EAAs

Essential amino acids are the nine the body cannot synthesise: leucine, isoleucine, valine, lysine, methionine, phenylalanine, threonine, tryptophan and histidine. Everything else can be made internally from other materials.

EAA supplements supply all nine in free form, meaning they require no digestion and are absorbed rapidly, typically reaching the bloodstream faster than protein from food or whey.

Formulations vary in ratio. Better products weight toward leucine, since it drives the anabolic signal, while still supplying meaningful amounts of the other eight. A product that is mostly leucine with trace amounts of the rest is a BCAA product wearing a different label, so the amino acid breakdown is worth reading.

EAAs address both halves of muscle protein synthesis. Leucine activates mTORC1 and initiates the process, while the remaining eight essential amino acids supply the material needed to actually construct new protein.

Non-essential amino acids are not included because the body can produce them from other substrates. Their absence does not limit the response in the way missing essentials do, which is why an EAA product is nutritionally sufficient for this purpose despite containing only nine of twenty.

Free-form amino acids bypass digestion, producing a faster and higher spike in plasma amino acids than intact protein. Whether that speed confers real advantage is debatable, but it is the basis for intra-workout use.

Studies measuring muscle protein synthesis directly have shown EAAs produce a robust response, comparable to that from whey containing equivalent essential amino acid content, and clearly superior to BCAAs alone.

Research in older adults is particularly supportive, with EAA supplementation shown to stimulate muscle protein synthesis in a group that responds poorly to ordinary protein feeding. Work in bed rest and immobilisation contexts has also been encouraging.

The important caveat is the same as for leucine: this evidence describes what happens when EAAs are added to a diet that is short of protein. For someone already eating adequate protein across the day, the additional benefit of an EAA supplement is small. It is a good product solving a problem many buyers do not have.

EAAs are ordinary dietary components and well tolerated. Digestive discomfort is occasionally reported, and unflavoured EAA powder is unpleasantly bitter, which is why almost all products are heavily flavoured.

Because the full spectrum is present, the amino acid competition problem associated with isolated BCAAs does not apply in the same way. Tryptophan is included rather than displaced, which is a meaningful advantage over BCAA products.

Anyone who has been advised to restrict specific amino acids in their diet should avoid EAA products, since they supply all nine essentials including phenylalanine. Anyone taking regular medication or under medical care should check before use.