Correspondence

Green Tea and Gastric Cancer in Japan

N Engl J Med 2001; 344:1867-1868June 14, 2001

Article

To the Editor:

Tsubono et al. (March 1 issue)1 reported that the consumption of five or more cups of green tea per day was not associated with a decreased risk of gastric cancer in a prospective study in Japan. However, this study did not address a possible protective effect of consumption of very large amounts of green tea. Case–control studies in Japan2,3 and China4,5 have suggested that a protective effect against gastric cancer may be conferred only by consumption of eight or more cups of green tea per day.

In two Japanese studies, a decreased risk of gastric cancer was associated with the highest level of consumption of green tea (10 or more cups per day in one study2 and 7 or more cups per day in the other3) but not with intermediate levels of consumption. In China, the use of four or more batches of green-tea leaves per day was associated with a substantial decrease in the risk of gastric cancer,4 and the use of more than 3 kg per year was associated with a moderately decreased risk.5 These amounts roughly correspond to 8 to 10 cups per day, if 2 or 3 cups are brewed from each batch and one batch comprises about 2 g of green-tea leaves.

Suminori Kono, M.D., Ph.D.
Kyushu University Faculty of Medical Sciences, Fukuoka 812-8582, Japan

5 References

1. 1

   Tsubono Y, Nishino Y, Komatsu S, et al. Green tea and the risk of gastric cancer in Japan. N Engl J Med 2001;344:632-636
   Full Text | Web of Science | Medline

2. 2

   Kono S, Ikeda M, Tokudome S, Kuratsune M. A case-control study of gastric cancer and diet in northern Kyushu, Japan. Jpn J Cancer Res 1988;79:1067-1074
   CrossRef | Medline

3. 3

   Inoue M, Tajima K, Hirose K, et al. Tea and coffee consumption and the risk of digestive tract cancers: data from a comparative case-referent study in Japan. Cancer Causes Control 1998;9:209-216
   CrossRef | Web of Science | Medline

4. 4

   Yu GP, Hsieh CC, Wang LY, Yu SZ, Li XL, Jin TH. Green-tea consumption and risk of stomach cancer: a population-based case-control study in Shanghai, China. Cancer Causes Control 1995;6:532-538
   CrossRef | Web of Science | Medline

5. 5

   Ji BT, Chow WH, Yang G, et al. The influence of cigarette smoking, alcohol, and green tea consumption on the risk of carcinoma of the cardia and distal stomach in Shanghai, China. Cancer 1996;77:2449-2457
   CrossRef | Web of Science | Medline

Author/Editor Response

The authors reply:

To the Editor: We found a nonsignificant increase in the risk of gastric cancer among subjects who consumed five or more cups of green tea per day, as compared with subjects who drank less than one cup per day, with a relative risk of 1.4 (95 percent confidence interval, 1.0 to 1.9) in the analysis that excluded cases of gastric cancer diagnosed within the first three years of follow-up. We could not divide this highest category of consumption into subcategories, such as 10 or more cups per day and 5 to 9 cups per day, because these subcategories were not included on the questionnaire completed by the subjects. Even if we could have included subcategories in our analysis, it is very unlikely that we would have observed a decreased risk among subjects who drank 10 or more cups of green tea per day and, at the same time, an increased risk among subjects who drank 5 to 9 cups per day.

Kono cites the findings of some case–control studies that patients with gastric cancer were less likely than control subjects to consume very large amounts of green tea as evidence that the risk of gastric cancer decreases only with very high consumption of green tea. In our article, we proposed an alternative and more plausible explanation for the results of these retrospective investigations. Patients with gastric cancer who used to drink very large amounts of green tea when they were healthy might have decreased their consumption because of abdominal symptoms, and this change in practice could have biased their recall of past intake so that they underestimated their true consumption, resulting in a spurious decrease in risk that is limited to a very high intake of green tea. None of the case–control studies referred to by Kono documented the validity of the questionnaires used to measure past consumption of green tea.

Yoshitaka Tsubono, M.D.
Ichiro Tsuji, M.D.
Shigeru Hisamichi, M.D.
Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan

Citing Articles (1)

Citing Articles

1. 1

   Seung Kwon Myung, Woo Kyung Bae, Seung Min Oh, Yeol Kim, Woong Ju, Joohon Sung, Yeon Ji Lee, Jeong Ah Ko, Jong Im Song, Hyuck Jae Choi. (2009) Green tea consumption and risk of stomach cancer: A meta-analysis of epidemiologic studies. International Journal of Cancer 124:3, 670-677
   CrossRef