Eating overnight dishes can cause cancer, which may be known by most people who pay more attention to health, but can overnight dishes really cause cancer? I'm afraid many people don't necessarily know why it causes cancer every so often. This paper tries to pay attention to the doubts about whether overnight dishes can be eaten with a strict scientific attitude. In this era when health knowledge is flying all over the sky, many people are actively or passively absorbing health knowledge, which has both advantages and disadvantages. Fortunately, people pay more attention to health than they did decades ago. This is a kind of progress in concept, which is the product of social development to a certain stage. That is to say, only when people have no worries about food and clothing can they focus on higher-level things such as maintaining health, otherwise they can only pay attention to food and clothing. The downside is that when all kinds of health-related knowledge appear in front of your eyes, you may not be able to tell whether it is correct with a professional eye. This may be misleading and even dangerous. Therefore, the knowledge we get from non-professionals or institutions is for reference only. Many people have heard that "you can't eat overnight dishes", so from a professional perspective, can you eat overnight dishes? To answer this question, we must know what happened to the overnight dish. Most plants contain nitrate, which is converted into nitrite by some enzymes in plants. Bacteria in the environment will also reduce nitrate in plants to nitrite, which will be converted into nitrosamines in human body. Nitrosamines are recognized as one of carcinogens. As we all know, the activity of enzymes needs a certain temperature, and when vegetables are cooked, the enzymes in vegetables will lose their activity. At this time, enzymes in vegetables will no longer be able to convert nitrate into nitrite, and then bacteria will play a role. It takes some time for bacteria to reproduce. When it reaches a certain amount, it may produce a considerable amount of nitrite, which should be the root cause of the so-called "overnight dish", but we can also see that the problem is not that it is not overnight. It's time. Time is the key. Cooking in the evening/kloc-after 0/0,/kloc-after 0/2 is overnight. Would you say you can't eat? Or 1 in the morning, and 1 1 in the evening is the dish of the day. If you rigidly believe that the food of the day is all right, will you feel comfortable? It can be seen that the problem lies in time, not overnight interval. Of course, this should also take into account the ambient temperature. The environmental temperature of the same pot of vegetables is different, and the number of bacteria reproduction at the same time may be different. Generally speaking, low temperature can inhibit bacterial reproduction. In this case, it is of little significance to simply consider whether this dish is overnight, because in natural environment, the temperature is high in summer and low in winter, and the summer dish may have deteriorated before overnight, while the winter dish may have been separated. So how harmful is this time-honored dish? Under the same conditions, do raw vegetables produce more nitrite or cooked vegetables produce more nitrite? In fact, the nitrate content of different varieties of vegetables is also different. Even the same vegetable is closely related to the type and quantity of chemical fertilizer applied. For example, if more ammonium nitrate fertilizer is applied, the nitrate content in vegetables will be higher. Generally, leafy vegetables will be higher. But in general, the food market is very rich now, and there is no need to store a lot of dishes to eat slowly. The best way is to eat it as soon as possible on the day of purchase and keep it fresh as much as possible, which is also conducive to the protection of vitamins, because the vitamins in vegetables will gradually decrease over time. Eating raw vegetables may produce less nitrite, because its cells also contain some substances that resist nitrate reduction by reductase, but try to keep them fresh unless some fresh vegetables, such as day lily, can cause poisoning.