Cocoa flavanols and episodic memory: grade C

Limited evidence. Direction: No effect.

C LimitedIndustry-funded

Educational guidance, not medical advice

Why this grade

Rubric condition met: C, direction none: only COSMOS-Web was null on a primary memory endpoint; COSMOS-Mind and COSMOS-Clinic tested memory as a secondary outcome, and all three are substudies of one parent trial, so N is not available

In COSMOS-Web (3,562 older adults), 500 mg/day of cocoa flavanols did not improve memory in all participants at 1 year (primary endpoint); COSMOS-Mind and COSMOS-Clinic found no effect on episodic memory composites, a secondary outcome. Benefits were reported only in subgroups with lower diet quality or flavanol intake, and in one small 12-week trial (37 completers). A 2026 meta-analysis found memory results inconsistent. COSMOS was supported by a Mars Edge grant. Evidence is in older adults.

How we grade evidence

Studies this grade rests on

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

Study	Year	Design	Participants	Result
Brickman 2014	2014	RCT	37	result not recorded
Brickman 2023	2023	RCT	3562	result not recorded
Baker 2023	2023	RCT	2262	result not recorded
Vyas 2024	2024	RCT	573	result not recorded
Arabpour 2026	2026	meta-analysis	2847	result not recorded

Enhancing dentate gyrus function with dietary flavanols improves cognition in older adults.

Brickman AM, Khan UA, Provenzano FA. Enhancing dentate gyrus function with dietary flavanols improves cognition in older adults Nat Neurosci, 2014. PMID 25344629

Result not recorded

Design: Randomized controlled trial, 12 weeks, high- vs low-flavanol with or without exercise (2x2)
Sample: n = 37
Population: Healthy sedentary adults aged 50-69
Funding: NIH grants AG034618, AG035015, AG025161, AG08702; James S. McDonnell Foundation; unrestricted grant from Mars, Inc.

Dietary flavanols restore hippocampal-dependent memory in older adults with lower diet quality and lower habitual flavanol consumption.

Brickman AM, Yeung LK, Alschuler DM. Dietary flavanols restore hippocampal-dependent memory in older adults with lower diet quality and lower habitual flavanol consumption Proc Natl Acad Sci U S A, 2023. PMID 37252983

Result not recorded

Design: Randomized, placebo-controlled trial, 3 years (COSMOS-Web)
Sample: n = 3,562
Population: Older adults; memory tested online
Funding: NIH grants; COSMOS supported by an investigator-initiated grant from Mars Edge (study pills donated)

Effect of cocoa extract supplementation on cognitive function: results from the clinic subcohort of the COSMOS trial.

Vyas CM, Manson JE, Sesso HD. Effect of cocoa extract supplementation on cognitive function: results from the clinic subcohort of the COSMOS trial Am J Clin Nutr, 2024. PMID 38070683

Result not recorded

Design: Randomized, placebo-controlled trial, 2-year in-person cognitive subcohort of COSMOS (COSMOS-Clinic)
Sample: n = 573
Population: Adults aged 60 and over (mean age 69.6)
Funding: NIH grants (NHLBI, NIA, NEI, NCATS, WHI); Crossref funder list also names Mars Edge Cocoa Flavanol Science Hub

Effects of cocoa extract and a multivitamin on cognitive function: A randomized clinical trial.

Baker LD, Manson JE, Rapp SR. Effects of cocoa extract and a multivitamin on cognitive function: A randomized clinical trial Alzheimers Dement, 2023. PMID 36102337

Result not recorded

Design: Randomized, placebo-controlled 2x2 factorial pragmatic trial, 3 years (COSMOS-Mind)
Sample: n = 2,262
Population: Older adults (mean age 73), cognition tested by telephone
Funding: National Institute on Aging (R01AG050657); parent COSMOS trial supported by an investigator-initiated grant from Mars Edge (Mars, Inc.), including study pills

Effect of Chronic Dark Chocolate or Cocoa Intake on Cognitive Function: A Grading of Recommendations Assessment, Development, and Evaluation (GRADE)-Assessed Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Arabpour Z, Arabpour Z, Jazayeri S. Effect of Chronic Dark Chocolate or Cocoa Intake on Cognitive Function: A Grading of Recommendations Assessment, Development, and Evaluation (GRADE)-Assessed Systematic Review and Meta-Analysis of Randomized Controlled Trials Nutr Rev, 2026. PMID 42641106

Result not recorded

Design: Systematic review and meta-analysis of 16 randomized controlled trials (GRADE-assessed; PROSPERO CRD42024568294)
Sample: n = 2,847
Population: Adults in chronic cocoa or dark chocolate trials (mixed healthy, older and clinical samples per included trials)
Funding: Vice Chancellor for Research and Technology, Iran University of Medical Sciences (grant 30885)

Search and history

Search (November 11, 2026): (cocoa[ti] OR flavanol*[ti]) AND (cognit*[tiab] OR memory[tiab]) AND randomized controlled trial[pt] AND humans[mh]

November 11, 2026 Graded N (proposed): Proposed in the monograph draft
November 12, 2026 N to C (proposed): Editor review ed-2026-11-11: Changed from N to C, direction none, after independent review finding F1: the rubric needs a population meta-analysis or at least 2 independent, adequately sized RCTs null on their primary outcome. Only COSMOS-Web was null on a primary memory endpoint; memory was secondary in COSMOS-Mind and COSMOS-Clinic, and the three share one parent trial (NCT02422745), randomization and sponsor. The 2026 meta-analysis pools mixed populations and calls memory results inconsistent. Older adults; industry-funded kept (4 of 5 studies Mars-linked).
November 13, 2026 C to C (approved): Editor sign-off November 13, 2026: grade matches the editor-approved final page