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L-serine

Supplement amino acid brain & moodsleep
Aka: serine
Brands seen in Singapore: California Gold Nutrition, Nutricost, NOW Foods, Vitamatic, Double Wood Supplements
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
Limited human evidence — circadian timing, rare genetic use
When to take
In the trial, 3 g went 30 min before bedtime
Pros & cons
Pros
  • One small trial: 3 g at night held circadian phase
  • 52-week use in one patient: no direct side effects
  • Not named in HSA's prohibited or restricted annexes
Cons
  • Not in HSA's vitamin/mineral tables — no SG cap
  • Human trials are tiny — 33 students, single patients
  • The sleep tag rests on one circadian-phase study
Sources
  1. Intake of L-serine before bedtime prevents the delay of the circadian phase in real life (Ohashi et al., J Physiol Anthropol 2022) · read 2026-08-27
    what it says
    “the subjects took 3.0 g of L-serine or a placebo 30 min before bedtime for 2 weeks … DLMO after intervention was significantly delayed … in the placebo group (p = 0.02) but not in the L-serine group”
  2. Clinical and metabolic consequences of L-serine supplementation in HSAN1C (Auranen et al., Cold Spring Harb Mol Case Stud 2017) · read 2026-08-27
    what it says
    “a 52-wk treatment in which the L-serine dose was titrated up to 400 mg/kg/day … There were no direct side effects from the treatment, but the patient developed a transitory toe ulceration”
  3. HSA — Guidelines on prohibited and restricted ingredients in HS and TM (Oct 2025), Annex A · read 2026-08-27
    what it says
    “Annex A: List of substances which are prohibited or restricted for use with … [serine is not listed among the 100+ named entries]”
  4. HSA — Health Supplements Guidelines (Jan 2026), Tables 4–5 vitamin and mineral limits · read 2026-08-27
    what it says
    “Table 4: Vitamins Limits … Table 5: Minerals Limits [neither table names serine; the limits cover named vitamins and minerals only]”
  5. iHerb Singapore — l-serine category page (default best-selling order) · read 2026-08-27
    what it says
    “California Gold Nutrition · Nutricost · NOW Foods · Vitamatic · Double Wood Supplements [first distinct brands, default order]”
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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.