"Overnight meal" refers not only to leftovers left over for one night, but also to meals left over for more than 6-8 hours. Some are leftovers from the last meal, and some are self-brought working meals. However, some kinds of food can't be eaten overnight (such as spinach, rape, chrysanthemum, Chinese cabbage, lettuce and other leafy vegetables)! Not only because of the pollution of pathogenic microorganisms, but also because of nitrite. Nitrite is produced by nitrate in meals under the action of microorganisms, and its toxicity will be stronger when heated. 1. Harm of Nitrite A large intake will lead to symptoms of hypoxia such as nausea, vomiting, dizziness and purple lips. CCTV's "Consumer Advocacy" column once reported that a little girl suffered from acute nitrite poisoning due to eating long-term rape and spinach, and passed out, only after emergency treatment could she save her life. A small amount of intake for many times will cause chronic poisoning, such as carcinogenesis (digestive tract canceration) and deformity of offspring. 2. Precautions for all kinds of food leafy vegetables, such as chrysanthemum, rape, cabbage, lettuce, spinach, etc., because the stems and leaves of plants contain a large amount of nitrate, nitrite will be generated under the action of some microorganisms; Followed by root vegetables; Fruits such as tomatoes, eggplant, loofah, zucchini and other vegetables contain little nitrate and are not easy to produce nitrite. Seafood, such as shrimp and crab, is easy to produce nitrite for a long time. Edible fungi, such as Pleurotus ostreatus and Lentinus edodes, are not easy to produce nitrite after long-term storage and are resistant to heating. Such "overnight meals" can be safely eaten and carried by office workers. Meat with less salt and more heating will not produce a lot of nitrite. This kind of "overnight meal" can be safely eaten and carried by office workers. When making soup stock, don't put salt first, put salt as you use it. Seal with plastic wrap and put in the refrigerator. In the aspect of raw vegetables, leafy and stem vegetables are best eaten and bought now. When stored, they are wrapped in plastic wrap and put in the refrigerator. The remaining rice should be wrapped in plastic wrap and put in the refrigerator.