The human stomach lining renews itself every three or four days.
Why it is true
The hydrochloric acid produced by the stomach is so strong that it would corrode the organ itself. To prevent autodigestion, the cells of the stomach wall are constantly replaced before the acid destroys them.
Source: Scientific American
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.
Related facts
The human stomach replaces its lining every three to four days.
The human stomach gets a completely new lining every few days to prevent it from digesting itself.
The human stomach produces a new lining every three to four days.
Human skin completely regenerates every month.