Multivitamin Benefits: What Large Trials Found (Physicians' Health Study II, COSMOS and Others)
What the Physicians' Health Study II, COSMOS and pooled reviews found about daily multivitamins and cancer, heart disease, thinking and death, and why the results are narrow.
Content last updated . This page has not been medically reviewed.
Quick answer
Large trials of a daily multivitamin found no clear effect on heart attacks, strokes or death, a small effect on total cancer in older men, and mixed results for thinking tests. The US Preventive Services Task Force (USPSTF) concluded in 2022 that evidence is insufficient to judge the balance of benefits and harms of multivitamins for preventing cardiovascular disease or cancer. [1] This page explains the main trials. The overall picture and safety are on multivitamins.
What the trials tested
| Study | Who and how long | Outcome | What it found | Label |
|---|---|---|---|---|
| Physicians' Health Study II, cancer (2012) | 14,641 US male physicians aged 50 or older; median 11.2 years; daily multivitamin or placebo [2] | Total cancer | Fewer cases with the multivitamin (17.0 vs 18.3 per 1,000 person-years; hazard ratio 0.92, 95% CI 0.86 to 0.998). No significant effect on prostate or colorectal cancer, or on cancer death. [2] | Promising but limited |
| Physicians' Health Study II, heart (2012) | Same men [3] | Heart attack, stroke, cardiovascular death | No significant effect (hazard ratio 1.01 for major events); total death not significantly different (hazard ratio 0.94, 95% CI 0.88 to 1.02). [3] | No good evidence of benefit |
| Physicians' Health Study II, thinking (2013) | 5,947 male physicians aged 65 or older; up to 4 phone tests over 12 years [4] | Global cognition and verbal memory | No difference from placebo. The authors noted the doses may be too low or the group too well nourished to benefit. [4] | No good evidence of benefit |
| COSMOS-Mind (2023) | 2,262 older adults, mean age 73; 3 years; a commercial multivitamin-mineral or placebo [5] | Global cognition | Small benefit (mean z-score 0.07, 95% CI 0.02 to 0.12); also memory and executive function. [5] | Promising but limited |
| COSMOS-Clinic and a pooled analysis of three COSMOS cognitive studies (2024) | 573 people in person for 2 years; pooled analysis of 573, 2,158 and 2,472 people [6] | Global cognition, episodic memory | Pooled benefit of 0.07 standard-deviation units on global cognition, which the authors equate to about 2 years less cognitive aging. [6] | Promising but limited |
| Pooled trials for the USPSTF (2022) | 84 studies of vitamin and mineral supplements, 739,803 people in all [7] | Cancer, heart disease, death | Multivitamin use was linked to slightly lower odds of any cancer (odds ratio 0.93); the authors said the evidence had important limitations. [7] | Mixed |
| Pooled trials of death (2013) | 21 articles, 91,074 people, average age 62, average 43 months [8] | Death from any cause | No effect (relative risk 0.98, 95% CI 0.94 to 1.02). [8] | No good evidence of benefit |
Where research is missing
Proper evidence not found for: trials in people with a confirmed deficiency (they are treated with the missing nutrient under a clinician), trials of specific commercial formulas beyond those above, and long-term results in children. We searched the USPSTF statement, the review behind it, NCCIH, the NIA and the PubMed abstracts listed below. COSMOS also tested cardiovascular and cancer outcomes for the multivitamin, but those results were not among the sources we read, so we do not report them here.Frequently asked questions
Does a daily multivitamin prevent cancer?
In one large trial of older male physicians, total cancer was modestly lower (hazard ratio 0.92). [2] The USPSTF still judged the evidence for preventing cancer insufficient. [1]
Does a multivitamin prevent heart attacks or strokes?
In the same men there was no significant effect on major cardiovascular events. [3]
Does a multivitamin improve memory?
Results are mixed: no benefit in male physicians aged 65 or older, [4] but a small benefit in COSMOS-Mind. [5]
Does a multivitamin help you live longer?
A pooled analysis of 21 articles found no effect on all-cause mortality. [8]
Do these trials apply to me?
Only partly. They tested one product in specific groups, mostly well-nourished older adults. Ask a clinician about your own situation.
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 the evidence labels
Labels used on this page: evidence in adequately nourished people, promising but limited, mixed, insufficient evidence, no good evidence of benefit.
How to read these results
- Small average effects. In the cancer trial the gap was about 1.3 cases per 1,000 person-years (17.0 minus 18.3). That is an average across thousands of men, not a promise for one person.
- Narrow groups. The Physicians' Health Study II enrolled male physicians, and COSMOS enrolled older US adults. Results do not transfer to younger people, pregnancy, or people with a diagnosed deficiency, and the reverse is also true.
- One product each. Each trial used one multivitamin at one set of amounts. Other formulas, forms and strengths were not tested, and the sources we read do not compare them.
- Tests, not diagnoses. The thinking trials used test scores. The National Institute on Aging still says no vitamin or supplement is recommended for preventing Alzheimer's or cognitive decline. [9]
- Funding and design. The 2013 Physicians' Health Study II cognition abstract lists the National Institutes of Health and several companies as funders. [4]
Safety and who should ask first
NCCIH says taking a multivitamin is unlikely to pose any health risks, but supplements may interact with medicines or matter before surgery. [10] The trial abstracts above do not report side-effect rates, so they cannot show that a product is right for you. Ask a clinician or pharmacist about medicines, pregnancy, kidney or liver disease and upcoming surgery; see medication interactions, side effects and what is in a multivitamin. Related reading: multivitamins and longevity trials and nootropic evidence by outcome.
References
- USPSTF recommendation statement, Vitamin, Mineral, and Multivitamin Supplementation to Prevent Cardiovascular Disease and Cancer (JAMA 2022). Read 2026-10-23.
- Gaziano et al., Multivitamins in the prevention of cancer in men: the Physicians' Health Study II randomized controlled trial (JAMA 2012). Read 2026-10-23.
- Sesso et al., Multivitamins in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial (JAMA 2012). Read 2026-10-23.
- Grodstein et al., Long-term multivitamin supplementation and cognitive function in men: a randomized trial (Ann Intern Med 2013). Read 2026-10-23.
- COSMOS-Mind: Effects of cocoa extract and a multivitamin on cognitive function, randomized clinical trial (Alzheimer's & Dementia 2023). Read 2026-10-23.
- COSMOS-Clinic and meta-analysis of three COSMOS cognitive studies, multivitamin-mineral and cognition (Am J Clin Nutr 2024). Read 2026-10-23.
- Evidence report for the USPSTF: Vitamin and Mineral Supplements for the Primary Prevention of Cardiovascular Disease and Cancer (JAMA 2022). Read 2026-10-23.
- Macpherson et al., Multivitamin-multimineral supplementation and mortality: a meta-analysis of randomized controlled trials (Am J Clin Nutr 2013). Read 2026-10-23.
- NIA: What Do We Know About Diet and Prevention of Alzheimer's Disease?. Read 2026-10-23.
- NCCIH: Using Dietary Supplements Wisely. 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.