Women who drink green tea may lower their risk of developing some digestive system cancers, especially cancers of the stomach/esophagus and colorectum, according to a study led by researchers from Vanderbilt-Ingram Cancer Center.
To determine green tea's impact on cancer risk, the investigators surveyed women enrolled in the Shanghai Women's Health Study, a population-based study of approximately 75,000 middle-aged and older Chinese women. Participants were asked if they drank tea, the type of tea consumed and how much they consumed. Most of the Chinese women reported drinking primarily green tea.
The researchers found that regular tea consumption - at least three times a week for more than six months - was linked with a 17 percent reduced risk of all digestive cancers combined. Women who consumed about two to three cups per day had a 21 percent lower risk of digestive tract cancers.
The trend toward fewer digestive cancers was strongest for stomach/esophageal and colorectal cancers.
For all digestive system cancers combined, the risk was reduced by 27 percent among women who had been drinking tea regularly for at least 20 years. For colorectal cancer, risk was reduced by 29 percent among the long-term tea drinkers. These results suggest long-term cumulative exposure may be particularly important.
Tea contains polyphenols, natural chemicals that include catechins like EGCG and ECG. Catechins have antioxidant properties and may inhibit cancer by reducing DNA damage and blocking tumor cell growth and invasion.
The researchers also asked about other lifestyle factors including the kinds of food eaten regularly, exercise habits, education level and occupation. Regular tea drinkers in the study were younger, had higher education, exercised more and consumed more fruits and vegetables. While the researchers adjusted for these factors, they could not rule out an effect from these and other unmeasured lifestyle habits.
The study was conducted in nonsmoking and nondrinking Chinese women to minimize the potential influence of these two risk factors on the results for tea consumption and digestive system cancer risk.
SOURCE: The American Journal of Clinical Nutrition, November 1, 2012.
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