The
Editor, CXpress
22 August 2002
It is with utter dismay that I noticed that
your health writer, who in the same issue (100,
31 July 2002) was credited with “educated and
informative writing”, found it necessary, under the introductory
context of “Are you a victim of nutritional misinformation?”
to include as an example, the statement “Green tea reduces
the risk of certain cancers”, qualified by her comment “More
green tea is consumed in Japan than any other country, yet they
have one of the highest rates of stomach cancer in the world. Drink
green tea if you enjoy it, not because it might reduce your risk
of cancer”. As an advertiser of green tea on the same page,
I am particularly insulted by such cheek, given the considerable
evidence to the contrary, which affront I trust shall be remedied
by your fully conveying the following facts to your misinformed
readers. I have summarised only the most recent scientific research
and expanded a little more deeply specifically on stomach cancer
for the continuing education of your misinformed health writer and
now your readers.
Green tea has been shown in experimental
animal studies, human cell line laboratory studies, human clinical
studies and also epidemiologically in large human population studies,
to significantly reduce the risk of, protect from or prevent several
cancers, and improve treatment thereof, including: <<biliary
tract>> (Takada M, et al, World
J Surg, 26(6), 2002); <<bladder>> (Kamat A, Lamm D,
Urol Clin North Am, 29(1), 2002); (Berger S, et al, Biochem Biophys
Res Commun, 288(1), 2001); <<breast>> (Sartippour M,
et al, Nutr Cancer, 40(2), 2001); <<colon>>
(Hong J, et al, Biochem Pharmacol,
62(9), 2001); <<colorectal>>
(Wargovich M, J Korean Med Sci, 16 Suppl: S81-6, 2001); <<leukemia>>
(Nakazato T, Kizaki M, Rinsho Ketsueki, 43(4), 2002); <<liver>>
(Bertram B, Bartsch H, Wien Med Wochenschr, 152(5-6), 2002); <<lung>>
(Fujimoto N, et al, Int J Oncol,
20(6), 2002); <<melanoma>>
(Liu J, et al, J Cell Biochem, 83(4), 2001); <<oral>>
(Hsu S, et al, Gen Dent, 50(2), 2002);
<<ovaries>>
(Zhang M, et al, Cancer Epidemiol Biomarkers Prev, 11(8), 2002)
<<pancreas>>
(Takada M, et al, Pancreas, 25(1), 2002); (Suzuki Y, Isemura
M, Cancer Lett, 173(1), 2001); <<prostate>>
(Gupta S, Mukhtar H, Urol Clin North
Am, 29(1), 2002); (Liao S, Hong Kong Med J, 7(4), 2001); <<skin>>
(Proniuk S, et al, J Pharm Sci, 91(1), 2002); (Katiyar S, et al,
J Photochem Photobiol B, 65(2-3), 2001).
Earlier studies included esophagal cancer
(Katiyar S, Mukhtar H, J Cell Biochem, 27:S59-S67, 1997) and
many other types, or cancer generally (Jankun
J, et al, Nature, 387:561, 1997); (Ahmad N, et al, J Natl Cancer
Inst, 89:1881–6, 1997); (Kohlmeier L, et al, Nutr Cancer,
27:1–13, 1997); (Imai K, et al, Prev Med, 26(6), 1997); (Sadzuka
Y, et al, Clin Cancer Res, 4:153–6, 1998); (Brown M, Altern
Med Rev, 4(5), 1999); (Nakachi K, et al, Biofactors, 13(1-4), 2000);
(Green Tea Monograph, Altern Med Rev, 5(4), 2000); (Jung Y, Ellis
L, Int J Exp Pathol, 82(6), 2001); (Sartippour M, et al, Int J Oncol,
21(3): 2002); (Jodoin J, et al, Biochim Biophys Acta, 1542(1-3),
2002); (Cao Y, et al, J Nutr Biochem, 13(7): 2002).
The positive results of green tea on cancer
significantly includes even the elderly
(Meydani M, Ann N Y Acad Sci, Apr; 928, 2001) and green
tea is now considered to be one of the most practical preventives
of lifestyle-related diseases, including cancer, resulting in prolongation
of life span (Sueoka N, et al, Ann
N Y Acad Sci, Apr, 928, 2001); (Weisburger J, Chung F, Food Chem
Toxicol, 40(8), 2002). Cooked meat increases the risk
of breast and colon cancer and green tea offers a practical means
of reducing this risk (Weisburger
J, et al, Mutat Res, 516(1-2), 2002). I shall resist
the temptation to summarise the thousands of studies on human health
parameters additional to cancer, other than to point out that it
covers the other biggest killers: cardiovascular and infectious
diseases, including AIDS (covered previously in CXpress).
Regarding stomach/gastric cancer, as with
any medical research, some studies will fail to demonstrate the
protective effect of green tea seen by others, in particular if
there is a research and publication bias favouring pharmaceuticals.
One such recent negative large human population study might have
influenced your health writer (Tsubono
Y, et al, New Engl J Med, 344(9), 2001), but as will
be shown, this study has been criticized for several weaknesses
and more rigorous subsequent studies have amply reaffirmed a protective
and therapeutic effect for green tea against stomach and several
other cancers.
The negative NEJM study was an epidemiological
study where exposure data was gathered via self-administered questionnaires
and follow-up data on patient status and cancer incidence gathered
from population and cancer registries and suffered from several
weaknesses, which were diligently avoided in subsequent studies
following critique of the NEJM paper. Confounding factors that could
limit this study and were identified by the NEJM authors themselves
included that there was no attempt to fully record all risky dietary
habits and behavior or the history of Helicobacter pylori infection,
nor other potential confounders such as the use of drugs, dietary
supplements and other complementary remedies.
The negative NEJM study was not considered
a definitive study by reviewing scientists, who pointed out that
participants who had behavior that put them at risk for gastric
cancer may have been drinking more green tea to counteract their
other risk factors, since behavior associated with a risk of gastric
cancer, such as smoking and eating salty foods were also high in
the study population; and reviewers also questioned why the study
did not include a group that drank 10 or more cups of tea a day,
which had consistently shown the strongest protective effect in
other studies (Taggart K, Medical
Post, 37 (12), 2001).
Other identified weaknesses included: that
the assignment of patients was not randomized; that not all patients
who entered the trial were properly accounted for and attributed
at its conclusion; and that while this study spanned an 8-year period,
dietary and health habit information was collected in the first
year only, whereas the gastric cancer data was collected during
the entire period, so potentially important changes over the course
of the follow-up were not evaluated (Malfair
Taylor S, J Informed Pharmacotherapy, 5:223-225, 2001).
Furthermore, study results were not adjusted for participant’s
history of cancer (Bandolier: Evidence-based
health care, 22 July, 2001).
Regarding <<<stomach cancer>>>,
green tea was shown to induce growth inhibition and apoptosis of
human stomach cancer cells, contributing to cancer chemoprevention
(Hibasami H, et al, Oncol Rep, 5(2), 1998); (Okabe S, et al, Jpn
J Cancer Res, 90(7), 1999); (Isemura M, et al, Biofactors, 13(1-4),
2000); (Hayakawa S, et al, Biosci Biotechnol Biochem, 65(2), 2001)
and to be very effective in human intervention studies
(Yan Y, Zhonghua Yu Fang Yi Xue Za Zhi, 27(3), 1993); (Yamane T,
et al, Cancer Res, 55(10): 1995); (Ji BT, et al, Cancer, 77(12),
1996); (Bushman J, Nutr Cancer, 31(3), 1998); (Inoue M, et al, Cancer
Causes Control, 9(2), 1998); (Oldreive C, et al, Chem Res Toxicol,
11(12), 1998); (Halliwell B, et al, Free Radic Res, 33(6), 2001);
(Salucci M, et al, Br J Cancer, 86(10), 2002).
Green tea was also shown to have significant
protective and preventive effects against stomach cancer in several
large epidemiological studies in China and Japan prior and similar
to the NEJM study paper (Yu G, et
al, Cancer Causes Control, 6(6), 1995); (Kono S, et al, Jpn J Cancer
Res, 79(10), 1988); (Ye W, et al, World J Gastroenterol, 4(6), 1998);
(Ye W, et al, Zhonghua Yu Fang Yi Xue Za Zhi, 32(2), 1998); (Wang
M, et al, Zhonghua Liu Xing Bing Xue Za Zhi, 20(2), 1999); (Setiawan
V, et al, W Int J Cancer, 92(4), 2001) as well as positive
studies subsequent to and improving on the methodology of the NEJM
paper (Bachrach U, Wang Y, Amino
Acids, 22(1), 2002); (Sun, C-L, et al, Research Results, Abstract
#2354, Amer Assoc Cancer Res, 93rd Ann Meeting, SF, CA, 6-10 April,
2002).
Green tea is significantly protective against
human cancer and your health writer is clearly wrong to have suggested
otherwise to your readers. I thank you in advance for the opportunity
to state the facts.
Stuart Thomson,
Director,
Gaia Research Institute
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