If you peruse the internet looking for answers to why cats eat grass, and whether they even should, you will likely not find the ‘real answer’. That may be because there just isn’t one. There are far more websites selling grass and promoting the eating of grass by your pet cats, than sites that objectively explain why your cat eats grass or if it is really a good thing or not. As a veterinarian, this is a question I am asked regularly, and although I certainly have an opinion about cats eating grass, I cannot cite any references or studies that back me up. (I am not saying there are none; I just don’t know of their existence.) The following is a brief discussion of the pros and cons of grass-eating by cats.
Source: Dave’s Garden