Studies have shown that every kilogram of toon sprouts contains more than 30 milligrams of nitrite, while the old leaves contain as much as 53.9 milligrams of nitrite per kilogram. Such high levels can easily lead to nitrite poisoning. Test results found that the nitrite content in washed toon leaves was 34.1 milligrams per kilogram, while the nitrite content in toon leaves scalded in boiling water was only 4.4 milligrams per kilogram. The experiment also proved that pickling toon with salt does not reduce its nitrite content. Therefore, it is best to eat toon that has been scalded in boiling water.