Do multivitamins help people live longer? What the research shows

Multivitamins are the most common dietary supplement in the US. About one in three adults takes one, and the main reason people give is to stay healthy and prevent disease.

Whether they do that is less clear. The largest study of multivitamins and death, covering 390,124 US adults, found daily users did not live longer. A national task force has concluded that the evidence is too thin to judge whether multivitamins help prevent heart disease or cancer, and trials have found at most small effects.

What vitamins do, and what a multivitamin supplies

Vitamins are nutrients the body needs in small amounts, and most come from food. There are 13: vitamins A, C, D, E and K, and eight B vitamins. A multivitamin combines many of these, often with minerals, in a single daily product.

People take them for broad reasons. The US Preventive Services Task Force reports that the most commonly cited reason for using supplements is for overall health and wellness and to fill nutrient gaps in the diet. That is a different question from treating a diagnosed deficiency, where a specific nutrient is given for a specific shortfall.

What the large multivitamin study found

A 2024 study in JAMA Network Open pooled three long-running US cohorts: the NIH-AARP Diet and Health Study, a cancer screening trial group and the Agricultural Health Study. Together they covered 390,124 adults, median age 61, who had no history of cancer or other chronic disease when they reported their multivitamin use in the 1990s and early 2000s.

The researchers followed them for up to 27 years, during which 164,762 died. They designed the analysis to handle two known problems: people who take supplements tend to have healthier habits, and people who fall ill sometimes start taking vitamins, which can make vitamins look harmful. Multivitamin use was not associated with lower risk of death at any point. In the first half of follow-up, daily users had a slightly higher risk, about 4%.

The authors concluded that multivitamin use was not associated with a mortality benefit. Deaths from the major causes, including heart disease and cancer, showed a similar pattern.

Who takes multivitamins

The same study shows why comparisons are tricky. Daily multivitamin users were more often women, 49.3% against 39.3% of non-users, and more often college educated, 42.0% against 37.9%. Fewer were current smokers, 11.0% against 13.0%. Differences like these can make supplements look helpful in studies even when they are not, which is why the researchers adjusted for them.

What trials show about multivitamins and cancer

Randomized trials avoid that problem but are rarer. In the Physicians’ Health Study II, 14,641 US male doctors aged 50 and older took a daily multivitamin or a placebo for a median of 11 years. Total cancer was slightly lower with the multivitamin, 17.0 against 18.3 cases per 1,000 person-years, about 8% fewer.

There was no clear effect on prostate cancer, colorectal cancer or other specific cancers, and no clear difference in cancer deaths. The authors described a modest reduction in total cancer in this large prevention trial of male physicians, a group that may not reflect the wider population.

What the newest multivitamin trials show

The largest recent test is COSMOS, a trial of 21,442 US women aged 65 and over and men aged 60 and over, who took a daily multivitamin or a placebo for a median of 3.6 years. Invasive cancer occurred in 518 people on the multivitamin and 535 on placebo. The authors concluded that a daily MVM supplement, compared with placebo, did not significantly reduce the incidence of total cancer, meaning the multivitamin-multimineral pill made no clear difference. Heart disease and deaths were also about the same, although lung cancer was less common with the multivitamin, a secondary finding.

A COSMOS substudy of 3,562 older adults tested memory online each year. People taking the multivitamin did slightly better on a word-list recall test after one year and across three years, an improvement the researchers estimated as equivalent to 3.1 years of age-related memory change. Other thinking tests showed no difference, and the result has yet to be confirmed in a separate trial.

What guidelines say about multivitamins

The US Preventive Services Task Force (USPSTF), an independent panel that reviews evidence on prevention, updated its advice on vitamin supplements in 2022. It concluded that the evidence is insufficient to determine the balance of benefits and harms of multivitamins for preventing heart disease or cancer, a finding it labels an I statement, meaning evidence is lacking.

It was firmer on two single supplements. The USPSTF recommends against the use of beta carotene or vitamin E supplements for preventing heart disease or cancer, having found that the harms of beta carotene outweigh its benefits and that vitamin E gives no net benefit. The statement applies to community-dwelling adults who are not pregnant.

Why multivitamin research is hard to interpret

Most multivitamin evidence is observational and relies on people reporting their own supplement use, often measured once, years before the outcomes. Products vary widely in what they contain and in dose.

The main trial enrolled only male doctors, and the cohort study only people without chronic disease at the start. Neither was designed to test multivitamins in people with poor diets, known deficiencies or conditions that affect how nutrients are absorbed.

What the multivitamin research cannot tell us yet

These studies say little about specific groups whose needs differ, such as people on restrictive diets or with health conditions that affect nutrition. They also do not test individual nutrients that can matter in particular situations, which the task force assessed separately.

What the multivitamin evidence adds up to

For generally healthy adults in the US, multivitamins have not been shown to help people live longer, and the evidence on heart disease and cancer is too limited for the USPSTF to judge. One large trial found a small drop in total cancer in older men.

The newest trial, COSMOS, found no effect on cancer or heart disease over about three and a half years, and a small memory signal that needs confirming. Whether a supplement makes sense for any one person depends on their diet, health and any diagnosed deficiency.