Daily Multivitamins May Slow Biological Aging, New COSMOS Trial Finds

Updated: March 2026

For years, multivitamins have been studied for their potential to support heart health, cognition, and overall longevity. But a key question has remained unanswered: can a daily multivitamin actually slow the biological aging process itself? A new prespecified ancillary analysis from the large COSMOS randomized clinical trial suggests the answer may be yes—at least modestly.

The study, published in Nature Medicine in 2026, examined whether two popular supplements—a daily multivitamin–multimineral (Centrum Silver) and cocoa extract rich in flavanols—could influence the rate of biological aging as measured by five state‑of‑the‑art DNA methylation “epigenetic clocks.” These clocks estimate how quickly the body is aging at the cellular level, independent of chronological age.

What the Researchers Tested

The trial included 958 older adults (482 women and 476 men) who were followed for two years. Researchers measured changes in five validated epigenetic aging clocks:

• PCHannum
• PCHorvath
• PCPhenoAge
• PCGrimAge
• DunedinPACE

These clocks are considered “second‑generation” biomarkers because they incorporate disease risk, mortality risk, and physiological decline—not just chronological aging.

Key Finding: Multivitamins Slowed Epigenetic Aging

Compared with placebo, daily multivitamin use produced a small but statistically significant slowing of biological aging on two of the most clinically relevant clocks:

• PCGrimAge: −0.113 years per year (95% CI −0.205 to −0.020; P = 0.017)
• PCPhenoAge: −0.214 years per year (95% CI −0.410 to −0.019; P = 0.032)

In simpler terms, participants taking a daily multivitamin aged slightly more slowly at the cellular level than those taking a placebo.

Stronger Benefits for Those Already Aging Faster

One of the most interesting findings was that multivitamins had a greater effect in people who entered the study with accelerated biological aging:

• Accelerated agers: −0.236 years per year
• Normal or slower agers: −0.013 years per year

This suggests that multivitamins may be most helpful for individuals whose biological aging is already outpacing their chronological age.

What About Cocoa Extract?

Despite earlier research showing cardiovascular and cognitive benefits from cocoa flavanols, the COSMOS epigenetic analysis found no measurable effect of cocoa extract on any of the five aging clocks.

What This Means for Older Adults

The results are encouraging but measured. The slowing of biological aging was modest—fractions of a year—but statistically meaningful. Importantly, the study authors emphasize that more research is needed to determine whether these small changes translate into real‑world improvements in healthspan or longevity.

Still, for older adults already taking a daily multivitamin for general health, this study adds a new layer of potential benefit: supporting healthier biological aging at the cellular level.

Practical Takeaways

• Daily multivitamins may help slow biological aging—especially in individuals with accelerated aging markers.
• The benefits were modest but statistically significant on two advanced epigenetic clocks.
• Cocoa extract did not influence epigenetic aging in this trial.
• Multivitamins remain low‑risk, widely available, and inexpensive for most adults.