Amino acids beyond protein

BCAAs: the incomplete set problem

Building a muscle protein requires all twenty amino acids present at once. BCAAs supply three of them. Leucine, one of the three, is the signal that switches the machinery on — which is why BCAAs do raise the signal and why the early studies looked encouraging.

But switching on a construction site without delivering the other materials does not build anything. When trials compared BCAAs against a complete protein containing the same amount of leucine, the complete protein won clearly.

So the honest description is that BCAAs are a partial and expensive version of something most people already eat. If your protein intake is adequate, they add nothing you did not have.

EAAs: the same idea, done properly

Essential amino acids supply all nine the body cannot make, which fixes the structural objection to BCAAs. They do stimulate muscle protein synthesis, and at smaller doses than whole protein.

Where they earn their place is narrow: someone who genuinely cannot eat — around illness, in the first days after surgery, in a very old person with no appetite. For a healthy person eating enough protein, they are a more expensive route to the same destination.

Glutamine: a good hypothesis that did not survive

The reasoning was sound. Glutamine is the fuel immune cells prefer, blood levels fall after prolonged exercise, and athletes get more upper-respiratory infections. Supply the missing fuel and the infections should fall.

They did not. Trials in fed athletes have generally found no benefit for immunity, recovery or performance. The likely explanation is that a person eating enough protein is already making plenty — glutamine is the most abundant amino acid in the body — and the post-exercise dip is transient rather than limiting.

It remains genuinely useful in clinical settings such as severe burns or gut disease. That is not the same population as a lifter, and it is where the sports claim borrowed its authority from.

Beta-alanine: the one that works, for one thing

Beta-alanine raises muscle carnosine, which buffers the acidity that builds during hard efforts. That improves performance in a specific window — efforts of roughly one to ten minutes, where acid accumulation is what limits you.

Outside that window it does little. It will not help a marathon and it will not help a single heavy triple. And it takes weeks of daily loading to raise carnosine, so it is not something to take before a session.

The tingling is harmless and is the one supplement side effect people reliably notice — split doses reduce it.