Is Multivitamins good for cognitive function?

The evidence points that way, though it's not yet conclusive. 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 reflected in an evidence score of 60/100 for its role in cognitive function, drawn from 10 studies (5 RCTs), with an estimated impact on longevity rated moderate (35/100).