Multivitamins and Memory Trials (COSMOS and Others): What They Found
What the COSMOS multivitamin trials and earlier studies found for memory and thinking in older adults, how big the effects were, and why results should not be carried to other groups.
Content last updated . This page has not been medically reviewed.
Quick answer
Large randomized trials of a daily multivitamin-mineral in older adults have given mixed results. The COSMOS trials found small benefits on memory and overall thinking scores compared with placebo. An earlier large trial in male physicians found none. The differences in effect are small, were measured by phone, web or clinic tests, and do not show that a multivitamin prevents dementia. This page is information only and does not tell anyone to start or stop a multivitamin. For the general picture, see multivitamins and multiminerals.
Evidence labels used here: evidence in adequately nourished people, mixed, promising but limited and insufficient evidence.
What COSMOS is
COSMOS (COcoa Supplement and Multivitamin Outcomes Study) is a 2 x 2 factorial trial of cocoa extract and a daily multivitamin-mineral among 21,442 US adults aged 60 and older, designed to look at cardiovascular disease and cancer prevention. Three cognitive substudies tested thinking and memory. [1]| Substudy | People and length | Multivitamin result versus placebo |
|---|---|---|
| COSMOS-Mind | 2,262 older adults (mean age 73), phone tests, 3 years | Small benefit on a global cognition score (mean z 0.07, 95% CI 0.02 to 0.12); also memory and executive function [2] |
| COSMOS-Web | 3,562 older adults, internet tests, 3 years | Better immediate recall on one memory test at 1 year; no significant effect on secondary outcomes [3] |
| COSMOS-Clinic | 573 people, in-person tests, 2 years | Global cognition difference not clearly above zero (0.06 SD units, CI -0.003 to 0.13); more favorable episodic memory change [1] |
| Combined (all three) | Non-overlapping participants | 0.07 SD units for global cognition and 0.06 for episodic memory [1] |
COSMOS-Mind also checked diagnoses. Over 3 years, the rates of mild cognitive impairment and dementia did not differ by multivitamin or cocoa extract, though the authors noted low statistical power. [4]
Earlier and wider evidence
- Physicians' Health Study II. In 5,947 male physicians aged 65 or older, a daily multivitamin versus placebo showed no difference in cognitive change over up to 12 years. The authors noted that vitamin amounts may be too low or the group too well nourished to benefit. [5]
- 2012 meta-analysis. Ten trials (3,200 people) found improvement in immediate free recall memory but not delayed recall or verbal fluency. [6]
- 2026 rapid review of meta-analyses. It reported that trials improved global cognition, episodic memory and immediate recall in older or cognitively intact adults, but found no benefits for mortality or several other outcomes, and reported a higher risk of age-related macular degeneration progression. It also said the definition of a multivitamin varied widely between studies. [7]
- NCCIH (2022 digest). It says research on a multivitamin or high amounts of individual vitamins has not shown clear cognitive benefits in well-nourished people. [8] This digest predates the COSMOS-Web and COSMOS-Clinic reports above.
Frequently asked questions
Did COSMOS show that multivitamins prevent memory loss?
No. It reported small benefits on test scores, and did not find a significant difference in mild cognitive impairment or dementia rates, with low power. [2] [4]
Why did the physicians' trial find nothing?
Different people (male physicians aged 65 or older) and a different product. The authors suggested vitamin amounts may have been too low or the group too well nourished. [5]
Do the results apply to younger adults?
Not shown. The large trials enrolled adults aged 60 or older. [1] [5]
Are multivitamins marketed for brain health the same?
Not necessarily. The trials tested specific products; other products differ in contents. [7]
Should I ask a clinician before starting?
Yes, especially if you take medicines or have a medical condition. [8]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
How to read these results
- Small effects. Differences are measured in fractions of a standard deviation. COSMOS-Web described its effect as equivalent to 3.1 years of age-related memory change on one test. [3] That is a test score, not a diagnosis or a daily-life outcome.
- Group. COSMOS enrolled older adults (about 89% non-Hispanic White in COSMOS-Mind). [2] The results do not transfer to young adults, children, pregnancy or people with deficiencies or kidney or liver conditions. Proper evidence not found in the trials we read for multivitamin effects on memory in younger healthy adults.
- Product. Trials used one commercial formula each; other multivitamins differ in vitamins, minerals and amounts. Marketing a "brain" multivitamin does not extend the trial results to it.
- Nutrient gaps. Trials in people with a deficiency do not apply to people who eat well, and the reverse. A clinician can advise whether a test for a deficiency makes sense (vitamin deficiency testing).
Safety and who should ask first
Multivitamins can interact with medicines, and the contents vary by product. Talk to a clinician or pharmacist, especially with kidney or liver conditions, blood thinners, pregnancy or breastfeeding, children, or before surgery (medicine interactions, supplements before surgery). Quality varies; see quality testing and certifications. Longevity-focused trials are covered in multivitamins and longevity. Never change a prescribed medicine because of a supplement. Memory change should be checked by a clinician (when to get help).
References
- Vyas CM et al. Effect of multivitamin-mineral supplementation versus placebo on cognitive function: results from the clinic subcohort of COSMOS and meta-analysis of 3 cognitive studies within COSMOS. Am J Clin Nutr 2024. PMID 38244989. Abstract read 2026-10-23.
- Baker LD et al. Effects of cocoa extract and a multivitamin on cognitive function: A randomized clinical trial (COSMOS-Mind). Alzheimers Dement 2023. PMID 36102337. Abstract read 2026-10-23.
- Yeung LK et al. Multivitamin Supplementation Improves Memory in Older Adults: A Randomized Clinical Trial (COSMOS-Web). Am J Clin Nutr 2023. PMID 37244291. Abstract read 2026-10-23.
- Sachs BC et al. Impact of multivitamin-mineral and cocoa extract on incidence of mild cognitive impairment and dementia: Results from COSMOS-Mind. Alzheimers Dement 2023. PMID 37035889. Abstract read 2026-10-23.
- Grodstein F et al. Long-term multivitamin supplementation and cognitive function in men: a randomized trial. Ann Intern Med 2013. PMID 24490265. Abstract read 2026-10-23.
- Grima NA et al. The effects of multivitamins on cognitive performance: a systematic review and meta-analysis. J Alzheimers Dis 2012. PMID 22330823. Abstract read 2026-10-23.
- Wang W et al. Multivitamin and mineral use: A rapid review of meta-analyses on health outcomes. Ageing Res Rev 2026. PMID 41308839. Abstract read 2026-10-23.
- National Center for Complementary and Integrative Health (NCCIH), Dietary Supplements and Cognitive Function, Dementia, and Alzheimer's Disease: What the Science Says (July 2022). Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.