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Glycine
3g before bed may improve subjective sleep quality and next-day alertness in small trials — also a building block for glutathione and collagen.
What the evidence says
Glycine doesn't have enough studies with structured effect-size data yet to pool a verdict. Browse the studies below for individual findings.
Most evidence is from high-quality meta-analyses and randomised trials published 1970–2026 with a typical study size of 24 participants.
Based on 71 studies · 7 meta-analyses · 60 RCTs · 2,616 total participants
Confidence
High confidenceWhat the studies found
By outcome
Small RCTs consistently report improved subjective sleep quality and a systematic review supports nervous-system benefits, but the sleep trials are small with high bias risk and the temperature mechanism is animal-only.
50 randomised trials
every one checked individually
Every randomised or controlled trial of Glycine indexed in PubMed, not a hand-picked subset. Meta-analyses and systematic reviews are deliberately excluded from this count: most of them cover many compounds at once, so counting them would inflate it.
PubMed · as of Jul 2026
34 trials ongoing or recruiting · 154 completed on ClinicalTrials.gov
39 of the completed trials have posted results
Registered trials show research momentum for Glycine, not proof of effect — a registration is a plan, and posted results are sponsor-reported, not peer-reviewed. They are never counted toward the evidence rating above.
Browse these trials on ClinicalTrials.govClinicalTrials.gov · as of Oct 2026
Under EU law (Reg. 1924/2006), EFSA reviews whether a specific health claim for Glycine meets the evidence standard. These are independent regulatory decisions on claims — not studies, and never counted toward the evidence score above.
“Not authorised” means the specific claim wording did not meet the EU’s evidence standard — often a matter of dossier or phrasing, not proof of no effect. EFSA judges marketing claims and is kept separate from our study-based evidence score.
Source: EU Register of nutrition and health claims (European Commission / EFSA) · register snapshot Feb 2013
Glycine is a non-essential amino acid involved in sleep, neurotransmission, and connective-tissue synthesis. Small RCTs suggest 3g before bed can improve subjective sleep quality and reduce next-day fatigue, though these studies had small samples and a high risk of bias.
An animal study suggests the mechanism involves lowering core body temperature via peripheral vasodilation, but this has not been confirmed in humans. Glycine is also a precursor for glutathione and is ~33% of collagen.
Lowers core temperature via peripheral vasodilation in animal models; proposed sleep mechanism
Acts as a co-agonist at NMDA receptors
Key building block for collagen production
How Glycine works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Glycine is a normal dietary amino acid; supplementation not well-studied in pregnancy
May be particularly beneficial for age-related sleep issues
May reduce clozapine effectiveness
May have additive effects
Tip: Take with small snack
Tip: Usually not problematic; may reduce over time
Glycine has an evidence score of 6.5/10 — moderate evidence based on 71 indexed studies, including 4 meta-analyses. 3g before bed may improve subjective sleep quality and next-day alertness in small trials — also a building block for glutathione and collagen. Representative study: PMID 32122256.
The commonly studied dose of Glycine is 3g before bed (no cited trial states the dose it used). Individual needs vary — start at the lower end of the range and adjust based on how you respond.
The best time to take Glycine is before bed. It can be taken on an empty stomach. Glycine acts as an inhibitory neurotransmitter and NMDA receptor co-agonist.
Glycine is generally well-tolerated and considered safe for most healthy adults at recommended doses. Reported side effects are uncommon and include vivid dreams, GI discomfort. Use caution if any of these apply to you: Clozapine users (glycine may affect drug efficacy).
Magnesium
Mixed evidenceSupports 300+ enzymatic reactions — critical for sleep, stress response, muscle function, and cognitive health.
Ashwagandha
Likely helpsReduces cortisol and anxiety while improving sleep quality and physical recovery in stressed adults.
Vitamin D3
Probably helpsHormone-like vitamin that regulates 1,000+ genes — deficiency is widespread and linked to poor immunity, depression, and bone loss.
L-Theanine
Too few graded studiesTea-derived amino acid that boosts alpha brain waves for calm, focused alertness — synergizes with caffeine to reduce jitteriness.
Stress, Anxiety & Cortisol
Ashwagandha, L-theanine, magnesium, saffron — what actually helps stress, and the safety caveats.
Supplement Timing & Combining
When to take what, with or without food, and which supplements compete vs pair well.
Sleep: What Actually Works
Melatonin, magnesium, glycine, L-theanine — tiered by evidence, plus a wind-down timeline.
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Reviewed by Dr. Baher Al Hakim · Last reviewed June 2026 · evidence from 71 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
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