It isn’t completely known why dogs eat grass. clearly, it helps them throw up by giving a little tickle to the stomach as needed, but this doesn’t explain why a healthy dog eats grass. i read an interesting theory once that linked a dog’s eating grass to the diet of their ancestors who would go right for the gut when consuming prey (that’s where the good stuff is, of course) That gut would most often belong to a grass-fed animal and thusly grass became a part of the diet.