Once-a-day multivitamins won't prevent death

An analysis of three prospective cohort studies with more than 20 years of follow-up found that taking a daily multivitamin for many years did not reduce the risk of death.

According to Ericka Loftfield, PhD, MPH, of the National Cancer Institute, and colleagues, taking a daily multivitamin was associated with a small increased risk of death during the first half of follow-up compared with not taking a multivitamin (HR 1.04, 95% CI 1.02-1.07).

No mortality benefit was seen in the later stages of follow-up (HR 1.04, 95% CI 0.99-1.08), nor was there any benefit seen for individual causes of death, such as heart disease, cancer, or cerebrovascular disease, the researchers said. Reported JAMA Network Open.

“We found no evidence that regular consumption of multivitamins increases life expectancy in healthy adults,” Loftfield and his colleagues wrote.

Peter Cohen, M.D., of the Cambridge Health Alliance in Massachusetts, who studies dietary supplements and was not involved in the paper, said the findings are consistent with data from previous randomized controlled trials.

“It's hard to worry [the mortality signal] Randomized controlled trials say multivitamins won't kill you.” Physicians' Health Survey IICohen said: Medpage Today“I would never tell a patient to stop taking their multivitamin.”

“This just suggests that taking a multivitamin for even 20 years is not going to extend your life,” he added.

Use of multivitamins fell 6 percent between 1999 and 2011, which may be due in part to published studies showing that multivitamins do not reduce the risk of cardiovascular disease, cancer, or death, the researchers said, though one in three adults still uses multivitamins, they added.

In 2022, the U.S. Preventive Services Task Force Insufficient evidence There are few studies supporting the harms or benefits of multivitamin use on mortality. One reason is that past studies, especially observational studies, are limited by confounding factors such as the effects of healthy and sick users. On the one hand, people who take multivitamins may have healthier eating habits, be more physically active, and smoke less. On the other hand, patients who are diagnosed with a disease may increase their multivitamin use due to the perceived health benefits.

To control for these potential sources of bias, the researchers analyzed data from 390,124 participants from three US prospective cohort studies: the NIH-AARP Diet and Health Study (n=327,732), the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (n=42,732), and the Agricultural Health Study (n=19,660).

Participants underwent baseline assessments from 1993 to 2001 and were followed up from 1998 to 2004. In addition, extended follow-up was also conducted for up to 27 years, with an overall median follow-up of 23.5 years. The first follow-up period included the first 12 years of follow-up, and the second period included the final 15 years of follow-up.

Patients were healthy at baseline and had no history of cancer or other chronic diseases. The median age was 61.4 years, and 55.4% were men. Patients self-reported use of multivitamins, and a detailed characterization of potential confounding factors was performed, the researchers said.

A total of 164,762 deaths occurred during the follow-up period.

Loftfield and colleagues found that daily multivitamin intake did not influence mortality risk by diet quality, nor did they find any effect by race or ethnicity.However, during the initial follow-up period, daily multivitamin intake was associated with a higher risk of all-cause mortality in the youngest age group (<55 years) (HR 1.15, 95% CI 1.05-1.26).

In a time-varying analysis of 234,593 participants from all three cohorts (those who had a baseline and second multivitamin use assessment), daily multivitamin use was associated with a 4% increased risk of all-cause mortality in the first follow-up period (HR 1.04, 95% CI 1.02-1.07) but not in the second period (HR 0.98, 95% CI 0.93-1.04).

“Results from a time-varying analysis incorporating the second assessment of multivitamin use were consistent with the pooled baseline estimates and support the conclusion of no mortality benefit,” the researchers wrote.

in With invited commentaryNeal Barnard, MD, PhD, of George Washington University in Washington, DC, and colleagues said the findings confirm “the largely negative results of previous studies” and “support the argument that, whenever possible, people should obtain vitamins from food rather than supplements.”

For example, the Nurses' Health Study and the Health Professionals Follow-up Study reported that increased fruit and vegetable intake was associated with reduced mortality, with the greatest benefits seen in people who ate at least five servings per day.

“Refocusing nutritional interventions on foods rather than supplements may confer mortality-reduction benefits not achieved with multivitamins,” Barnard and colleagues write. “Healthy dietary patterns include providing micronutrients, as well as healthy macronutrients and dietary fiber, and limiting intake of saturated fat and cholesterol.”

This study was limited by the possibility of residual confounding due to inadequate or unmeasured confounders, the possibility of selection bias as participants with missing data may differ from those with complete data, and the fact that all three studies included primarily Caucasians.