Editorial NexoScience
If you have ever stood in the vitamin aisle turning a bottle of multivitamins over in your hand, weighing whether that daily habit is actually doing anything for you, you are part of a very large club. Close to a third of adults in the United States report taking a multivitamin, and most say they do it to stay healthy and head off disease before it starts.
The evidence on multivitamins and mortality has been a mess for decades. Some observational studies found a lower risk of dying among regular users. Others found no difference at all, and a few even pointed the other way. In 2022, the US Preventive Services Task Force pooled nine randomized trials and concluded there simply was not enough evidence to say whether multivitamins help or harm when it comes to preventing cardiovascular disease or cancer. Part of the problem was follow-up time: most trials only tracked people for a few years, far too short a window to see how a daily supplement habit plays out over an entire adult life.
Researchers just pooled three of the largest long-running health studies in the country to close that gap. The team, based at the National Cancer Institute, combined data from the NIH-AARP Diet and Health Study, the PLCO Cancer Screening Trial, and the Agricultural Health Study, three cohorts that between them tracked 390,124 generally healthy adults for more than twenty years. Participants who already had cancer, diabetes, a heart attack or a stroke at the start were excluded, so the analysis reflects what a daily multivitamin does for people who are not already managing a major illness. Over a combined 7.8 million person-years of follow-up, 164,762 of those participants died.
Daily multivitamin users did not live longer, and their risk of dying was actually slightly higher. Compared with people who never used a multivitamin, daily users had a 4% higher risk of death from any cause during the first half of the follow-up period, a small but statistically real difference. When the researchers broke deaths down by cause, the picture stayed unremarkable rather than alarming: risk of dying from heart disease, cancer, or stroke specifically hovered close to 1.0, meaning multivitamin use was not clearly tied to more or fewer deaths from any one of those conditions. A second analysis that checked in on participants’ multivitamin habits years after baseline told the same story.
None of this means a daily multivitamin is doing you harm, and that distinction matters. This is an observational study, not a trial where researchers randomly assigned people to take a pill or a placebo, so it cannot prove that multivitamins caused those extra deaths. The authors point to two well-known biases that push observational data in opposite directions. People who start taking supplements because they are already unwell tend to skew the numbers toward looking harmful, a pattern researchers call the sick user effect. People who take supplements because they already eat well and exercise tend to skew the numbers toward looking protective, the healthy user effect. The researchers adjusted statistically for smoking, diet quality, physical activity, alcohol, education and several other factors, and the small increase in risk persisted, but they are careful to note that some of that gap could still come from confounders nobody measured.
One subgroup showed a clearer signal than the rest. Adults younger than 55 who took a daily multivitamin had a 15% higher risk of death than non-users in that same age group, the strongest single association in the entire analysis. Beyond age, the researchers found no meaningful differences in the multivitamin-mortality relationship by sex, race and ethnicity, or overall diet quality, which helps rule out the possibility that the result is really about who tends to take multivitamins rather than the vitamins themselves.
The study leans mostly on White participants and relies on people accurately recalling how often they took a pill years earlier, both real limits the authors acknowledge. But with three large cohorts, decades of tracking and hundreds of thousands of participants, it is one of the most complete pictures yet of what a daily multivitamin habit is associated with over an entire adult lifetime, and the honest answer is: probably not a longer one.
Source: Loftfield E, O’Connell CP, Abnet CC, Graubard BI, Liao LM, Beane Freeman LE, Hofmann JN, Freedman ND, Sinha R. “Multivitamin Use and Mortality Risk in 3 Prospective US Cohorts.” JAMA Network Open, 2024;7(6):e2418729. DOI: 10.1001/jamanetworkopen.2024.18729
