Protein & Amino Acids
Glycine
The simplest amino acid with underappreciated breadth. Improves sleep onset, is the primary building block of collagen, and supports gut lining integrity.
Effective Dose
3–5g / day
per clinical evidence
Evidence Level
Moderate
Protein & Amino Acids
Mechanism
NMDA receptor co-agonist, collagen substrate, sleep improvement
primary action
Best For
Sleep quality
Collagen synthesis, Gut health
This profile is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare professional before starting any supplementation, especially if you have pre-existing conditions or take medications.
What Is Glycine?
Glycine is the most abundant amino acid in the human body by total mass — it constitutes ~33% of collagen. It is also a major inhibitory neurotransmitter in the spinal cord and brainstem, and a co-agonist at NMDA receptors in the hippocampus. Modern diets are relatively deficient in glycine (collagen-rich cuts of meat are rarely consumed).
How It Works: The Science
Glycine acts on glycine receptors (strychnine-sensitive Cl⁻ channels) in the spinal cord, reducing motor neuron excitability. In the brain, it co-activates NMDA receptors alongside glutamate, playing a dual inhibitory-excitatory role. For sleep, glycine lowers core body temperature (a key sleep onset signal) via peripheral vasodilation mediated by glycine receptors.
Primary Mechanism
NMDA receptor co-agonist, collagen substrate, sleep improvement
Evidence-Based Benefits
Dosage Guide
Effective Dose
3–5g / day
3–5g at bedtime for sleep. 10–15g/day for collagen support (high doses found in traditional bone broth). Mildly sweet taste — mixes easily in water.
Safety Profile & Side Effects
One of the safest amino acids. No known adverse effects at supplemental doses. The body produces ~3g/day endogenously — supplementation simply tops up intake.
Who Should (and Shouldn't) Take It
Those with poor sleep quality, athletes with connective tissue concerns, and anyone not eating nose-to-tail animal foods (the primary dietary glycine source).
Frequently Asked Questions
Related Ingredients
Medical Disclaimer
Ingredient profiles are for informational purposes only and do not constitute medical advice. Consult a qualified healthcare professional before starting any supplementation, especially if you have pre-existing conditions or take medications. Full disclaimer →