Some of them are black, which sometimes leads to black stool, such as Sheng Di. If these foods are eaten for a long time, it is indeed possible to cause the intestinal wall to turn black. In addition, in the laxative functions such as rhubarb and senna, long-term consumption may make the inner wall of large intestine black. But after stopping for a while, most of them can return to their original colors. It is correct to prevent tumor recurrence after tumor surgery, but it is not necessary to drink it every day. Under normal circumstances, patients should stop drinking for 3 months or replace a small amount of substances, which will not only prevent tumor recurrence, but also damage the stomach.