Spinach and tofu can't be cooked at the same time, because fresh spinach contains oxalic acid, which will react with calcium in tofu to produce calcium oxalate, which is easy to form stones after being absorbed by the human body.

If you want to cook soup with spinach and tofu, you can first scald the spinach with boiling water and remove the oxalic acid inside, which will not affect the absorption of calcium in tofu.