Supplement analysis backed by scientific evidence · PT

← All supplements
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.

Evidence last reviewed: August 2026

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.

Scientific references

Where to buy

View on iHerb

Referral link — this site may earn a commission on purchases.

Related in General health