Daily Multivitamin May Reduce Cancer Risk, Clinical Trial Finds (NYT)

By RONI CARYN RABIN
Published: October 17, 2012 60 Comments

After a series of conflicting reports about whether vitamin pills can
stave off chronic disease, researchers announced on 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.

While many studies have focused on the effects of high doses of
particular vitamins or minerals, like calcium and vitamin D, this
clinical trial examined whether a common daily multivitamin had an
effect on overall cancer risk. A randomized, double-blinded study of
the kind considered the gold standard in medicine, the study was one
of the largest and longest efforts to address questions about vitamin
use.

The findings are to be presented Wednesday at an American Association
for Cancer Research conference on cancer prevention in Anaheim,
Calif., and 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 study’s 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, Dr. 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 than daily use of multivitamins.

“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,” Dr. 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
Corporation. 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 all Americans take some form of a vitamin supplement,
and at least one-third take a multivitamin. But many recent vitamin
studies have been disappointing, finding not only a lack of benefit
but even some harm associated with large doses of certain supplements.
The 2010 dietary guidelines for Americans state there is no evidence
to support taking a multivitamin or mineral supplement to prevent
chronic disease.

The American Cancer Society recommends that people eat a balanced
diet, but that those who take supplements choose a balanced
multivitamin that contains no more than 100 percent of the daily value
of most nutrients.

Though several researchers said they were somewhat surprised by the
findings, others called the results encouraging.

“It is a small overall effect, but from a public health standpoint it
could be of great importance,” said Dr. E. Robert Greenberg, an
affiliate at Fred Hutchinson Cancer Research Center in Seattle. “Other
than quitting smoking, there’s not much else out there that has shown
it will reduce your cancer risk by nearly 10 percent.”

Multivitamin use had no effect on the incidence of prostate cancer,
which was the most common cancer diagnosed in the study participants.
When researchers looked at the effect of vitamin use on all other
cancers, they found a 12 percent reduction in occurrence. Overall
cancer deaths were reduced among vitamin users, but the difference was
not statistically significant.

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.

While the research effort may have benefited from the fact that the
physicians who participated were very diligent about taking their
pills, the researchers also suggested that the effect of multivitamin
use may have been muted because the participants were very
health-conscious to begin with.

Dr. David Chapin, 73, a gynecologist at Beth Israel Deaconess Medical
Center in Boston who participated in the trial, said that although he
had “never believed” in vitamins, he might start taking a daily
multivitamin now, despite the modest benefit.

“A lot of studies make big news, but when you look at the
nitty-gritty, they don’t show all that much,” Dr. Chapin said, adding
that he recently discovered he had been taking a placebo pill. “This
was a very reliable study, it was very well designed and administered,
and it went on and on and on.”