A daily multivitamin slows aging? It slowed a clock.

Claim

A MULTIVITAMIN SLOWS AGING?

Catch

IT'S A CLOCK

Verdict

A CLOCK NOT A LIFESPAN

The study: this is a prespecified ancillary analysis of the COSMOS trial (COcoa Supplement and Multivitamin Outcomes Study), a large randomized clinical trial in older adults. 958 participants — 482 women and 476 men — were randomized to a daily multivitamin-multimineral supplement (Centrum Silver), a cocoa extract (500 mg cocoa flavanols/day, including 80 mg (-)-epicatechin), both, or placebo. Researchers measured five DNA methylation "epigenetic clocks" of biological aging (PCHannum, PCHorvath, PCPhenoAge, PCGrimAge and DunedinPACE) at baseline, one year and two years.

The finding: daily multivitamin supplementation modestly reduced the rate of increase of second-generation epigenetic clocks. On PCGrimAge, the between-group difference in yearly change was −0.113 years (95% CI −0.205 to −0.020; P = 0.017). On PCPhenoAge it was −0.214 years (95% CI −0.410 to −0.019; P = 0.032) — roughly two and a half months less biological aging per year of supplement. The effect was stronger in people whose biological age was already ahead of their chronological age at baseline (−0.236 [−0.380 to −0.091]) than in those with normal or decelerated biological aging (−0.013 [−0.130 to 0.104]; P = 0.018 for interaction). Cocoa extract had no effect on any of the five clocks.

The catch, part one — it was a clock, not a body. Two of five clocks moved; PCHannum, PCHorvath and DunedinPACE did not. Epigenetic clocks are biomarkers that estimate biological age from patterns of DNA methylation. Slowing one is not the same as slowing ageing, and it is not the same as living longer — no lifespan, disease or mortality outcome was tested here. The authors themselves call the effects "statistically significant but small" and say additional studies are needed to determine the clinical relevance.

The catch, part two — who paid. The study was funded by the National Institutes of Health, and Mars Edge (a segment of Mars Incorporated) supported COSMOS with infrastructure and donated the study pills and packaging; Pfizer Consumer Healthcare (now Haleon) also donated the Centrum Silver and placebo pills and packaging. Manson and Sesso received investigator-initiated grants from Mars Edge, and Sesso also from Haleon, FOXO Technologies, the Massachusetts Life Sciences Center, Pure Encapsulations and the American Pistachio Growers; one author was formerly an FOXO employee. The companies state they had no role in study design, data collection, analysis or manuscript preparation — but the pills being tested were a specific brand, supplied by the companies that benefit from the result.

SOURCES

1. Li S, Hamaya R, Zhu H, et al. "Effects of daily multivitamin–multimineral and cocoa extract supplementation on epigenetic aging clocks in the COSMOS randomized clinical trial." Nature Medicine. 2026;32(3):1012. DOI: 10.1038/s41591-026-04239-3. PMID 41803341.
2. Mass General Brigham press release, "Scientists say a daily multivitamin may help slow aging" (via ScienceDaily, 14 May 2026) — funding and competing-interest details

Disclaimer: For information only, not medical advice. This study measured a biomarker, not lifespan or disease risk, and it does not establish that a multivitamin slows aging in a way that matters. If you are considering starting a supplement, or have questions about what you already take, talk to your doctor or a registered dietitian.