Why Does My Cat Eat Grass (and then barf)?

October 25, 2013

By Julia Williams

Ok, first things first —“Why do cats eat grass” is the million dollar question. Several theories have been bandied about, but the reality is that no one knows for sure. It’s not like we can ask our cats why grass is so appealing to them even though 95% of the time it comes right back up. Oh, we can ask them alright, but I’m not even sure they know the answer.

So…do cats eat grass because they have a dietary deficiency? Do they munch on the green stuff to induce yakking because they’re not feeling well? Do they just like the way grass tastes? Is the predisposition to eat grass something cats inherited from their wild feline ancestors? Is grass beneficial for cats? Could it be harmful?

Those are all great questions, but so far, only the last one has a definitive answer (more on that later). Let’s explore some of the theories on why cats eat grass.

The Juices in Grass Contain Folic Acid

Folic acid is an essential vitamin for a cat’s bodily functions. Folic acid also aids the production of hemoglobin, the protein that moves oxygen in the blood. A folic acid deficiency could lead to anemia and stunted growth. So the theory is that cats might instinctively know they’re deficient in folic acid and they eat grass to correct the situation.

Does Grass Provide Nutrients?

Another theory is that cats might eat grass for its nutrients. Companies that sell cat grass seeds say that grass provides numerous benefits, such as getting rid of hairballs, aiding digestion, making the cat’s coat shinier and freshening their breath. The grass is touted as a great source of vitamins, minerals, enzymes, fiber and chlorophyll.

Some veterinarians, however, aren’t sold on the benefits of cats eating grass. Dr. Plotnick of Manhattan Cat Specialists said “As far as I know, there’s no science to back up the claim that cats need nutrients they can only get from eating grass.”

Does Grass Offer Digestive Benefits?

Another theory is that cats use grass as a “natural laxative” and a way to rid the digestive tract of something unpleasant. Grass may add fiber and bulk to a cat’s diet and help them pass fur through their intestinal tract, which lessens the formation of hairballs. Some say cats might also be eating grass to settle an upset stomach, akin to a human popping an antacid.

Why Do Cats Upchuck After Eating Grass?

Just a minute or two after snacking on grass, many cats barf it right back up. Worse, the Golden Rule every cat follows is “always on the carpet, never the linoleum!” But why do they yak the grass? I’m told it’s because cats lack the necessary enzymes to break down the grass.

Is Grass Eating an Inherited Trait?

Another hypothesis suggests that plant eating is a behavior cats inherited from their wild ancestors. The theory is that ingesting grass likely played an ongoing role in the purging of intestinal parasites the wild felines were regularly exposed to.

Is Eating Grass Bad?

Eating small amounts of grass is typically not harmful, but if your cat eats large quantities daily, you should see your vet to rule out possible intestinal distress.

Outdoor cats also run the risk of eating chemically treated grass. Even if you don’t use pesticides, herbicides and fertilizers on your lawn, your neighbors might. So what can you do if you just don’t want to keep your kitty indoors? You can try growing some “kitty greens” indoors for your cat, the theory being that if she eats it she will be less likely to munch on the neighbor’s lawn (although there is no guarantee).

How to Grow Your Own Cat Grass

You can either purchase a complete cat grass growing kit or just the seeds – typically rye, wheat, oat or a combination. Check the catnip section at your local pet store or the seed aisle in home improvement stores. You can also try growing fresh catnip from seed to satisfy kitty’s urge to munch on greens. See my article on Growing Cat Grass for more information.

Top photo by dichohecho
Middle photo by Kuba Bożanowski
Bottom photo by Joe Thomissen

Read more articles by Julia Williams

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  1. meowmeowmans says:

    We don’t know about grass, but Moosey loves to eat lettuce. Ha ha!

  2. Since my cats have been eating grass since the beginning of time, I just truly think it is instinctive to them and nothing will stop them from chomping on it. With pet food diets being so specifically formulated, maybe grass will be a new ingredient!

  3. I like to eat grass. Sometimes I yak it up and sometimes I don’t.


  4. That was informative for the human! Truth is we will not let on why we eat grass except that we just like it! 🙂

  5. Terre Pruitt says:

    My cat loves to eat grass and throw up. Because I know she will do that after eating the grass I have gotten into the routine of just taking the pot of grass outside and letting her eat it out there so I don’t have to deal with cleaning up the carpet. Plus — she is an indoor kitty so outside (on a leash) is a treat for her.

    I grew up with dogs not cats, and usually our dogs would eat the grass and NOT throw up . . . so the grass = vomit with the cat was a surprise to me!

    Thanks, Julia. I always love your cat related posts!