What do the states mean?+
- Solid: well studied, and it works.
- Half-there: the science is still forming.
- A ghost: almost no real studies.
- Hollow: well studied, and it does not work.
- A cord: the pair itself has been tested together.
- Air: nobody has ever tested this pair.
The full scoring method: How we score
Glycine benefits: where the science stands
For sleep: not settled yet.
Sleep is what most people take glycine for, and the strongest evidence says it helps (a combined review). As of August 2026, the verdicts on this page rest on evidence from 2 trials, drawn from the strongest research among the 1,622 papers on PubMed that mention glycine. Every claim is checked below.
1,622 papers on PubMed · evidence from 2 trials · 1 caution
Claim by claim
- SleepThe science is still forming. Results lean positive, but there is not much yet.
- Blood pressureThe science is still forming. Results lean positive, but there is not much yet.
Pairs people ask about
The two sources we read
- 2013Randomized trial · 60 people · benefit for blood pressuresource
- 2024Meta-analysis · benefit for sleepsource
Chosen as the strongest evidence out of 1,622 papers on PubMed. Every row links to its paper.
Fair questions
Does glycine work?+
For sleep, it is not settled. Results lean positive, but there is not much yet.
Is glycine safe?+
One caution is recorded: Glycine is widely sold as a sleep aid. The human trials behind that come from one research group at Ajinomoto, an amino acid manufacturer, and are described in the company’s own review rather than pooled by independent analysts. We found no independent meta-analysis of glycine for sleep, so there is nothing here we can score.
Why only 2 sources, when PubMed lists 1,622?+
The 1,622 is every paper that mentions glycine in any way: animal studies, blood measurements, papers where it is a side note. The strongest sources are combined reviews, and each one already gathers every trial its authors could find. Our 2 cover 2 trials between them, and every one is linked above. Both counts are measured, not estimated.