With three new studies finding that a daily multivitamin won't help boost the average American's health, the experts behind the research are urging people to abandon use of the supplements.
The studies found that popping a daily multivitamin didn't ward off heart problems or memory loss, and wasn't tied to a longer life span.
The studies, published in the Dec. 17 issue of the journal Annals of Internal Medicine, found that multivitamin and mineral supplements did not work any better in these respects than placebo pills.
Dietary supplements are a multibillion-dollar industry in the United States, and multivitamins account for nearly half of all vitamin sales, according to the U.S. Office of Dietary Supplements.
But a growing body of evidence suggests that multivitamins offer little or nothing in the way of health benefits, and some studies suggest that high doses of certain vitamins might cause harm.
As a result, the authors behind the new research said, it's time for most people to stop taking them.
"We believe that it's clear that vitamins are not working," said Dr. Eliseo Guallar, a professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health.
In a strongly worded editorial on the three studies, Guallar and his co-authors urged people to stop spending money on multivitamins.
Even a representatives of the vitamin industry asked people to temper their hopes about dietary supplements.
"We all need to manage our expectations about why we're taking multivitamins," Duffy MacKay, vice president of scientific and regulatory affairs for the Council for Responsible Nutrition, a trade group that represents supplement manufacturers, said in a prepared statement.
"Research shows that the two main reasons people take multivitamins are for overall health and wellness and to fill in nutrient gaps," MacKay said. "Science still demonstrates that multivitamins work for those purposes, and that alone provides reason for people to take a multivitamin."
However, Guallar said, it's not clear that taking supplements to fill gaps in a less-than-perfect diet really translates into any kind of health boost.
"It would be great if all dietary problems could be solved with a pill," he said. "Unfortunately, that's not the case."
For the first study, researchers randomly assigned almost 6,000 male doctors over the age of 65 to take either a daily Centrum Silver multivitamin or a look-alike placebo pill. Every few years, the researchers gave the men a battery of tests over the telephone to check their memories.
The men in the study were in pretty good health to begin with, and 84 percent said they faithfully took their pills each day.
After 12 years, there was no difference in memory problems between the two groups.
"No matter which way we broke it down, there was a null effect," said study author Jacqueline O'Brien, a research associate at Brigham and Women's Hospital in Boston. "Supplements are often marketed to have benefits for brain health and things like that, and this is a pretty clear takeaway message."
The same study, however, has previously found that multivitamins might modestly reduce the risk of cancer and cataracts. Cancer risk was reduced by 8 percent, while the risk of cataracts dropped by 9 percent, compared to placebo.
In the second study, researchers randomly assigned 1,700 heart attack survivors enrolled in a trial of therapy known as intravenous chelation to a daily regimen of high doses of vitamins and minerals or placebo pills.
Participants were asked to take six large pills a day, and researchers think many developed pill fatigue. Nearly half the participants in each part of the study stopped taking their medication before the end of the study. The average time people stuck with it was about two and a half years.
After an average of 55 months, there was no significant difference between the two groups in a composite measure that counted the number of deaths, second heart attacks, strokes, episodes of serious chest pain and procedures to open blocked arteries.
The third study, a research review, assessed the evidence from 27 studies on vitamin and mineral supplements that included more than 450,000 people. That study, conducted for the U.S. Preventive Services Task Force, found no evidence that supplements offer a benefit for heart disease or that they delay death from any cause. They found only a minimal benefit for cancer risk.
The results of the studies are so clear and consistent, the editorial writers said, that it's time to stop wasting research money looking for evidence of a benefit.
"The probability of a meaningful effect is so small that it's not worth doing study after study and spending research dollars on these questions," Guallar said.
