Tier 2 — strong

The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers

Bannai M, Kawai N, Ono K, Nakahara K, Murakami N
Frontiers in neurology 2012 3:61

Bibliography

PubMed
PMID 22529837
PubMed Central
PMC3328957
DOI
10.3389/fneur.2012.00061
Funding
Partly supported by the PROBRAIN program. The study involved Ajinomoto investigators and employee volunteers.
Competing interests
The authors reported no conflicts; Ajinomoto affiliations and recruitment of employee volunteers are relevant context.

Study snapshot

DesignRandomized controlled human intervention
ModelAdult humans
Sample10 men enrolled; 7 included in the final analysis
InterventionGlycine 3 g 30 minutes before bed versus flavored placebo; time in bed reduced by 25%
Duration3 consecutive nights per crossover condition
EndpointsSubjective fatigue and sleepiness; Psychomotor vigilance; Memory and reaction-time tasks

What the study showed, in plain terms

In this small sleep-restriction experiment, bedtime glycine improved selected next-day fatigue and vigilance measures. The experiment tested short-term resilience to curtailed sleep, rather than treatment of chronic insomnia.

Key findings

  • Only seven participants contributed to the main analysis.
  • Selected fatigue and vigilance outcomes favored glycine; not every performance measure improved.
  • The publication also includes separate rat experiments, which are not additional human trial participants.

What this study can and cannot tell us

Single-blind design, very small male-only sample, multiple outcomes and short follow-up limit confidence.

Participants were Ajinomoto employees; results do not establish that glycine compensates for sustained sleep deprivation.

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Editorial review

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