Tier 2 — strong

Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes

Yamadera W, Inagawa K, Chiba S, Bannai M, Takahashi M, Nakayama K
Sleep and Biological Rhythms 2007 5(2):126-131

Bibliography

DOI
10.1111/j.1479-8425.2007.00262.x
Funding
A separate funding statement was not available in the publisher abstract. Several investigators were affiliated with Ajinomoto.
Competing interests
Ajinomoto affiliations are disclosed in the publisher record. A separate competing-interest declaration was not available in the abstract.

Study snapshot

DesignRandomized controlled human intervention
ModelAdult humans
Sample11 adults with persistent unsatisfactory sleep
InterventionGlycine 3 g about 1 hour before bed versus placebo
DurationTwo-night crossover experiment
EndpointsPolysomnographic sleep latency; Subjective sleep quality; Daytime sleepiness; Memory recognition

What the study showed, in plain terms

This small crossover experiment combined sleep questionnaires with polysomnography. It reported selected sleep-onset and next-day benefits without changing the overall architecture of sleep.

Key findings

  • Latency to sleep onset and slow-wave sleep shortened in the reported analysis.
  • Subjective quality and selected next-day measures favored glycine.
  • Sleep architecture did not significantly change.

What this study can and cannot tell us

Only eleven participants and very short observation.

Single-blind design and manufacturer-affiliated investigators limit certainty; the original issue year is 2007 despite a later publisher-platform migration date.

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Editorial review

Reviewed by the Biohack Blueprint research team

Last verified

Dr. Khaled Mahmoud, MBBChCritical Care Medicine, Longevity Science & Editorial Direction