1, starch-rich vegetables (such as potatoes, taro, yam, etc.) must be cooked, otherwise the starch grains will not break and the human body cannot digest them;

2. Vegetables containing some harmful substances, such as the seeds of some leguminous vegetables and potato chips, contain a kind of toxic protein called lectin, which can cause red blood cells in human blood to agglutinate. After people eat it, it will cause nausea, vomiting, diarrhea and even death in severe cases. When cooked thoroughly, toxic protein will lose its toxicity and can be safely eaten.

In addition, it is reported recently that American scientists have found through long-term research that vegetables commonly used by people, such as tomatoes, potatoes, eggplant and cauliflower, all contain trace amounts of nicotine. If these vegetables are eaten raw without cooking, they may be harmful to human body, just like passive smoking. In fact, this is not the latest discovery at all. This research report first appeared in a medical journal of1August, 993. Later, because many experts questioned the results of this research, there was no further study on "whether eating raw vegetables is harmful to nicotine". However, the unanimous opinion of experts is that the nicotine content ingested by the human body is too "insignificant" to cause medical reactions, and it will not endanger health. We can ignore this reason. If we consider him, we will have nothing to eat.