Do multivitamins actually work?

Do multivitamins actually work?

For a generally healthy, well-fed adult, probably not for the big outcomes most people hope for, like preventing heart disease, cancer or an earlier death. The US government's own evidence review found the data simply isn't strong enough to say either way, and the largest mortality study to date, following nearly 390,000 adults for more than two decades, found no benefit. The one place a major trial did find a real signal is memory: multivitamins modestly slowed cognitive decline in adults over 60.

What the biggest US review actually concluded

The US Preventive Services Task Force, the government panel that reviews preventive medicine, updated its guidance on vitamin and mineral supplements in 2022. For multivitamins specifically, the task force issued what is called an "I statement," meaning the current evidence is insufficient to assess the balance of benefits and harms for preventing cardiovascular disease or cancer. That is a genuinely different verdict from "they don't work," and also different from "they're proven to help." It means the trials that exist are not good enough, large enough, or long enough to answer the question cleanly, so the task force leaves the decision to individual judgment rather than issuing a recommendation. The same review did reach a firmer conclusion on two specific ingredients: it recommends against taking beta carotene or vitamin E supplements for heart disease or cancer prevention, because beta carotene's harms outweigh its benefits and vitamin E shows no net benefit at all.

The mortality study that should end the insurance-policy argument

The most direct test of whether a daily multivitamin extends your life came out in 2024, published in JAMA Network Open. Researchers pooled three long-running US cohort studies covering close to 390,000 generally healthy adults with no history of cancer or chronic disease, and tracked them for more than 20 years. Daily multivitamin users were not less likely to die from any cause than people who didn't take one, and there was no difference in deaths from cancer, heart disease or stroke specifically. The researchers, including lead author Erikka Loftfield of the National Cancer Institute, noted that the finding doesn't rule out multivitamins mattering for people with a documented nutritional deficiency, since the study excluded anyone with existing chronic disease. But for the healthy population most people picture when they reach for a bottle of Centrum or One A Day, this is about as clean a null result as population research gets.

Where the evidence actually gets interesting: memory

This is the part most "multivitamins are useless" takes skip over. The COSMOS trial, run out of Brigham and Women's Hospital and Columbia University, randomized more than 3,500 adults aged 60 and older to a daily multivitamin or a placebo and tracked their memory and cognition every year for three years. The multivitamin group scored meaningfully better, an effect the researchers estimated at the equivalent of 3.1 years of slowed memory aging compared with placebo, with the benefit holding up across the full three years. A companion study, COSMOS-Mind, tested 2,200 older adults over the same period and found multivitamin use associated with a 60% slower rate of global cognitive decline, worth about 1.8 years. "Supplementation with multivitamins may be a simple and inexpensive way for older adults to slow down memory loss," said Lok-Kin Yeung, who co-led the COSMOS-Web analysis at Columbia University. Adam Brickman, who co-led the same study, was more measured about where this leaves things: "the findings are promising and certainly set the stage for important follow-up studies." Both trials used the Centrum Silver formulation, and the research team has flagged that results still need checking in more diverse, lower-income populations before anyone calls the question settled.

Why the research keeps landing on "we don't know"

Part of the reason multivitamin trials produce such a mixed picture is that they are genuinely hard to run well. Trials vary in which formulation they test, how long they follow people, and how healthy or deficient the starting population already is, and a multivitamin bought off a shelf is a bundle of a dozen or more nutrients rather than one isolated variable, which makes it difficult to credit or blame any single ingredient for an effect. Observational cohort studies, like the 390,000-person mortality analysis, can only show association, not cause and effect, since people who choose to take a daily vitamin may also eat better or exercise more for reasons the data can't fully strip out. That's part of why a government review built to weigh decades of this kind of evidence still landed on "insufficient," rather than a clean yes or no.

When a multivitamin has genuinely strong evidence behind it

The confusion around multivitamins mostly comes from lumping together two very different situations. Broad daily use in someone who already eats a varied diet is the case with weak evidence, outlined above. Targeted use for a real, specific gap is a different story, and the evidence there is solid: folic acid before and during early pregnancy to prevent neural tube defects, vitamin B12 for many older adults and for anyone eating a vegan diet, vitamin D for people who get little sun exposure, and iron for a diagnosed deficiency confirmed by bloodwork. None of those are "insurance" decisions made on a hunch. They're responses to a known shortfall, which is a completely different category from popping a multivitamin because it feels like a reasonable habit.

What this means if you already take one, or are deciding whether to start

If you already take a multivitamin and tolerate it fine, the honest picture from this research is that it's unlikely to be hurting you and may be doing something modest for memory if you're over 60, even though it isn't proven to protect your heart or lower your cancer risk. If you're deciding whether to start, the better first move is usually a conversation with a doctor or a basic bloodwork panel to find out whether you actually have a gap worth filling, the same logic that applies to deciding whether fish oil is worth taking. A multivitamin is not a substitute for eating vegetables, and it will not undo the effect of a genuinely poor diet. It is, at best, a modest top-up for a few specific nutrients, with the clearest upside currently sitting in brain aging rather than heart or cancer risk.

Our take

The evidence splits cleanly into two piles: weak to nonexistent for preventing heart disease, cancer or death in a healthy adult, and genuinely encouraging, if not yet settled, for slowing memory decline after 60. Treat a multivitamin as a small, specific bet rather than a general insurance policy, and treat a documented deficiency, not a vague sense that your diet could be better, as the real reason to start one.

This is general information, not medical advice. Talk to a clinician before changing anything, especially if you are pregnant, nursing, or managing a condition.