Multivitamins: Who Actually Needs Them According to the Evidence

What the Evidence Actually Shows

The Physicians' Health Study II — one of the largest and longest randomized controlled trials of multivitamin supplementation — followed 14,641 male physicians for over 11 years. Results: a modest but statistically significant 8% reduction in total cancer incidence. No significant effect on cardiovascular disease, stroke, or all-cause mortality.

A comprehensive 2013 U.S. Preventive Services Task Force review concluded that evidence was insufficient to recommend multivitamins for the prevention of cardiovascular disease or cancer in healthy adults. The 2022 update maintained this position.

This does not mean multivitamins are useless — it means they are not a blanket solution for people already eating reasonably well.

The Nutritional Insurance Framework

The strongest honest case for a daily multivitamin is nutritional insurance — filling micronutrient gaps without expecting it to prevent specific diseases. Population data consistently shows that large fractions of Americans fall below the estimated average requirement for several micronutrients even while consuming adequate calories:

• Vitamin D: approximately 42% deficient by blood test
• Magnesium: approximately 45–70% below the RDA through diet alone
• Vitamin K: widespread inadequacy in populations not eating dark leafy greens regularly
• Vitamin B12: increasingly deficient in older adults and anyone on proton pump inhibitors
• Iodine: declining in populations reducing dairy and iodized salt use

A quality multivitamin addresses these gaps at a cost of roughly $0.10–0.50 per day. For people with imperfect diets — which describes most people some of the time — this is genuinely reasonable insurance.

Who Has the Strongest Case for a Daily Multivitamin

Adults over 50: B12 absorption declines with reduced stomach acid production; vitamin D synthesis decreases; magnesium absorption decreases. Multivitamin use is sensibly supported in this group.

Plant-based eaters: B12 is absent from plant foods entirely. Zinc, iron, omega-3, and iodine are lower in bioavailability from plant sources. A multivitamin plus targeted B12 supplementation is appropriate.

Pregnant women and those trying to conceive: Folate (ideally methylfolate) and iron are critically important preconceptionally and during pregnancy. This is one of the clearest evidence-supported indications for supplementation.

People with malabsorption conditions: Celiac disease, Crohn's disease, gastric bypass surgery, and long-term PPI or metformin use all impair nutrient absorption systematically.

Those with highly restricted caloric intakes: Individuals following very low-calorie diets, elite athletes with high training loads and high micronutrient turnover, and those recovering from illness.

What to Look for in a Quality Multivitamin

Active forms only:

• Folate as methylfolate (5-MTHF), not folic acid — especially important for anyone with MTHFR variants
• B12 as methylcobalamin, not cyanocobalamin
• Vitamin D as D3 (cholecalciferol), not D2
• Vitamin E as mixed tocopherols, not dl-alpha-tocopherol

Appropriate doses:

• Avoid products with excessive single-nutrient doses (1,000% of RDA for B vitamins is not beneficial)
• Ensure iron is included only if you are deficient — excess iron promotes oxidative stress in those who are replete

Third-party tested: Look for USP, NSF International, or ConsumerLab certification to verify label accuracy and contamination testing.