For years, the standard line on multivitamins was "expensive urine." Then a group of researchers at Harvard, Columbia and Wake Forest ran one of the biggest supplement trials ever done, and the results surprised a lot of people.
The trial is called COSMOS, and its brain studies found that a simple daily multivitamin improved memory in older adults compared with a placebo. Not by a little, either: one team estimated the effect was equal to about three years of age-related memory change.
Here's what the researchers actually did, what they found, what it doesn't tell us, and how to use it.
The short version
| Question | Answer |
|---|---|
| What was tested? | A standard daily multivitamin vs. a placebo (cocoa extract was tested separately) |
| Who took part? | Adults aged 60 and up in the U.S. |
| How many people? | 3,562 in COSMOS-Web; 2,262 in COSMOS-Mind; 573 in COSMOS-Clinic |
| How long? | 2-3 years |
| Main result | Better memory scores with the multivitamin vs. placebo |
| Size of the effect | About 3 years of memory aging (COSMOS-Web); about 2 years of cognitive aging (combined analysis) |
The takeaway: a basic, affordable multivitamin taken every day for a few years gave a measurable memory benefit in older adults.
Why this study matters
Most supplement studies are small, short and funded by the company selling the product. COSMOS is the opposite.
It's a large, randomized, placebo-controlled trial, the gold standard for research. The parent study enrolled 21,442 U.S. adults, and three separate teams used it to study the brain with three different testing methods: online tests, phone interviews and in-person exams.
When three different groups, using three different methods, all land on a benefit for the same simple intervention, that's worth paying attention to.
What the researchers did
COSMOS (the COcoa Supplement and Multivitamin Outcomes Study) gave participants either a daily multivitamin or a placebo, and separately either a cocoa extract or a placebo. Nobody knew which they were getting.
The three brain studies tested memory and thinking in different ways:
- COSMOS-Web tracked 3,562 adults with online memory tests every year for three years. The main measure was immediate recall: how many words people could remember from a list (Yeung et al., 2023).
- COSMOS-Mind followed 2,262 adults with phone-based thinking tests every year for three years (Baker et al., 2022).
- COSMOS-Clinic brought 573 adults in for detailed, in-person testing over two years. The researchers then combined all three studies in one analysis (Vyas et al., 2024).
What they found
1. Better memory after one year. In COSMOS-Web, the multivitamin group remembered more words than the placebo group after one year, and the benefit held on average across the three years. The researchers estimated the improvement was equal to about 3.1 years of age-related memory change.
2. Better overall thinking scores. In COSMOS-Mind, the multivitamin group did significantly better on a combined measure of overall thinking, and the researchers also saw benefits for memory and executive function (the skills you use to plan and focus).
3. The combined picture held up. When the researchers pooled the three studies, the multivitamin showed a clear benefit for both overall thinking and memory. The size of the effect on overall thinking was equal to about two years of cognitive aging.
What about cocoa? The cocoa extract didn't improve thinking scores in COSMOS-Mind. The multivitamin was the standout.
What it doesn't tell us
Good science is clear about its limits, and so are we:
- Participants were 60 and older. We don't yet know if younger adults see the same benefit, though covering nutrient gaps matters at any age.
- The effects are modest on any single day. This isn't a pill you'll "feel" by lunchtime. It's a small, steady advantage that builds over years.
- They used one standard multivitamin. The trial used a common store-bought formula, not anything exotic. That's good news: the benefit came from covering the basics, not from a special ingredient.
- It doesn't replace a good diet. A multivitamin fills gaps. Whole foods, exercise and sleep still do the heavy lifting.
How to use this in your routine
The simplest reading of COSMOS is this: consistency beats intensity. The people who benefited took one multivitamin every day for years.
Take one serving a day with a meal. Some vitamins are fat-soluble, so lunch or breakfast with some fat in it is a good fit.
Pair it with the basics. A multivitamin works best alongside sleep, movement and a diet built around whole foods. If you're building a fuller routine, it's the anchor of Rhonda Patrick's supplement stack.
Count your vitamin D. Check how much vitamin D is already in your multivitamin before you add a separate vitamin D3. Many adults, especially office workers, still benefit from a little extra.
Think long term. Set a reminder or keep the bottle next to the coffee maker. The benefit in COSMOS came from years of daily use.
Common questions
Does a multivitamin really help memory? In the COSMOS trials, adults aged 60 and up who took a daily multivitamin had better memory scores than those on placebo, with an effect equal to about two to three years of age-related change.
Which multivitamin did COSMOS use? A standard, widely available daily multivitamin-mineral formula. The point is that the benefit came from covering everyday nutrient basics.
I'm younger than 60. Is this relevant to me? The trial didn't test younger adults, so we can't say the memory result applies directly. But a daily multivitamin is still a simple way to cover gaps in an imperfect diet at any age.
What else supports memory? Sleep, exercise and creatine all have interesting research behind them. Our guide to creatine for your brain covers a 2024 meta-analysis on creatine and memory.
The bottom line
COSMOS is one of the strongest pieces of evidence we have for a daily multivitamin. Three separate studies, more than 5,000 people in the combined analysis, and a consistent result: better memory in older adults who took a simple multivitamin every day.
It isn't magic, and it isn't fast. But it's cheap, easy and backed by real data. Take one a day, with a meal, and stick with it.
Shop the basics: Complete Multivitamin, Vitamin D3 2,000 IU and Creatine Monohydrate.
Sources
- Yeung LK, et al. Multivitamin supplementation improves memory in older adults: a randomized clinical trial. American Journal of Clinical Nutrition. 2023;118(1):273-282. doi:10.1016/j.ajcnut.2023.05.011
- Baker LD, et al. Effects of cocoa extract and a multivitamin on cognitive function: a randomized clinical trial. Alzheimer's & Dementia. 2023;19(4):1308-1319 (published online 2022). doi:10.1002/alz.12767
- Vyas CM, et al. Effect of multivitamin-mineral supplementation versus placebo on cognitive function: results from the clinic subcohort of the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized clinical trial and meta-analysis of 3 cognitive studies within COSMOS. American Journal of Clinical Nutrition. 2024;119(3):692-701. doi:10.1016/j.ajcnut.2023.12.011
- Xu C, Bi S, Zhang W, Luo L. The effects of creatine supplementation on cognitive function in adults: a systematic review and meta-analysis. Frontiers in Nutrition. 2024;11:1424972. doi:10.3389/fnut.2024.1424972
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
