Do dogs ever eat grass to supplement missing nutrients in their diet like fiber? Dogs do not know what nutrients they may be lacking, so no. However, a diet low in fiber may increase the desire for something more substantial. I heard of dogs that have had grass eating reduced or eliminated by feeding them a high fiber diet. I had a dog brought to me that ate tree bark, mulch, and feces. His depraved appetite for those inedibles was completely gone once the high fiber diet I recommended was in place.
Do dogs eat grass to improve their digestion? Dogs do not understand about “digestion.” However, they do learn what makes them sick and what seems to help. Grass can do both. If dogs have a bad feeling in their stomach, they may eat grass to make themselves throw up and feel better. There may be a genetic trait that causes them to engage in grass eating in this context. One component of grass, pectin, is supposed to provide some relief for people with gastroesophageal reflux disease (GERD). Maybe dogs with reflux find it helpful too through instinct and learning. Somewhat equivocally, pectin has been used to treat diarrhea, but too much can cause diarrhea. One problem with grass eating is that if the grass is not “thrown up” along with stomach contents, or passes uneventfully through the gastrointestinal tract, it can become lodged in the dogs anus on the way out. The poor dog then starts looking anxious and tries scooting its bottom along the ground to try to remove the protruding grass … or needs its brave owner help to relieve the situation by unplugging it.
Will dogs eat grass when they are anxious? Some people think dogs sometimes eat grass because they are bored. I do not think this is a good explanation. I have never heard of them eating grass because they are anxious – but if feeling unwell makes them anxious, then perhaps anxiety caused by the unwellness (e.g. tummy ache) may lead them head for the green self-cure!
Do dogs eat grass when they have intestinal worms? Once again, they do not know they have worms. They do know that all is not right “down below” and are drawn to eating grass in this situation as the only medicine they know (see above). The grass does not help in this situation but grass eating and diarrhea are definitely signs a dog may have “worms” or some other GI illness. If worms (nematodes) are present, de-wormers work well and fast, relieving diarrhea and grass eating simultaneously. Another point is that worm-egg-ridden diarrhea contaminates the grass – so if another dog comes along and scoffs the contaminated grass, it too winds up with worms. Whip worms are particularly hard to treat, not responding to some conventional de-wormers.
What are some other reasons dogs might eat grass? A lot of dogs eat fresh grass in the spring. Why not have some natural salad after a winter inside eating dry, brown kibble? New grass has an attractive odor to us and perhaps out dogs. The chemical that causes the exhilarating odor of new-cut grass is (Z)-3-hexenal. Drawn by odor and the desire the munch something fresh, off to the new grass they go, like cows. Why? Because it smells and tasted good.
Take home message: Grass eating is usually harmless to dogs, unless the grass is contaminated with chemicals, like fertilizer or weed killer, or parasites (there are those worms again but also potentially bacteria too, especially if the grass is well trodden by many dogs (as in dog parks). There is the possibility of the dog throwing up, but dogs are good at that, and it may even provide a valuable service. Then again, there is the stuck-in-the-butt syndrome if the dog eats to much long-bladed grass in one sitting. Everything is moderation, you might think, but some grass-hungry hounds, like some of us, do not know when to stop!