Does glycine improve daytime sleepiness, fatigue, and performance in sleep-restricted healthy subjects, and does it affect circadian rhythms?
Front Neurol · 2012 · PMID 22529837 · DOI 10.3389/fneur.2012.00061
Glycine supplementation can reduce daytime sleepiness and fatigue and improve vigilance after acute sleep restriction, possibly by modulating SCN function.
The question
Does glycine improve daytime sleepiness, fatigue, and performance in sleep-restricted healthy subjects, and does it affect circadian rhythms?
What they tested
Glycine may improve sleep quality and reduce daytime sleepiness and fatigue, potentially by modulating circadian rhythms.
How they did it
Healthy subjects with sleep restricted to 25% less than usual for three nights ingested 3g of glycine or placebo before bedtime. Daytime sleepiness and fatigue were assessed using a visual analog scale (VAS) and a questionnaire. Performance was evaluated using a PC performance test program. Additionally, plasma melatonin and the expression of circadian-modulated genes in the rat suprachiasmatic nucleus (SCN) were measured to assess effects on circadian rhythms.
What they found
In subjects given glycine, VAS data showed a significant reduction in fatigue and a tendency toward reduced sleepiness. The questionnaire also indicated improved daytime sleepiness and fatigue. PC performance tests revealed significant improvement in psychomotor vigilance. Glycine did not significantly affect plasma melatonin concentrations or the expression levels of clock genes like Bmal1 and Per2. However, a glycine-induced increase in neuropeptides arginine vasopressin and vasoactive intestinal polypeptide was observed in the light period.
What it means
Glycine improves daytime sleepiness and fatigue induced by acute sleep restriction and enhances psychomotor vigilance. While it did not alter the circadian clock directly, glycine modulated SCN function by increasing certain neuropeptides, which may indirectly contribute to its beneficial effects on sleepiness and fatigue.
Limitations
The study involved acute sleep restriction and did not observe direct alterations in the circadian clock itself, suggesting an indirect mechanism for glycine's effects on sleepiness and fatigue.
The paper at a glance
| Magellan’s evidence label | collagen and methylation substrate (our label for this citation — see PubMed for the paper’s own title and authors) |
|---|---|
| Journal | Front Neurol |
| Year | 2012 |
| PMID | 22529837 ↗ |
| DOI | 10.3389/fneur.2012.00061 ↗ |
| Topic | Sleep, circadian rhythm & stress |
Read the source: PubMed record (authors, abstract, full citation) ↗ · Publisher via doi.org ↗
Where Magellan uses this paper
This citation sits behind the evidence grade on the pages below. Grades are set from the research and are independent of affiliate commissions.
Glycine Powder
Small human trials report that about 3 g of glycine before bedtime improves subjective sleep quality and reduces next-day fatigue and sleepiness after partial sleep restriction, with mechanistic work attributing these effects to NMDA-receptor-mediated thermoregulation in the suprachiasmatic nucleus;
All-in-One Longevity Formulation
Several of NOVOS Core's ingredients have genuine, though mostly early-stage, human or animal evidence relevant to aging: trials of GlyNAC (glycine plus N-acetylcysteine) improved oxidative stress, mitochondrial function, strength and walking performance in older adults — though at glycine doses far above what the…
NOVOS Core is a multi-ingredient dietary supplement marketed for longevity that combines about a dozen…
Glycine is the smallest and simplest proteinogenic amino acid, synthesized endogenously but often in…
Research describes the compound or intervention studied. It is not a claim about any specific product.
Molecules & mechanisms in this paper
Each of these is named in the paper’s own words above. Open the monograph for the full mechanism and its other citations.
Cite this page
These citations point at this summary. To cite the original paper with its full author list, use the PubMed record or doi.org.
Magellan Longevity. (2026). Does glycine improve daytime sleepiness, fatigue, and performance in sleep-restricted healthy subjects, and does it affect circadian rhythms? [Plain-English summary of Front Neurol 2012, PMID 22529837, DOI 10.3389/fneur.2012.00061]. Magellan Longevity. https://magellanlongevity.com/study/s125.html@misc{magellan_s125,
title = {Does glycine improve daytime sleepiness, fatigue, and performance in sleep-restricted healthy subjects, and does it affect circadian rhythms?},
author = {{Magellan Longevity}},
year = {2026},
howpublished = {\url{https://magellanlongevity.com/study/s125.html}},
note = {Plain-English summary of PubMed PMID 22529837; DOI 10.3389/fneur.2012.00061; Front Neurol 2012. Reviewed by Gabriel Radu, DO},
urldate = {2026-08-11}
}https://magellanlongevity.com/study/s125.htmlRelated studies in the Magellan library
- Supplementing Glycine and N-Acetylcysteine (GlyNAC) in Older Adults Improves Glutathione…The Journals of Gerontology: Series A · 2022 · PMID 35975308
- New Functions and Potential Applications of Amino AcidsAdv Biochem Eng Biotechnol · 2017 · PMID 27872968
- GlyNAC supplementation in older adults improves glutathione deficiency, oxidative stress…Clin Transl Med · 2021 · PMID 33783984
- Caloric restriction, resveratrol and melatonin: Role of SIRT1 and implications for aging and…Mechanisms of Ageing and Development · 2015 · PMID 25824609
- Systematic review of light exposure impact on human circadian rhythmChronobiology International · 2019 · PMID 30311830
- Effects of Organic Light-Emitting Diodes on Circadian Rhythm and SleepPsychiatry Investig · 2021 · PMID 33993687
All 23 Magellan summaries on sleep, circadian rhythm & stress →
Prefer the interactive version? Open this summary in the Magellan app → · Browse all 314 study summaries →