Do multivitamins do anything if you already eat well?
If your diet is already solid, a daily multivitamin does almost nothing for how long or how well you live. It's insurance against gaps you probably don't have — and correcting a real deficiency is a separate, fixable problem.
Multivitamins are the best-selling supplement in the country, and the pitch is intuitive: cover your bases, fill in whatever the diet missed. The trouble is that when researchers actually test that idea in people who already eat reasonably well, the needle barely moves.
The mortality data is about as clean as nutrition research gets. A 2024 analysis pooled nearly 390,000 healthy U.S. adults followed for over two decades and found daily multivitamin users were no less likely to die than non-users — if anything slightly more, which is almost certainly people reaching for pills once they’re already sick. A meta-analysis of 21 randomized trials and 91,000 people landed in the same place: no effect on death from any cause. The U.S. Preventive Services Task Force reviewed the whole field in 2022 and declined to recommend multivitamins for preventing heart disease or cancer.
None of that means vitamins don’t matter. It means a pill can’t improve on a status you’ve already topped off through food.
Where the signal isn’t quite zero
Two honest exceptions keep this from being open-and-shut. The Physicians’ Health Study II — a real randomized trial in over 14,000 men — found a modest 8% drop in total cancer among daily multivitamin takers. And the COSMOS-Mind trial reported a small but measurable cognition benefit in older adults over three years. Both are worth watching. Neither is strong enough yet to build a habit around, and both were in older populations, not 25-year-olds chasing a bigger squat.
Deficiency is a different question
The whole “no benefit” story assumes you aren’t actually short on anything. If you are — low iron, B12 on a vegan diet, vitamin D in a sunless winter, folate in pregnancy — correcting that gap does real, sometimes dramatic good. That’s not the multivitamin being magic; it’s the one nutrient you were missing.
Practical version: if you eat a varied diet, a daily multivitamin is a cheap, low-harm habit that probably isn’t doing much. Put the attention on the one or two nutrients you have a genuine reason to be low on, and test if you’re unsure.