Stomach cancer.
Laboratory studies have found that green tea polyphenols inhibit the growth of stomach cancer cells in test tubes. But studies in people have been less conclusive. In two studies that compared green tea drinkers with nondrinkers, researchers found that people who drank tea were about half as likely to develop stomach cancer and stomach inflammation as those who did not drink green tea. However, a clinical study with more than 26,000 men and women in Japan found no association between green tea and stomach cancer risk. Some studies even suggest that green tea may increase the risk of stomach cancer.
More studies are underway to see whether green tea helps reduce the risk of stomach cancer.