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Gly8.5
Glycine Research
Likely helpsHigh safety
26 peer-reviewed studies
What the evidence says
Likely helps
Glycine appears to help in 6 of 6 studies with measurable effects — the evidence leans clearly favourable.
Most evidence is from high-quality meta-analyses and randomised trials published 2005–2026 with a typical study size of 20 participants.
Based on 26 studies · 5 meta-analyses · 15 RCTs · 1,601 total participants
Confidence
High
What the studies found
6helped· 20 more without graded effect data
By outcome
Therapeutic & clinical
Likely helps8 studies
Sleep & insomniaSignificantly improved deep sleep quality · First night · Reduces core body temperature to promote rapid sleep onset · 30-60 minutes · Improves subjective sleep quality and reduces next-day fatigue · 1-2 weeks
Energy & fatigueLess daytime fatigue from better sleep · 1 week
Mostly mechanism / observational3 studies
Glucose & metabolic
Too few graded studies1 study
Neuroprotection & brain aging
Too few graded studies1 study
Safety profile
Too few graded studies1 study
By the numbers
Pulled from 16 studies with measurable effects
Likely real effects
100%
across studies
People studied
1,601
typical study: 20 people
Strongest designs
20
5 pooled, 15 randomised
Showed benefit
100%
6/6 studies
How long studies ran
1–3 months
1
3+ months
1
Populations Studied
Patients with schizophrenia3
Adults with sleep issues1
Healthy recreationally active young men and women1
General population1
Active research area
16 studies in the last 5 years · Latest meta-analysis: 2025
200520152026
1Overall clinical symptoms in schizophreniaMeta-AnalysisCited 34×n=326 · medium study2020
The meta-analysis suggests that sarcosine may be associated with treatment effect on overall clinical symptoms in patients with schizophrenia but not cognitive functions.
Chang CH et al. · Journal of psychopharmacology (Oxford, England) (2020)
Large benefit
← WorseNo effectBetter →
Likely real
Sarcosine use achieved more significant effects than the use of its comparators in relieving overall clinical symptoms (SMD = 0.51, CI = 0.26-0.76, p < 0.01).
Moreover, studies with the low Positive and Negative Syndrome Scale range of 70-79 showed significant effect size (ES)s of 0.67 (95% CI: 0.03-1.31, p = 0.04).
In addition, trials enrolling patients with stable clinical symptoms had significant ESs: 0.53 (95% CI: 0.21-0.85, p < 0.01).
This systematic-review examined the effects of Glycine.
Soh J et al. · GeroScience (2024)
The nervous system demonstrated the most positive effects, including improved psychiatric symptoms from longer-term glycine administration in psychiatric populations.
While longer-term glycine administration improved sleep in healthy populations, these studies had small sample sizes with a high risk of bias.
Larger and long-term studies with more robust study designs in healthy populations to examine the effects of glycine administration on preventing, delaying or reversing the ageing process are warranted.
Pooled effect sizes were determined with standardized mean differences (SMD), random effects adjusted by false discovery rate, and heterogeneity was examined by I2 statistics.
Other parameters studied were not altered.
Our findings show depletion of the glutamatergic system and emphasize the importance of understanding glutamate-mediated neurotoxicity in AD.
5Effect of glutamatergic drugs on schizophrenia symptomsMeta-AnalysisCited 61×n=132 · medium study2006
In general, all glutamatergic drugs appeared to be ineffective in further reducing positive symptoms of the disease when added to the existing antipsychotic treatment.
Tuominen HJ et al. · The Cochrane database of systematic reviews (2006)
Large benefit
← WorseNo effectBetter →
Likely real
NMDA receptor co-agonists glycine and D-serine showed some effects in reducing the negative symptoms of schizophrenia (n=132, SMD -0.66, CI -1.0 to -0.3, p=0.0004), but the magnitude of the effect was moderate.
Available rating scale data on positive symptoms and cognitive functioning did not indicate a statistically significant effect of glycine or D-serine.
In general, all glutamatergic drugs appeared to be ineffective in further reducing positive symptoms of the disease when added to the existing antipsychotic treatment.
6Negative symptoms of schizophreniaMeta-AnalysisCited 157×n=132 · medium study2005
In the current limited data set, a moderate amelioration of negative symptoms of schizophrenia was found, but no other statistically significant beneficial effects on symptoms of schizophrenia.
Tuominen HJ et al. · Schizophrenia research (2005)
Large benefit
← WorseNo effectBetter →
Likely real
NMDA receptor co-agonists glycine and D-serine are effective in reducing negative symptoms (N = 132, fixed effect model SMD = -0.66, 95% CI -1.02 to -0.29, p = 0.0004) of schizophrenia, the magnitude of the effect is moderate.
D-Cycloserine, a partial agonist of NMDA receptors, is less effective towards negative symptoms (N = 119, fixed effect model SMD = -0.11, 95% CI -0.48 to 0.25, p = 0.6).
Available derived data on cognitive functioning do not indicate a significant effect of glycine or D-serine (N = 80, random effect model WMD = -2.79, 95% CI -6.17 to 0.60, p = 0.11).
7Muscle connective protein synthesis ratesRCTCited 1×n=21 · very small study2025
The ingestion of a single bolus of collagen hydrolysate or free amino acids substantially increases circulating amino acids concentrations, particularly glycine, but does not further increase myofibrillar or muscle connective protein synthesis rates at rest or during recovery from exercise in healthy, recreationally active young men and women.
Aussieker T et al. · Medicine and science in sports and exercise (2025)
8Sleep onset latencyRCTCited 21×n=9 · very small study2023
Data demonstrate that using the proposed blend of novel nutritional ingredients during free living conditions reduced sleep onset latency, increased total sleep duration, and increased sleep efficiency, leading to reduced perceptions of morning sleepiness.
Langan-Evans C et al. · Medicine and science in sports and exercise (2023)
Noticeable benefit
← WorseNo effectBetter →
Likely real
The intervention trial reduced sleep onset latency (-24 ± 25 min; P = 0.002), increased total sleep time (22 ± 32 min; P = 0.01), and increased sleep efficiency (2.4% ± 3.9%; P = 0.03), while also reducing morning sleepiness ( P = 0.02).
Throughout the study, 75% of participants remained blinded to sleep assessment as a primary outcome measure, with 56% subjectively indicating improved sleep during the intervention trial.
Data demonstrate that using the proposed blend of novel nutritional ingredients during free living conditions reduced sleep onset latency, increased total sleep duration, and increased sleep efficiency, leading to reduced perceptions of morning sleepiness.
9Facial skin moisture and elasticityRCTCited 71×2016
This study demonstrated that the use of the collagen hydrolysate with a higher content of Pro-Hyp and Hyp-Gly led to more improvement in facial skin conditions, including facial skin moisture, elasticity, wrinkles and roughness.
Inoue N et al. · Journal of the science of food and agriculture (2016)
This study demonstrated that the use of the collagen hydrolysate with a higher content of Pro-Hyp and Hyp-Gly led to more improvement in facial skin conditions, including facial skin moisture, elasticity, wrinkles and roughness.
11Communication and Symbolic Behavior Scales Developmental ProfileRCTCited 132×n=187 · medium study2023
This rct examined the effects of Glycine.
Neul JL et al. · Nature medicine (2023)
Noticeable benefit
← WorseNo effectBetter →
Likely real
For the key secondary efficacy endpoint, LSM change from baseline to week 12 in the Communication and Symbolic Behavior Scales Developmental Profile Infant-Toddler Checklist Social Composite score was -0.1 versus -1.1 (P = 0.0064; effect size, 0.43).
Common treatment-emergent adverse events included diarrhea (80.6% for trofinetide versus 19.1% for placebo), which was mostly mild to moderate in severity.
Significant improvement for trofinetide compared with placebo was observed for the coprimary efficacy endpoints, suggesting that trofinetide provides benefit in treating the core symptoms of Rett syndrome.
In conclusion, whey protein supplementation enhances whole body anabolism, and may improve acute recovery of exercise performance after a strenuous bout of resistance exercise.
West DWD et al. · Nutrients (2017)
Net protein balance tended to improve in PRO (P = 0.064; effect size (ES) = 0.61, PRO vs.
Over 24 h, net balance was enhanced in PRO (P = 0.036) but not in CHO (P = 0.84; ES = 0.69, PRO vs.
At 10 h, there were small-to-moderate effects for enhanced recovery of the MVC (ES = 0.56), mean power (ES = 0.49), and CMJ variables (ES: 0.27-0.49) in PRO.
CP supplementation did not influence sleep quantity, latency, or efficiency, but reduced awakenings and improved cognitive function in physically active males with sleep complaints.
Thomas C et al. · European journal of nutrition (2024)
CP supplementation did not influence sleep quantity, latency, or efficiency, but reduced awakenings and improved cognitive function in physically active males with sleep complaints.
Ingestion of a whey (25 g) plus collagen (5 g) protein blend increases both myofibrillar and muscle connective protein synthesis rates at rest and further increases myofibrillar but not muscle connective protein synthesis rates during recovery from exercise in recreationally active, young men.
Aussieker T et al. · Medicine and science in sports and exercise (2025)
In addition, myofibrillar protein synthesis rates were higher in BLEND compared with PLA in both the rested (0.038 ± 0.008 and 0.031 ± 0.006%·h -1 , respectively; P < 0.05) and exercised (0.052 ± 0.011 and 0.039 ± 0.009%·h -1 , respectively; P < 0.01) leg.
Muscle connective protein synthesis rates were higher in BLEND compared with PLA in the rested (0.062 ± 0.013 and 0.051 ± 0.010%·h -1 , respectively; P < 0.05), but not the exercised (0.090 ± 0.021 and 0.079 ± 0.016%·h -1 , respectively; P = 0.11) leg.
Ingestion of a whey (25 g) plus collagen (5 g) protein blend increases both myofibrillar and muscle connective protein synthesis rates at rest and further increases myofibrillar but not muscle connective protein synthesis rates during recovery from exercise in recreationally active, young men.
16Collagen synthesisRCTCited 143×n=8 · very small study2017
These data suggest that adding gelatin to an intermittent exercise program improves collagen synthesis and could play a beneficial role in injury prevention and tissue repair.
Shaw G et al. · The American journal of clinical nutrition (2017)
These data suggest that adding gelatin to an intermittent exercise program improves collagen synthesis and could play a beneficial role in injury prevention and tissue repair.
This trial was registered at the Australian New Zealand Clinical Trials Registry as ACTRN12616001092482.
17Glutathione deficiency and oxidative stressRCTCited 118×n=12 · very small study2023
GlyNAC supplementation in OA for 16-weeks was safe and well-tolerated.
Kumar P et al. · The journals of gerontology. Series A, Biological sciences and medical sciences (2023)
GlyNAC supplementation in OA for 16-weeks was safe and well-tolerated.
By combining the benefits of glycine, NAC and GSH, GlyNAC is an effective nutritional supplement that improves and reverses multiple age-associated abnormalities to promote health in aging humans.
Song Y et al. · Diabetes, obesity & metabolism (2026)
In addition to modulating the aging process, urea cycle amino acids exhibit altered levels in kidney diseases and frequently serve as indicators of disease severity.
Furthermore, we propose several promising therapeutic strategies, including nutritional interventions directed at specific amino acids and pharmacological therapies that target the modulation of amino acid metabolism.
The relationship between amino acid availability and aging in kidney disease is not merely linear but involves a complex and dynamic interplay.
19Muscle preservation and sarcopenia managementSystematic Review2026
Medicinal plants offer a multifaceted approach to muscle preservation, with promising relevance for aging, metabolic dysfunction, and disease-related sarcopenia.
Yazdanpanah Z et al. · Phytomedicine : international journal of phytotherapy and phytopharmacology (2026)
Medicinal plants offer a multifaceted approach to muscle preservation, with promising relevance for aging, metabolic dysfunction, and disease-related sarcopenia.
Despite robust preclinical evidence, clinical translation is limited by methodological variability and dosing challenges.