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PQQ (pyrroloquinoline quinone) and attention: grade C

Limited evidence. Direction: Benefit.

Evidence maturity: EmergingIndustry-fundedShort-term only

Educational guidance, not medical advice

Why this grade

Rubric condition met: Two small RCTs with industry-employed authors, positive on attention measures (C); not B under the B rule (each under 100 participants, both industry-linked)

In 41 healthy older adults, 20 mg/day of BioPQQ for 12 weeks produced a smaller change in Stroop interference (a measure of selective attention) than placebo, in a trial co-authored by a Mitsubishi Gas Chemical researcher. The Ryusendo-funded trial of 64 adults also reported better complex attention scores. Both trials are small, industry-linked and short, so the grade is C.

How sure are we?

Evidence maturity: Emerging Cognitive RCTs from two different maker companies.

Tested as: PQQ disodium salt

Who paid for the studies
All industry-funded
Risk of bias
Some concerns. Abstracts do not state which cognitive outcome was primary (D5 some concerns); Tamakoshi 2023 gives no sample size or primary outcome.
Trial registry check
Not checked yet
Outcome measured
A test score, rating scale or performance measure
Who was studied
Older adults only
Doses used in studies
20-21.5 mg a day
  • Could rise: Would move to B with an independent, preregistered RCT of at least 100 adults positive on a prespecified primary outcome.
  • Could fall: Would move to C none if such a trial were null.

Science is provisional. This grade reflects the evidence we found as of . Next review: .

Maturity sits beside each grade. The grade says what the evidence shows; maturity says how much of it there is and how well it is confirmed.

Established
many trials from several independent teams, including at least one registered in advance
Emerging
two or more trials, or one large registered trial, not yet independently confirmed
Early signal
one trial, small pilots, or results only on secondary outcomes
Mechanistic only
lab, animal or biomarker data, or uncontrolled reports; no controlled human results
Traditional use only
a traditional-use monograph and nothing else

How we grade evidence

Studies this grade rests on

EffectMixedNo effectSize shows participants (n)201520202025RCTShiojima 2022, 2022: RCT, n = 64, result not recordedItoh 2016, 2016: RCT, n = 41, result not recorded
each study this grade rests on, by publication year and design. Solid: effect versus the comparator; half-filled: mixed; hollow: no effect; dashed: result not recorded yet. Larger marks had more participants.
Show the numbers
StudyYearDesignParticipantsResult
Itoh 20162016RCT41result not recorded
Shiojima 20222022RCT64result not recorded

Effect of the Antioxidant Supplement Pyrroloquinoline Quinone Disodium Salt (BioPQQ™) on Cognitive Functions.

Itoh Y, Hine K, Miura H. Effect of the Antioxidant Supplement Pyrroloquinoline Quinone Disodium Salt (BioPQQ™) on Cognitive Functions Adv Exp Med Biol, 2016. PMID 26782228

Result not recorded
Design
Randomized, placebo-controlled, double-blind trial, 12 weeks
Sample
n = 41
Population
Healthy older adults
Funding
not stated in the PubMed or Crossref record; full text not read. One author affiliated with Mitsubishi Gas Chemical (PubMed affiliations).

Effect of Dietary Pyrroloquinoline Quinone Disodium Salt on Cognitive Function in Healthy Volunteers: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Study.

Shiojima Y, Takahashi M, Takahashi R. Effect of Dietary Pyrroloquinoline Quinone Disodium Salt on Cognitive Function in Healthy Volunteers: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Study J Am Nutr Assoc, 2022. PMID 34415830

Result not recorded
Design
Randomized, double-blind, placebo-controlled, parallel-group trial, 12 weeks
Sample
n = 64
Population
Healthy Japanese adults aged 40 to under 80 who felt more forgetful (58 completers, mean age about 71)
Funding
Ryusendo Co., Ltd. (Crossref funder); the first four authors list Ryusendo R&D affiliations

Search and history

Search (): pyrroloquinoline[tiab] AND (cognitive[tiab] OR memory[tiab] OR attention[tiab] OR cognition[tiab])

  • Graded C (awaiting approval)
  • C to C (approved): Editor sign-off November 13, 2026: grade matches the editor-approved final page
  • C to C (approved) (maturity: emerging): Maturity, bias summary and re-check date added