Healthnotes Newswire (March 1, 2001)—Consumption of green tea does not lower the risk of stomach cancer, according to the findings of a large Japanese study published in today’s New England Journal of Medicine.¹

Starting in January 1984, researchers asked 33,453 residents (40 years of age or older) of Miyagi Prefecture in Japan to complete a questionnaire on various health habits, including the consumption of green tea. This area of Japan was chosen because of a high incidence of stomach cancer. People were also asked about smoking, drinking, dietary habits, and personal disease history.

The frequency of green tea consumption was divided into five levels: never, occasionally, one or two cups per day, three or four cups per day, and five or more cups per day. While 19% of respondents reported drinking less than one cup per day, 17% said they drank one or more cups per day, 22% drank three or four cups per day, and 42% drank five or more cups per day.

Following people in the study for eight years, the researchers found no association between green tea consumption and decreased risk of stomach cancer—even when comparing people who were drinking five cups or more per day with those drinking less than one cup per day. While heavy smoking (20 or more cigarettes per day), a known risk factor for stomach cancer, was more frequently seen in men consuming over five cups of green tea per day (which was not the case for women), this was countered by the fact that both men and women drinking the highest level of green tea also consumed more green and yellow vegetables and fruits—foods thought to decrease risk of stomach cancer.

The results of this study appear to contradict the findings of earlier Chinese and Japanese studies that suggested a protective effect of green tea against stomach cancer.^{2 3 4 5} However, as pointed out by the researchers of the new study, previous reports may have been misleading because they depended on people’s memories regarding green tea consumption in previous years. The new study questioned people about green tea consumption at the time the question was asked—years before the stomach cancer was diagnosed.

While the results of this study are supported by a Hawaiian study of similar design with Japanese adults,⁶ it is unfortunate that the researchers did not break the high green tea intake group up into smaller groups. Earlier Japanese studies have suggested that a whopping ten cups (almost two quarts) or more of green tea may be needed to reduce the risk of various forms of cancer,⁷ and the current trial did not evaluate the risk of stomach cancer in a group whose members had all consumed such high amounts of green tea.

Because of its high content of health-promoting bioflavonoids (also called polyphenols), green tea should continue to be a part of a sensible diet that is high in vegetables, fruits, and grains, and lower in processed foods and animal products, such as red meat. The results of this study suggest that green tea may not have the power to prevent stomach cancer.