Coffee Cuts Liver Cancer Risk
Coffee drinkers may have reason to smile:
Daily coffee consumption seems to reduce the risk of liver cancer,
a new study finds.
And drinking decaffeinated coffee
seems to cut colorectal cancer risk, another study claims.
Both papers appear in the Feb.
16 issue of the Journal of the National Cancer Institute.
"We were surprised. We didn't expect
the decaf findings," said Karin B. Michels, an associate professor
of epidemiology at Harvard Medical School, and lead author of
the study that looked at caffeine consumption and colorectal cancer
The researchers were trying to
confirm conflicting results from earlier studies, some finding
that coffee reduced colorectal cancer risk and others revealing
no effect. They evaluated data from two large studies, the Nurses'
Health Study and the Health Professionals' Follow-up Study, together
including more than 173,000 men and women. The goal was to look
at the association between coffee, tea and caffeine consumption
and the incidence of colorectal cancer.
They found no association between
consumption of caffeinated coffee or tea and the incidence of
colon or rectal cancer in either group. But they found that those
who regularly drank two or more cups of decaffeinated coffee a
day had about half the rate of rectal cancer as those who never
drank decaf coffee.
It had been theorized that increased
bowel motility [movements] from coffee consumption was "one of
the most important mechanisms" in the reduction of cancer risk,
said Michels. "We set out to confirm that, but we did not find
an association between caffeine consumption and lower cancer risk."
It could be, she speculated, that
decaffeinated coffee has an effect on bowel motility, but something
in caffeine cancels out that effect.
The finding needs to be confirmed
in other studies, Michels said, before any recommendation about
coffee drinking can be made.
In the second study, Dr. Manami
Inoue of the National Cancer Center in Tokyo and colleagues followed
more than 90,000 middle-aged and elderly Japanese men and women
for 10 years. They found that those who drank coffee daily or
almost daily had half the risk of liver cancer, compared to those
who did not drink coffee. They didn't differentiate between caffeinated
or decaffeinated coffee, but noted that decaf coffee is rarely
consumed in Japan.
The rate of liver cancer among
those who never drank coffee was 547.2 cases per 100,000 people
over a decade, but the rate among daily coffee drinkers was 214.6
cases per 100,000 over the same period.
"In our study, liver cancer risk
significantly decreased with the amount of coffee consumed (compared
with nondrinkers, 48 percent decrease with 1-2 cups per day; 52
percent decrease for 3-4 cups per day; 76 percent decrease for
5 cups per day)," Inoue said. "Our results are consistent with,
but more pronounced than, those of previous case-control studies."
About 17,550 new cases of primary
liver and bile duct cancers are expected to be diagnosed this
year in the United States, according to the American Cancer Society.
About 104,950 new cases of colon cancer and 40,340 of rectal cancer
are expected to be diagnosed this year as well.
Dr. Michael J. Thun, head of epidemiological
research for the American Cancer Society, said the two new studies
are interesting, but the results shouldn't prompt any recommendations
or changes in coffee-consumption habits.
"There isn't anything in these
studies that would persuade people to give up or take up coffee
drinking," Thun said, adding, "The liver finding is interesting,
but needs to be replicated."
The finding that decaffeinated,
but not regular, coffee reduced colorectal cancer risk is surprising
to Thun, as it was to the study authors. "But it is important
not to overinterpret," Thun said. Again, more research is needed
to be sure the finding isn't a fluke, he added.
While the associations both bear
more study, Thun said, "it's much too soon to go changing your
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Reference Source 101
February 16, 2005