After years of research showing dietary supplements failed to prevent cancer, a new study of multivitamin use in men has a surprising message: This one worked.
Turns out, a daily dose of Centrum Silver multivitamins reduced the total risk of cancer in study participants by 8 percent, according to gold-standard research that included nearly 15,000 male doctors older than 50 for up to 13 years.
“It does appear that there is a modest reduction in cancer among middle-aged and older men,” said Dr. J. Michael Gaziano, chief of the division of aging at Brigham and Women’s Hospital and a researcher at the VA Boston Healthcare System.
The study also found that multivitamin use cut site-specific cancers, except for prostate cancer, by 12 percent, and suggested a 12 percent reduction in deaths caused by cancer, though that figure wasn’t statistically significant.
“Even total mortality went in the right direction,” said Gaziano, whose new data comes from the Physicians Health Study II published Wednesday in the Journal of the American Medical Association.
The finding is important in a country where more than half of U.S. adults use dietary supplements, according to the Centers for Disease Control and Prevention -- and where the most common supplement is a daily multivitamin.
Several recent studies -- including Gaziano’s own work -- have looked at whether taking specific vitamins such as C, E and B12 prevent cancer. They’ve come up empty; a few even found a higher risk of certain illnesses.
The difference, Gaziano said, is that many of those studies were limited in scope and size and they used single supplements at high doses, much higher than a daily vitamin would provide.
By contrast, the new study is the first of its kind.
“The Physicians' Health Study II represents the only large-scale, randomized, double-blind, placebo-controlled trial testing the long-term effects of a common multivitamin in the prevention of chronic disease,” the authors write.
Study participants included 14,641 U.S. men, all doctors, who received either a pack of daily supplements, including the Centrum Silver vitamins, or daily dummy pills between July 1997 and June 2011.
The doctors, who were followed for between 10 and 13 years, were excellent patients. They were pretty healthy, with a mean body mass index of 26 -- just barely overweight -- and only 3.6 percent of them smoked. They were also good sports: By the end of the trial, more than two-thirds of the docs were still taking their pills as directed, the study found.
“They are very compliant,” Gaziano said.
Take Dr. Dean Rising, 72, a Springfield, Mo., pediatrician who has participated in both phases of the Physicians' Health Study, two large-scale studies spanning 30 years. He took photos of himself and his daily "vitamins" on seven continents, including a shot a few years ago in Antartica.
"This is the sort of thing where if you don't have people testing these things, you never know the results," explained Rising.
As it turns out, he learned last year that he was enrolled in the placebo arm of the Phase II study, so he never got any vitamins at all. Now, he says, he makes sure to take one every day.
"I think it means you need a variety of different vitamins in your diet," he said of the new results.
Experts agree. The new study suggests that boosting nutrition, even with the modest nudge of a daily vitamin, could have far-reaching health benefits, said Dr. Demetrius Albanes, a senior investigator and expert in nutritional epidemiology with the National Cancer Institute.
“It’s exciting. It’s encouraging,” said Albanes.
But others cautioned that it’s too soon to make sweeping recommendations based on a single study, especially when previous trials have been mixed or have even shown harm, said Susan Gapstur, vice president of the epidemiology research program for the American Cancer Society.
“It’s important to remember that this study, as credible as it is, is still just one trial,” said “Typically we like to see these kinds of findings replicated by other studies, and in other populations, before coming to solid conclusions.”
In addition, the trial only included men who are healthier than the general population, and, of course, it excluded women. Further research would need to conduct a similar test of multivitamin use in women to determine whether that also reduced cancer risk, experts said.
Still, the results of the study could send some older men racing to buy bottles of Centrum Silver, the best-selling multivitamin produced by Pfizer, the drug company that now owns the brand. Gaziano said he picked that multivitamin early on because he thought it was a quality product that would "last over the years."
An estimated 18 million multivitamins and 18 million placebo pills were donated during the course of the trial, said MacKay Jimeson, a Pfizer spokesman who noted that the company is “very pleased” that researchers chose Centrum Silver for the study.
Gaziano said the pills and packaging were the extent of his drug company support.
For his part, Gaziano is pleased not only with the results, but also with finishing a project that occupied 17 years of his life.
“As a long-term chronic disease trialist, it feels very good to be done,” he said. “You just have to be patient. I think that when we’re talking about prevention of cancer, we’re talking about decades.”