The pill millions of Americans already swallow with breakfast produced a small but statistically significant boost to memory and global cognition in older adults, according to three placebo-controlled trials pooled under the COSMOS program at Mass General Brigham and Harvard. The combined effect was equivalent to slowing global cognitive aging by roughly two years compared with placebo.
The evidence comes from a randomized controlled trial, not an observational study, which puts it on firmer ground than most supplement research. The trial was run by investigators at Brigham and Women's Hospital, Massachusetts General Hospital, Columbia University and Wake Forest University, and covered by NIH Research Matters in June 2023.
What the three COSMOS trials found
COSMOS stands for the COcoa Supplement and Multivitamin Outcomes Study. The cognitive strand ran three separate analyses in adults aged 60 and older, using different methods to measure thinking and memory. A meta-analysis published in the American Journal of Clinical Nutrition in January 2024 combined more than 5,000 non-overlapping participants.
In the largest strand, COSMOS-Web, 3,562 women and men with a mean age of 71 took a daily Centrum Silver multivitamin or placebo for three years. Immediate recall memory improved by the end of the first year in the multivitamin group and held through year three. Researchers estimated the effect was equivalent to 3.1 years of age-related memory change.
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The pooled analysis showed a consistent benefit for episodic memory and global cognition. It did not find a significant benefit for executive function or attention.
Modest effect, honest framing
The effect size is small. Cohen's d for the primary endpoint in COSMOS-Web was 0.070, which is a modest signal by clinical standards. The researchers frame the multivitamin as a low-cost addition to brain health, not a replacement for anything else.
"Cognitive decline is among the top health concerns for most older adults, and a daily supplement of multivitamins has the potential as an appealing and accessible approach to slow cognitive aging," said Chirag Vyas, MBBS, MPH, an instructor in the Department of Psychiatry at Massachusetts General Hospital and first author of the meta-analysis.
Olivia Okereke, MD, director of geriatric psychiatry at Massachusetts General Hospital and senior author, said the results "provide evidence for the role of a daily multivitamin in supporting better cognitive aging."
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What the trial does and does not show
The trials tested a standard once-daily multivitamin-mineral supplement, not a high-dose formula or a single nutrient. Benefits were most consistent in adults over 60, and earlier COSMOS-Web analyses suggested a stronger memory signal in participants with a history of cardiovascular disease.
The findings do not mean a multivitamin protects against Alzheimer's disease, and they do not replace medical care for memory concerns. Anyone noticing a real change in memory or thinking should see their doctor rather than reach for a supplement.
Where multivitamins fit in a brain-health routine
A daily multivitamin is one tool among several. The National Institute on Aging points to regular physical activity, quality sleep, blood pressure control and a Mediterranean-style diet as the most consistent levers for brain aging. Four lifestyle changes have been shown to slow cognitive decline even in adults already at higher risk for Alzheimer's.
The COSMOS trials were funded by the National Institutes of Health and Mars Edge, with multivitamin and placebo tablets donated by Pfizer Consumer Healthcare (now Haleon), a detail the authors disclose in the published papers. Talk to your doctor before starting any supplement if you take prescription medication or have a chronic condition.
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This article is made and published by Emil Martesen, who may have used AI in the preparation.