After a series of conflicting reports about whether vitamin pills can stave off chronic disease, researchers announced Wednesday that a large clinical trial of nearly 15,000 older, male physicians followed for more than a decade found that those taking a daily multivitamin experienced 8 percent fewer cancers than the subjects taking dummy pills.
This trial examined whether a common daily multivitamin had an effect on overall cancer risk. A randomized, double-blind study of the kind considered the gold standard in medicine, the study was one of the largest and longest to address vitamin use.
The paper was published online in the Journal of the American Medical Association.
The reduction in total cancers was small but statistically significant, said the lead author, Dr. J. Michael Gaziano, a cardiologist at Brigham and Women's Hospital and the VA Boston Healthcare System. While the main reason to take a multivitamin is to prevent nutritional deficiencies, Gaziano said, "it certainly appears there is a modest reduction in the risk of cancer from a typical multivitamin."
He noted that other measures are likely to protect against cancer more effectively.
"It would be a big mistake for people to go out and take a multivitamin instead of quitting smoking or doing other things that we have a higher suspicion play a bigger role, like eating a good diet and getting exercise," Gaziano said. "You've got to keep wearing your sunscreen."
The study was supported by the National Institutes of Health and a grant, initiated by the investigators, from the chemical company BASF Corp. Pfizer provided the multivitamins. The sponsors did not have input into the study design, data analysis or manuscript preparation, the authors said.
About half of Americans take a vitamin supplement, and at least one-third take a multivitamin. But many recent vitamin studies have found not only a lack of benefit but even some harm associated with large doses of certain supplements.
A major limitation of the study is that it included only male physicians, who were particularly healthy, with extremely low smoking rates, said Marji McCullough, a nutritional epidemiologist with the American Cancer Society.
"We still need to find out whether these findings can be applied to others in the population," she said.