This is simply not true. In fact, according to PetMD, less than 10% of dogs who have a symptom of eating grass are found to be sick by a veterinarian. It seems there are additional myths out there assuming dogs eat grass to throw up to heal an upset stomach. Again, this is false. Grass does not make your dog throw up and your dog is not sick because they eat grass.
If your dog is outside for long periods of time, they may sleep if they are bored. But for the most part, they will not eat grass. To avoid boredom, be sure to have plenty of things to do when outside such as playing Frisbee with them and being outside to play catch or run with them. If you have plenty of chew toys inside, throw a couple outside to see if he plays with them.
Some say your dog is asking for more fiber when they eat grass. This is hard to prove, but if you want to examine if this is the case for your dog, consider switching to a high-fiber dog food variety. If you notice less grass eating, this may be the case. However, most say this does not change the grass eating habit of their dog when they do this.
The reality is most veterinarians consider dogs eating grass as a common behavior. It has been observed with dogs in the wild as well. In a small scale study, dogs were found to eat grass because they enjoy the taste. Does your dog enjoy vegetables? If your dog is like mine and likes carrots and celery, maybe they enjoy the taste of grass as an additional vegetable in their diet. The truth: dogs are pretty smart and don’t do things that may harm or hurt them. Score one more point for the dogs!