Side cabbage overnight in the refrigerator can not eat again, because cabbage overnight this time, will produce a lot of nitrates, after heating, will be converted into carcinogenic substances harmful to the human body. Overnight dishes contain a lot of bacterial reproduction, especially in the refrigerator, a long time in a humid state, will breed a lot of bacteria, in the heating can not be completely killed bacteria, often eat overnight dishes, but also cause gastrointestinal diseases.