Glycine — full guide

Overview

Glycine is a non-essential yet vital amino acid for the human body.
It plays a central role in:

Collagen synthesis (skin, tendons, joints),
Glutathione production, the body’s main cellular antioxidant,
Sleep regulation through calming neurotransmission.

It’s one of the most abundant and well-tolerated amino acids, widely used to promote cellular recovery and longevity.

What the evidence shows

Area	Evidence level	Observed effects
Sleep & relaxation	Moderate	Shortens sleep onset and improves quality (3 g before bedtime).
Collagen & skin	Moderate	Supports collagen structure; improves elasticity and wound healing.
Antioxidant & metabolism	Moderate	Component of glutathione; protects mitochondria and the liver.
Longevity & aging	Preliminary	In synergy (GlyNAC), reduces oxidative stress and improves mitochondrial function.

Overall level: Moderate for sleep, collagen, and cellular protection.

Mechanism of action

Inhibitory neurotransmitter: binds NMDA and glycine receptors, lowering body temperature and promoting deep sleep.
Collagen precursor: three glycine molecules for each hydroxyproline — essential for tissue strength.
Antioxidant role: combines with cysteine and glutamate to form glutathione (GSH), the key cellular detox molecule.
Metabolism & liver: improves insulin sensitivity and supports liver function (preclinical data).

💊 Dosage & forms

Use	Typical dosage	Timing
Sleep / relaxation	3 g	30–60 min before bedtime
Antioxidant (GlyNAC)	2–5 g glycine + 600 mg NAC	1–2× daily
Collagen / recovery	3–10 g	Spread throughout the day or post-workout

Forms: pure powder (naturally sweet taste) or capsules.
Absorption: excellent oral bioavailability.
Typical duration of trials: 4–12 weeks.

💡 Tip: Mix into a warm evening drink or post-workout shake.

Useful synergies

Combination	Main benefit
Glycine + NAC (GlyNAC)	Increases glutathione and supports mitochondrial health
Glycine + Hydrolyzed Collagen	Supports skin, joints, and healing
Glycine + Magnesium / L-theanine	Calms the nervous system and enhances sleep
Glycine + Vitamin C	Optimizes collagen synthesis

🟢 Proven benefits

Promotes deep, restorative sleep.
Supports collagen production for skin and connective tissues.
Enhances antioxidant protection via glutathione.
Improves mitochondrial function and recovery.

🟡 What remains uncertain

Direct impact on human lifespan.
Long-term effects on metabolic health and chronic diseases.
Optimal doses for neuroprotection and glucose balance.

⚠️ Risks & interactions

Consult a healthcare professional if you have metabolic or kidney disorders, or during pregnancy/breastfeeding.
Very high doses may cause drowsiness or mild digestive discomfort.
Generally very well tolerated; rare cases of drowsiness or mild digestive issues at high doses.
May potentiate the effects of sedatives, hypnotics, or other CNS-acting medications.
Often combined with NAC or glutamine in antioxidant formulas (possible synergy).

✅ Quality tips

Choose pure glycine (≥99%) without additives or artificial flavors.
Prefer powder form for flexible dosing.
Compatible with most diets: vegan, gluten-free, sugar-free.
Combine with NAC or hydrolyzed collagen for a full anti-aging effect.

Sources

- https://ods.od.nih.gov/ - https://www.canada.ca/en/health-canada.html - https://pubmed.ncbi.nlm.nih.gov/34980253/ - https://examine.com/supplements/glycine/

PubMed (PMID: 34980253) — Glycine and Metabolic Health
Examine.com — Glycine Sleep / Longevity Review
NIH/ODS — Amino Acids and Metabolism
Health Canada — Nutritional Reference Values