Sauerkraut can only be eaten occasionally. If you overeat for a long time, it may cause urinary calculi. In addition, vitamin C was destroyed a lot in the pickling process of sauerkraut. If the human body lacks vitamin C, it will reduce the ability to inhibit the deposition of calcium oxalate crystals in the kidney and reduce the formation of stones. Eating pickled cabbage with too much nitrite will turn protein in the blood into methemoglobin with no oxygen-carrying function, and make red blood cells lose their oxygen-carrying ability, leading to hypoxia in tissues, leading to poisoning symptoms such as cyanosis of skin and lips, headache, dizziness, nausea, vomiting and palpitation, and even death in severe cases. Moldy sauerkraut has obvious carcinogenicity and cannot be eaten.