A large randomized, placebo-controlled trial published in JAMA (Physicians’ Health Study II) followed nearly 15,000 male physicians aged 50 and older for over a decade. The study found that daily multivitamin use was associated with a small but statistically significant reduction in total cancer incidence compared with placebo.
The effect was modest, and the findings do not suggest that multivitamins prevent cancer or replace other preventive strategies. The study population also limits generalization to women or younger individuals.
At most, the results suggest that long-term micronutrient adequacy may slightly reduce cumulative disease risk, particularly in people with marginal intake. Multivitamins should be viewed as nutritional insurance, not a cancer-prevention strategy.
