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Head-to-head evidence comparison — which supplement is right for you?
5-HTP vs Glycine: Glycine has the stronger overall evidence (6.5 vs 5.5/10); they're alternatives for perceived sleep quality — the best pick depends on your goals. Take the 60-second quiz for a pick tailored to your goals.
Glycine wins 3 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Too few graded studies
0 of 1 studies with measurable effects showed benefit.
Top outcomes
Verdict
Too few graded studies
1 of 2 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (2)
Outcomes where both 5-HTP and Glycine have evidence — compare verdict strength side-by-side.
50-100mg for sleep; 150-300mg for mood (a typical label dose. The cited 100-300 mg study tested tolerability in 15 healthy men also given carbidopa, not mood)
For sleep: 30-45 minutes before bed, For mood: 2-3 divided doses with meals
Capsules
3g before bed (no cited trial states the dose it used)
30-60 minutes before bed
Powder (dissolves easily, tastes sweet)
and 6 more not shown
2-4 weeks
1-2 weeks
2-4 weeks
First 1-2 weeks
First few nights
Next morning
Immediate
Early pharmacological interventions for universal prevention of post-traumatic stress disorder (PTSD)
The Cochrane database of systematic reviews (2022) · Systematic review · n=2023
Cochrane review of 13 randomised trials in 2,023 adults exposed to a traumatic event, testing eight drug or nutritional interventions for universal PTSD prevention, 5-hydroxytryptophan among them.
Combination pharmacotherapy for the treatment of fibromyalgia in adults
The Cochrane database of systematic reviews (2018) · Systematic review · n=1474
Cochrane review of 16 trials in 1,474 adults with fibromyalgia testing combinations of drugs, one of which combined a monoamine oxidase inhibitor with 5-hydroxytryptophan in 200 participants.
The Impact of 5-Hydroxytryptophan Supplementation on Cognitive Function and Mood in Singapore Older Adults: A Randomized Controlled Trial
Nutrients (2025) · Rct · n=30
Results: A significant time effect was observed in the MoCA score, which was mainly explained by a significant increase in the 5-HTP group (week 0 vs. week 12: 26.6 ± 1.4 a.u. vs. 27.6 ± 1.4 a.u., p < 0.05).
The effect of glycine administration on the characteristics of physiological systems in human adults: A systematic review
GeroScience (2024) · Systematic review
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=358
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=28
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.
Glycine has a higher evidence score (6.5/10 vs 5.5/10) and wins in 3 of 3 categories.
For perceived sleep quality, Glycine has a higher relevance score (95 vs 68).
No documented interaction was found in the data searched. This does not establish that this exact combination is safe.
Saffron, EPA omega-3, SAMe have real adjunct evidence — but these aren’t a substitute for care, and some interact dangerously.
Ashwagandha, L-theanine, magnesium, saffron — what actually helps stress, and the safety caveats.
When to take what, with or without food, and which supplements compete vs pair well.
Melatonin, magnesium, glycine, L-theanine — tiered by evidence, plus a wind-down timeline.
The right pick depends on your goals. Answer a few quick questions for a personalised recommendation — or dig into the full evidence on each.