How many studies support Multivitamins?

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. That's backed by 10 published studies in Vitaebase's database, including 5 randomized controlled trials and 4 meta-analyses, the most recent from 2025 -- a fairly substantial body of research for a single topic.