A multivitamin may slow epigenetic aging in older adults. But don’t rush to buy them just yet

We all need our vitamins, but there has been little evidence to suggest that multivitamins actually improve people’s health. Now research emerging from the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) suggests that taking a daily multivitamin can slow two epigenetic markers of aging in older adults (Nat. Med. 2026, DOI: 10.1038/s41591-026-04239-3).

One way to monitor a person’s age and health are epigenetic clocks, which are measures of levels of DNA methylation. Howard D. Sesso, an epidemiologist at Brigham and Women’s Hospital and Harvard Medical School who helped lead the COSMOS study, says that for two of the five epigenetic clocks used in the study, daily multivitamin supplementation in adults over 60 years old “translated to about a 4-month improvement in the trajectory of biological aging from those two clocks versus placebo.”

Daniel Belsky, an epidemiologist at Columbia University and the inventor of the DunedinPACE epigenetic clock, says that “epigenetic clocks are in some ways ideal end points for interventions like multivitamin supplementation” because multivitamins aren’t meant to aid in improving any one specific health outcome. Instead, epigenetic clocks are “able to capture those subtle improvements across the kind of range of possible outcomes.” Belsky wrote a companion article about the finding but was otherwise not involved.

It is, however, hard to say whether improvements in epigenetic clocks mean that multivitamins make people healthier. Epigenetic clocks are rarely used as a clinical diagnostic, and the COSMOS study results alone are probably not enough to be used in clinical decision-making, both Sesso and Belsky say.

“People should not read this study and think, oh, I should take a multivitamin. And the reason for that is there’s a critical piece of evidence that’s missing,” Belsky says. “We know that these clocks predict health-span outcomes, and now from this trial, we know that these clocks are modified by multivitamin supplementation. What we need to know, in addition to those two pieces of information, is that people who take multivitamins or some other intervention that modifies their epigenetic clock have a corresponding improvement in their actual health span.”

But Sesso’s earlier work might provide that link. An earlier paper published evaluating results from the COSMOS study showed that taking a multivitamin was “shown to improve cognition, convincingly,” he says (Am. J. Clin. Nutr. 2024, DOI: 10.1016/j.ajcnut.2023.12.011). And the results from another large randomized controlled trial that Sesso helped lead, the Physicians’ Health Study, showed that multivitamins “reduced total cancer risk by 8% and eye disease, cataracts, by 9%” (JAMA 2012, DOI: 10.1001/jama.2012.14641; Ophthalmology 2013, DOI: 10.1016/j.ophtha.2013.09.038).

The Physicians’ Health Study results are what Sesso says convinced him to start taking a multivitamin after he turned 50. “It all starts with a healthy diet and lifestyle. Maybe a multivitamin could be an important addition to that,” he says.