(P44-35-26) Safety and Efficacy of Adult Multivitamins – Unsupported, or Underappreciated?

Objectives: The objective was to systematically map and synthesize clinical trial evidence evaluating the effects of adult multivitamins on nutritional status, health outcomes, and safety across healthy, at-risk, and diseased populations.

Methods: This scoping review was pre-registered (https://osf.io/t476d) and conducted using the Joanna Briggs Institute framework. Multivitamins were defined as dietary supplements ingested in capsule or tablet form that provide ≥50% of the U.S. life-stage-specific RDA or AI for at least half (≥14) of the vitamins and minerals with established values, including at least 2+ vitamins and 2+ minerals, without exceeding any ULs. MEDLINE/PubMed, Cochrane Library, and Scopus were searched from inception for English-language adult clinical trials. Dual independent screening was performed, and data extraction was quality-checked using artificial intelligence and further verified by the principal investigator. Evidence was synthesized across all studies and within population subgroups.

Results: Among 134 included articles (90 primary trials and 44 interim, secondary, or post-hoc analyses), no serious adverse events were reported across studies, and multivitamin use demonstrated a strong safety profile. Daily multivitamin use consistently improved nutritional status—particularly among individuals with borderline or suboptimal baseline nutrition—consistently improving folate, vitamins B6 and B12, and homocysteine levels, while often improving carotenoids, vitamins A, D, and E, and iron status. Changes in minerals (e.g., magnesium, selenium, etc) were generally small or absent. Reductions in cancer risk and cognitive decline among middle-aged and/or older adults appeared dependent on factors such as intervention duration and baseline health status but inconsistent across trials. Multivitamin use is unlikely to reduce cardiovascular disease, related events, or cardiovascular mortality.

Conclusions: Future trials should be adequately powered and of sufficient duration, incorporate objective assessments of daily compliance, rigorously monitor baseline through endline nutritional status and key confounders, and employ pre-specified statistical analysis plans. Lack of a standard of identity for multivitamins limits study comparability.

Funding Sources: Haleon