Full profile
| Best for | Sleep quality support (evening use) · Next-day alertness |
|---|---|
| Evidence grade | Emerging — Emerging — mostly preclinical or preliminary human data |
| Studied dose range | 3 g, taken shortly before sleep. |
| Time to effect | Same-night sleep-quality effect; next-day alertness follows. |
| Best form | Plain glycine powder or capsules. |
Evidence, honestly graded
Leans toward a B-minus on the strength of a replicated sleep-quality and next-day-alertness signal, but the trial base is concentrated with Ajinomoto (the amino-acid manufacturer funding most of the research), so it's held at Emerging pending more independent replication. Positioned for an evening slot, not daytime — this is not a daytime cognitive active.
See the full grading rubric — study type, replication, population match, and dose adequacy — in The Evidence Standard.
Side effects
- Very safe
- Mild GI upset at high doses in some users
Interactions
- No material known interactions
Stacks well with
- Magnesium (evening slot, sleep-adjacent)
What to look for on a label
- Position explicitly as an evening/pre-sleep ingredient — do not group it with daytime focus actives.
References
- Bannai M, Kawai N, Ono K, Nakahara K, Murakami N (2012). Frontiers in Neurology, 3:61Reduced daytime fatigue/sleepiness and improved psychomotor vigilance the next day.
- Yamadera et al. (2007); Inagawa et al. (2006) — glycine and subjective sleep quality. Earlier small crossover trials reporting improved subjective sleep quality (with polysomnographic correlates) at 3 g pre-sleep. Sleep Biol Rhythms; both Ajinomoto-linked — the single-manufacturer concentration is the reason the grade is held at Emerging rather than B despite the replicated direction of effect.
Entries above without a linked identifier are either editorial summaries of a wider body of literature or references to a named authority (a regulator or government monograph) cited by name rather than by a single paper.
Grades and studied doses are our conservative reading of the human research, shown for education. They are not product claims, and a studied dose is not a recommended dose.
Revision history
Every change to this ingredient's evidence status, dated and explained. The full cross-library log lives at Evidence Updates.
- 2026-07-07New profile
Initial profile published at Grade Emerging: a replicated pre-sleep sleep-quality and next-day-alertness signal, held below B because the trial base is concentrated with a single amino-acid manufacturer.
See how Glycine compares on grade, dose, and goal in the Evidence Explorer.
