There is no doubt that fresh vegetables is most popular in our daily life. But little people known nitrite content is very little in the fresh vegetables. The content of nitrite will reach a peak after the vegetables have been stored about one to three days at room temperature. It will also reach a peak after vegetables have been stored about three to five days at cold storage conditions. So you should eat the fresh vegetables as soon as possible, especially for green leafy vegetables.
Many people think overnight food may produce carcinogenic nitrite. In fact, it is not correct. Because the nitrite is not carcinogenic, but the nitrosamine is carcinogenic. However it is not means that the overnight food is without any problem. Nitrite content in the overnight food is more higher than in the dishes which just doing. Nitrite can converted into nitrosamines in human body. So you had better eat overnight food as less as possible.
Since the nitrosamines carcinogen, we need to pay attention to eat more food which could inhibit the formation of nitrosamines. For example, the garlic can inhibit the nitrate reducing bacteria in the stomach and reduce the content of nitrite in the stomach. Besides we also suggest that you can drink tea in day time. Tea polyphenols in tea can also prevent the formation of nitrosamine.