← All supplements

Threonine

Supplement amino acid general nutrition
Aka: L-threonine
Brands seen in Singapore: California Gold Nutrition, Life Extension, NOW Foods, Doctor's Best, Nutricost
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
An essential amino acid — complete protein foods supply it
Pros & cons
Pros
  • One of the nine essential amino acids (NIH ODS)
  • A requirement in adults is measured: 19 mg/kg a day
Cons
  • Limited human evidence for supplementing it
  • Hospital study: threonine levels tracked no outcome
  • No HSA limit and no UL — absence is not a clearance
Sources
  1. Threonine requirement of young men determined by indicator amino acid oxidation with use of L-[1-13C]phenylalanine (Wilson et al., Am J Clin Nutr 2000; PMID 10702170) · read 2026-08-27
    what it says
    “Threonine is an indispensable amino acid with a complex degradative pathway ... the mean threonine requirement, based on indicator oxidation, was 19.0 mg*kg(-)(1)*d(-)(1) with an upper safe intake of 26.2 mg*kg(-)(1)*d(-)(1)”
  2. The Association of the Essential Amino Acids Lysine, Methionine, and Threonine with Clinical Outcomes in Patients at Nutritional Risk: Secondary Analysis of a Randomized Clinical Trial (Nutrients 2024; PMC11357570) · read 2026-08-27
    what it says
    “Lysine, methionine, and threonine are essential amino acids with vital functions for muscle and connective tissue health, metabolic balance, and the immune system ... The results for lysine and threonine did not show statistically significant differences regarding clinical outcomes.”
  3. Europe PMC REST search, 27 Aug 26 — threonine in title plus supplementation/requirement/review, MED source, sorted by citations (133 hits; the most-cited supplementation studies are in poultry and pigs, not people) · read 2026-08-27
    what it says
    “"hitCount":133 ... "Effects of threonine supplementation on the growth performance, immunity, oxidative status, intestinal integrity, and barrier function of broilers at the early age."”
  4. NIH ODS — Dietary Supplements for Exercise and Athletic Performance (Health Professional), protein section · read 2026-08-27
    what it says
    “The nine EAAs are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Most complete proteins (those that contain all EAAs) are composed of about 40% EAAs”
  5. HSA Health Supplements Guidelines (GL-CHPB-3-001 Rev. 020, January 2026) — working definition and Tables 4–5 (vitamins, minerals) · read 2026-08-27
    what it says
    “HS are products that are used to supplement a diet ... contains one or more, or a combination of the following ingredients: a. Vitamins, minerals, amino acids, fatty acids, enzymes, probiotics and other bioactive substances”
  6. HSA Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines (GL-CHPB-1-012, Oct 2025), Annexes A/B · read 2026-08-27
    what it says
    “The objective of this guideline is to highlight the substances of concern when used in HS and TM and is not meant to be an exhaustive list.”
  7. iHerb Singapore — Amino Acids category page (default sort), read 27 Aug 26; sg.iherb.com has no L-threonine category · read 2026-08-27
    what it says
    “Amino Acids 1 - 48 of 1,602 results ... California Gold Nutrition, L-Theanine ... Life Extension, Glutathione, Cysteine & C ... NOW Foods, L-Arginine ... Doctor's Best, PepZin GI(R) ... Nutricost, L-Theanine”
Report a correction View as JSON

Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.