Thanks for comment... Human stomach contain acid which is powerful enough to ruin even metal, acids are measured on pH scale, it goes from 0 to 14 with 0 being high acidic and 14 being low. Stomach acid has pH measurement from 1 to 3 and this is approx same value of acid used in batteries and this acid if put on piece of wood it would eat it right through, question arises how come this acid doesn't drill a hole in our stomach well that's because there are special stomach cells to protect it and builds a protecting coating around stomach walls.