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
PQQ benefits: where the science stands
For memory and focus: not settled yet.
On memory and focus, the strongest evidence says it helps (two trials, 84 people in all). As of August 2026, the verdicts on this page rest on evidence from 4 trials, drawn from the strongest research among the 35 papers on PubMed that mention PQQ. Every claim is checked below.
35 papers on PubMed · evidence from 4 trials
Claim by claim
- Memory and focusThe science is still forming. Results lean positive, but there is not much yet.
- CholesterolAlmost no real studies. Nothing clear so far.
- EnduranceAlmost no real studies. Nothing clear so far.
- Weight and body fatAlmost no real studies. Nothing clear so far.
Pairs people ask about
The four sources we read
- 2015Randomized trial · 29 people · no clear effect on cholesterolsource
- 2016Randomized trial · 20 people · benefit for memory and focussource
- 2020Randomized trial · 23 people · no clear effect on endurance; no clear effect on weight and body fatsource
- 2022Randomized trial · 64 people · benefit for memory and focussource
Chosen as the strongest evidence out of 35 papers on PubMed. Every row links to its paper.
Fair questions
Does PQQ work?+
For memory and focus, it is not settled. Results lean positive, but there is not much yet.
Is PQQ safe?+
No caution is recorded on this page. That is not a safety guarantee; the studies we read were not safety trials.
How many studies exist?+
35 on PubMed for PQQ itself; the count is measured from PubMed, not estimated. We read the four strongest and linked every one above.