The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers.
Level 3 - non-randomized controlled study
Placebo-controlled human trial (randomization not specified) combined with animal mechanism study.
PubMed 22529837 · doi:10.3389/fneur.2012.00061
What was done
Healthy volunteers underwent 25% sleep restriction for three consecutive nights and ingested 3 g of glycine or placebo before bedtime. Subjective daytime sleepiness and fatigue were assessed using visual analog scales (VAS) and questionnaires, and performance was evaluated using a personal computer psychomotor vigilance test. In a parallel animal study, plasma melatonin and suprachiasmatic nucleus (SCN) clock gene and neuropeptide expression were measured in rats.
What was found
The abstract provides no numerical data, confidence intervals, or exact p-values. It reports that glycine ingestion significantly reduced VAS fatigue scores and showed a tendency toward reduced sleepiness compared to placebo, alongside significant performance improvement on the psychomotor vigilance test. In rats, glycine did not alter plasma melatonin or clock genes (Bmal1, Per2), but increased light-period SCN expression of arginine vasopressin and vasoactive intestinal polypeptide.
Why it matters
These findings suggest that oral glycine before sleep may alleviate daytime neurobehavioral fatigue caused by acute partial sleep restriction.
Limits
The abstract does not report sample size, participant demographics, blinding, or whether allocation was randomized. No numerical outcomes or effect sizes are provided. The model evaluates only short-term (three-day) partial sleep restriction in healthy individuals rather than clinical insomnia.
Cited by
- supports Glycine promotes relaxation and supports sleep.