moves it
Protein is found in every cell of the body. It gives the body its structure, lets the body move, and helps fight germs. The body also uses protein to repair damaged cells and to make new ones.
What is an amino acid?
The small pieces that make up protein, 20 kinds
A protein is many small pieces called amino acids, linked together in a long chain. There are 20 kinds of amino acids. Just as letters of the alphabet make different words depending on how you join them, the 20 pieces make different proteins depending on the order they are linked in.
Why 'essential'?
Of the 20, the body cannot make 9
The body can make the rest of the 20 itself, so they are called non-essential amino acids. The 9 it cannot make must be eaten, so they are the essential amino acids. They are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
Where are they found?
Meat, fish, eggs, milk and soy have all 9
Meat, fish, eggs, milk and soy contain all 9, so they are called complete proteins. You do not need all 9 at every meal; eating a mix of protein foods over the whole day is enough.
What they do in muscle
The material for muscle protein synthesis
Muscle protein is broken down and rebuilt a little at a time all day. Making new protein is called 'synthesis', and breaking it down is called 'breakdown'. While you go without food, breakdown is larger, and muscle grows only when synthesis is larger than breakdown. When people took EAAs after exercise, their muscle switched from more breakdown to more synthesis.
What is an EAA supplement?
Already in pieces, so it is absorbed quickly
Protein in food is cut into amino acid pieces in the stomach and small intestine, and then passes into the blood. Passing into the blood like this is called absorption. An EAA supplement is the 9 amino acids, each made into powder and mixed, so it skips the cutting step and is absorbed faster than food.
How are BCAAs different?
BCAAs hold only 3 of the 9
BCAAs are just 3 of the 9 essential amino acids: leucine, isoleucine and valine. Muscle protein synthesis needs all 9. So when BCAAs are taken alone, the body has to get the rest by breaking down muscle protein. The BCAA entry covers this in detail.
Are they safe?
No side effects reported, except in a very rare inborn disease
No side effects from taking EAAs have been reported. Taking more than twice the amount people usually get from food, on top of that food, stayed within the safe range. The exception is a very rare disease in which the body cannot process leucine, isoleucine and valine from birth: maple syrup urine disease, named for the smell of the urine. There are no data confirming safety for people with kidney disease.
A common misunderstanding
Do you need EAA powder to build muscle?
No. All 9 that muscle protein synthesis needs are found in protein foods such as meat, eggs, milk and soy. Eating protein foods as usual covers the daily need for EAAs. What makes the powder different from food is that it skips the cutting step and is absorbed quickly.
Summary
The 9 the body cannot make, also found in food
EAAs are the 9 amino acids the body cannot make and must eat, and they are the material for muscle protein synthesis. Protein foods contain all 9, so you do not need separate powder to build muscle. Related terms: BCAA, leucine, complete protein.