Why is it black after eating stinky tofu?

After eating stinky tofu stool is black usually considered and iron intake, peptic ulcer, gastric cancer and other factors, as follows:

1, iron intake

stinky tofu iron and digestive juice oxidation reaction, the formation of black iron sulfide, resulting in black stools.

2, peptic ulcer

When peptic ulcer occurs and the blood vessels rupture on the surface of the ulcer, blood will be mixed in the stool, making it

black.3, gastric cancer

When gastric cancer occurs, tumor cells may destroy normal gastric mucosa tissue, causing bleeding, resulting in black stools.