A new study suggests that taking a daily multivitamin may slow biological aging in older adults by roughly four months over the course of two years.

The research, published Monday (March 9) in the journal Nature Medicine, analyzed blood samples from 958 healthy older adults with an average age of 70 who participated in the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) — a large randomized clinical trial run by Mass General Brigham in Boston, Massachusetts.

Participants were split into four groups and randomly assigned to take one of the following combinations daily: cocoa extract and a multivitamin; a multivitamin and a placebo; cocoa extract and a placebo; or two placebos. To measure how participants aged, researchers analyzed five biomarkers that track tiny changes in DNA over time to estimate biological age.

Compared to the placebo-only group, the multivitamin group showed slower aging on two of the five clocks — both linked to mortality risk. One clock, called PCGrimAge, showed a slowing of about 1.4 months, while the other, PCPhenoAge, showed a slowing of about 2.6 months. Combined, the findings suggest about four months of slowed biological aging over the two-year trial.

Howard Sesso, associate director of the Division of Preventive Medicine at Mass General Brigham and the study's senior author, said the findings point to a promising direction for healthy aging research. "There is a lot of interest today in identifying ways to not just live longer, but to live better," Sesso was quoted as saying in a press release. "It was exciting to see the benefits of a multivitamin linked with markers of biological aging."

The benefit was more pronounced in participants who already showed signs of accelerated biological aging at the start of the trial. That group saw roughly double the slowing on the PCGrimAge clock — about 2.8 months.

Sesso was careful to note that slowing biological aging markers by four months does not mean a multivitamin adds four months to a person's life. "What it means is that your trajectory of health moving forward should stand to benefit," he explained. "It's hard to know what those four months truly translate to."

The COSMOS team plans follow-up research to determine whether the slowing of biological aging persists after the trial ends, and how the effects of a daily multivitamin may extend to clinical outcomes — including cognition, cancer risk, and cataracts.

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