L-Threonine
Also known as: threonine, L-Thr, 2-amino-3-hydroxybutanoic acid
Effective Dosage
3-12 g/day (safety established up to 12 g/day in healthy adult males)
What the Science Says
L-Threonine is an essential amino acid your body cannot make on its own — you must get it from food or supplements. A clinical safety trial found doses up to 12 g/day were well-tolerated in healthy adult males over 4 weeks, with no serious adverse effects. Animal research suggests it may support intestinal barrier function and reduce gut inflammation, but these effects have not been confirmed in human clinical trials.
What It Doesn't Do
No human evidence it directly improves gut health on its own. Not proven to boost immunity, build muscle, or enhance athletic performance in humans. The glucose-lowering effect seen in one study came from a multi-ingredient blend — L-threonine alone cannot be credited. No evidence it treats any disease or condition.
Evidence-Based Benefits
L-Threonine is an essential amino acid that plays a crucial role in protein synthesis and is important for the production of antibodies, which support immune function. It may also contribute to muscle recovery and overall fitness performance, particularly in athletes.
Strong EvidenceEffective at: 500-2000 mg daily
Source: auto-research
Absorption & Bioavailability
Good — plasma levels of L-threonine and its metabolite L-2-aminobutyrate measurably increased after supplementation with 6 g/day or more, confirming absorption in humans.
Red Flags to Watch For
- Most supporting research is in animals (chickens, pigs), not humans — do not assume animal findings apply to you
- A non-specific rise in liver enzyme (AST) and creatine kinase was observed at 9 g/day in one trial — significance is unclear but warrants caution at high doses
- Products claiming gut repair or immune benefits from L-threonine alone lack direct human clinical evidence
- Often sold in multi-ingredient blends, making it impossible to attribute any effect to L-threonine specifically
Products Containing L-Threonine
See how L-Threonine is used in these analyzed products:
Research Sources
- PubMed
- NIH DSLD
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-04-06