Glycine and Sleep Quality
Yes, taking glycine (3 grams) before bedtime can improve subjective sleep quality and reduce sleep fragmentation, though the evidence base is limited to small studies in specific populations.
Evidence for Glycine's Sleep Benefits
The available research demonstrates modest but consistent benefits of glycine supplementation on sleep parameters:
Subjective Sleep Quality Improvements
- Glycine (3g before bedtime) significantly improved subjective sleep quality in individuals with insomniac tendencies and reduced daytime fatigue in sleep-restricted healthy volunteers 1, 2.
- In physically active males with sleep complaints, glycine-rich collagen peptides (15g containing approximately 3-4g glycine) reduced both objective awakenings measured by polysomnography (21.3 vs. 29.3 awakenings) and subjective awakenings over 7 nights 3.
Proposed Mechanism of Action
- Glycine appears to work by decreasing core body temperature through increased cutaneous blood flow, which facilitates sleep onset since the initiation of sleep naturally involves core temperature reduction 1.
- Oral glycine administration increases both plasma and cerebrospinal fluid glycine concentrations, suggesting central nervous system penetration 1.
- Glycine may modulate neuropeptides in the suprachiasmatic nucleus (SCN) without directly altering circadian clock genes, potentially contributing to improved sleep quality 2.
Cognitive and Performance Benefits
- Beyond sleep improvements, glycine supplementation improved psychomotor vigilance and cognitive function (Stroop test performance) the morning after sleep restriction 2, 3.
- Daytime sleepiness and fatigue were reduced following glycine supplementation in sleep-restricted individuals 2.
Practical Dosing Protocol
The evidence-based dosing protocol is 3 grams of glycine taken 1 hour before bedtime 1, 2. Alternatively, 15 grams of glycine-rich collagen peptides (providing approximately 3-4g glycine) can be used 3.
Important Caveats and Context
Limited Evidence Base
- The research on glycine for sleep consists primarily of small studies (n=13-19 participants) in specific populations (individuals with mild sleep complaints, sleep-restricted volunteers, athletic males) 1, 2, 3.
- No major clinical practice guidelines currently recommend glycine as a sleep intervention, as the evidence base remains preliminary 4.
Comparison to Established Sleep Interventions
While glycine shows promise, evidence-based sleep hygiene practices remain the foundation of sleep improvement and should be implemented first:
- Maintain consistent sleep-wake schedules, even on weekends 4.
- Seek bright light exposure during the day (especially morning) and avoid bright light at night 4.
- Keep the bedroom cool, dark, and comfortable 4.
- Avoid caffeine at least 6 hours before bedtime and avoid nicotine and alcohol close to bedtime 4.
- Limit electronic device use before bed (except diabetes management devices if applicable) 4.
- Exercise regularly during the day, as physical activity shows moderate evidence for improving sleep onset, duration, and efficiency, with evening exercise generally not impairing sleep unless vigorous intensity within 1 hour of bedtime 4.
When to Consider More Established Interventions
- For clinically significant insomnia, cognitive behavioral therapy for insomnia (CBT-I) has stronger evidence than glycine and should be the first-line treatment 4.
- Melatonin has more extensive research supporting its use for sleep onset, duration, and efficiency, with established dosing protocols (0.5mg 3-4 hours before bed for circadian phase advance, or 1-5mg 30 minutes before bed for sedation depending on age) 4.
Clinical Bottom Line
Glycine supplementation (3g before bedtime) represents a low-risk, potentially beneficial adjunct for individuals with mild sleep complaints who have already optimized sleep hygiene practices 1, 2, 3. However, it should not replace evidence-based sleep hygiene education or more established interventions like CBT-I for clinically significant sleep disorders 4. The supplement appears safe with no reported adverse effects in the available studies, making it a reasonable trial for motivated patients seeking additional sleep support beyond behavioral modifications 1, 2, 5, 6.