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Limited evidenceGeneral health

L-Threonine

An essential amino acid used heavily by the gut to make mucin. It is well tolerated as a supplement, but no human trial shows that taking extra does anything for gut barrier or immunity.

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What the science says

  • Safety and tolerability established, efficacy not Limited evidence

    A randomised double-blind controlled trial in healthy adults evaluated graded L-threonine supplementation and concluded it was safely tolerated. The trial was designed to test safe intake, not to demonstrate a health benefit, and reported none.

  • Gut and bone effects are preclinical Limited evidence

    The mucin and intestinal barrier findings that drive marketing come from livestock and rodent work, such as an animal study of a threonine-enriched protein and gut microbiota. No controlled human trial has tested threonine for intestinal barrier function or immunity.

Dosage & safety

Studied doseThe safety trial in healthy adults tested graded intakes above the requirement of roughly 15 mg/kg/day. Supplement labels typically suggest 500–1000 mg/day, which is a label dose with no efficacy data behind it.
SafetyNo adverse effects at ordinary supplement doses in healthy adults. Single amino acids taken in gram quantities can compete with others for transport; caution with kidney or liver impairment, and no data in pregnancy or childhood.

How to take it

TimingTiming does not matter.
With food?Take away from a high-protein meal if you want absorption of the free amino acid, otherwise it makes no practical difference.
Worth knowingThere is no efficacy evidence behind the label dose, so treat this as an experiment rather than a treatment for anything.

Interactions

With other supplements

  • other single amino acids in gram doses

    Gram quantities of one amino acid compete with others for shared transporters. do not stack multiple gram-dose amino acids

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does L-threonine improve gut health?

Unproven: the mucin and gut-barrier findings behind L-threonine marketing come from livestock and rodent studies, and no controlled human trial has tested threonine for intestinal barrier function or immunity.

Is L-threonine safe to take?

A randomized double-blind trial in healthy adults found graded L-threonine supplementation was safely tolerated, though it was designed to test safety, not benefit. Be cautious with kidney or liver impairment, and there are no data in pregnancy or childhood.

How much L-threonine per day?

Labels typically suggest 500–1000 mg/day of L-threonine, a label dose with no efficacy data behind it; the dietary requirement is roughly 15 mg/kg/day. Treat it as an experiment rather than a treatment for anything.

Scientific references

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