SupplementsMultivitaminHealthy agingMicronutrients
A daily multivitamin-mineral (MVM) is the most-used supplement in the world — and one of the most argued-about. The honest summary: it is not a shortcut around a poor diet, and a well-nourished young adult may gain little. But recent large, randomised trials have shifted the picture for older adults, where it has better randomised evidence than most everyday supplements — though, as below, that evidence is about test scores rather than about getting ill.
Key takeaways
- Two large 2023 randomised trials (COSMOS-Web and COSMOS-Mind) found a daily multivitamin modestly improved memory and global cognition in adults 60+ — roughly the equivalent of slowing cognitive aging by 1.8–3.1 years.12
- In older men, a daily MVM gave a modest 8% reduction in total cancer over ~11 years.3
- For the general population, expert reviewers (USPSTF, 2022) still find insufficient evidence that a multivitamin prevents heart disease or cancer — and advise against high-dose beta-carotene and vitamin E.4
- It is best seen as a low-cost insurance policy for nutrient gaps, most useful in older adults, pregnancy, and restrictive or low diets — not a replacement for food.
What it is
A multivitamin-mineral supplement combines most essential vitamins and several minerals in a single daily dose, usually at or near the recommended daily amount. The idea is not to megadose any one nutrient, but to close small gaps across the board — the nutrients that are easy to fall short on when diet, appetite or absorption isn’t perfect. Quality and formulation vary enormously, which is much of why older, low-quality products showed little benefit.
The newest evidence — cognition in older adults
This is what changed the conversation. The COSMOS program ran several large, placebo-controlled randomised trials of a daily multivitamin in older adults — the strongest study design there is.
COSMOS-Web (2023)3,562 adults aged 60+, 3 years. The multivitamin group performed significantly better on memory tests from year 1, sustained across all 3 years — an estimated ~3.1 years less memory aging versus placebo.1
COSMOS-Mind (2023)2,262 adults aged 65+, 3 years. Daily MVM improved global cognition, episodic memory and executive function — roughly a 60% slowing of cognitive aging (~1.8 years). Benefit looked larger in those with cardiovascular disease.2
ConsistencyA pooled analysis of the three COSMOS cognitive substudies found a consistent, statistically significant benefit — unusual for this field, where single studies often conflict. Worth knowing how big it is: global cognition improved by 0.07 standard-deviation units (95% CI 0.03–0.11). That is a clear signal across thousands of people, but small enough that no individual would notice it. The “1.8–3.1 years” figures above are that effect converted into time units, not a directly measured outcome.8
Important caveats: the effect is modest, the mechanism isn’t proven, and the researchers themselves say it needs replicating in more diverse populations. It is a promising signal, not a settled fact.
Cancer & other outcomes
Total cancerIn the Physicians’ Health Study II (14,641 male doctors aged 50+, ~11 years), a daily multivitamin produced an 8% reduction in total cancer (HR 0.92, 95% CI 0.86–0.998, P=0.04) — a result that only just cleared statistical significance. Cancer deaths were not significantly reduced (HR 0.88, 0.77–1.01).3
CataractThe same trial found a small reduction in cataract risk.3
No effect onIt did not reduce heart attacks, stroke, or overall mortality — benefits are real but narrow, not a longevity cure.3
Where the evidence is weak
Balance matters. For healthy, well-nourished adults in general, the picture is much less rosy:
Prevention (general)The US Preventive Services Task Force (2022) concluded there is insufficient evidence that multivitamins prevent cardiovascular disease or cancer in the general adult population.4
Two to avoidThe same review advised against beta-carotene (increased lung-cancer risk in smokers) and against vitamin E (no benefit) — so formulation matters.4
The same trial, real outcomesThis matters for how you read the cognition results above: they come from substudies of a 21,442-person trial that also measured whether people got ill. Over a median 3.6 years the multivitamin did not reduce invasive cancer (HR 0.97, 0.86–1.09), cardiovascular disease (HR 0.98, 0.86–1.12) or death from any cause (HR 0.93, 0.81–1.08).5
Mortality, at scaleThe largest analysis to date followed 390,124 US adults for up to 27 years and found multivitamin users had no lower mortality — if anything marginally higher (HR 1.04, 1.02–1.07), after careful adjustment for the tendency of people in poor health to start taking supplements.6
“Slows biological aging” headlinesA 2026 COSMOS substudy (958 adults, 2 years) reported that a daily multivitamin slowed two of five DNA-methylation “epigenetic clocks” — roughly one to three months of estimated biological age per year. Read it carefully: three of the five clocks showed nothing, neither p-value (0.017 and 0.032) would survive correction for testing five outcomes, both confidence intervals nearly touch zero, and the study pills were donated by the manufacturer of the multivitamin being tested. Epigenetic clocks are research tools, not validated measures of health or lifespan.7
Not a food replacementA pill delivers isolated nutrients, not the fibre, phytochemicals and food matrix of a real diet. Food first remains the rule.
Who benefits — by age & life stage
Older adults (60+)The strongest case. Appetite and intake often fall, and vitamin B12 absorption declines with age (atrophic gastritis). This is also the group with the new cognitive-benefit evidence.1
Pregnancy & trying to conceiveA prenatal formula matters here — folate (neural-tube defects), plus iron and iodine. Use a pregnancy-specific product, not a generic one.
Vegan / very restrictive dietsHigher risk of gaps in B12, iron, zinc, iodine, vitamin D and omega-3 — a multivitamin (plus dedicated B12) is sensible.
Malabsorption & low intakeBariatric surgery, coeliac/IBD, chronic dieting, or simply eating little — a broad, gentle top-up is reasonable.
Well-fed younger adultsLikely the least to gain. A varied diet usually covers the bases; a multivitamin is optional insurance, not a need.
How to choose one
Sensible dosesLook for nutrients at or near 100% of daily needs, not mega-doses. More is not better for a broad-spectrum product.
The right formsPrefer methylcobalamin or cyanocobalamin B12, vitamin D3, folate/methylfolate, and vitamin K2 where included.
What to avoidHigh-dose beta-carotene and high-dose vitamin E; avoid iron unless you need it (most men and postmenopausal women don’t).4
Third-party testedChoose a brand with independent testing for label accuracy and contaminants.
Age/sex-appropriate“50+”, prenatal, or iron-free men’s formulas exist for a reason — match it to you.
Dose & safety
A standard once-daily MVM at RDA-level doses is very safe for most adults. Cautions:
Fat-soluble vitaminsA, D, E, K can accumulate — don’t stack a multivitamin on top of several separate high-dose supplements without checking totals.
IronOnly take iron-containing formulas if you actually need iron; excess is harmful, especially for men.
SmokersAvoid products with high-dose beta-carotene.4
MedicationsVitamin K can interact with warfarin; check with a pharmacist if you take blood thinners or other regular medication.
References
Adult research summary for education, not a prescription. A multivitamin is a food supplement, not a treatment for disease.
- Yeung LK, et al. Multivitamin Supplementation Improves Memory in Older Adults: A Randomized Clinical Trial (COSMOS-Web), and meta-analysis of 3 COSMOS cognitive studies. Am J Clin Nutr 2023. pmc.ncbi.nlm.nih.gov
- Baker LD, et al. Effects of cocoa extract and a multivitamin on cognitive function (COSMOS-Mind). Alzheimers Dement 2023;19(4):1308–1319. pubmed.ncbi.nlm.nih.gov
- Gaziano JM, et al. Multivitamins in the Prevention of Cancer in Men: the Physicians’ Health Study II Randomized Controlled Trial. JAMA 2012;308(18):1871–1880. pubmed.ncbi.nlm.nih.gov
- Vitamin, Mineral, and Multivitamin Supplementation to Prevent Cardiovascular Disease and Cancer: US Preventive Services Task Force Recommendation Statement. JAMA 2022;327(23):2326–2333. jamanetwork.com
- Sesso HD, et al. Multivitamins in the prevention of cancer and cardiovascular disease: the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized clinical trial. Am J Clin Nutr 2022;115(6):1501–1510. pubmed.ncbi.nlm.nih.gov
- Loftfield E, et al. Multivitamin use and mortality risk in 3 prospective US cohorts. JAMA Netw Open 2024;7(6):e2418729. pubmed.ncbi.nlm.nih.gov
- Li S, et al. Effects of daily multivitamin-multimineral and cocoa extract supplementation on epigenetic aging clocks in the COSMOS randomized clinical trial. Nat Med 2026;32(3):1012–1022. pubmed.ncbi.nlm.nih.gov
- Vyas CM, et al. Effect of multivitamin-mineral supplementation versus placebo on cognitive function: results from the clinic subcohort of the COSMOS trial and meta-analysis of three cognitive studies. Am J Clin Nutr 2024;119(3):692–701. pubmed.ncbi.nlm.nih.gov
This article summarises nutrition science for education. It is not a substitute for individual medical advice; consult a professional before starting a supplement, in pregnancy, or alongside medication.