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Head-to-head evidence comparison — which supplement is right for you?
Glycine and Melatonin are closely matched across evidence, studies, and safety.
Verdict
Likely helps
6 of 6 studies with measurable effects showed benefit.
Top outcomes
Verdict
Likely helps
14 of 19 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (2)
Outcomes where both Glycine and Melatonin have evidence — compare verdict strength side-by-side.
3g before bed
30-60 minutes before bed
Powder (dissolves easily, tastes sweet)
0.5-1mg
30-60 minutes before bed
Immediate-release tablet or sublingual
First night
Next morning
First night
Immediate
Same night
1-3 days
Next morning
First week
The effect of glycine administration on the characteristics of physiological systems in human adults: A systematic review
GeroScience (2024) · Systematic review · n=34
The nervous system demonstrated the most positive effects, including improved psychiatric symptoms from longer-term glycine administration in psychiatric populations.
Glutamatergic drugs for schizophrenia
The Cochrane database of systematic reviews (2006) · Meta analysis · n=132
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.
Ingestion of a Whey Plus Collagen Protein Blend Increases Myofibrillar and Muscle Connective Protein Synthesis Rates
Medicine and science in sports and exercise (2025) · Rct · n=14
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.
Melatonin in cancer treatment
The Cochrane database of systematic reviews (2025) · Meta analysis · n=126
We downgraded the certainty of the evidence because of high risk of bias, small sample size, the width of the 95% confidence interval, and indirectness due to inadequate reporting of cancer type.
Comparative Efficacy, Tolerability, and Acceptability of Donanemab, Lecanemab, Aducanumab, Melatonin, and Aerobic Exercise for a Short Time on Cognitive Function in Mild Cognitive Impairment and Mild Alzheimer's Disease: A Systematic Review and Network Meta-Analysis
Journal of Alzheimer's disease : JAD (2024) · Meta analysis · n=4599
Melatonin may be a better potential disease-modifying treatment for cognitive decline in mild AD and MCI.
Melatonin for sleep disorders in people with autism: Systematic review and meta-analysis
Progress in neuro-psychopharmacology & biological psychiatry (2023) · Meta analysis · n=595
According to the global analysis, the wake after sleep onset and night awakening parameters were not statistically significant.
Based on systematic review showing nervous system benefits. Limited specific RCT data for sleep outcomes. Effects may vary significantly between individuals.
Based on meta-analyses showing 7-12 minute reduction in sleep onset. Higher doses showed diminishing returns and increased morning grogginess. Sublingual forms may be more effective at lower doses.
AI-estimated from published studies. Interpret as directional guidance.
Both Glycine and Melatonin are closely matched — the best choice depends on your specific health goals.
For fix sleep schedule / jet lag, Melatonin has a higher relevance score (98 vs 60).
No known interactions between Glycine and Melatonin have been documented in our database. However, always consult a healthcare provider before combining supplements.