20-Year Study Finds Daily Multivitamins Don’t Extend Lifespan

A large, decades-long study of over 390,000 U.S. adults challenges a widespread assumption about daily multivitamins.

Multivitamins are a daily habit for millions of Americans, often taken with the expectation that they will extend life or prevent disease. But one of the largest and longest-running studies to examine this belief suggests otherwise.

Researchers analyzed data from 390,124 generally healthy U.S. adults who were followed for more than 20 years and found no evidence that taking a daily multivitamin lowers the risk of death. The study, led by scientists at the National Cancer Institute and published in JAMA Network Open, also found no meaningful differences in deaths from cancer, heart disease, or stroke.

Something Unexpected

During the early years of follow-up, people who reported daily multivitamin use had a slightly higher risk of death, about 4 percent higher than nonusers. Researchers say this small increase may reflect underlying differences between groups rather than a direct harmful effect.

Participants were drawn from three major U.S. cohorts and tracked for up to 27 years, allowing researchers to account for factors that often complicate nutrition studies. Multivitamin users, for example, were more likely to have healthier diets, exercise more, and smoke less. Others may have started taking supplements after health concerns emerged.

That does not mean supplements have no role. Certain groups clearly benefit from targeted use. Folic acid during pregnancy helps prevent serious birth defects. People who have undergone bariatric surgery may need supplements to replace lost nutrients, and specific combinations of vitamins can slow the progression of age-related eye disease.

Potential Risks

At the same time, supplements are not risk-free. High doses of certain nutrients can cause harm, and interactions with medications are a real concern. For example, vitamin K can interfere with blood thinners, while excess iron has been linked to conditions such as heart disease and diabetes. Large clinical trials have also shown that beta carotene supplements can increase lung cancer risk in smokers, even though the same nutrient from food is associated with benefits.

The findings suggest health outcomes depend on more than isolated nutrients. Diets rich in vegetables, fruits, legumes, and whole grains consistently show links to longer life. Populations known for exceptional longevity, often referred to as Blue Zones, rely on these foods as dietary staples rather than supplements.

The new findings do not close the door on all supplement use, but they do challenge a common assumption: for generally healthy adults, taking a daily multivitamin appears unlikely to extend lifespan.

References:

"Multivitamin Use and Mortality Risk in 3 Prospective US Cohorts" by Erikka Loftfield, Caitlin P. O'Connell, Christian C. Abnet, Barry I. Graubard, Linda M. Liao, Laura E. Beane Freeman, Jonathan N. Hofmann, Neal D. Freedman and Rashmi Sinha, 26 June 2024, JAMA Network Open.
DOI: 10.1001/jamanetworkopen.2024.18729

"The Limited Value of Multivitamin Supplements" by Neal D. Barnard, Hana Kahleova and Roxanne Becker, 26 June 2024, JAMA Network Open.
DOI: 10.1001/jamanetworkopen.2024.18965