Do Multivitamins Help Your Brain? What the COSMOS Trials Show
By Peter Benson, Cognitive Enhancement Researcher · Updated October 2026 · Citations re-verified
Short answer: Multivitamins and cognitive function have one of the better supplement evidence bases. In the COSMOS trials, a daily multivitamin modestly slowed cognitive decline in older adults, roughly equivalent to two years of cognitive ageing. But an earlier large trial in male doctors found no benefit, and there’s no evidence for younger, well-fed people.
⚕️ Educational information, not medical advice — full disclaimer. A multivitamin isn’t a treatment for a diagnosed deficiency. If you take warfarin, thyroid medicine or certain antibiotics, are pregnant, or already take other vitamin or mineral supplements, check with your doctor or pharmacist first. This page contains no affiliate links.
Most supplements sold for the brain fail once they’re tested in large randomised trials. Multivitamins are an unusual case: a large, placebo-controlled programme of trials found a small but consistent benefit for cognition in older adults. That makes them worth a closer look than the usual dismissal.
This guide to multivitamins and cognitive function covers what the COSMOS trials found, how big the effect was, the trial that disagreed, who the evidence applies to, and safety. It sits in the Nootropics & Supplements hub.
On this page
What did the COSMOS trials find?
COSMOS (the COcoa Supplement and Multivitamin Outcomes Study) randomised more than 21,000 US adults aged 60 and over to a cocoa extract, a multivitamin (Centrum Silver), both or placebo. Three sub-studies measured cognition. In COSMOS-Mind, 2,262 people aged 65 and over had cognitive tests by phone for three years. The cocoa extract had no effect, but the multivitamin improved global cognition compared with placebo, and the effect appeared larger in people with a history of cardiovascular disease (Baker et al., 2023).
In COSMOS-Web, about 3,500 people took memory tests online. The multivitamin group remembered more words after one year, the trial’s main outcome, and the advantage held over three years; it had no effect on other memory tests or on executive function (Yeung et al., 2023). A third, smaller in-person study of 573 people found a benefit for episodic memory but not a statistically significant one for global cognition. Pooling all three studies, more than 5,000 people in total, showed a significant benefit for both global cognition and episodic memory (Vyas et al., 2024).
What makes this more credible than a typical supplement study is that three separate studies, using different testing methods, pointed in the same direction.
How big is the effect?
Small. The researchers estimated the pooled effect on global cognition was equivalent to about two years less cognitive ageing over the trial period (Vyas et al., 2024). That may matter across a population, but it’s subtle for any one person; it’s not something you’d notice day to day.
Cognition was also a secondary question for COSMOS as a whole. In the main trial, the multivitamin didn’t reduce total invasive cancer (518 cases versus 535 on placebo) or cardiovascular events (COSMOS investigators). The US Preventive Services Task Force concluded in 2022 that the evidence is insufficient to judge the benefits and harms of multivitamins for preventing cardiovascular disease or cancer (USPSTF, 2022).
Reactions to the cognition results differed. One COSMOS leader, JoAnn Manson, called them exciting and said they support multivitamins as a safe, affordable option for older adults. The Alzheimer’s Association said it was not ready to recommend widespread use and called for independent confirmation in larger, more diverse groups (NutraIngredients, 2022).
Did any trial find no benefit?
Yes. The Physicians’ Health Study II gave Centrum Silver or placebo to 5,947 male doctors aged 65 and over and tested their cognition repeatedly over an average of about 8.5 years. There was no difference in global cognition or verbal memory (Grodstein et al., 2013). The authors suggested the doctors may have been too well nourished to benefit.
The trials differed in who they enrolled (well-educated male doctors versus a broader mixed-sex population), how cognition was tested, and when testing began. Funding is also worth knowing: COSMOS-Mind was funded by the US National Institute on Aging, the multivitamin was supplied by its manufacturer (then Pfizer Consumer Healthcare, now Haleon), and the cocoa extract by Mars Edge (NutraIngredients, 2022). That doesn’t invalidate the results, but it’s a reason to want independent replication.
Who is likely to benefit from a multivitamin?
No one knows for certain why COSMOS found a benefit. One plausible explanation is that a multivitamin fills small nutrient shortfalls that become more common with age, as appetite, absorption and dietary variety decline. That fits the PHS II authors’ point about a well-nourished population, and the pattern seen with vitamin D, where correcting a shortfall matters more than adding extra. It remains a hypothesis.
On the evidence, the people it speaks to are older adults, especially those with a limited diet. A young, healthy, well-fed adult hoping for a study edge is outside what COSMOS tested, and there’s no good reason to expect a cognitive effect; see what to expect from nootropics. For everyone, a multivitamin is an addition to a good diet, not a substitute; the stronger nutrition evidence is for overall dietary patterns, along with the wider brain-health fundamentals and approaches to preventing cognitive decline.
Multivitamins and cognitive function: claims ranked by evidence
🟢 Stronger or replicated evidence · 🟡 Limited, mixed or preliminary evidence · 🔴 Not established or not supported
What did the trials use?
Both COSMOS and PHS II used Centrum Silver, a standard once-daily multivitamin-mineral that provides roughly the daily value of most vitamins and minerals; neither tested “high-potency” or megadose formulas. Participants took it for two to three years in COSMOS and about a decade in PHS II. That’s a research reference, not a recommendation of a particular product. If you choose one, a complete, daily-value-level formula is closer to what was studied than a high-dose one. Several of the vitamins are fat-soluble, so many people take it with a meal.
Worked example — same headline, different relevance
A 72-year-old with a small appetite and a limited diet. This is close to the people COSMOS studied. A standard daily multivitamin is a reasonable thing to discuss with their doctor, especially to check it doesn’t clash with their medicines. The realistic expectation is a small, long-term effect, not one they’ll feel.
A 28-year-old who eats well and wants an exam edge. COSMOS says little about them. If their diet has real gaps, fixing the diet comes first; a multivitamin isn’t a study aid.
Someone already taking separate vitamin D, zinc and vitamin A. Adding a multivitamin could push some nutrients towards or past their upper limits. Check the labels, or ask a pharmacist, before combining them.
The NeuroEdge Formula Multivitamin Self-Testing Framework
For multivitamins, the framework is about fit and safety, because any effect is too small to notice. Not a prescription.
1. Check the fit
The evidence is in adults 60 and over. If you’re younger and eat well, don’t expect a cognitive effect.
2. Diet first
A multivitamin adds to a good diet; it doesn’t replace one. Fix obvious gaps in what you eat first.
3. Check for overlap
Add up what your other supplements and fortified foods already provide, so you don’t exceed upper limits, especially for vitamin A, iron and zinc.
4. Check your medicines
Vitamin K and some minerals interact with medicines such as warfarin, thyroid hormone and some antibiotics. Ask a pharmacist.
Peter’s Testing Notes
A personal note, not tracked data
I take a daily multivitamin now. I was sceptical of multivitamins for a long time, and the COSMOS results made me take them more seriously, though they’re still a modest finding in older adults rather than a reason to expect a cognitive boost.
An earlier version of these notes included personal details I can’t stand behind, so those have been removed.
Are multivitamins safe?
Generally, at standard doses. Long-term use was well tolerated in PHS II and COSMOS. The COSMOS investigators report a favourable safety profile overall, though people taking the multivitamin reported a higher rate of gastrointestinal bleeding (COSMOS investigators).
Doubling up. The bigger risk is combining a multivitamin with separate supplements and fortified foods. Fat-soluble vitamins such as A and D build up in the body, and high intakes of preformed vitamin A (retinol), iron or zinc can cause harm. Check your total intake against the upper limits, or ask a pharmacist; see are nootropics safe?.
Iron. Many formulas contain iron. Men and postmenopausal women usually don’t need extra iron, so ask your doctor whether an iron-free formula suits you.
Medicine interactions. Vitamin K can interact with warfarin; NIH advises people on warfarin to keep their vitamin K intake about the same every day (NIH ODS). Calcium, iron, magnesium and zinc can reduce absorption of some medicines, including thyroid hormone and some antibiotics, so timing matters. Ask your pharmacist. This isn’t a complete list.
Key takeaways
| → | COSMOS found a small, consistent cognitive benefit in older adults across three studies and more than 5,000 people. |
| → | The effect is modest, about two years of cognitive ageing by the researchers’ estimate, and not something you’d feel. |
| → | Not every trial agrees: PHS II found no benefit in well-nourished male doctors. |
| → | There’s no evidence for younger, well-fed adults, and a multivitamin doesn’t replace a good diet. |
| → | Watch for overlap and interactions: check totals if you take other supplements, and ask a pharmacist about your medicines. |
Frequently asked questions
Do multivitamins improve brain function?
In older adults, modestly. Three COSMOS studies found a daily multivitamin slightly improved global cognition and memory over two to three years. But an earlier trial in male doctors found no benefit, and there’s no evidence in younger people.
Will a multivitamin help me study or focus?
Probably not if you’re young and eat reasonably well. COSMOS studied adults 60 and over, and there’s no good evidence that a multivitamin sharpens attention or study performance in healthy young people.
Why did COSMOS and the Physicians’ Health Study disagree?
They enrolled different people (a broad older population versus well-educated male doctors), tested cognition differently, and the doctors may already have been well nourished. COSMOS is the strongest positive evidence so far, but it hasn’t been independently replicated.
Which multivitamin did the trials use?
Both used Centrum Silver, a standard once-daily formula at roughly daily-value levels, not a high-potency product. That’s a research reference, not a product recommendation.
Can a multivitamin replace a healthy diet?
No. A multivitamin can’t supply the fibre, fats and other components of food, and the stronger nutrition evidence for the brain is for overall dietary patterns.
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⚕️ Educational Information, Not Medical Advice
This article is educational and is not medical advice. I’m a cognitive enhancement researcher, not a medical doctor. Multivitamins can interact with medicines such as warfarin, thyroid hormone and some antibiotics, and combining them with other supplements can exceed safe limits. Consult a qualified healthcare provider before use, particularly if you take prescription medicines or other supplements, or are pregnant or breastfeeding.
Scientific references
1. Baker, L. D., Manson, J. E., Rapp, S. R., et al. (2023). Effects of cocoa extract and a multivitamin on cognitive function: a randomized clinical trial. Alzheimer’s & Dementia (online September 2022). DOI: 10.1002/alz.12767
2. Yeung, L.-K., Alschuler, D. M., Wall, M., et al. (2023). Multivitamin supplementation improves memory in older adults: a randomized clinical trial. American Journal of Clinical Nutrition, 118(1), 273–282. PMID: 37244291
3. Vyas, C. M., Manson, J. E., Sesso, H. D., et al. (2024). Effect of multivitamin-mineral supplementation versus placebo on cognitive function: results from the clinic subcohort of the COSMOS randomized clinical trial and meta-analysis of 3 cognitive studies within COSMOS. American Journal of Clinical Nutrition. DOI: 10.1016/j.ajcnut.2023.12.011
4. Grodstein, F., O’Brien, J., Kang, J. H., et al. (2013). Long-term multivitamin supplementation and cognitive function in men: a randomized trial. Annals of Internal Medicine, 159(12), 806–814. DOI: 10.7326/0003-4819-159-12-201312170-00006
5. COSMOS investigators. Study findings (main cocoa extract and multivitamin results, safety). cosmostrial.org
6. US Preventive Services Task Force. (2022). Vitamin, mineral, and multivitamin supplementation to prevent cardiovascular disease and cancer. Summary in American Family Physician, 106(5). aafp.org
7. NutraIngredients. (2022, 14 September). Daily multivitamin may improve cognition, may protect against decline: RCT (funding, product suppliers and Alzheimer’s Association comment). nutraingredients.com
8. NIH Office of Dietary Supplements. Vitamin K fact sheet for consumers. ods.od.nih.gov
Cognitive Enhancement Researcher | 18+ Years Independent Research
Peter is not a clinician; this guide is educational, not medical advice. It was rewritten in October 2026 to add the COSMOS-Web results, the main COSMOS cancer and heart findings, the 2022 USPSTF statement and the trials’ funding, to correct how the researchers’ own conclusions were described, and to remove personal details that could not be confirmed. Read about how NeuroEdge Formula evaluates research.
Last reviewed: October 2026 | Educational content only. Not medical advice.
