Sodium nitrate and sodium nitrite are harmful chemicals to human body, which make low-iron hemoglobin in blood oxidized to methemoglobin, lose oxygen transmission ability, and cause tissue hypoxia damage. Especially in the case of gastrointestinal dysfunction and excessive proliferation of nitrate-reducing bacteria in the intestine, excessive consumption of lunch meat or lunch meat with sodium nitrite residue exceeding 0. 1% can cause symptoms of nitrite poisoning, such as headache, drowsiness, vomiting, abdominal pain, fever and shortness of breath. Therefore, lunch meat should be eaten less.