Conditionally essential amino acid
Glutamine
Limited evidenceThe most abundant amino acid in the blood, often oversold for muscle recovery.
What it is
Glutamine fuels immune and gut-lining cells. The body normally makes plenty, but needs can increase during severe illness or trauma.
Food sources
Meat and fishEggsDairyTofu
What the research shows
- In healthy, well-fed athletes, studies generally show little benefit for muscle growth or strength.
- Clinical research in critical illness is a separate area with its own mixed findings.
Read the published research on PubMed →
Food first: most people get what they need from a varied diet with enough total protein. Talk to a provider or registered dietitian before adding a supplement, especially if you take medication or have a health condition.
Similar evidence level
Conditionally essential amino acid
Arginine
A precursor to nitric oxide, though oral supplements are poorly absorbed for that purpose.
Limited evidenceNonessential amino acidGlycine
The simplest amino acid, a major part of collagen, and studied for sleep.
Limited evidenceNonessential amino acidTyrosine
A building block for dopamine and norepinephrine, studied under acute stress.
Limited evidence