RESEARCH MONOGRAPH · KDC-MN-106

Glycine

May 9, 2026 Kodiac biolabs Research Revised May 30, 2026 2 min read

Our opinion on this compound

82/100

The amino acid that quietly hits multiple aging-relevant pathways. Underpriced for what you get

Glycine is one of those molecules where the longevity scene mostly missed the point. It's the simplest amino acid, dirt cheap, and it shows up in some of the more interesting geroscience axes. The ITP at NIA ran glycine in mice and got a small but reproducible lifespan extension, which is more than most molecules they test get to claim. The dosing was in feed at percent-level concentrations, which is a lot of glycine, but the signal was real.

Mechanism is multi-pronged in an interesting way. Glycine is rate-limiting for glutathione synthesis (along with cysteine), so old people with glutathione decline can benefit from glycine plus N-acetylcysteine combinations (the GlyNAC work from Sekhar at Baylor in older adults is one of the more striking aging intervention trials in recent years, with mitochondrial and metabolic improvements that look real). Glycine is also a co-agonist at NMDA receptors and an inhibitory neurotransmitter at glycine receptors, so it has CNS effects independent of the glutathione story. And it's part of the methionine restriction story: methionine restriction extends mouse lifespan, and high glycine appears to recapitulate parts of that signal possibly through methionine clearance.

The sleep angle is also interesting and underrated. Bannai's group at Ajinomoto showed glycine before sleep improved subjective sleep quality and reduced sleep onset latency in poor sleepers, with measurable effects on core body temperature drop. Not a huge effect size but consistent across small trials.

What we like: cheap, well-tolerated, multiple plausible aging-relevant mechanisms, real animal data, real human trials in older adults via GlyNAC. The combination with NAC is where the interesting clinical work is happening.

What we dont like is the dosing question. The animal and human studies typically use gram-level glycine doses, which is a lot. Whether smaller intake levels matter is unclear. And the methionine restriction story has subtleties (glycine in absence of methionine restriction may not fully recapitulate the effect).

Sourcing: glycine is among the cheapest amino acids on the planet, pharmacopoeia-grade is widely available, stability is unremarkable. Quality is rarely an issue. Taste is faintly sweet, dissolves easily in water.

Underrated. Honestly. The GlyNAC work alone is worth the read.

Evidence: 70
Mechanism: 78
Reliability: 72
Safety: 92
Sourcing: 95
Value: 95
Signal: 72
Staying power: 80

Plain-language summary Intrigue 56 / 100

Glycine is the smallest amino acid, both a building block of proteins and a neurotransmitter. It functions as a co-agonist at NMDA receptors. Studied as a sleep aid and as part of GlyNAC (glycine + NAC) for longevity. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Amino acid / NMDA co-agonist

The simplest amino acid with multiple biological roles including methionine restriction mimetic effects studied for lifespan extension.

Abstract

Glycine (CAS 56-40-6; molecular formula C2H5NO2; molecular weight 75.07) is the simplest amino acid, with multiple biological roles: protein synthesis, neurotransmission (inhibitory glycinergic synapses, NMDA co-agonist at the glycine modulatory site), heme synthesis (precursor to porphyrin), and as a substrate for hepatic conjugation. Glycine has been studied as a methionine restriction mimetic; methionine restriction extends lifespan in rodents, and glycine supplementation diverts methionine away from protein synthesis through enhanced one-carbon transfer reactions, producing similar metabolic phenotype to methionine restriction. The compound is also a potent NMDA glycine site co-agonist with sleep-promoting effects studied at gram-level evening doses. Reported research dose ranges in the literature span roughly 3 grams (sleep studies) to 5 to 10 grams (methionine restriction mimetic studies); the compound is exceptionally safe with rare adverse events.

Mechanism of action

Multiple roles. NMDA glycine site co-agonist (sleep effects). Methionine restriction mimetic through one-carbon metabolism.

Reported research dose ranges

Reported research dose ranges in the literature span roughly 3 grams (sleep studies) to 5 to 10 grams (metabolic studies).

References

Brind J, et al. Dietary glycine supplementation mimics lifespan extension by dietary methionine restriction. FASEB J 2011.

Read the full monograph

The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, reported research dose ranges, sourcing and quality verification, reconstitution and handling, stack interaction considerations, and a curated reference list. Available as a research-use-only PDF download.

KDC-MN-106

The full reference document is provided strictly for research use only. It reports research dose ranges from the published literature, not instructions for use in humans or animals.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

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Glycine

Abstract

Mechanism of action

Reported research dose ranges

References

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Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

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