Leftovers contain nitrites, which do not necessarily cause cancer when eaten, but increase the risk of cancer. Cancer is caused by a combination of factors, not just from eating leftovers. The nitrite in leftovers is far from being carcinogenic, so occasional intake will not cause cancer. However, frequent consumption of leftovers is not good for your health, so it is not recommended. Leftovers do produce nitrite, but the amount of nitrite produced is very low and generally does not lead to the development of cancer. So don’t worry too much, occasional consumption won’t have much effect. The reason why it is not recommended to consume leftovers is that leftovers can cause bacteria to multiply or deteriorate if they are left for too long or improperly stored. When we consume leftovers regularly it may affect our health and may lead to gastrointestinal discomfort or Helicobacter pylori infection, so it is not recommended to consume them regularly. It is recommended to store raw food separately from cooked food, and if you need to store the leftovers, they should be sealed and stored in a timely manner instead of waiting for the food to get cold.