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Ornithine

Supplement amino acid sleep
Aka: L-ornithine, ornithine alpha-ketoglutarate
Brands seen in Singapore: Swanson, NOW Foods, Nutricost, Source Naturals, Vitacost
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
Sleep quality and stress markers — two small RCTS, mixed
When to take
Trials dosed daily, or 1 h before a stress test
Studied for
Trials dosed daily for weeks
Pros & cons
Pros
  • 400 mg/day for 8 weeks cut the cortisol/dhea-s ratio
  • Perceived sleep quality improved in that SAMe RCT
  • A 4-week study set a noael of 12 g/day in men
Cons
  • Only two small RCTS — 52 and 65 participants
  • A later RCT found no effect on saliva cortisol
  • Plasma aspartic and glutamic acid rose at the top dose
Sources
  1. Randomised controlled trial of the effects of L-ornithine on stress markers and sleep quality in healthy workers (Miyake et al., Nutr J 2014; PMC4055948) · read 2026-08-27
    what it says
    “Fifty-two apparently healthy Japanese adults … were randomly divided into either the L-ornithine (400 mg/day) or placebo group … Serum cortisol levels and the cortisol/DHEA-S ratio were significantly decreased in the L-ornithine group”
  2. Miyake et al., Nutrition Journal 2014 — sleep and mood outcomes · read 2026-08-27
    what it says
    “Also, anger was reduced and perceived sleep quality was improved in the L-ornithine group.”
  3. Effects of Oral Ingestion of L-Ornithine on Mental Stress and Fatigue Based on the Trier Social Stress Test in Healthy Humans (Moriyasu et al., J Clin Med 2024; PMC11676746) · read 2026-08-27
    what it says
    “We randomly assigned 65 participants into two groups, ingesting orally either 1600 mg of L-ornithine or a placebo for 7 days … While L-ornithine did not affect saliva cortisol levels”
  4. Moriyasu et al., J Clin Med 2024 — mood outcomes · read 2026-08-27
    what it says
    “it significantly improved the fatigue-inertia and anger-hostility scales of the Profile of Mood States on the morning after the TSST”
  5. Subchronic tolerance trials of graded oral supplementation with ornithine hydrochloride or citrulline in healthy adults (Miura et al., Amino Acids 2023; PMC9791970) · read 2026-08-27
    what it says
    “A clinical, no-observed-adverse-effect-level (NOAEL) of ornithine hydrochloride and citrulline supplementation in healthy adult males was determined to be 12 g/day and 24 g/day (4 weeks), respectively.”
  6. Miura et al., Amino Acids 2023 — findings at the highest dosages · read 2026-08-27
    what it says
    “In the ornithine hydrochloride supplementation group, minor increase in plasma aspartic acid and glutamic acid concentrations was observed at the highest intake dosages.”
  7. HSA register of therapeutic products (data.gov.sg open data, 5,511 rows) — filtered locally 27 Aug 26 for ornithine · read 2026-08-27
    what it says
    “HEPA-MERZ INFUSION CONCENTRATE 5G/10 ML | L-Ornithine-L-Aspartate | Prescription Only”
  8. HSA Health Supplements Guidelines GL-CHPB-3-001 Rev. No. 020 (January 2026) — s3.1 working definition and clause 4.8 (Tables 4-5 cover vitamins and minerals only) · read 2026-08-27
    what it says
    “Vitamins, minerals, amino acids, fatty acids, enzymes, probiotics and other bioactive substances … HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits stated in Tables 4 and 5.”
  9. HSA Guidelines on Prohibited and Restricted Ingredients in HS and TM, GL-CHPB-1-012 Rev. No. 001 (Oct 2025), Annex A/B — full text searched 27 Aug 26, no row for ornithine · 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.”
  10. iHerb Singapore category page "Ornithine", default best-selling order, first 5 distinct brands · read 2026-08-27
    what it says
    “Ornithine”
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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.