Inhibitory effect of Chinese tea on N-nitrosation in vitro and in vivo

The inhibitory effect of 145 samples of Chinese tea on the formation of N-nitrosomorpholine was studied in vitro. The rates of inhibition by green tea, crush, tear, curl (CTC) black tea, brick tea, jasmine tea, Oolong tea, sun-dried tea and black tea were positively correlated with their polyphenol contents. An inhibitory effect of green and black tea on endogenous N-nitrosation was also confirmed in humans. Drinking tea after a meal had a greater effect than drinking it before a meal.