A study published Wednesday by the Journal of the American Medical Association (JAMA) showed that in a large population of men over 50, long-term use of multivitamins resulted in a statistically significant reduction in incidence of cancer versus placebo.
The study—titled “Multivitamins in the Prevention of Cancer in Men” as part of The Physicians’ Health Study (PHS) II Randomized Controlled Trial—followed 14,641 generally healthy physicians from 1997 to 2011, and found an 8 percent reduction in incidence of cancer among multivitamin users.
There was no significant effect on prostate, colorectal or any other specific form of cancer, nor did multivitamins show an impact on reducing risk of cancer mortality. Only the difference in total cancer rates was found to be statistically significant.
The study was supported by the National Institutes of Health, with a grant from chemical company BASF—the largest supplier of ingredients to the supplement industry. Pfizer supplied its Centrum Silver brand multivitamin for use in the study. This trial was one of the largest and longest of its kind.
“This carries a lot of weight because of its robust nature, its large population, how good the compliance rate was, and how they could record various parameters because of very complete randomization,” said Duffy MacKay, ND, vice president of scientific and regulatory affairs at the Council for Responsible Nutrition (CRN).
Finally, some good news for supplements
The study is a rare gem in a recent raft of negative supplement trials, including a meta-analysis published in JAMA that discounts omega-3s’ ability to prevent heart failure. Most long-term supplement trials focus on single nutrients and produce conflicting results, especially when combed over by meta-analyses.
“To date, large-scale randomized trials testing single or small numbers of higher-dose individual vitamins and minerals for cancer have generally found a lack of effect,” the study’s authors wrote.
But this could be a watershed moment for a supplement industry that has seen a gradual debunking of some of its largest product categories, such as calcium and vitamin E. At more than $5 billion in 2011 sales, multivitamins are the supplement industry’s largest product category.
“Other than quitting smoking, there’s not much else out there that has shown it will reduce your cancer risk by nearly 10 percent,” Dr. E. Robert Greenberg, of Fred Hutchison Cancer Research Center, told the New York Times.
“We’re just seeing the first results,” MacKay said, adding that cardiovascular disease was another primary endpoint of the PHS, with cognitive function and eye disease as secondary endpoints.
Is the study significant enough?
Others are more skeptical. “This is a case of a statistically significant but not particularly impactful result,” Indiana University oncologist George Sledge told Forbes. “The reduction in cancer incidence is small but real, but at the end of the day no one lived any longer.”
The study essentially shows that for every 100 people over 10 years, 18 would get cancer if taking placebo, while only 17.3 would get cancer if taking Centrum. In those terms, the results seem like small beans; however, scale that out to the entire adult population of the United States, and perhaps that bean hill is worth exploring, at least from a cost analysis standpoint. Would there be a significant difference in healthcare expenditures on that small population of cancer patients versus the cost of daily supplementation?
MacKay suggested that the evidence will give clinicians more reason to recommend that their patients take multivitamins. “It makes the choice more prudent,” he said, because the study bears out that multivitamins are safe and have a tangible benefit. Many doctors have historically been cautious about recommending vitamins because of a lack of randomized, double-blind, placebo-controlled evidence.
It could also have an effect on new U.S. dietary guidelines, which are now in the process of being evaluated and will be released in 2015. New guidelines come out every five years.
“Right now is the time when new studies and new evidence becomes important,” MacKay said. “The guideline committee did not have this study on hand in 2010.” The 2010 dietary guidelines do not recognize multivitamins as having any benefit in preventing chronic disease.