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.