Ask A Vet: 5 Reasons That Cats Eat Grass

| Published on June 3, 2016


Cats are carnivores which means that they must consume meat to survive. But everyone who has a cat knows that cats like to nibble on grass and chew plants. Have you ever wondered why? Sometimes they eat and swallow the plant material and sometimes, they seem to just grab it to chew and spit it out. No one knows for sure why cats eat grass, but there are some theories.

  1. Are They Sick? Lots of people believe that cats eat grass when they feel nauseated, but there is no science to support that cats ingest grass in order to vomit, but since we cannot ask the cats (or at least they won’t answer), we cannot say for sure. It seems that normal healthy cats love to chew on grass, so this is probably not always the case.
  2. Is their Diet Unbalanced? Other people think that it is an indication of a dietary deficiency. Since cats are hyper carnivores and do not glean much nutrition from plants, it is not likely that a cat would be driven to eat grass by a nutritional deficiency, but make sure that your cat eats a high quality balanced diet that is specifically designed for a feline system, so you do not have to worry about deficiency.
  3. Driven By Instinct? People have postulated that in the wild, cats’ ancestors would have ingested prey that had plant matter in their bowels and this drives cats to seek it, but science has not proven this view.
  4. What about Worms? There have been studies in wild chimps that suggested they ingest plant material to increase intestinal motility 1 and help rid them of intestinal parasites. Most of our pet cats are protected from parasites, but instincts may still drive their behavior and because of their grooming habits, they are more prone to swallowing hair so increased intestinal mobility may be a helpful mechanism.
  5. Could It Be Fun? Maybe the most likely reason that cats eat grass is because it is a rewarding and fun behavior. In a study of giant pandas (whose peculiar plant appetite has landed them on the endangered species list) scientists examined why they would choose to eat only bamboo. What they found is that eating and appetite are a very complex interaction of internal chemicals, including dopamine, which is thought to be associated with pleasure-reward in many species. Their findings seemed to suggest that the giant panda eats bamboo to help stimulate dopamine metabolism in their brain. Eating bamboo allows the panda to experience “reward” (i.e. pleasure) and so the panda chooses to eat it. 2 Maybe cats chew grass because it causes a release of dopamine reward for them too.


No matter what the real reason is (and it may be different for different cats or a combination of all the above), you can rest assured that grass eating is a common behavior of normal, healthy cats. Make sure that all plant material that is accessible to your cat is safe for him to chew on and if your cat seems ill or vomits more than occasionally (whether associated with grass eating or not), you should see a veterinarian. All cats should be on a regular parasite control program that is overseen by a veterinarian regardless of whether they eat grass or not.


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  1. Self-induced increase of gut motility and the control of parasitic infections in wild chimpanzees Huffman MA, Canton J.. Int J Primatol 2001;22:329–346.
  2. Why Does the Giant Panda Eat Bamboo? A Comparative Analysis of Appetite-Reward-Related Genes among Mammals.  Ke Jin et al.  PLoS One. 2011; 6(7): e22602.Published online 2011 Jul 27



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