There are promising preliminary studies regarding the correlation of tea consumption and the risk of certain types of cancer, including breast, lung and skin cancers and cancer of the mouth. Several in vitro studies describe possible mechanisms for the anticarcinogenic potential, including tea flavonoids' ability to bind directly to carcinogens, to induce cell death and arrest, and to inhibit other actions believed to be involved in cancer risk.
Specifically, in one study, scientists examined the effect of treating superficial precancerous lesions (leukoplakia) in the mucosal lining of the mouth with tea. After the six-month trial, partial regression of the lesions was observed in more than 37 percent of the people treated with tea as compared to only 10 percent of those treated with a placebo.
Studies on tea and stomach cancer have yielded interesting results. In a population-based study among 944 Polish women, those who drank black tea daily had a reduced risk of stomach cancer. Other studies conducted in Japan with green tea have found that a high intake of green tea was associated with a reduction in the risk of stomach cancer and in the risk of precancerous chronic atrophic gastritis.
Additionally, an Iowa Women's Study followed post-menopausal women for eight years and found that participants who drank two or more cups of tea per day had a reduced risk of developing digestive and urinary tract cancers.