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Cocoa flavanols and working memory: grade C

Limited evidence. Direction: No effect.

C LimitedShort-term onlySingle research group

Educational guidance, not medical advice

Why this grade

Rubric condition met: C, direction none: small acute placebo-controlled crossover trials from one research group were null; N needs a meta-analysis or at least 2 independent, adequately sized RCTs

Four placebo-controlled crossover trials in healthy young adults (36-80 participants each, 415-623 mg flavanols) found no acute benefit for working memory, cognitive control or temporal attention; one found faster visual search. All four come from one research group at the University of Groningen, and two used cocoa powders donated by Barry Callebaut.

How we grade evidence

Studies this grade rests on

EffectMixedNo effectSize shows participants (n)2015202020252030Crossover RCTAlt 2022, 2022: crossover RCT, n = 80, result not recordedKarabay 2018, 2018: crossover RCT, n = 48, result not recordedAky 2024, 2024: crossover RCT, n = 48, result not recordedAltinok 2025, 2025: crossover RCT, n = 36, 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
Karabay 20182018crossover RCT48result not recorded
Alt 20222022crossover RCT80result not recorded
Aky 20242024crossover RCT48result not recorded
Altinok 20252025crossover RCT36result not recorded

Acute effects of cocoa flavanols on cognitive control and response inhibition.

Altinok A, Moruzzi M, Akyürek EG. Acute effects of cocoa flavanols on cognitive control and response inhibition Nutrition, 2025. PMID 40614481

Result not recorded
Design
Pre-registered randomized, double-blind, placebo-controlled crossover trial (acute)
Sample
n = 36
Population
Healthy adults
Funding
not stated; authors declare no competing interests

The acute effects of cocoa flavanols on temporal and spatial attention.

Karabay A, Saija JD, Field DT. The acute effects of cocoa flavanols on temporal and spatial attention Psychopharmacology (Berl), 2018. PMID 29502273

Result not recorded
Design
Pre-registered randomized, double-blind, placebo- and baseline-controlled crossover trial (acute)
Sample
n = 48
Population
University students
Funding
University of Groningen (Crossref funder list)

Concurrent consumption of cocoa flavanols and caffeine does not acutely modulate working memory and attention.

Akyürek EG, Altınok A, Karabay A. Concurrent consumption of cocoa flavanols and caffeine does not acutely modulate working memory and attention Eur J Nutr, 2024. PMID 39607519

Result not recorded
Design
Randomized, double-blind, placebo-controlled crossover trial (acute), cocoa flavanols and caffeine
Sample
n = 48
Population
Healthy young adults
Funding
No financial support received (per paper)

Acute effects of cocoa flavanols on visual working memory: maintenance and updating.

Altınok A, Karabay A, Akyürek EG. Acute effects of cocoa flavanols on visual working memory: maintenance and updating Eur J Nutr, 2022. PMID 35031887

Result not recorded
Design
Two randomized, double-blind, placebo-controlled crossover experiments (acute)
Sample
n = 80
Population
Healthy young adults (48 and 32 in two experiments)
Funding
not stated

Search and history

Search (): (cocoa[ti] OR flavanol*[ti]) AND (cognit*[tiab] OR memory[tiab]) AND randomized controlled trial[pt] AND humans[mh]

  • Graded N (proposed): Proposed in the monograph draft
  • N to C (proposed): Editor review ed-2026-11-11: Policy 3.5 ruling: null results from small acute crossovers by one research group give C with direction none ("Limited, mixed"), not N; short-term only and single research group kept.
  • C to C (approved): Editor sign-off November 13, 2026: grade matches the editor-approved final page