Glycine
Glycine
Glycine is the simplest non-essential amino acid, serving as both a structural protein component and a multifunctional signaling molecule throughout the body. It is widely used to support sleep quality, collagen synthesis, metabolic health, and cognitive function, with substantial research backing its role in improving sleep onset and slow-wave sleep architecture. As the most abundant amino acid in collagen, it is also popular among athletes and individuals seeking to support joint, tendon, and skin health.
Mechanism of Action
Glycine acts as an inhibitory neurotransmitter in the brainstem and spinal cord by binding to strychnine-sensitive glycine receptors (GlyR), hyperpolarizing neurons and promoting relaxation and sleep. In the central nervous system it also serves as a co-agonist at NMDA glutamate receptors, modulating excitatory neurotransmission and influencing cognition and neuroprotection. Additionally, glycine is a key substrate for glutathione synthesis, creatine biosynthesis, heme production, and bile acid conjugation, making it central to antioxidant defense, energy metabolism, and detoxification pathways.
Evidence by Health Goal(17 goals)
Dosing Protocols
30–60 minutes before bed
This dose range is well-supported by clinical trials for improving sleep quality and reducing core body temperature. Higher doses of 9–15g/day have been used in metabolic and collagen-support contexts, split across meals. Powder form is preferable for higher doses due to capsule volume.
With meals or alongside collagen/protein intake
Higher dosing protocol used to support collagen synthesis, joint health, gut integrity (leaky gut), or to compensate for glycine deficiency common in high-meat diets. Often stacked with collagen peptides or vitamin C for synergistic connective tissue support.
Safety & Side Effects
Glycine has an excellent safety profile and is well-tolerated across a broad dose range; it is considered GRAS (Generally Recognized As Safe) by the FDA with no established upper tolerable limit. The primary concerns are mild gastrointestinal effects at high doses and potential additive sedation when combined with CNS depressants.
Possible Side Effects
- !Loose stools or mild diarrhea at doses above 10g
- !Nausea when taken in high doses on an empty stomach
- !Mild sedation or drowsiness, particularly when taken during the day
- !Soft or slightly sweet taste that some users find unpleasant in powder form
- !Rare: headache at very high doses (>30g/day) in sensitive individuals
- !Theoretical reduction in alertness if taken in excess prior to tasks requiring vigilance
Interactions
- -May potentiate CNS depressants (benzodiazepines, alcohol, sedative antihistamines) — use caution and reduce concurrent doses
- -May enhance clozapine efficacy when used as an adjunct in schizophrenia treatment — monitor under medical supervision
- -Potentially synergistic with magnesium glycinate or L-theanine for sleep — may produce pronounced sedation in sensitive individuals
- -High-dose glycine may theoretically lower blood pressure — use caution with antihypertensive medications
- -May improve insulin sensitivity — monitor blood glucose if using alongside antidiabetic medications or insulin
Cost & Where to Buy
Glycine powder is one of the most affordable amino acid supplements available. Bulk powder (500g–1kg) from reputable suppliers costs as little as $15–25 per kilogram, making monthly costs very low at standard sleep doses (3–5g/day). Branded capsule products are significantly more expensive per gram.
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