If you select to eat or drink any food/drink item , and whilst eating choose to exchange an item on the ground for the item you're currently eating - your character will eat the item in question, but the item will remain on the ground, completely unchanged.
You can essentially eat/drink forever, with no harm to the item.
Percentage based food items will simply not lose any content, remain at the same percentage as before. {F30873} {F30874} {F30875} {F30876} {F30877} {F30878}