Key findings from detailed records
In a small crossover study, 3 g glycine before bed during 3 nights of restricted sleep improved selected next-day vigilance measures. Fatigue improved on day 1, not day 3. Only 7 healthy men were analyzed.
KNOWLEDGE RECORD
- Category
- Sleep and stress
- Last Reviewed
Names and related search termsGlycine / Glycine
Study type: small exploratory studies.
OUTCOME-SPECIFIC EVIDENCE
Scientific Evidence Profile
Assessment pending
An outcome-specific assessment has not yet been completed. This is not a finding that the ingredient is ineffective. The study records below remain available.
This profile concerns the stated outcome and population, not the ingredient as a whole. It is not a probability of benefit, a safety rating, a product efficacy rating or an indication of product adoption.
How we assess evidenceIngredient Profile
- What is it?
- Glycine is the simplest protein-forming amino acid. Unlike the other standard amino acids, it has no asymmetric carbon centre. [1]
Sources for this profile
Compound properties and formulation properties are different. These sources do not establish the efficacy of a finished supplement.
- PubChem — Glycine (CID 750) Chemical identity reference. Maintained by NCBI, U.S. National Library of Medicine. Database record; not a clinical trial.
Profile sources checked:
Read the evidence in context
- Evidence: what was measured in the stated population or experimental model.
- Inference: an interpretation connecting findings; its applicability depends on the study conditions.
- Hypothesis: a proposed explanation or effect that remains to be tested.
Why It Matters #
Does glycine change next-day fatigue during short-term sleep restriction? Check the detailed records for study conditions and use the literature map to compare other populations and outcomes.
What Was Studied #
10 healthy male participants, with 7 analyzed; employees of Ajinomoto. Single-blind, randomized crossover trial. Outcomes: Next-day sleepiness, fatigue and performance tasks. Prespecified primary/secondary classification was not verified.[1]
What Was Found #
Subjective fatigue improved on day 1, but not day 3. Psychomotor vigilance improved on both days under the study’s sleep-restriction conditions.[1]
What the Evidence Means #
Very small, short-term and single-blind. It does not establish treatment for chronic insomnia or long-term sleep improvement.[1]
Comparing similar populations, formulations, durations and outcomes helps identify where findings agree and where they differ.
What We Can Learn #
Read this as preliminary human sleep evidence. This selected study alone does not justify an “S” rating or a claim of high reproducibility.
What Remains Unknown #
Further questions include reproducibility across populations and formulations, and the long-term balance of benefits and harms. Use the literature map as a starting point for these questions.
LITERATURE MAP / 10 PAPERS
Compare papers by conditions and findings.
Distinguish glycine alone from combinations with cysteine or NAC. Sleep, metabolism and adjunctive use in psychiatric conditions address different questions.
Selected: 2026-09-21. Bibliographic information checked against Europe PMC / PubMed. Editorial selection considered major papers and a range of populations and questions. This is not a systematic search covering all recent research.
10 RECORDS
A dash marks fields outside the bibliographic record. Use detailed records to compare findings and design records to connect mechanisms.
No papers match. Change the search conditions.
The literature map is an index of research questions and references. Individual assessment of results, doses, funding and COI is limited to the detailed study records. Related reports from the same trial may be included; paper counts are not counts of independent trials.
Explore the research Study Records
Listed doses describe study conditions, not recommended intake.
The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers.
PubMed 22529837DOI: 10.3389/fneur.2012.00061
- Authors
- Bannai M, Kawai N, Ono K, Nakahara K, Murakami N.
- Journal
- Frontiers in neurology
- Publication year
- 2012
- Study design
- Single-blind, randomized crossover trial
- Participants
- 10 healthy male participants, with 7 analyzed; employees of Ajinomoto.
- Dose and intervention
- 3 g 30 minutes before bedtime versus placebo
- Duration
- 3 nights per condition, with time in bed reduced by 25% from usual.
- Outcomes and their role in the study
- Next-day sleepiness, fatigue and performance tasks. Prespecified primary/secondary classification was not verified.
- Findings
- Subjective fatigue improved on day 1, but not day 3. Psychomotor vigilance improved on both days under the study’s sleep-restriction conditions.
- Limitations
- Very small, short-term and single-blind. It does not establish treatment for chronic insomnia or long-term sleep improvement.
- Funding
- Partly supported by PROBRAIN, the Program for Promotion of Basic Research Activities for Innovative Bioscience.
- Conflict of Interest
- The authors declared no commercial or financial conflicts. Author affiliations included Ajinomoto, and the human volunteers were Ajinomoto employees; these study relationships are relevant context.
- Scope of source review
- Primary-paper methods, relevant results, limitations and funding/COI checked on 2026-10-24. This record assesses the stated claims, not every analysis in the paper.
Cite this page
LÍFSVARÐA. Glycine: Does glycine change next-day fatigue during short-term sleep restriction? Version 1.1 / Updated 2026-10-24
https://lifsvarda.com/knowledge/glycine/Edited by LÍFSVARÐA (product brand).Editorial policy
Sources and updates
- Bannai M, Kawai N, Ono K, Nakahara K, Murakami N. (2012). The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers.Primary-paper methods, relevant results, limitations and funding/COI checked on 2026-10-24. This record assesses the stated claims, not every analysis in the paper.
First published: 2026-09-21 / Version 1.1. Updated 2026-09-23: Added a research comparison table and links to design records. Source notes identify the scope of verification when the full paper has not been reviewed. Research summaries and LÍFSVARÐA’s interpretation are distinguished.