Tier 2 — strong

Subjective effects of glycine ingestion before bedtime on sleep quality

Inagawa K, Hiraoka T, Kohda T, Yamadera W, Takahashi M
Sleep and Biological Rhythms 2006 4(1):75-77

Bibliography

DOI
10.1111/j.1479-8425.2006.00193.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
Sample19 women with complaints about sleep quality
InterventionGlycine 3 g before bed versus flavored placebo
Duration4-day crossover study
EndpointsMorning fatigue; Subjective alertness; Sleep questionnaires

What the study showed, in plain terms

This early sleep study reported improvements in selected morning feelings after bedtime glycine. Its principal evidence is subjective, with a small, brief crossover sample.

Key findings

  • Morning fatigue and selected alertness-related questionnaire items favored glycine.
  • The trial did not establish long-term treatment of chronic insomnia.

What this study can and cannot tell us

Small female-only sample, multiple subjective outcomes and brief follow-up.

Several authors were affiliated with Ajinomoto; independent replication remains important.

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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