Last verified: 17 days ago
L-Threonine
Also known as: threonine, L-Thr, 2-amino-3-hydroxybutanoic acid
Evidence under review. — Not yet rated
Essential amino acid. Safe up to 12g/day. Limited human evidence for specific health benefits.
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What it does
L-Threonine is an essential amino acid your body cannot make on its own — you must get it from food or supplements. It plays a role in protein synthesis and is a key building block of mucin, the...
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Evidence quality
Evidence base hasn't been formally rated yet. See research below.
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Clinical dose
3-12 g daily based on safety data; no established therapeutic dose for specific outcomes
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. It plays a role in protein synthesis and is a key building block of mucin, the protein that lines and protects your gut wall. Animal studies suggest it may help reduce gut inflammation and support intestinal barrier integrity, though human clinical evidence for these specific benefits is currently limited.
What It Doesn't Do
No proven muscle-building benefit on its own in humans. No evidence it boosts immunity in people. The gut-health benefits seen in animal studies haven't been confirmed in human trials. Don't expect it to lower blood sugar — the glucose study used a multi-ingredient blend, so L-threonine alone gets no credit.
Evidence-Based Benefits
Safe and well-tolerated at doses up to 12 g/day in healthy adult males over 4 weeks.
Moderate EvidenceEffective at: Up to 12 g/day
Supporting studies (click to view on PubMed):
May help protect intestinal lining and reduce gut inflammation under inflammatory stress.
Weak EvidenceEffective at: No established human dose
Supporting studies (click to view on PubMed):
Absorption & Bioavailability
Good — plasma L-threonine and its metabolite L-2-aminobutyrate measurably increased at doses of 6 g/day and above in a clinical trial, confirming absorption.
Red Flags to Watch For
- Most gut-health and anti-inflammatory evidence comes from animal (poultry) studies, not humans — don't assume the same effects apply to you
- A minor, non-specific increase in liver enzyme (AST) and creatine kinase was observed at 9 g/day in one trial — significance is unclear but worth monitoring at high doses
- The blood sugar benefit seen in one study came from a multi-ingredient supplement (amino acids + chromium), not L-threonine alone — single-ingredient claims are not supported
- Products in over 1,000 registered supplements means it's widely used, but widespread use is not the same as proven efficacy
Products Containing L-Threonine
See how L-Threonine is used in these analyzed products:
Elm & Rye Vegan Protein Blend
Supplement
Thorne Amino Complex Berry Powder NSF
Supplement
Double Wood Supplements Essential Amino Acids
Supplement
Optimum Nutrition 100% Gold Standard Whey
Supplement
Swolverine INTRA
Supplement
Hormone Harmony PLUS+
Supplement
Everyday Dose
Supplement
Frequently Asked Questions
What does L-Threonine do?
Essential amino acid. Safe up to 12g/day. Limited human evidence for specific health benefits.
What is the effective dose of L-Threonine?
3-12 g daily based on safety data; no established therapeutic dose for specific outcomes
Is L-Threonine safe?
Most gut-health and anti-inflammatory evidence comes from animal (poultry) studies, not humans — don't assume the same effects apply to you
What doesn't L-Threonine do?
No proven muscle-building benefit on its own in humans.
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: 2026-05-25