I always thought cats ate grass as either a purgative (to help with things like the periodic need to cough up a hair ball, or something else causing gastric distress) or a kind of digestive tonic (in smaller amts). Im pretty sure its a self-treatment thing, and NOT a nutritional deficienct craving thing ... but im not an expert, and I could be wrong. Either way, its not bad for them, and anything that helps soothe their urges helps avoid the more destructive tendencies of understimulated cats. Addendum: the 2 best things you can do for a cat's overall happiness is giving it a well balanced raw diet (ala BARF or PMR), and a stimulating cat friendly environment (window perch for sightseeing, wall gangways, freedom from loud noises and strong smells, and a companion to play with).
