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In a reversal of previous research, a comprehensive study shows that drinking green tea offers no protection against stomach cancer.
Gastric cancer was once the leading cause of cancer-related death in most countries, including the United States. Since 1930 the incidence of gastric cancer has steadily decreased throughout the world, with dramatic decreases in the West. In 1994, gastric cancer was the eighth leading cause of cancer-related deaths in the United States
The research team in Japan, followed 26,000 men and women for 8 years and reported that there was no health benefit among those who drank large or small amounts of green tea.
Stomach cancer is currently the second-leading cause of cancer deaths worldwide. In recent decades, the number of cases has been steadily declining, possibly due to higher consumption of fresh fruits and vegetables and less consumption of salt-preserved foods caused by refrigeration. But stomach cancer is still the leading form of cancer in Japan among men and women, accounting for 18% of all cancer-related deaths.
Green tea is widely consumed in Asia and is the most popular beverage in Japan. Unlike black tea, green tea is made by steaming fresh leaves at high temperature, which inactivates the oxidizing enzymes and leaves the polyphenols intact.
Studies in animals have shown that the polyphenols in green tea, of which epigallocatechin-3-gallate is the main constituent, have antimutagenic, anticarcinogenic, and antiinflammatory effects.
Several previous studies have shown that green tea contains high levels of antioxidants -- chemicals that may help ward off cell damage and possibly cancer. Other research has suggested that green tea may help prevent stomach cancer, and cancers of the pancreas, bladder and colon.
However, people had to drink as many as 10 cups a day to achieve this result, which can dramatically raise caffeine intake. As an alternative, some people consume a daily capsule of green-tea extract. The amount of polyphenols in one capsule of green-tea extract is equivalent to the amount in 10 cups of tea.
Over the course of the study, 419 people were diagnosed with gastric cancer.
But researchers found no significant association between a diagnosis of cancer and the amount of green tea consumed.
This kind of prospective study, where researchers follow a population into the future, is considered methodologically sounder than earlier studies, which retrospectively traced cancer patients back in time. Specifically, those patients may have been drinking less green tea due to gastrointestinal problems related to their cancer, and may have incorrectly recalled their green tea consumption over the years, thus biasing the results, suggest the study's authors.
The New England Journal of Medicine March 1, 2001; 344: 632-636, 675-676
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