Amino acid / NMDA co-agonist

Plain-language summaryIntrigue 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. Used as a sleep aid (3 grams before bed) 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 Kodiac editorial, not peer-reviewed.

Our opinion on this compoundBasic amino acid

29/100

Foundational amino acid with interesting longevity angles that haven’t moved beyond rodents

Glycine is as basic as it gets. The simplest proteinogenic amino acid, it shows up everywhere in biology: glycinergic inhibitory neurotransmission, hepatic conjugation reactions, heme precursor synthesis, structural collagen content. Its ubiquity is also the problem. When evaluating a compound as a serious research target, “it does a lot of things reasonably well” isn’t a ringing endorsement. It’s a description of a nutrient.

The two angles that generate any real interest here are the methionine restriction mimetic story and the NMDA glycine-site co-agonism. We think the methionine restriction angle is genuinely interesting biology. Methionine restriction reliably extends lifespan in rodents, and the mechanism involves suppressed methionine flux through the transmethylation pathway. Glycine supplementation at 5-10 g/day can shift that flux by enhancing one-carbon transfer reactions, producing a metabolic phenotype that approximates dietary methionine restriction without actually restricting methionine intake. The Brind group published the core preclinical rationale around 2011, and subsequent work has continued to support the rodent model. The problem is that its been well over a decade and human longevity data is essentially nonexistent. This is a promising story in mice that hasnt moved.

The NMDA co-agonist angle is less exciting than it sounds. Glycine binds the modulatory glycine site on NMDA receptors, the same site targeted by more interesting compounds like D-cycloserine or GLYX-13. Bannai et al. (2012) showed 3 g before bed improved subjective sleep quality and reduced daytime sleepiness in a small Japanese cohort. Real effect, real mechanism, modest replication in subsequent work. But as a probe for NMDA biology, glycine is outclassed by D-serine, which carries roughly three-fold higher affinity at GluN2B-containing receptors, and by more selective pharmacological tools developed since. You’d use glycine here only if cost and sourcing are the binding constraints.

Differentiation is the core issue. Glycine is priced at pennies per gram, freely available from dozens of food-grade suppliers, and studied across hundreds of labs over decades. There’s no axis where it clearly bests alternatives. For NMDA research, D-serine and GLYX-13 are better probes. For longevity and methionine restriction work, alpha-ketoglutarate and caloric restriction mimetics are further along the clinical pipeline. For sleep, there are more studied interventions.

Honestly, we don’t see a compelling case for adding glycine to a serious research stack unless you’re specifically interrogating one-carbon metabolism or building a methionine restriction mimetic protocol where cost is a real constraint. Even then, the frontier work is upstream of glycine, not in it. It’s a supporting player, not a lead compound.

Novelty: 18
Mechanism promise: 32
In-category differentiation: 18
Evidence quality: 40
Translational signal: 38
Research bench value: 40

Rationale Glycine scores below the basic-aa cap on its own merits: the methionine restriction mimetic story is real but over a decade old with no human longevity data, the NMDA glycine-site angle is outclassed by more selective probes, and differentiation across all categories is essentially zero. Calculated overall of 29 falls under the 32 cap, so the cap doesn’t bind, but the category classification stands.

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 at 3-gram bedtime doses. Doses for sleep are 3 grams orally; doses for methionine restriction mimetic effects are 5 to 10 grams per day; the compound is exceptionally safe with rare adverse events.

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The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, sourcing and quality verification, and a curated reference list. Embedded inline below; download for offline reading.

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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.

Tag: Amino acid / NMDA co-agonist

Glycine

Abstract

Read the full monograph