Those who have problems with kidney stones will definitely want to avoid eating spinach as much as possible. Because spinach contains oxalate which in effect combines with calcium to form calcium-oxalate kidney stones, it is a bad idea to eat too much of it if you are already at risk for developing these.

Calcium-oxalate stones tend to be the most common type of stones found in the body, though they can still be fairly painful and annoying to deal with, which is precisely why it is important for those with kidney stones to keep from eating too much spinach on a regular basis.