A study that changes something in the multivitamin evidence base
For years, the scientific consensus on multivitamins was stable: for healthy people with a varied diet, multivitamin supplementation provides no clinically measurable benefit. Multivitamin sales exceed $50 billion annually worldwide, largely without validation of their effectiveness for the general population.
The COSMOS trial complicates that picture. It's one of the first large-scale randomized trials to measure the effect of multivitamin supplementation on biological aging markers.
What the COSMOS trial measured
COSMOS (COcoa Supplement and Multivitamin Outcomes Study) is a large randomized controlled trial. Among its findings: participants who took daily multivitamins for 2 years showed reduced biological aging as measured by epigenetic clocks, compared to a placebo group.
The estimated reduction: approximately 1.7 to 2 years of biological aging. Epigenetic clocks, such as GrimAge and PhenoAge, estimate biological age from DNA methylation patterns. They predict mortality and disease risk better than chronological age.
Important limitations of the study
The COSMOS trial population was primarily adults aged 60 and older, a population where micronutrient deficiencies are more common.
This is the central limitation: the observed effect may largely reflect correction of nutritional deficiencies in older adults, rather than an effect of supplementation beyond optimal intake levels. For young or middle-aged adults with a balanced diet, the results don't mechanically transfer.
Additionally, epigenetic clocks are statistical predictors of aging, not direct mechanisms. Reducing your epigenetic biological age by 2 years doesn't guarantee 2 extra years of life — and other interventions targeting biological aging come with their own layers of evidence and uncertainty.
What this means in practice
The COSMOS trial is a positive signal for multivitamins, particularly in adults over 60 or those likely to have micronutrient deficiencies (restrictive diets, reduced absorption, limited dietary variety).
For this population, a basic daily multivitamin now has data justification beyond simply covering baseline nutritional needs.
For young or middle-aged adults with a varied and balanced diet, the study doesn't provide direct evidence of an aging benefit. Food quality itself remains the priority over supplementation, a position now reinforced by the latest US Dietary Guidelines.