Glycine
Research reviewed: Up until 03/2026
Glycine is a dietary supplement with 11 published peer-reviewed studies involving 580 participants, researched for Sleep Quality, Metabolic Health, Cognitive Function.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Sleep Quality
StrongMetabolic Health
StrongCognitive Function
StrongResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Sleep Quality
To evaluate the effect of glycine on sleep quality in humans with poor sleep
Study Type
Randomised, double-blind, placebo-controlled, crossover
Purpose
To evaluate the effect of glycine on sleep quality in humans with poor sleep
Dose
3 g glycine before bed
Participants
11 volunteers with poor sleep
Duration
3 nights crossover
Results
Glycine significantly improved subjective sleep quality, sleep latency, and reduced fatigue next day.
How They Measured It
Polysomnography, PSQI, fatigue VAS
To evaluate the effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers
Study Type
Randomised, single-blind, crossover
Purpose
To evaluate the effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers
Dose
3 g/day glycine
Participants
20 healthy adults
Duration
3 nights
Results
Glycine significantly reduced daytime sleepiness and improved cognitive performance after sleep restriction.
How They Measured It
Psychomotor vigilance task, sleepiness scale, cognitive tests
To assess glycine supplementation on sleep quality in adults with chronic insomnia
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To assess glycine supplementation on sleep quality in adults with chronic insomnia
Dose
3 g before bedtime
Participants
30 adults with insomnia
Duration
4 weeks
Results
Significant improvements in PSQI scores, sleep efficiency, and total sleep time vs placebo.
How They Measured It
PSQI, sleep diary, actigraphy
Metabolic Health
To evaluate glycine supplementation on insulin secretion and glycaemic control in prediabetes
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate glycine supplementation on insulin secretion and glycaemic control in prediabetes
Dose
5 g 3x daily with meals
Participants
60 prediabetic adults
Duration
3 months
Results
Glycine significantly improved insulin secretion and postprandial glucose response vs placebo.
How They Measured It
Insulin secretion (C-peptide), blood glucose, HbA1c
To assess glycine supplementation effect on oxidative stress in metabolic syndrome patients
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To assess glycine supplementation effect on oxidative stress in metabolic syndrome patients
Dose
15 g/day glycine
Participants
60 metabolic syndrome patients
Duration
3 months
Results
Significant reduction in oxidative stress markers and CRP; improved antioxidant capacity vs placebo.
How They Measured It
MDA, antioxidant enzymes, CRP, IL-6
To investigate glycine supplementation effects on liver function in NAFLD patients
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To investigate glycine supplementation effects on liver function in NAFLD patients
Dose
3 g 3x daily
Participants
45 NAFLD patients
Duration
6 months
Results
Significant reduction in liver enzymes and hepatic steatosis grade vs placebo.
How They Measured It
Liver enzymes (ALT, AST), liver fat by ultrasound
To assess glycine and N-acetylcysteine combination on glutathione production in elderly
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To assess glycine and N-acetylcysteine combination on glutathione production in elderly
Dose
1.33 mmol/kg/day glycine + NAC
Participants
16 elderly adults
Duration
24 weeks
Results
GlyNAC supplementation restored glutathione levels and significantly improved muscle strength and cognition.
How They Measured It
Erythrocyte glutathione, oxidative stress, muscle strength
Cognitive Function
To evaluate glycine effects on working memory and psychomotor function
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate glycine effects on working memory and psychomotor function
Dose
100 mg/kg body weight
Participants
32 healthy adults
Duration
Acute dose crossover
Results
Glycine significantly improved working memory performance and reaction time vs placebo.
How They Measured It
Cognitive tests, psychomotor performance
To investigate glycine supplementation on schizophrenia symptoms
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To investigate glycine supplementation on schizophrenia symptoms
Dose
0.8 g/kg/day glycine
Participants
22 schizophrenia patients
Duration
6 weeks
Results
Glycine significantly improved negative symptoms of schizophrenia and cognitive performance.
How They Measured It
PANSS, BPRS cognitive subscale
To assess the effect of GlyNAC on multiple hallmarks of aging in older adults
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To assess the effect of GlyNAC on multiple hallmarks of aging in older adults
Dose
Glycine 7.1 g + NAC 8 g daily
Participants
25 older adults
Duration
24 weeks
Results
GlyNAC improved glutathione, mitochondrial function, oxidative stress, and multiple aging biomarkers.
How They Measured It
Mitochondrial function, oxidative stress, inflammation, cognition, muscle strength
To evaluate glycine effect on collagen synthesis and skin quality
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate glycine effect on collagen synthesis and skin quality
Dose
3 g/day glycine
Participants
50 healthy women
Duration
12 weeks
Results
Glycine supplementation significantly improved skin hydration, elasticity, and collagen synthesis markers.
How They Measured It
Skin elasticity (cutometry), collagen biomarkers
Frequently Asked Questions
Common questions about Glycine research
There are currently 11 peer-reviewed studies on Glycine (Glycine), involving 580 total participants. Research covers Sleep quality, Metabolic health, Cognitive function. The overall evidence strength is rated as Very Strong.
The evidence is currently rated as "Very Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (11 human studies), and reported outcomes.
Glycine has been researched for: Sleep quality, Metabolic health, Cognitive function. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 11 out of 11 studies are human trials. Human trials carry more weight in our evidence scoring system.
Similar Supplements
Other supplements researched for similar health goals
