People have always believed that overnight tea cannot be consumed because it produces secondary amines, which can transform into carcinogens - nitrosamines. Actually, the amount of secondary amines obtained from tea leaves is extremely limited, far less than the intake from staple foods. Secondary amines themselves are not carcinogenic; they need to coexist with nitrates under certain conditions and undergo chemical reactions to form nitrosamines. Only when nitrosamines accumulate and reach a certain amount do they become carcinogenic. Drinking tea allows us to intake more tea polyphenols and vitamin C, which can effectively prevent the human body from synthesizing nitrosamines, serving as natural inhibitors of nitrosamines.