Multivitamins

Research summary

• The most rigorous recent evidence comes from the COSMOS trial, a large randomized study that found daily multivitamin supplementation modestly improved memory and cognitive function in older adults over multiple years of follow-up, corroborating earlier smaller randomized trials including in the Physicians' Health Study II.
• This cognitive finding is genuinely encouraging and came from a well-designed trial, in contrast to the broader disease-prevention literature: an umbrella review of nutritional supplements and cardiovascular outcomes in Annals of Internal Medicine found little consistent evidence that multivitamins reduce cardiovascular events, and a 2013 meta-analysis of randomized trials found no clear reduction in all-cause mortality.
• A dedicated COSMOS analysis on cancer and cardiovascular disease similarly found no significant reduction in those specific outcomes.
• One 2025 trial also reported modest improvements in mood, stress and loneliness with 12-week supplementation, an unexpected but preliminary finding.
• The overall picture is: real evidence for a modest cognitive benefit, but not for broad prevention of major chronic disease.