A daily multivitamin slowed brain and biological aging in the COSMOS trial

You have probably heard that multivitamins are a waste of money. For years that was the common line. New data pushes back on it. It comes from a large trial called COSMOS. The trial used a plain, off-the-shelf multivitamin. And it found small but real gains for the ageing brain and body.

What COSMOS is

COSMOS stands for the Cocoa Supplement and Multivitamin Outcomes Study. It enrolled more than 21,000 older adults in the US. Half took a daily multivitamin. Half took a dummy pill. The multivitamin was a standard Centrum Silver. The trial was randomised, double-blind, and placebo-controlled. That is the gold standard for this kind of work.

Better memory, younger brain

One arm of COSMOS tested memory and thinking. It is called COSMOS-Mind. It followed about 2,200 adults aged 65 and up for three years. The multivitamin group did better on memory tests. The gap showed up in the first year and held for the full three. The team put the size of the gain at roughly two years of slower brain ageing.

Slower aging clocks

A newer arm looked at biological age. It used epigenetic clocks. These read tiny chemical marks on your DNA. The marks shift as you age, so they work like a clock. This study tracked 958 adults for two years. It was published in Nature Medicine in 2026.

The multivitamin slowed two of these clocks. They are known as PCGrimAge and PCPhenoAge. Both track the risk of dying. The slow-down was small: about 2.7 to 5 months over two years. The effect was largest in people who were already ageing faster than their years.

Why a small number is not nothing

Two to five months sounds tiny. I don’t think it is trivial. Steve Horvath helped build the first epigenetic clocks. His point about results like this is simple. Safe, cheap habits can matter if you keep them up. A few months saved each year does little on its own. Held for years or decades, it adds up. Two months a year, kept up, could grow into a couple of years of slower ageing.

The honest caveats

This is not a magic pill. The gains are modest. Other teams still need to repeat the work. A multivitamin does not replace real food, sleep, or exercise. It works best when it fills a gap in your diet that you would not fill any other way. But “small and steady” is the whole point. The old case was that multivitamins do nothing. These trials suggest they do a little — for memory and for biological age — when you take them day after day.

If you take one for years, take a good one

Here is the catch. The benefit comes from taking the pill every day, for years. So the pill has to hold what the label says. Supplements are loosely policed. A daily product over a decade is a lot of doses to get right. A third-party mark helps. It means an outside lab checked the contents, the dose, and the purity.

Two marks fit multivitamins well:

• NSF Certified for Sport. It checks the ingredients, the label claim, and contaminant limits. It also screens each batch and audits the plant.
• USP Verified. It checks identity, strength, how the pill breaks down, and a set of contaminant limits, with GMP audits of the plant.

You can browse all multivitamins on Certwell — or narrow to NSF Certified for Sport or USP Verified options — or read the longer guide on how each certification compares.