Background. Based on previous studies on the blocking effect of Chinese tea in the formation of N-nitroso compounds in rats and humans, experiments were carried out to study the effects of Chinese tea on the occurrence of esophageal tumors induced by N-nitrosomethylbenzylamine (NMBzA) in rats. Methods. In the first experiment, rats were given two precursors of NMBzA, i.e., sodium nitrite and methyl benzylamine, p.o. After 12 weeks, the incidence of esophageal tumors was 95%. However, in the five groups of tea (green tea, jasmine tea, black tea, and oolong tea)-treated rats, the incidences were only 5-19%. In the second experiment, preformed NMBzA was administered to rats. Results. The incidences of esophageal tumors in the five tea-treated groups were 42-67%, while in the positive control group, without tea, the incidence was 90%. Histopathological examination showed the same protective effects of tea treatment. In a separate study, a significant reduction of O6-methylguanine (MeG) and the ratio of O6-MeG to N7-MeG was observed in rats treated with oolong tea and jasmine tea. © 1992.
