CHICAGO (AP) — There is more evidence that taking
vitamin E pills can be risky. A study that followed up on men who took high
doses of the vitamin for about five years found they had a slightly increased
risk of prostate cancer — even after they quit taking the pills.
Doctors say it's another sign that people should be
careful about using vitamins and other supplements.
"People tend to think of vitamins as innocuous
substances, almost like chicken soup — take a little and it can't hurt,"
said lead author Dr. Eric Klein of the Cleveland Clinic. The study shows that
is not true.
"If you have normal levels, the vitamin is
probably of no benefit, and if you take too much, you can be harmed,"
Klein said.
Men randomly assigned to take a 400-unit capsule of
vitamin E every day for about five years were 17 percent more likely to get
prostate cancer than those given dummy pills. That dose, commonly found in
over-the-counter supplements, is almost 20 times higher than the recommended
adult amount, which is about 23 units daily.
The results mean for every 1,000 men who took
vitamin E, there were 11 additional cases of prostate cancer, compared with men
taking dummy pills.
The study was actually launched to try to confirm
less rigorous research suggesting vitamin E might protect against prostate
cancer. Overall, about 160 of every 1,000 U.S. men will develop prostate cancer
in their lifetime.
Risks increase as men age. Detection can be tricky
since symptoms such as frequent urination can also be caused by harmless
conditions, and doctors disagree about the benefits of screening tests.
Treatment is also complex since some slow-growing prostate cancers are not
deadly but some procedures, including surgery, can damage sexual function and
cause incontinence.
Just last week, a government-convened panel of
experts recommended against routine PSA screening for prostate cancer. That draft
advice is open for public comment.
What should vitamin E users do, given the new study
results? About 13 percent of American men take it, according to a supplement
trade group.
Dr. Otis Brawley, chief medical officer for the
American Cancer Society, says they should stop taking large doses and talk to
their doctors about risks and benefits from prostate cancer screening. Smaller
doses, typically found in multivitamins, are probably fine, said Brawley, who
was not involved in the research.
Vitamin E is found in foods such as nuts, seeds and
vegetable oils. The nutrient helps nerves, muscles, blood vessels and the
immune system function.
Vitamin E supplements have long been promoted for
disease prevention, but scientific research has disproven many claims and
suggested they might increase risks for some conditions, including heart
failure.
Brawley noted that the study echoes previous
thinking on beta-carotene, which once was thought to protect against cancer but
more recently has been linked with increased risks for lung cancer, especially
in smokers.
"There should be a global warning that ...
excessive use of vitamins has not been proven to be beneficial and may be the
opposite," Brawley said.
Experts generally agree that foods are the best
sources for vitamins.
The new research appears in Wednesday's Journal of
the American Medical Association. The National Cancer Institute and National
Center for Complementary and Alternative Medicine paid for the
multimillion-dollar study.
Joe Latina, a cabinet shop owner in Aurora, Ohio,
was among study participants. He said researchers gave him pills they said
"might slow down prostate cancer." Now 71 and cancer-free, he says he
doesn't know whether he was given vitamins or dummy pills.
Latina said he "was kind of surprised" by
the study results, but is not stressing out over the possibility that he still
might get cancer.
"I'm a positive thinker," he said.
"I'm not walking around saying, 'Oh my God, the other shoe is going to
drop. I don't think I have any way to control it."
The study involved more than 35,000 healthy men
aged 50 and older, from the United States, Canada and Puerto Rico. They were
randomly assigned to take daily vitamin E or selenium supplements, both pills
or dummy pills. The study was halted after about five years when there were
signs of no benefit and a possible increased risk for prostate cancer in
vitamin E users. The researchers continued tracking the men even after they
stopped taking pills.
The follow-up found that a potential link between
selenium and diabetes was a false alarm, but it confirmed signs of a vitamin
E-prostate cancer link. Over a total of about seven years, there were 76 cases
of prostate cancer diagnosed per 1,000 men, versus 65 cases in men given dummy
pills.
"The implications of our observations are
substantial," the study authors said.
The results suggest that extra risks associated
with taking relatively high doses of vitamin E continue even after supplements
are stopped. The researchers said it is unclear how vitamin E would harm the
prostate.
There was no increased risk for men who took both
vitamin E and selenium, suggesting that selenium might somehow counter the
harmful effects of vitamin E, the study authors said.
Duffy MacKay of the Council for Responsible
Nutrition, a supplement makers' trade group, said the study shouldn't be
interpreted as questioning the benefits of vitamin E as an essential nutrient,
and he said there is evidence that many Americans don't get enough.
Copyright
2011 The Associated Press.
