By RONI CARYN RABIN
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 doctors 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 clinical trial, the kind considered
the most rigorous type of study, it was one of the largest and longest
efforts to address questions about vitamin use.
The findings were 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 the 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.
Pfizer provided the multivitamins. The sponsors did not influence 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 that 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 doctors,
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.
The research effort might have benefited from the fact that the doctors
who participated were diligent about taking their pills, and the
researchers suggested that the effect of multivitamin use might have
been muted because the participants were 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.”
Source: http://www.nytimes.com/2012/10/18/health/daily-multivitamin-may-reduce-cancer-risk-clinical-trial-finds.html?partner=MYWAY&ei=5065&_r=0
Source: http://www.nytimes.com/2012/10/18/health/daily-multivitamin-may-reduce-cancer-risk-clinical-trial-finds.html?partner=MYWAY&ei=5065&_r=0
