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

MedlinePlus explains that vitamins are substances the body needs to grow and develop normally, and that there are 13 of them, including vitamins A, C, D, E and K and the B vitamins. It notes that you can usually get all your vitamins from the foods you eat, and that the body can also make vitamins D and K. A multivitamin combines many of these vitamins, often with minerals, in a single daily product.

Some people need more of particular vitamins. MedlinePlus notes that people who eat a vegetarian diet may need to take a vitamin B12 supplement. It also says that high doses of some vitamins can cause problems.

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 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.

MedlinePlus describes a balanced diet with a variety of foods as the best way to get enough vitamins. Whether a supplement makes sense for any one person depends on their diet, health and any diagnosed deficiency.