What the Research Says
Multivitamins are the most studied supplement category, yet evidence for their benefits has historically been mixed. The tide shifted meaningfully with two landmark trials. The Physicians' Health Study II (Sesso et al., 2012), following 14,641 male physicians for over 11 years, found that daily multivitamin use modestly but significantly reduced total cancer incidence by 8%. The COSMOS-Mind trial (Baker et al., 2022), a well-designed ancillary study of the COcoa Supplement and Multivitamin Outcomes Study, demonstrated that daily multivitamin supplementation significantly improved global cognition in 2,262 older adults over 3 years, with benefits equivalent to approximately 2 years of reduced cognitive aging.
The nutritional insurance argument is well supported. Ward (2014) analyzed NHANES data showing that multivitamin/mineral users had substantially lower rates of nutrient inadequacy for vitamins A, C, D, E, calcium, and magnesium compared to non-users. Blumberg et al. (2017) extended this analysis and found that without multivitamin use, a significant proportion of the U.S. population would fall below the Estimated Average Requirement for multiple micronutrients.
Conversely, the U.S. Preventive Services Task Force (2022) concluded that evidence is insufficient to recommend multivitamins for cardiovascular disease or cancer mortality prevention in the general population — a nuanced position that acknowledges the COSMOS and PHS-II findings while noting limitations. For specific populations — older adults, those with malabsorption conditions, individuals on restrictive diets, and people taking medications that deplete nutrients (e.g., PPIs depleting B12 per Lam et al., 2013) — the case for multivitamin use is considerably stronger.
