According to follow-up findings from the large-scale Cocoa Supplement Multivitamins Outcomes Study (COSMOS), two years of multivitamin supplementation was associated with slower biological aging across several DNA-based measurements. According to the authors, compared to placebo, the effect was equal to roughly four fewer months of biological aging over the course of the study. The findings were published in Nature Medicine.

“There is a lot of interest today in identifying ways to not just live longer, but to live better,” said senior author Howard Sesso, ScD, MPH, associate director of the division of preventive medicine in the Mass General Brigham Department of Medicine. “It was exciting to see benefits of a multivitamin linked with markers of biological aging. This study opens the door to learning more about accessible, safe interventions that contribute to healthier, higher-quality aging.”

Researchers used “epigenetic clocks,” which measure biological aging by examining small changes in DNA over time. The clocks focus on DNA methylation, which shifts naturally with age, and can be used to estimate aging speed and serve as predictors of disease and mortality, according to the researchers.

The study relied on the DNA methylation data from blood samples collected from 958 healthy participants who were 70 years old on average.

Participants in the study were randomly assigned to receive a daily cocoa extract and multivitamin; a daily cocoa extract and a placebo; a placebo and a multivitamin; or a placebo only.

Five separate “epigenetic clocks” were used at the beginning of the study, and again at one- and two-year follow-up. Those who took a multivitamin showed slower biological aging across all five measurements, with statistically significant changes observed in two of the clocks.

Overall, the findings suggested that multivitamin use reduced biological aging composites by about four months during the two-year period. The strongest effects were observed in those whose biological markers were suggestive of someone older than they were at baseline.

“We plan to do follow-up research to determine if the slowing of biological aging, observed through these five epigenetic clocks, and additional or new ones, persists after the trial ends,” said co-author and collaborator Yanbin Dong, MD, PhD, director of the Georgia Prention Institute at the Medical College of Georgia at Augusta University.

The COSMOS team plans to continue studying whether the effects of multivitamin use could explain previous findings connected to improved cognition, lower cancer risk, and lower risk of cataracts, the authors said.

“A lot of people take a multivitamin without necessarily knowing any benefits from taking it, so the more we can learn about its potential health benefits, the better,” said Sesso. “Within COSMOS, we are fortunate and excited to build upon a rich resource of biomarker data to test how two interventions may improve biological aging and reduce age-related clinical outcomes.”

Similarly, a post-hoc analysis of the COSMOS study published in 2025 found that cocoa supplements also promoted healthy aging benefits, with those who took a cocoa supplement experiencing reductions in a key age-related marker of inflammation.