Nucleo Longevity
it

Glycine

glycine

A simple amino acid studied for sleep quality and, with NAC, for aging biomarkers.

TypeSupplement / dietary

The grade answers: What does the human evidence support for: Sleep, methylation & metabolic support?

Grade

C

Limited

The grade rates evidence quality — it is not advice to take or buy.

Class
Amino acid
Primary use
Sleep, methylation & metabolic support
Evidence strength
low
Last reviewed
2026-07-01

Bottom line

Cheap, safe, with a modest evidence base for sleep quality and a role in the experimental GlyNAC combination. As a stand-alone longevity molecule the human data are thin.

What the evidence says

Glycine is a non-essential amino acid with a few small trials suggesting improved subjective sleep quality and next-day alertness when taken before bed, plus a supporting role in the GlyNAC (glycine + N-acetylcysteine) work aimed at restoring glutathione and mitochondrial markers in older adults. On its own the longevity evidence is early and mechanistic rather than outcome-based. Grade C: safe and mildly useful for sleep, unproven as an aging intervention.

Key studies

  1. [1]

    Glycine before sleep and sleep quality · RCT

    Small improvements in subjective sleep and next-day alertness.

    Open on PubMed ↗
  2. [2]

    GlyNAC (glycine + NAC) and aging markers in older adults · pilot trial

    Improved glutathione and mitochondrial markers in small trials.

    Open on PubMed ↗
  3. [3]

    Glycine metabolism and physiology (review) · review

    Background on its many metabolic roles.

    Open on PubMed ↗
See all studies on PubMed ↗

Mechanism

Acts as an inhibitory neurotransmitter and glutathione precursor, contributes to collagen and creatine synthesis, and may lower core body temperature to aid sleep onset.

Safety

Very well tolerated as a dietary amino acid; high doses may cause mild GI upset. No significant safety concerns at studied intakes.

Dosage context

Sleep studies commonly use ~3 g before bed; GlyNAC protocols use higher, weight-based doses under study conditions. No validated longevity dose exists for glycine alone.

Examples of application

  • Taken ~3 g before bed for sleep quality.
  • Also the glycine half of the experimental GlyNAC combination.
  • Cheap and gentle, not a transformative aging intervention.

From the field

Glycine is the quiet ingredient behind the GlyNAC headlines. On its own it's a reasonable, cheap sleep aid — not the aging reversal the combination studies get spun into.

Related molecules

GlyNAC (glycine + NAC)C
How we assign grades → Method