3/5
Moderate
evidence
Sleep / recovery evidence brief
Glycine
Small human sleep and next-day fatigue studies suggest glycine can help some users feel better rested; gym benefits would be indirect.
Headline Finding
Small 3 g bedtime crossover trials improved subjective sleep quality, daytime fatigue, or next-day alertness.
Dose Context
Human sleep studies often use about 3 g before bed; collagen or protein intake is not equivalent.
Important Caveat
Reasonable as a sleep-adjacent ingredient, but not as a muscle-building, tendon-repair, or direct performance supplement.
Source Drawer
Linked Research
- Review Human sleep review
- Trial Daytime performance trial
- Review Performance/recovery update
- Systematic review Physiological systems systematic review
- Review Sleep mechanism review
- Meta-analysis Sleep supplements meta-analysis
How To Read This Rating
The score reflects evidence that the supplement does its stated job. Some jobs are direct, such as strength, endurance, or recovery; others are indirect, such as sleep, mood, appetite, or health support. A real effect can still receive a cautious practical rating when dose, safety, product quality, or audience fit remain uncertain.
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