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esearchers reporting on a case-control study, appearing in the June 1, 1994,
issue of the Journal of the National Cancer Institute, found that
Chinese men and women who drink green tea have a reduced risk of up to 60
percent of developing esophageal cancer.
 Researchers from the National
Cancer Institute (NCI) and the Shanghai Cancer Institute used a cancer
registry to identify 902 esophageal cancer paitents from urban Shanghai,
People's Republic of China. This esophageal cancer study is part of a larger,
multisite study that included pancreatic, colon, and rectal cancers.
"This is the first epidemiologic
study to demonstrate that green tea may protect against esophageal cancer
in humans," said Joseph McLaughlin, Ph.D., the lead researcher from NCI.
Animal studies have shown
that green tea infusions and extracts protect against esophageal cancer, but
this study is the first investigation involving humans to support the
experimental evidence, Dr. McLaughlin said.
Because 80 percent of tea
consumed worldwide is black tea, there have been few studies on green tea,
which is consumed mainly in Asian countries. Furthermore, large-scale
studies had been nonexistent in Asia until a few years ago.
Patients ages 30 to 74 years
who were diagnosed with esophageal cancer between October 1990 and January 1993
were interviewed on their residential and medical history, height and weight,
diet, smoking habits, alcohol use, tea consumption, family history of cancer,
occupation, physical activity, and reproductive history. There were 1,552
people without the disease (control subjects) who answered the same questions.
Information about tea consumption
included types of tea consumed, frequency of consumption, and age at which
tea drinking began. Researchers measured consumption in grams of tea leaves
consumed per month. A tea drinker was defined as someone who drank at least
one cup of tea per week for 6 months or longer.
The study found that drinking
green tea was associated with a 50 percent lower risk of esophageal cancer
in women. Among men, risk was also reduced, but this finding was not statistically
significant. However, green tea drinking was linked to a 60 percent reduction of
esophageal cancer among both men and women who did not smoke.
Individuals who drank burning-hot
fluids (tea and soup) did not reap full benefits from the green tea, which
lowered -- but did not eliminate -- cancer risk. These people experienced a
fivefold increase in esophageal cancer risk over people who did not drink
burning-hot liquids. Studies in China and other countries have shown that
such repeated thermal irritation of the esophagus may be responsible for the
drinkers' increased esophageal cancer risk. Subjects who drank green tea and
avoided burning-hot fluids had significantly lowered cancer risk.
Scientists speculate that the
protective effects of green tea arise out of polyphenol compounds in the
tea. Polyphenols are a class of compounds that have strong antioxidant
properties (the ability to halt enzymes that produce carcinogens) and also
are able to inhibit cancer cell growth.
According to Dr. McLaughlin,
additional epidemiologic studies are needed to confirm the findings from
this research. Should they be confirmed, Dr. McLaughlin believes that
clinical trials should be undertaken to determine the preventative effects
of green tea. These trials would allow researchers to better understand the
biochemical mechanisms involved in the inhibition of esophageal cancer and
to determine whether green tea can truly prevent its occurrence.
This year, about 11,000 Americans
will be diagnosed with esophageal cancer and 10,400 people will die of the
disease.
- As reported by National Cancer Institute
June 1994
The Cancer Information Service (CIS), a program of the
National Cancer Institute, provides a nationwide telephone service for cancer
patients and their families, the public, and health care professionals. CIS
information specialists have extensive training in providing up-to-date and
understandable information about cancer and cancer research. They can answer
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addition, CIS offices serve specific geographic areas and have information
about cancer-related services and resources in their region. The toll-free
number of the CIS is 1-800-4-CANCER (1-800-422-6237).
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