multivitamins re-enter the scientific conversation as a possible, modest lever on biological aging after a prespecified ancillary analysis of the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) reported slowed epigenetic clock progression in older adults.
What If Multivitamins Slow Biological Aging?
The Nature Medicine prespecified ancillary study of COSMOS evaluated the 2-year effect of a daily multivitamin–multimineral (MVM) and a cocoa extract on five DNA methylation measures of biological aging (PCHannum, PCHorvath, PCPhenoAge, PCGrimAge and DunedinPACE) among 958 participants. The trial found that, compared with placebo, daily MVM supplementation modestly reduced the rate of increase of second-generation epigenetic clocks: a between-group difference in yearly change of −0. 113 years for PCGrimAge and −0. 214 years for PCPhenoAge. The analysis also found that MVM had a stronger effect on PCGrimAge among participants with accelerated biological aging at baseline (−0. 236) compared with those with normal or decelerated biological aging (−0. 013; interaction P = 0. 018). The cocoa extract showed no effect on the five epigenetic clocks tested.
What Happens Now That COSMOS Shows Modest Clock Effects?
Howard Sesso, an epidemiologist and associate professor of medicine at Harvard Medical School and senior author affiliated with Mass General Brigham in the trial, and the COSMOS team describe these findings as encouraging but limited in scope. Key signals from the ancillary analysis are constrained by the short two-year window and the small size of the epigenetic shifts. The study text notes that although statistically significant, the effects are small and that additional studies are needed to determine clinical relevance and whether changes in epigenetic clocks explain previously observed benefits of MVM supplementation on age-related chronic conditions.
- Best case: Larger, longer randomized trials replicate clock slowing and link those changes to meaningful clinical outcomes.
- Most likely: MVM produces modest biological-clock shifts in some older adults, especially those with accelerated aging or nutrient gaps, but translation to tangible health endpoints remains uncertain.
- Most challenging: Clock effects do not translate into improved clinical outcomes and remain statistically interesting but clinically marginal.
What Should Readers Expect and Do?
The COSMOS ancillary analysis provides a clearer mechanistic signal than many prior supplement studies, but it stops short of establishing that daily multivitamins change how people live and age in meaningful clinical ways. The trial measured DNA methylation–based clocks rather than direct clinical endpoints, and the authors flag the need for larger samples and longer follow-up to assess whether the epigenetic shifts lead to reduced incidence of age-related chronic conditions. For older adults with dietary gaps or established nutrient insufficiencies, the observed pattern—that individuals with faster baseline biological aging showed larger clock benefits—suggests targeted research and clinical judgment rather than universal supplementation. Clinicians and researchers should treat these results as an early, evidence-based prompt for follow-up trials; individuals should discuss nutrient needs with health professionals before altering supplement regimens.
In short, the COSMOS ancillary study advances the conversation: it offers quantified, trial-based evidence that daily multivitamins can nudge epigenetic aging markers in older adults, but it leaves open the critical question of clinical impact—multivitamins
