Multivitamins are the most popular supplement, but research consistently shows they don't do much for most people. Here's what we actually know.
What Large Trials Show
The Physicians' Health Study II (14,641 men) No significant reduction in major cardiovascular events or cancer mortality. Small reduction in total cancer incidence.
The Women's Health Initiative (161,808 women) No effect on heart disease, cancer, or total mortality after 8 years.
The COSMOS trial (21,442 adults) No cardiovascular benefit. Possible modest cognitive benefit in older adults with poor baseline nutrition.
The pattern: In generally healthy, well-nourished populations, multivitamins don't move the needle on major health outcomes.
Why They Don't Work as Expected
Most people aren't deficient in "a bit of everything": Multivitamins assume you're slightly low in many nutrients. In reality, if you're eating anything close to a varied diet, you're probably adequate in most and potentially deficient in only a few (D, omega-3s, magnesium).
Doses are often too low: To fit everything in one pill, doses are compromises. Not enough D to fix deficiency. Not enough magnesium to matter.
Wrong forms sometimes: Cheap multis use less bioavailable forms (folic acid vs methylfolate, cyanocobalamin vs methylcobalamin).
Nutrients in isolation: Food provides nutrients in natural matrices with fiber and phytochemicals. Pills don't replicate this.
Who Might Benefit
Older adults (65+): Absorption decreases with age. B12 deficiency becomes common. Appetite often decreases. A multi can help cover gaps.
Pregnant women (prenatals): Prenatal vitamins are a specific type of multivitamin with targeted nutrients (folate, iron, DHA). Evidence supports their use.
People with restricted diets: Vegans, vegetarians, those with food allergies, or anyone excluding major food groups may have predictable gaps.
Post-bariatric surgery: Absorption is permanently impaired. Targeted supplementation including multis is often necessary.
Food insecurity: If you genuinely can't afford or access nutritious food, a basic multi provides a safety net.
A Smarter Approach
Instead of a multivitamin, consider:
1. Get tested: A blood test can identify actual deficiencies. Vitamin D, B12, iron, and ferritin are commonly checked.
2. Target what you need: Taking vitamin D if you're deficient is more effective than a multi with 400 IU of D.
3. Consider your diet: Vegan? You need B12 for sure. Don't eat fish? Omega-3s. Dairy-free? Consider calcium and D.
4. Quality over quantity: A few targeted, well-dosed supplements beat a mediocre multi with 30 random ingredients at subtherapeutic doses.
The Bottom Line
For most healthy adults, multivitamins are expensive peace of mind that doesn't translate to better health outcomes. Targeted supplementation based on actual needs is a smarter strategy.